Merge pull request #26413 from hashicorp/mildwonkey/the-rest-of-the-owl-tree

The Last Chapter in our Epic Saga: `EvalTree()` Refactor

terraform/eval.go

@@ -1,62 +0,0 @@
-package terraform
-
-import (
-	"log"
-
-	"github.com/hashicorp/terraform/tfdiags"
-)
-
-// EvalNode is the interface that must be implemented by graph nodes to
-// evaluate/execute.
-type EvalNode interface {
-	// Eval evaluates this node with the given context. The second parameter
-	// are the argument values. These will match in order and 1-1 with the
-	// results of the Args() return value.
-	Eval(EvalContext) (interface{}, error)
-}
-
-// GraphNodeEvalable is the interface that graph nodes must implement
-// to enable valuation.
-type GraphNodeEvalable interface {
-	EvalTree() EvalNode
-}
-
-// EvalEarlyExitError is a special error return value that can be returned
-// by eval nodes that does an early exit.
-type EvalEarlyExitError struct{}
-
-func (EvalEarlyExitError) Error() string { return "early exit" }
-
-// Eval evaluates the given EvalNode with the given context, properly
-// evaluating all args in the correct order.
-func Eval(n EvalNode, ctx EvalContext) (interface{}, error) {
-	// Call the lower level eval which doesn't understand early exit,
-	// and if we early exit, it isn't an error.
-	result, err := EvalRaw(n, ctx)
-	if err != nil {
-		if _, ok := err.(EvalEarlyExitError); ok {
-			return nil, nil
-		}
-	}
-
-	return result, err
-}
-
-// EvalRaw is like Eval except that it returns all errors, even if they
-// signal something normal such as EvalEarlyExitError.
-func EvalRaw(n EvalNode, ctx EvalContext) (interface{}, error) {
-	log.Printf("[TRACE] eval: %T", n)
-	output, err := n.Eval(ctx)
-	if err != nil {
-		switch err.(type) {
-		case EvalEarlyExitError:
-			log.Printf("[TRACE] eval: %T, early exit err: %s", n, err)
-		case tfdiags.NonFatalError:
-			log.Printf("[WARN] eval: %T, non-fatal err: %s", n, err)
-		default:
-			log.Printf("[ERROR] eval: %T, err: %s", n, err)
-		}
-	}
-
-	return output, err
-}

terraform/eval_check_prevent_destroy.go

@@ -1,47 +0,0 @@
-package terraform
-
-import (
-	"fmt"
-
-	"github.com/hashicorp/terraform/plans"
-
-	"github.com/hashicorp/hcl/v2"
-
-	"github.com/hashicorp/terraform/addrs"
-	"github.com/hashicorp/terraform/configs"
-	"github.com/hashicorp/terraform/tfdiags"
-)
-
-// EvalPreventDestroy is an EvalNode implementation that returns an
-// error if a resource has PreventDestroy configured and the diff
-// would destroy the resource.
-type EvalCheckPreventDestroy struct {
-	Addr   addrs.ResourceInstance
-	Config *configs.Resource
-	Change **plans.ResourceInstanceChange
-}
-
-func (n *EvalCheckPreventDestroy) Eval(ctx EvalContext) (interface{}, error) {
-	if n.Change == nil || *n.Change == nil || n.Config == nil || n.Config.Managed == nil {
-		return nil, nil
-	}
-
-	change := *n.Change
-	preventDestroy := n.Config.Managed.PreventDestroy
-
-	if (change.Action == plans.Delete || change.Action.IsReplace()) && preventDestroy {
-		var diags tfdiags.Diagnostics
-		diags = diags.Append(&hcl.Diagnostic{
-			Severity: hcl.DiagError,
-			Summary:  "Instance cannot be destroyed",
-			Detail: fmt.Sprintf(
-				"Resource %s has lifecycle.prevent_destroy set, but the plan calls for this resource to be destroyed. To avoid this error and continue with the plan, either disable lifecycle.prevent_destroy or reduce the scope of the plan using the -target flag.",
-				n.Addr.Absolute(ctx.Path()).String(),
-			),
-			Subject: &n.Config.DeclRange,
-		})
-		return nil, diags.Err()
-	}
-
-	return nil, nil
-}

terraform/eval_diff.go

@@ -781,49 +781,6 @@ func (n *EvalReduceDiff) Eval(ctx EvalContext) (interface{}, error) {
 	return nil, nil
 }
 
-// EvalReadDiff is an EvalNode implementation that retrieves the planned
-// change for a particular resource instance object.
-type EvalReadDiff struct {
-	Addr           addrs.ResourceInstance
-	DeposedKey     states.DeposedKey
-	ProviderSchema **ProviderSchema
-	Change         **plans.ResourceInstanceChange
-}
-
-func (n *EvalReadDiff) Eval(ctx EvalContext) (interface{}, error) {
-	providerSchema := *n.ProviderSchema
-	changes := ctx.Changes()
-	addr := n.Addr.Absolute(ctx.Path())
-
-	schema, _ := providerSchema.SchemaForResourceAddr(n.Addr.ContainingResource())
-	if schema == nil {
-		// Should be caught during validation, so we don't bother with a pretty error here
-		return nil, fmt.Errorf("provider does not support resource type %q", n.Addr.Resource.Type)
-	}
-
-	gen := states.CurrentGen
-	if n.DeposedKey != states.NotDeposed {
-		gen = n.DeposedKey
-	}
-	csrc := changes.GetResourceInstanceChange(addr, gen)
-	if csrc == nil {
-		log.Printf("[TRACE] EvalReadDiff: No planned change recorded for %s", addr)
-		return nil, nil
-	}
-
-	change, err := csrc.Decode(schema.ImpliedType())
-	if err != nil {
-		return nil, fmt.Errorf("failed to decode planned changes for %s: %s", addr, err)
-	}
-	if n.Change != nil {
-		*n.Change = change
-	}
-
-	log.Printf("[TRACE] EvalReadDiff: Read %s change from plan for %s", change.Action, addr)
-
-	return nil, nil
-}
-
 // EvalWriteDiff is an EvalNode implementation that saves a planned change
 // for an instance object into the set of global planned changes.
 type EvalWriteDiff struct {

terraform/eval_error.go

@@ -1,20 +1,7 @@
 package terraform
 
-// EvalReturnError is an EvalNode implementation that returns an
+// EvalEarlyExitError is a special error return value that can be returned
-// error if it is present.
+// by eval nodes that does an early exit.
-//
+type EvalEarlyExitError struct{}
-// This is useful for scenarios where an error has been captured by
-// another EvalNode (like EvalApply) for special EvalTree-based error
-// handling, and that handling has completed, so the error should be
-// returned normally.
-type EvalReturnError struct {
-	Error *error
-}
 
-func (n *EvalReturnError) Eval(ctx EvalContext) (interface{}, error) {
+func (EvalEarlyExitError) Error() string { return "early exit" }
-	if n.Error == nil {
-		return nil, nil
-	}
-
-	return nil, *n.Error
-}

terraform/eval_filter.go

@@ -1,25 +0,0 @@
-package terraform
-
-// EvalNodeFilterFunc is the callback used to replace a node with
-// another to node. To not do the replacement, just return the input node.
-type EvalNodeFilterFunc func(EvalNode) EvalNode
-
-// EvalNodeFilterable is an interface that can be implemented by
-// EvalNodes to allow filtering of sub-elements. Note that this isn't
-// a common thing to implement and you probably don't need it.
-type EvalNodeFilterable interface {
-	EvalNode
-	Filter(EvalNodeFilterFunc)
-}
-
-// EvalFilter runs the filter on the given node and returns the
-// final filtered value. This should be called rather than checking
-// the EvalNode directly since this will properly handle EvalNodeFilterables.
-func EvalFilter(node EvalNode, fn EvalNodeFilterFunc) EvalNode {
-	if f, ok := node.(EvalNodeFilterable); ok {
-		f.Filter(fn)
-		return node
-	}
-
-	return fn(node)
-}

terraform/eval_filter_operation.go

@@ -1,49 +0,0 @@
-package terraform
-
-// EvalNodeOpFilterable is an interface that EvalNodes can implement
-// to be filterable by the operation that is being run on Terraform.
-type EvalNodeOpFilterable interface {
-	IncludeInOp(walkOperation) bool
-}
-
-// EvalNodeFilterOp returns a filter function that filters nodes that
-// include themselves in specific operations.
-func EvalNodeFilterOp(op walkOperation) EvalNodeFilterFunc {
-	return func(n EvalNode) EvalNode {
-		include := true
-		if of, ok := n.(EvalNodeOpFilterable); ok {
-			include = of.IncludeInOp(op)
-		}
-		if include {
-			return n
-		}
-
-		return EvalNoop{}
-	}
-}
-
-// EvalOpFilter is an EvalNode implementation that is a proxy to
-// another node but filters based on the operation.
-type EvalOpFilter struct {
-	// Ops is the list of operations to include this node in.
-	Ops []walkOperation
-
-	// Node is the node to execute
-	Node EvalNode
-}
-
-// TODO: test
-func (n *EvalOpFilter) Eval(ctx EvalContext) (interface{}, error) {
-	return EvalRaw(n.Node, ctx)
-}
-
-// EvalNodeOpFilterable impl.
-func (n *EvalOpFilter) IncludeInOp(op walkOperation) bool {
-	for _, v := range n.Ops {
-		if v == op {
-			return true
-		}
-	}
-
-	return false
-}

terraform/eval_if.go

@@ -1,26 +0,0 @@
-package terraform
-
-// EvalIf is an EvalNode that is a conditional.
-type EvalIf struct {
-	If   func(EvalContext) (bool, error)
-	Then EvalNode
-	Else EvalNode
-}
-
-// TODO: test
-func (n *EvalIf) Eval(ctx EvalContext) (interface{}, error) {
-	yes, err := n.If(ctx)
-	if err != nil {
-		return nil, err
-	}
-
-	if yes {
-		return EvalRaw(n.Then, ctx)
-	} else {
-		if n.Else != nil {
-			return EvalRaw(n.Else, ctx)
-		}
-	}
-
-	return nil, nil
-}

terraform/eval_noop.go

@@ -1,8 +0,0 @@
-package terraform
-
-// EvalNoop is an EvalNode that does nothing.
-type EvalNoop struct{}
-
-func (EvalNoop) Eval(EvalContext) (interface{}, error) {
-	return nil, nil
-}

terraform/eval_provider.go

@@ -60,42 +60,3 @@ func GetProvider(ctx EvalContext, addr addrs.AbsProviderConfig) (providers.Inter
 	schema := ctx.ProviderSchema(addr)
 	return provider, schema, nil
 }
-
-// EvalGetProvider is an EvalNode implementation that retrieves an already
-// initialized provider instance for the given name.
-//
-// Unlike most eval nodes, this takes an _absolute_ provider configuration,
-// because providers can be passed into and inherited between modules.
-// Resource nodes must therefore know the absolute path of the provider they
-// will use, which is usually accomplished by implementing
-// interface GraphNodeProviderConsumer.
-type EvalGetProvider struct {
-	Addr   addrs.AbsProviderConfig
-	Output *providers.Interface
-
-	// If non-nil, Schema will be updated after eval to refer to the
-	// schema of the provider.
-	Schema **ProviderSchema
-}
-
-func (n *EvalGetProvider) Eval(ctx EvalContext) (interface{}, error) {
-	if n.Addr.Provider.Type == "" {
-		// Should never happen
-		panic("EvalGetProvider used with uninitialized provider configuration address")
-	}
-
-	result := ctx.Provider(n.Addr)
-	if result == nil {
-		return nil, fmt.Errorf("provider %s not initialized", n.Addr)
-	}
-
-	if n.Output != nil {
-		*n.Output = result
-	}
-
-	if n.Schema != nil {
-		*n.Schema = ctx.ProviderSchema(n.Addr)
-	}
-
-	return nil, nil
-}

terraform/eval_provider_test.go

@@ -9,7 +9,6 @@ import (
 	"github.com/hashicorp/terraform/addrs"
 	"github.com/hashicorp/terraform/configs"
 	"github.com/hashicorp/terraform/configs/configschema"
-	"github.com/hashicorp/terraform/providers"
 )
 
 func TestBuildProviderConfig(t *testing.T) {
@@ -54,30 +53,3 @@ func TestBuildProviderConfig(t *testing.T) {
 		t.Fatalf("incorrect merged config\ngot:  %#v\nwant: %#v", got, want)
 	}
 }
-
-func TestEvalGetProvider_impl(t *testing.T) {
-	var _ EvalNode = new(EvalGetProvider)
-}
-
-func TestEvalGetProvider(t *testing.T) {
-	var actual providers.Interface
-	n := &EvalGetProvider{
-		Addr:   addrs.RootModuleInstance.ProviderConfigDefault(addrs.NewDefaultProvider("foo")),
-		Output: &actual,
-	}
-	provider := &MockProvider{}
-	ctx := &MockEvalContext{ProviderProvider: provider}
-	if _, err := n.Eval(ctx); err != nil {
-		t.Fatalf("err: %s", err)
-	}
-	if actual != provider {
-		t.Fatalf("bad: %#v", actual)
-	}
-
-	if !ctx.ProviderCalled {
-		t.Fatal("should be called")
-	}
-	if ctx.ProviderAddr.String() != `provider["registry.terraform.io/hashicorp/foo"]` {
-		t.Fatalf("wrong provider address %s", ctx.ProviderAddr)
-	}
-}

terraform/eval_sequence.go

@@ -1,42 +0,0 @@
-package terraform
-
-import (
-	"github.com/hashicorp/terraform/tfdiags"
-)
-
-// EvalSequence is an EvalNode that evaluates in sequence.
-type EvalSequence struct {
-	Nodes []EvalNode
-}
-
-func (n *EvalSequence) Eval(ctx EvalContext) (interface{}, error) {
-	var diags tfdiags.Diagnostics
-
-	for _, n := range n.Nodes {
-		if n == nil {
-			continue
-		}
-
-		if _, err := EvalRaw(n, ctx); err != nil {
-			if _, isEarlyExit := err.(EvalEarlyExitError); isEarlyExit {
-				// In this path we abort early, losing any non-error
-				// diagnostics we saw earlier.
-				return nil, err
-			}
-			diags = diags.Append(err)
-			if diags.HasErrors() {
-				// Halt if we get some errors, but warnings are okay.
-				break
-			}
-		}
-	}
-
-	return nil, diags.ErrWithWarnings()
-}
-
-// EvalNodeFilterable impl.
-func (n *EvalSequence) Filter(fn EvalNodeFilterFunc) {
-	for i, node := range n.Nodes {
-		n.Nodes[i] = fn(node)
-	}
-}

terraform/eval_sequence_test.go

@@ -1,9 +0,0 @@
-package terraform
-
-import (
-	"testing"
-)
-
-func TestEvalSequence_impl(t *testing.T) {
-	var _ EvalNodeFilterable = new(EvalSequence)
-}

terraform/eval_state.go

@@ -149,35 +149,7 @@ func (n *EvalReadStateDeposed) Eval(ctx EvalContext) (interface{}, error) {
 	return obj, nil
 }
 
-// EvalUpdateStateHook is an EvalNode implementation that calls the
-// PostStateUpdate hook with the current state.
-type EvalUpdateStateHook struct{}
-
-func (n *EvalUpdateStateHook) Eval(ctx EvalContext) (interface{}, error) {
-	// In principle we could grab the lock here just long enough to take a
-	// deep copy and then pass that to our hooks below, but we'll instead
-	// hold the hook for the duration to avoid the potential confusing
-	// situation of us racing to call PostStateUpdate concurrently with
-	// different state snapshots.
-	stateSync := ctx.State()
-	state := stateSync.Lock().DeepCopy()
-	defer stateSync.Unlock()
-
-	// Call the hook
-	err := ctx.Hook(func(h Hook) (HookAction, error) {
-		return h.PostStateUpdate(state)
-	})
-	if err != nil {
-		return nil, err
-	}
-
-	return nil, nil
-}
-
 // UpdateStateHook calls the PostStateUpdate hook with the current state.
-//
-// TODO: UpdateStateHook will eventually replace EvalUpdateStateHook, at which
-// point EvalUpdateStateHook can be removed and this comment updated.
 func UpdateStateHook(ctx EvalContext) error {
 	// In principle we could grab the lock here just long enough to take a
 	// deep copy and then pass that to our hooks below, but we'll instead

terraform/eval_state_test.go

@@ -12,29 +12,6 @@ import (
 	"github.com/hashicorp/terraform/states"
 )
 
-func TestEvalUpdateStateHook(t *testing.T) {
-	mockHook := new(MockHook)
-
-	state := states.NewState()
-	state.Module(addrs.RootModuleInstance).SetLocalValue("foo", cty.StringVal("hello"))
-
-	ctx := new(MockEvalContext)
-	ctx.HookHook = mockHook
-	ctx.StateState = state.SyncWrapper()
-
-	node := &EvalUpdateStateHook{}
-	if _, err := node.Eval(ctx); err != nil {
-		t.Fatalf("err: %s", err)
-	}
-
-	if !mockHook.PostStateUpdateCalled {
-		t.Fatal("should call PostStateUpdate")
-	}
-	if mockHook.PostStateUpdateState.LocalValue(addrs.LocalValue{Name: "foo"}.Absolute(addrs.RootModuleInstance)) != cty.StringVal("hello") {
-		t.Fatalf("wrong state passed to hook: %s", spew.Sdump(mockHook.PostStateUpdateState))
-	}
-}
-
 func TestEvalReadState(t *testing.T) {
 	var output *states.ResourceInstanceObject
 	mockProvider := mockProviderWithResourceTypeSchema("aws_instance", &configschema.Block{
@@ -50,7 +27,7 @@ func TestEvalReadState(t *testing.T) {
 
 	cases := map[string]struct {
 		Resources          map[string]*ResourceState
-		Node               EvalNode
+		Node               *EvalReadState
 		ExpectedInstanceId string
 	}{
 		"ReadState gets primary instance state": {
@@ -74,6 +51,59 @@ func TestEvalReadState(t *testing.T) {
 			},
 			ExpectedInstanceId: "i-abc123",
 		},
+	}
+
+	for k, c := range cases {
+		t.Run(k, func(t *testing.T) {
+			ctx := new(MockEvalContext)
+			state := MustShimLegacyState(&State{
+				Modules: []*ModuleState{
+					&ModuleState{
+						Path:      rootModulePath,
+						Resources: c.Resources,
+					},
+				},
+			})
+			ctx.StateState = state.SyncWrapper()
+			ctx.PathPath = addrs.RootModuleInstance
+
+			result, err := c.Node.Eval(ctx)
+			if err != nil {
+				t.Fatalf("[%s] Got err: %#v", k, err)
+			}
+
+			expected := c.ExpectedInstanceId
+			if !(result != nil && instanceObjectIdForTests(result.(*states.ResourceInstanceObject)) == expected) {
+				t.Fatalf("[%s] Expected return with ID %#v, got: %#v", k, expected, result)
+			}
+
+			if !(output != nil && output.Value.GetAttr("id") == cty.StringVal(expected)) {
+				t.Fatalf("[%s] Expected output with ID %#v, got: %#v", k, expected, output)
+			}
+
+			output = nil
+		})
+	}
+}
+
+func TestEvalReadStateDeposed(t *testing.T) {
+	var output *states.ResourceInstanceObject
+	mockProvider := mockProviderWithResourceTypeSchema("aws_instance", &configschema.Block{
+		Attributes: map[string]*configschema.Attribute{
+			"id": {
+				Type:     cty.String,
+				Optional: true,
+			},
+		},
+	})
+	providerSchema := mockProvider.GetSchemaReturn
+	provider := providers.Interface(mockProvider)
+
+	cases := map[string]struct {
+		Resources          map[string]*ResourceState
+		Node               *EvalReadStateDeposed
+		ExpectedInstanceId string
+	}{
 		"ReadStateDeposed gets deposed instance": {
 			Resources: map[string]*ResourceState{
 				"aws_instance.bar": &ResourceState{
@@ -97,7 +127,6 @@ func TestEvalReadState(t *testing.T) {
 			ExpectedInstanceId: "i-abc123",
 		},
 	}
-
 	for k, c := range cases {
 		t.Run(k, func(t *testing.T) {
 			ctx := new(MockEvalContext)
@@ -225,9 +254,6 @@ aws_instance.foo: (1 deposed)
 	`)
 }
 
-// Same test as TestEvalUpdateStateHook, similar function, slightly different
-// signature. The EvalUpdateStateHook test and function will be removed when the
-// EvalNode Removal is complete.
 func TestUpdateStateHook(t *testing.T) {
 	mockHook := new(MockHook)
 

terraform/eval_test.go

@@ -1,40 +0,0 @@
-package terraform
-
-import (
-	"testing"
-)
-
-func TestMockEvalContext_impl(t *testing.T) {
-	var _ EvalContext = new(MockEvalContext)
-}
-
-func TestEval(t *testing.T) {
-	var result int
-	n := &testEvalAdd{
-		Items:  []int{10, 32},
-		Result: &result,
-	}
-
-	if _, err := Eval(n, nil); err != nil {
-		t.Fatalf("err: %s", err)
-	}
-
-	if result != 42 {
-		t.Fatalf("bad: %#v", result)
-	}
-}
-
-type testEvalAdd struct {
-	Items  []int
-	Result *int
-}
-
-func (n *testEvalAdd) Eval(ctx EvalContext) (interface{}, error) {
-	result := 0
-	for _, item := range n.Items {
-		result += item
-	}
-
-	*n.Result = result
-	return nil, nil
-}

terraform/graph.go

@@ -1,7 +1,6 @@
 package terraform
 
 import (
-	"fmt"
 	"log"
 
 	"github.com/hashicorp/terraform/tfdiags"
@@ -57,38 +56,12 @@ func (g *Graph) walk(walker GraphWalker) tfdiags.Diagnostics {
 
 		// If the node is exec-able, then execute it.
 		if ev, ok := v.(GraphNodeExecutable); ok {
-			// A node must not be both Evalable and Executable. This will be
-			// removed when GraphNodeEvalable is fully removed.
-			if _, ok := v.(GraphNodeEvalable); ok {
-				panic(fmt.Sprintf(
-					"%T implements both GraphNodeEvalable and GraphNodeExecutable", v,
-				))
-			}
 			diags = diags.Append(walker.Execute(vertexCtx, ev))
 			if diags.HasErrors() {
 				return
 			}
 		}
 
-		// If the node is eval-able, then evaluate it.
-		if ev, ok := v.(GraphNodeEvalable); ok {
-			tree := ev.EvalTree()
-			if tree == nil {
-				panic(fmt.Sprintf("%q (%T): nil eval tree", dag.VertexName(v), v))
-			}
-
-			// Allow the walker to change our tree if needed. Eval,
-			// then callback with the output.
-			log.Printf("[TRACE] vertex %q: evaluating", dag.VertexName(v))
-
-			tree = walker.EnterEvalTree(v, tree)
-			output, err := Eval(tree, vertexCtx)
-			diags = diags.Append(walker.ExitEvalTree(v, output, err))
-			if diags.HasErrors() {
-				return
-			}
-		}
-
 		// If the node is dynamically expanded, then expand it
 		if ev, ok := v.(GraphNodeDynamicExpandable); ok {
 			log.Printf("[TRACE] vertex %q: expanding dynamic subgraph", dag.VertexName(v))

terraform/graph_walk.go

@@ -2,7 +2,6 @@ package terraform
 
 import (
 	"github.com/hashicorp/terraform/addrs"
-	"github.com/hashicorp/terraform/dag"
 	"github.com/hashicorp/terraform/tfdiags"
 )
 
@@ -12,8 +11,6 @@ type GraphWalker interface {
 	EvalContext() EvalContext
 	EnterPath(addrs.ModuleInstance) EvalContext
 	ExitPath(addrs.ModuleInstance)
-	EnterEvalTree(dag.Vertex, EvalNode) EvalNode
-	ExitEvalTree(dag.Vertex, interface{}, error) tfdiags.Diagnostics
 	Execute(EvalContext, GraphNodeExecutable) tfdiags.Diagnostics
 }
 
@@ -22,11 +19,7 @@ type GraphWalker interface {
 // implementing all the required functions.
 type NullGraphWalker struct{}
 
-func (NullGraphWalker) EvalContext() EvalContext                        { return new(MockEvalContext) }
+func (NullGraphWalker) EvalContext() EvalContext                                     { return new(MockEvalContext) }
-func (NullGraphWalker) EnterPath(addrs.ModuleInstance) EvalContext      { return new(MockEvalContext) }
+func (NullGraphWalker) EnterPath(addrs.ModuleInstance) EvalContext                   { return new(MockEvalContext) }
-func (NullGraphWalker) ExitPath(addrs.ModuleInstance)                   {}
+func (NullGraphWalker) ExitPath(addrs.ModuleInstance)                                {}
-func (NullGraphWalker) EnterEvalTree(v dag.Vertex, n EvalNode) EvalNode { return n }
-func (NullGraphWalker) ExitEvalTree(dag.Vertex, interface{}, error) tfdiags.Diagnostics {
-	return nil
-}
 func (NullGraphWalker) Execute(EvalContext, GraphNodeExecutable) tfdiags.Diagnostics { return nil }

terraform/graph_walk_context.go

@@ -2,14 +2,12 @@ package terraform
 
 import (
 	"context"
-	"log"
 	"sync"
 
 	"github.com/zclconf/go-cty/cty"
 
 	"github.com/hashicorp/terraform/addrs"
 	"github.com/hashicorp/terraform/configs/configschema"
-	"github.com/hashicorp/terraform/dag"
 	"github.com/hashicorp/terraform/instances"
 	"github.com/hashicorp/terraform/plans"
 	"github.com/hashicorp/terraform/providers"
@@ -106,49 +104,6 @@ func (w *ContextGraphWalker) EvalContext() EvalContext {
 	return ctx
 }
 
-func (w *ContextGraphWalker) EnterEvalTree(v dag.Vertex, n EvalNode) EvalNode {
-	log.Printf("[TRACE] [%s] Entering eval tree: %s", w.Operation, dag.VertexName(v))
-
-	// Acquire a lock on the semaphore
-	w.Context.parallelSem.Acquire()
-
-	// We want to filter the evaluation tree to only include operations
-	// that belong in this operation.
-	return EvalFilter(n, EvalNodeFilterOp(w.Operation))
-}
-
-func (w *ContextGraphWalker) ExitEvalTree(v dag.Vertex, output interface{}, err error) tfdiags.Diagnostics {
-	log.Printf("[TRACE] [%s] Exiting eval tree: %s", w.Operation, dag.VertexName(v))
-
-	// Release the semaphore
-	w.Context.parallelSem.Release()
-
-	if err == nil {
-		return nil
-	}
-
-	// Acquire the lock because anything is going to require a lock.
-	w.errorLock.Lock()
-	defer w.errorLock.Unlock()
-
-	// If the error is non-fatal then we'll accumulate its diagnostics in our
-	// non-fatal list, rather than returning it directly, so that the graph
-	// walk can continue.
-	if nferr, ok := err.(tfdiags.NonFatalError); ok {
-		log.Printf("[WARN] %s: %s", dag.VertexName(v), nferr)
-		w.NonFatalDiagnostics = w.NonFatalDiagnostics.Append(nferr.Diagnostics)
-		return nil
-	}
-
-	// Otherwise, we'll let our usual diagnostics machinery figure out how to
-	// unpack this as one or more diagnostic messages and return that. If we
-	// get down here then the returned diagnostics will contain at least one
-	// error, causing the graph walk to halt.
-	var diags tfdiags.Diagnostics
-	diags = diags.Append(err)
-	return diags
-}
-
 func (w *ContextGraphWalker) init() {
 	w.contexts = make(map[string]*BuiltinEvalContext)
 	w.providerCache = make(map[string]providers.Interface)

terraform/node_resource_abstract.go

@@ -498,6 +498,8 @@ func (n *NodeAbstractResource) WriteResourceState(ctx EvalContext, addr addrs.Ab
 	return nil
 }
 
+// ReadResourceInstanceState reads the current object for a specific instance in
+// the state.
 func (n *NodeAbstractResource) ReadResourceInstanceState(ctx EvalContext, addr addrs.AbsResourceInstance) (*states.ResourceInstanceObject, error) {
 	provider, providerSchema, err := GetProvider(ctx, n.ResolvedProvider)
 
@@ -540,12 +542,40 @@ func (n *NodeAbstractResource) ReadResourceInstanceState(ctx EvalContext, addr a
 	return obj, nil
 }
 
-// CheckPreventDestroy returns an error if a resource has PreventDestroy
+// ReadDiff returns the planned change for a particular resource instance
-// configured and the diff would destroy the resource.
+// object.
-func (n *NodeAbstractResource) CheckPreventDestroy(addr addrs.AbsResourceInstance, change *plans.ResourceInstanceChange) error {
+func (n *NodeAbstractResourceInstance) ReadDiff(ctx EvalContext, providerSchema *ProviderSchema) (*plans.ResourceInstanceChange, error) {
+	changes := ctx.Changes()
+	addr := n.ResourceInstanceAddr()
+
+	schema, _ := providerSchema.SchemaForResourceAddr(addr.Resource.Resource)
+	if schema == nil {
+		// Should be caught during validation, so we don't bother with a pretty error here
+		return nil, fmt.Errorf("provider does not support resource type %q", addr.Resource.Resource.Type)
+	}
+
+	gen := states.CurrentGen
+	csrc := changes.GetResourceInstanceChange(addr, gen)
+	if csrc == nil {
+		log.Printf("[TRACE] EvalReadDiff: No planned change recorded for %s", n.Addr)
+		return nil, nil
+	}
+
+	change, err := csrc.Decode(schema.ImpliedType())
+	if err != nil {
+		return nil, fmt.Errorf("failed to decode planned changes for %s: %s", n.Addr, err)
+	}
+
+	log.Printf("[TRACE] EvalReadDiff: Read %s change from plan for %s", change.Action, n.Addr)
+
+	return change, nil
+}
+
+func (n *NodeAbstractResourceInstance) checkPreventDestroy(change *plans.ResourceInstanceChange) error {
 	if change == nil || n.Config == nil || n.Config.Managed == nil {
 		return nil
 	}
+
 	preventDestroy := n.Config.Managed.PreventDestroy
 
 	if (change.Action == plans.Delete || change.Action.IsReplace()) && preventDestroy {
@@ -555,7 +585,7 @@ func (n *NodeAbstractResource) CheckPreventDestroy(addr addrs.AbsResourceInstanc
 			Summary:  "Instance cannot be destroyed",
 			Detail: fmt.Sprintf(
 				"Resource %s has lifecycle.prevent_destroy set, but the plan calls for this resource to be destroyed. To avoid this error and continue with the plan, either disable lifecycle.prevent_destroy or reduce the scope of the plan using the -target flag.",
-				addr,
+				n.Addr.String(),
 			),
 			Subject: &n.Config.DeclRange,
 		})

terraform/node_resource_apply_instance.go

@@ -6,7 +6,6 @@ import (
 	"github.com/hashicorp/terraform/addrs"
 	"github.com/hashicorp/terraform/configs"
 	"github.com/hashicorp/terraform/plans"
-	"github.com/hashicorp/terraform/providers"
 	"github.com/hashicorp/terraform/states"
 	"github.com/hashicorp/terraform/tfdiags"
 )
@@ -34,7 +33,7 @@ var (
 	_ GraphNodeCreator            = (*NodeApplyableResourceInstance)(nil)
 	_ GraphNodeReferencer         = (*NodeApplyableResourceInstance)(nil)
 	_ GraphNodeDeposer            = (*NodeApplyableResourceInstance)(nil)
-	_ GraphNodeEvalable           = (*NodeApplyableResourceInstance)(nil)
+	_ GraphNodeExecutable         = (*NodeApplyableResourceInstance)(nil)
 	_ GraphNodeAttachDependencies = (*NodeApplyableResourceInstance)(nil)
 )
 
@@ -101,8 +100,8 @@ func (n *NodeApplyableResourceInstance) AttachDependencies(deps []addrs.ConfigRe
 	n.Dependencies = deps
 }
 
-// GraphNodeEvalable
+// GraphNodeExecutable
-func (n *NodeApplyableResourceInstance) EvalTree() EvalNode {
+func (n *NodeApplyableResourceInstance) Execute(ctx EvalContext, op walkOperation) error {
 	addr := n.ResourceInstanceAddr()
 
 	if n.Config == nil {
@@ -120,319 +119,334 @@ func (n *NodeApplyableResourceInstance) EvalTree() EvalNode {
 				addr,
 			),
 		))
-		err := diags.Err()
+		return diags.Err()
-		return &EvalReturnError{
-			Error: &err,
-		}
 	}
 
 	// Eval info is different depending on what kind of resource this is
 	switch n.Config.Mode {
 	case addrs.ManagedResourceMode:
-		return n.evalTreeManagedResource(addr)
+		return n.managedResourceExecute(ctx)
 	case addrs.DataResourceMode:
-		return n.evalTreeDataResource(addr)
+		return n.dataResourceExecute(ctx)
 	default:
 		panic(fmt.Errorf("unsupported resource mode %s", n.Config.Mode))
 	}
 }
 
-func (n *NodeApplyableResourceInstance) evalTreeDataResource(addr addrs.AbsResourceInstance) EvalNode {
+func (n *NodeApplyableResourceInstance) dataResourceExecute(ctx EvalContext) error {
-	var provider providers.Interface
+	addr := n.ResourceInstanceAddr().Resource
-	var providerSchema *ProviderSchema
+
-	var change *plans.ResourceInstanceChange
+	provider, providerSchema, err := GetProvider(ctx, n.ResolvedProvider)
+	if err != nil {
+		return err
+	}
+
+	change, err := n.ReadDiff(ctx, providerSchema)
+	if err != nil {
+		return err
+	}
+	// Stop early if we don't actually have a diff
+	if change == nil {
+		return EvalEarlyExitError{}
+	}
+
+	// In this particular call to EvalReadData we include our planned
+	// change, which signals that we expect this read to complete fully
+	// with no unknown values; it'll produce an error if not.
 	var state *states.ResourceInstanceObject
-
+	readDataApply := &evalReadDataApply{
-	return &EvalSequence{
+		evalReadData{
-		Nodes: []EvalNode{
+			Addr:           addr,
-			&EvalGetProvider{
+			Config:         n.Config,
-				Addr:   n.ResolvedProvider,
+			Planned:        &change,
-				Output: &provider,
+			Provider:       &provider,
-				Schema: &providerSchema,
+			ProviderAddr:   n.ResolvedProvider,
-			},
+			ProviderMetas:  n.ProviderMetas,
-
+			ProviderSchema: &providerSchema,
-			// Get the saved diff for apply
+			State:          &state,
-			&EvalReadDiff{
-				Addr:           addr.Resource,
-				ProviderSchema: &providerSchema,
-				Change:         &change,
-			},
-
-			// Stop early if we don't actually have a diff
-			&EvalIf{
-				If: func(ctx EvalContext) (bool, error) {
-					if change == nil {
-						return true, EvalEarlyExitError{}
-					}
-					return true, nil
-				},
-				Then: EvalNoop{},
-			},
-
-			// In this particular call to EvalReadData we include our planned
-			// change, which signals that we expect this read to complete fully
-			// with no unknown values; it'll produce an error if not.
-			&evalReadDataApply{
-				evalReadData{
-					Addr:           addr.Resource,
-					Config:         n.Config,
-					Planned:        &change,
-					Provider:       &provider,
-					ProviderAddr:   n.ResolvedProvider,
-					ProviderMetas:  n.ProviderMetas,
-					ProviderSchema: &providerSchema,
-					State:          &state,
-				},
-			},
-
-			&EvalWriteState{
-				Addr:           addr.Resource,
-				ProviderAddr:   n.ResolvedProvider,
-				ProviderSchema: &providerSchema,
-				State:          &state,
-			},
-
-			// Clear the diff now that we've applied it, so
-			// later nodes won't see a diff that's now a no-op.
-			&EvalWriteDiff{
-				Addr:           addr.Resource,
-				ProviderSchema: &providerSchema,
-				Change:         nil,
-			},
-
-			&EvalUpdateStateHook{},
 		},
 	}
+	_, err = readDataApply.Eval(ctx)
+	if err != nil {
+		return err
+	}
+
+	writeState := &EvalWriteState{
+		Addr:           addr,
+		ProviderAddr:   n.ResolvedProvider,
+		ProviderSchema: &providerSchema,
+		State:          &state,
+	}
+	_, err = writeState.Eval(ctx)
+	if err != nil {
+		return err
+	}
+
+	writeDiff := &EvalWriteDiff{
+		Addr:           addr,
+		ProviderSchema: &providerSchema,
+		Change:         nil,
+	}
+	_, err = writeDiff.Eval(ctx)
+	if err != nil {
+		return err
+	}
+
+	UpdateStateHook(ctx)
+	return nil
 }
 
-func (n *NodeApplyableResourceInstance) evalTreeManagedResource(addr addrs.AbsResourceInstance) EvalNode {
+func (n *NodeApplyableResourceInstance) managedResourceExecute(ctx EvalContext) error {
 	// Declare a bunch of variables that are used for state during
 	// evaluation. Most of this are written to by-address below.
-	var provider providers.Interface
-	var providerSchema *ProviderSchema
-	var diff, diffApply *plans.ResourceInstanceChange
 	var state *states.ResourceInstanceObject
-	var err error
 	var createNew bool
 	var createBeforeDestroyEnabled bool
 	var deposedKey states.DeposedKey
 
-	return &EvalSequence{
+	addr := n.ResourceInstanceAddr().Resource
-		Nodes: []EvalNode{
+	provider, providerSchema, err := GetProvider(ctx, n.ResolvedProvider)
-			&EvalGetProvider{
+	if err != nil {
-				Addr:   n.ResolvedProvider,
+		return err
-				Output: &provider,
-				Schema: &providerSchema,
-			},
-
-			// Get the saved diff for apply
-			&EvalReadDiff{
-				Addr:           addr.Resource,
-				ProviderSchema: &providerSchema,
-				Change:         &diffApply,
-			},
-
-			// We don't want to do any destroys
-			// (these are handled by NodeDestroyResourceInstance instead)
-			&EvalIf{
-				If: func(ctx EvalContext) (bool, error) {
-					if diffApply == nil {
-						return true, EvalEarlyExitError{}
-					}
-					if diffApply.Action == plans.Delete {
-						return true, EvalEarlyExitError{}
-					}
-					return true, nil
-				},
-				Then: EvalNoop{},
-			},
-
-			&EvalIf{
-				If: func(ctx EvalContext) (bool, error) {
-					destroy := false
-					if diffApply != nil {
-						destroy = (diffApply.Action == plans.Delete || diffApply.Action.IsReplace())
-
-						// Get the stored action for CBD if we have a plan already
-						createBeforeDestroyEnabled = diffApply.Change.Action == plans.CreateThenDelete
-					}
-
-					if destroy && n.CreateBeforeDestroy() {
-						createBeforeDestroyEnabled = true
-					}
-
-					return createBeforeDestroyEnabled, nil
-				},
-				Then: &EvalDeposeState{
-					Addr:      addr.Resource,
-					ForceKey:  n.PreallocatedDeposedKey,
-					OutputKey: &deposedKey,
-				},
-			},
-
-			&EvalReadState{
-				Addr:           addr.Resource,
-				Provider:       &provider,
-				ProviderSchema: &providerSchema,
-
-				Output: &state,
-			},
-
-			// Get the saved diff
-			&EvalReadDiff{
-				Addr:           addr.Resource,
-				ProviderSchema: &providerSchema,
-				Change:         &diff,
-			},
-
-			// Make a new diff, in case we've learned new values in the state
-			// during apply which we can now incorporate.
-			&EvalDiff{
-				Addr:           addr.Resource,
-				Config:         n.Config,
-				Provider:       &provider,
-				ProviderAddr:   n.ResolvedProvider,
-				ProviderMetas:  n.ProviderMetas,
-				ProviderSchema: &providerSchema,
-				State:          &state,
-				PreviousDiff:   &diff,
-				OutputChange:   &diffApply,
-				OutputState:    &state,
-			},
-
-			// Compare the diffs
-			&EvalCheckPlannedChange{
-				Addr:           addr.Resource,
-				ProviderAddr:   n.ResolvedProvider,
-				ProviderSchema: &providerSchema,
-				Planned:        &diff,
-				Actual:         &diffApply,
-			},
-
-			&EvalGetProvider{
-				Addr:   n.ResolvedProvider,
-				Output: &provider,
-				Schema: &providerSchema,
-			},
-			&EvalReadState{
-				Addr:           addr.Resource,
-				Provider:       &provider,
-				ProviderSchema: &providerSchema,
-
-				Output: &state,
-			},
-
-			&EvalReduceDiff{
-				Addr:      addr.Resource,
-				InChange:  &diffApply,
-				Destroy:   false,
-				OutChange: &diffApply,
-			},
-
-			// EvalReduceDiff may have simplified our planned change
-			// into a NoOp if it only requires destroying, since destroying
-			// is handled by NodeDestroyResourceInstance.
-			&EvalIf{
-				If: func(ctx EvalContext) (bool, error) {
-					if diffApply == nil || diffApply.Action == plans.NoOp {
-						return true, EvalEarlyExitError{}
-					}
-					return true, nil
-				},
-				Then: EvalNoop{},
-			},
-
-			// Call pre-apply hook
-			&EvalApplyPre{
-				Addr:   addr.Resource,
-				State:  &state,
-				Change: &diffApply,
-			},
-			&EvalApply{
-				Addr:                addr.Resource,
-				Config:              n.Config,
-				State:               &state,
-				Change:              &diffApply,
-				Provider:            &provider,
-				ProviderAddr:        n.ResolvedProvider,
-				ProviderMetas:       n.ProviderMetas,
-				ProviderSchema:      &providerSchema,
-				Output:              &state,
-				Error:               &err,
-				CreateNew:           &createNew,
-				CreateBeforeDestroy: n.CreateBeforeDestroy(),
-			},
-			&EvalMaybeTainted{
-				Addr:   addr.Resource,
-				State:  &state,
-				Change: &diffApply,
-				Error:  &err,
-			},
-			&EvalWriteState{
-				Addr:           addr.Resource,
-				ProviderAddr:   n.ResolvedProvider,
-				ProviderSchema: &providerSchema,
-				State:          &state,
-				Dependencies:   &n.Dependencies,
-			},
-			&EvalApplyProvisioners{
-				Addr:           addr.Resource,
-				State:          &state, // EvalApplyProvisioners will skip if already tainted
-				ResourceConfig: n.Config,
-				CreateNew:      &createNew,
-				Error:          &err,
-				When:           configs.ProvisionerWhenCreate,
-			},
-			&EvalMaybeTainted{
-				Addr:   addr.Resource,
-				State:  &state,
-				Change: &diffApply,
-				Error:  &err,
-			},
-			&EvalWriteState{
-				Addr:           addr.Resource,
-				ProviderAddr:   n.ResolvedProvider,
-				ProviderSchema: &providerSchema,
-				State:          &state,
-				Dependencies:   &n.Dependencies,
-			},
-			&EvalIf{
-				If: func(ctx EvalContext) (bool, error) {
-					return createBeforeDestroyEnabled && err != nil, nil
-				},
-				Then: &EvalMaybeRestoreDeposedObject{
-					Addr:          addr.Resource,
-					PlannedChange: &diffApply,
-					Key:           &deposedKey,
-				},
-			},
-
-			// We clear the diff out here so that future nodes
-			// don't see a diff that is already complete. There
-			// is no longer a diff!
-			&EvalIf{
-				If: func(ctx EvalContext) (bool, error) {
-					if !diff.Action.IsReplace() {
-						return true, nil
-					}
-					if !n.CreateBeforeDestroy() {
-						return true, nil
-					}
-					return false, nil
-				},
-				Then: &EvalWriteDiff{
-					Addr:           addr.Resource,
-					ProviderSchema: &providerSchema,
-					Change:         nil,
-				},
-			},
-
-			&EvalApplyPost{
-				Addr:  addr.Resource,
-				State: &state,
-				Error: &err,
-			},
-			&EvalUpdateStateHook{},
-		},
 	}
+
+	// Get the saved diff for apply
+	diffApply, err := n.ReadDiff(ctx, providerSchema)
+	if err != nil {
+		return err
+	}
+
+	// We don't want to do any destroys
+	// (these are handled by NodeDestroyResourceInstance instead)
+	if diffApply == nil || diffApply.Action == plans.Delete {
+		return EvalEarlyExitError{}
+	}
+
+	destroy := (diffApply.Action == plans.Delete || diffApply.Action.IsReplace())
+	// Get the stored action for CBD if we have a plan already
+	createBeforeDestroyEnabled = diffApply.Change.Action == plans.CreateThenDelete
+
+	if destroy && n.CreateBeforeDestroy() {
+		createBeforeDestroyEnabled = true
+	}
+
+	if createBeforeDestroyEnabled {
+		deposeState := &EvalDeposeState{
+			Addr:      addr,
+			ForceKey:  n.PreallocatedDeposedKey,
+			OutputKey: &deposedKey,
+		}
+		_, err = deposeState.Eval(ctx)
+		if err != nil {
+			return err
+		}
+	}
+
+	readState := &EvalReadState{
+		Addr:           addr,
+		Provider:       &provider,
+		ProviderSchema: &providerSchema,
+
+		Output: &state,
+	}
+	_, err = readState.Eval(ctx)
+	if err != nil {
+		return err
+	}
+
+	// Get the saved diff
+	diff, err := n.ReadDiff(ctx, providerSchema)
+	if err != nil {
+		return err
+	}
+
+	// Make a new diff, in case we've learned new values in the state
+	// during apply which we can now incorporate.
+	evalDiff := &EvalDiff{
+		Addr:           addr,
+		Config:         n.Config,
+		Provider:       &provider,
+		ProviderAddr:   n.ResolvedProvider,
+		ProviderMetas:  n.ProviderMetas,
+		ProviderSchema: &providerSchema,
+		State:          &state,
+		PreviousDiff:   &diff,
+		OutputChange:   &diffApply,
+		OutputState:    &state,
+	}
+	_, err = evalDiff.Eval(ctx)
+	if err != nil {
+		return err
+	}
+
+	// Compare the diffs
+	checkPlannedChange := &EvalCheckPlannedChange{
+		Addr:           addr,
+		ProviderAddr:   n.ResolvedProvider,
+		ProviderSchema: &providerSchema,
+		Planned:        &diff,
+		Actual:         &diffApply,
+	}
+	_, err = checkPlannedChange.Eval(ctx)
+	if err != nil {
+		return err
+	}
+
+	readState = &EvalReadState{
+		Addr:           addr,
+		Provider:       &provider,
+		ProviderSchema: &providerSchema,
+
+		Output: &state,
+	}
+	_, err = readState.Eval(ctx)
+	if err != nil {
+		return err
+	}
+
+	reduceDiff := &EvalReduceDiff{
+		Addr:      addr,
+		InChange:  &diffApply,
+		Destroy:   false,
+		OutChange: &diffApply,
+	}
+	_, err = reduceDiff.Eval(ctx)
+	if err != nil {
+		return err
+	}
+
+	// EvalReduceDiff may have simplified our planned change
+	// into a NoOp if it only requires destroying, since destroying
+	// is handled by NodeDestroyResourceInstance.
+	if diffApply == nil || diffApply.Action == plans.NoOp {
+		return EvalEarlyExitError{}
+	}
+
+	evalApplyPre := &EvalApplyPre{
+		Addr:   addr,
+		State:  &state,
+		Change: &diffApply,
+	}
+	_, err = evalApplyPre.Eval(ctx)
+	if err != nil {
+		return err
+	}
+
+	var applyError error
+	evalApply := &EvalApply{
+		Addr:                addr,
+		Config:              n.Config,
+		State:               &state,
+		Change:              &diffApply,
+		Provider:            &provider,
+		ProviderAddr:        n.ResolvedProvider,
+		ProviderMetas:       n.ProviderMetas,
+		ProviderSchema:      &providerSchema,
+		Output:              &state,
+		Error:               &applyError,
+		CreateNew:           &createNew,
+		CreateBeforeDestroy: n.CreateBeforeDestroy(),
+	}
+	_, err = evalApply.Eval(ctx)
+	if err != nil {
+		return err
+	}
+
+	evalMaybeTainted := &EvalMaybeTainted{
+		Addr:   addr,
+		State:  &state,
+		Change: &diffApply,
+		Error:  &applyError,
+	}
+	_, err = evalMaybeTainted.Eval(ctx)
+	if err != nil {
+		return err
+	}
+
+	writeState := &EvalWriteState{
+		Addr:           addr,
+		ProviderAddr:   n.ResolvedProvider,
+		ProviderSchema: &providerSchema,
+		State:          &state,
+		Dependencies:   &n.Dependencies,
+	}
+	_, err = writeState.Eval(ctx)
+	if err != nil {
+		return err
+	}
+
+	applyProvisioners := &EvalApplyProvisioners{
+		Addr:           addr,
+		State:          &state, // EvalApplyProvisioners will skip if already tainted
+		ResourceConfig: n.Config,
+		CreateNew:      &createNew,
+		Error:          &applyError,
+		When:           configs.ProvisionerWhenCreate,
+	}
+	_, err = applyProvisioners.Eval(ctx)
+	if err != nil {
+		return err
+	}
+
+	evalMaybeTainted = &EvalMaybeTainted{
+		Addr:   addr,
+		State:  &state,
+		Change: &diffApply,
+		Error:  &applyError,
+	}
+	_, err = evalMaybeTainted.Eval(ctx)
+	if err != nil {
+		return err
+	}
+
+	writeState = &EvalWriteState{
+		Addr:           addr,
+		ProviderAddr:   n.ResolvedProvider,
+		ProviderSchema: &providerSchema,
+		State:          &state,
+		Dependencies:   &n.Dependencies,
+	}
+	_, err = writeState.Eval(ctx)
+	if err != nil {
+		return err
+	}
+
+	if createBeforeDestroyEnabled && applyError != nil {
+		maybeRestoreDesposedObject := &EvalMaybeRestoreDeposedObject{
+			Addr:          addr,
+			PlannedChange: &diffApply,
+			Key:           &deposedKey,
+		}
+		_, err := maybeRestoreDesposedObject.Eval(ctx)
+		if err != nil {
+			return err
+		}
+	}
+
+	// We clear the diff out here so that future nodes don't see a diff that is
+	// already complete. There is no longer a diff!
+	if !diff.Action.IsReplace() || !n.CreateBeforeDestroy() {
+		writeDiff := &EvalWriteDiff{
+			Addr:           addr,
+			ProviderSchema: &providerSchema,
+			Change:         nil,
+		}
+		_, err := writeDiff.Eval(ctx)
+		if err != nil {
+			return err
+		}
+	}
+
+	applyPost := &EvalApplyPost{
+		Addr:  addr,
+		State: &state,
+		Error: &applyError,
+	}
+	_, err = applyPost.Eval(ctx)
+	if err != nil {
+		return err
+	}
+
+	UpdateStateHook(ctx)
+	return nil
 }

terraform/node_resource_destroy.go

@@ -143,12 +143,7 @@ func (n *NodeDestroyResourceInstance) Execute(ctx EvalContext, op walkOperation)
 			return err
 		}
 
-		evalReadDiff := &EvalReadDiff{
+		changeApply, err = n.ReadDiff(ctx, providerSchema)
-			Addr:           addr.Resource,
-			ProviderSchema: &providerSchema,
-			Change:         &changeApply,
-		}
-		_, err = evalReadDiff.Eval(ctx)
 		if err != nil {
 			return err
 		}

terraform/node_resource_destroy_deposed.go

@@ -6,7 +6,6 @@ import (
 	"github.com/hashicorp/terraform/addrs"
 	"github.com/hashicorp/terraform/dag"
 	"github.com/hashicorp/terraform/plans"
-	"github.com/hashicorp/terraform/providers"
 	"github.com/hashicorp/terraform/states"
 )
 
@@ -37,7 +36,7 @@ var (
 	_ GraphNodeResourceInstance              = (*NodePlanDeposedResourceInstanceObject)(nil)
 	_ GraphNodeReferenceable                 = (*NodePlanDeposedResourceInstanceObject)(nil)
 	_ GraphNodeReferencer                    = (*NodePlanDeposedResourceInstanceObject)(nil)
-	_ GraphNodeEvalable                      = (*NodePlanDeposedResourceInstanceObject)(nil)
+	_ GraphNodeExecutable                    = (*NodePlanDeposedResourceInstanceObject)(nil)
 	_ GraphNodeProviderConsumer              = (*NodePlanDeposedResourceInstanceObject)(nil)
 	_ GraphNodeProvisionerConsumer           = (*NodePlanDeposedResourceInstanceObject)(nil)
 )
@@ -64,55 +63,58 @@ func (n *NodePlanDeposedResourceInstanceObject) References() []*addrs.Reference
 }
 
 // GraphNodeEvalable impl.
-func (n *NodePlanDeposedResourceInstanceObject) EvalTree() EvalNode {
+func (n *NodePlanDeposedResourceInstanceObject) Execute(ctx EvalContext, op walkOperation) error {
 	addr := n.ResourceInstanceAddr()
 
-	var provider providers.Interface
+	provider, providerSchema, err := GetProvider(ctx, n.ResolvedProvider)
-	var providerSchema *ProviderSchema
+	if err != nil {
-	var state *states.ResourceInstanceObject
+		return err
-
+	}
-	seq := &EvalSequence{Nodes: make([]EvalNode, 0, 5)}
 
 	// During the plan walk we always produce a planned destroy change, because
 	// destroying is the only supported action for deposed objects.
 	var change *plans.ResourceInstanceChange
-	seq.Nodes = append(seq.Nodes, &EvalOpFilter{
+	var state *states.ResourceInstanceObject
-		Ops: []walkOperation{walkPlan, walkPlanDestroy},
-		Node: &EvalSequence{
-			Nodes: []EvalNode{
-				&EvalGetProvider{
-					Addr:   n.ResolvedProvider,
-					Output: &provider,
-					Schema: &providerSchema,
-				},
-				&EvalReadStateDeposed{
-					Addr:           addr.Resource,
-					Output:         &state,
-					Key:            n.DeposedKey,
-					Provider:       &provider,
-					ProviderSchema: &providerSchema,
-				},
-				&EvalDiffDestroy{
-					Addr:         addr.Resource,
-					ProviderAddr: n.ResolvedProvider,
-					DeposedKey:   n.DeposedKey,
-					State:        &state,
-					Output:       &change,
-				},
-				&EvalWriteDiff{
-					Addr:           addr.Resource,
-					DeposedKey:     n.DeposedKey,
-					ProviderSchema: &providerSchema,
-					Change:         &change,
-				},
-				// Since deposed objects cannot be referenced by expressions
-				// elsewhere, we don't need to also record the planned new
-				// state in this case.
-			},
-		},
-	})
 
-	return seq
+	switch op {
+	case walkPlan, walkPlanDestroy:
+
+		readStateDeposed := &EvalReadStateDeposed{
+			Addr:           addr.Resource,
+			Output:         &state,
+			Key:            n.DeposedKey,
+			Provider:       &provider,
+			ProviderSchema: &providerSchema,
+		}
+		_, err = readStateDeposed.Eval(ctx)
+		if err != nil {
+			return err
+		}
+
+		diffDestroy := &EvalDiffDestroy{
+			Addr:         addr.Resource,
+			ProviderAddr: n.ResolvedProvider,
+			DeposedKey:   n.DeposedKey,
+			State:        &state,
+			Output:       &change,
+		}
+		_, err = diffDestroy.Eval(ctx)
+		if err != nil {
+			return err
+		}
+
+		writeDiff := &EvalWriteDiff{
+			Addr:           addr.Resource,
+			DeposedKey:     n.DeposedKey,
+			ProviderSchema: &providerSchema,
+			Change:         &change,
+		}
+		_, err = writeDiff.Eval(ctx)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
 }
 
 // NodeDestroyDeposedResourceInstanceObject represents deposed resource
@@ -133,7 +135,7 @@ var (
 	_ GraphNodeDestroyerCBD                  = (*NodeDestroyDeposedResourceInstanceObject)(nil)
 	_ GraphNodeReferenceable                 = (*NodeDestroyDeposedResourceInstanceObject)(nil)
 	_ GraphNodeReferencer                    = (*NodeDestroyDeposedResourceInstanceObject)(nil)
-	_ GraphNodeEvalable                      = (*NodeDestroyDeposedResourceInstanceObject)(nil)
+	_ GraphNodeExecutable                    = (*NodeDestroyDeposedResourceInstanceObject)(nil)
 	_ GraphNodeProviderConsumer              = (*NodeDestroyDeposedResourceInstanceObject)(nil)
 	_ GraphNodeProvisionerConsumer           = (*NodeDestroyDeposedResourceInstanceObject)(nil)
 )
@@ -181,74 +183,98 @@ func (n *NodeDestroyDeposedResourceInstanceObject) ModifyCreateBeforeDestroy(v b
 	return nil
 }
 
-// GraphNodeEvalable impl.
+// GraphNodeExecutable impl.
-func (n *NodeDestroyDeposedResourceInstanceObject) EvalTree() EvalNode {
+func (n *NodeDestroyDeposedResourceInstanceObject) Execute(ctx EvalContext, op walkOperation) error {
-	addr := n.ResourceInstanceAddr()
+	addr := n.ResourceInstanceAddr().Resource
 
-	var provider providers.Interface
-	var providerSchema *ProviderSchema
 	var state *states.ResourceInstanceObject
 	var change *plans.ResourceInstanceChange
-	var err error
+	var applyError error
 
-	return &EvalSequence{
+	provider, providerSchema, err := GetProvider(ctx, n.ResolvedProvider)
-		Nodes: []EvalNode{
+	if err != nil {
-			&EvalGetProvider{
+		return err
-				Addr:   n.ResolvedProvider,
-				Output: &provider,
-				Schema: &providerSchema,
-			},
-			&EvalReadStateDeposed{
-				Addr:           addr.Resource,
-				Output:         &state,
-				Key:            n.DeposedKey,
-				Provider:       &provider,
-				ProviderSchema: &providerSchema,
-			},
-			&EvalDiffDestroy{
-				Addr:         addr.Resource,
-				ProviderAddr: n.ResolvedProvider,
-				State:        &state,
-				Output:       &change,
-			},
-			// Call pre-apply hook
-			&EvalApplyPre{
-				Addr:   addr.Resource,
-				State:  &state,
-				Change: &change,
-			},
-			&EvalApply{
-				Addr:           addr.Resource,
-				Config:         nil, // No configuration because we are destroying
-				State:          &state,
-				Change:         &change,
-				Provider:       &provider,
-				ProviderAddr:   n.ResolvedProvider,
-				ProviderSchema: &providerSchema,
-				Output:         &state,
-				Error:          &err,
-			},
-			// Always write the resource back to the state deposed... if it
-			// was successfully destroyed it will be pruned. If it was not, it will
-			// be caught on the next run.
-			&EvalWriteStateDeposed{
-				Addr:           addr.Resource,
-				Key:            n.DeposedKey,
-				ProviderAddr:   n.ResolvedProvider,
-				ProviderSchema: &providerSchema,
-				State:          &state,
-			},
-			&EvalApplyPost{
-				Addr:  addr.Resource,
-				State: &state,
-				Error: &err,
-			},
-			&EvalReturnError{
-				Error: &err,
-			},
-			&EvalUpdateStateHook{},
-		},
 	}
+
+	readStateDeposed := &EvalReadStateDeposed{
+		Addr:           addr,
+		Output:         &state,
+		Key:            n.DeposedKey,
+		Provider:       &provider,
+		ProviderSchema: &providerSchema,
+	}
+	_, err = readStateDeposed.Eval(ctx)
+	if err != nil {
+		return err
+	}
+
+	diffDestroy := &EvalDiffDestroy{
+		Addr:         addr,
+		ProviderAddr: n.ResolvedProvider,
+		State:        &state,
+		Output:       &change,
+	}
+	_, err = diffDestroy.Eval(ctx)
+	if err != nil {
+		return err
+	}
+
+	// Call pre-apply hook
+	applyPre := &EvalApplyPre{
+		Addr:   addr,
+		State:  &state,
+		Change: &change,
+	}
+	_, err = applyPre.Eval(ctx)
+	if err != nil {
+		return err
+	}
+
+	apply := &EvalApply{
+		Addr:           addr,
+		Config:         nil, // No configuration because we are destroying
+		State:          &state,
+		Change:         &change,
+		Provider:       &provider,
+		ProviderAddr:   n.ResolvedProvider,
+		ProviderSchema: &providerSchema,
+		Output:         &state,
+		Error:          &applyError,
+	}
+	_, err = apply.Eval(ctx)
+	if err != nil {
+		return err
+	}
+
+	// Always write the resource back to the state deposed. If it
+	// was successfully destroyed it will be pruned. If it was not, it will
+	// be caught on the next run.
+	writeStateDeposed := &EvalWriteStateDeposed{
+		Addr:           addr,
+		Key:            n.DeposedKey,
+		ProviderAddr:   n.ResolvedProvider,
+		ProviderSchema: &providerSchema,
+		State:          &state,
+	}
+	_, err = writeStateDeposed.Eval(ctx)
+	if err != nil {
+		return err
+	}
+
+	applyPost := &EvalApplyPost{
+		Addr:  addr,
+		State: &state,
+		Error: &applyError,
+	}
+	_, err = applyPost.Eval(ctx)
+	if err != nil {
+		return err
+	}
+	if applyError != nil {
+		return applyError
+	}
+	UpdateStateHook(ctx)
+	return nil
 }
 
 // GraphNodeDeposer is an optional interface implemented by graph nodes that

terraform/node_resource_destroy_deposed_test.go

@@ -0,0 +1,130 @@
+package terraform
+
+import (
+	"testing"
+
+	"github.com/hashicorp/terraform/addrs"
+	"github.com/hashicorp/terraform/configs/configschema"
+	"github.com/hashicorp/terraform/plans"
+	"github.com/hashicorp/terraform/providers"
+	"github.com/hashicorp/terraform/states"
+	"github.com/zclconf/go-cty/cty"
+)
+
+func TestNodePlanDeposedResourceInstanceObject_Execute(t *testing.T) {
+	deposedKey := states.NewDeposedKey()
+	state := states.NewState()
+	absResource := mustResourceInstanceAddr("test_instance.foo")
+	state.Module(addrs.RootModuleInstance).SetResourceInstanceDeposed(
+		absResource.Resource,
+		deposedKey,
+		&states.ResourceInstanceObjectSrc{
+			Status:    states.ObjectTainted,
+			AttrsJSON: []byte(`{"id":"bar"}`),
+		},
+		mustProviderConfig(`provider["registry.terraform.io/hashicorp/test"]`),
+	)
+
+	p := testProvider("test")
+	p.UpgradeResourceStateResponse = providers.UpgradeResourceStateResponse{
+		UpgradedState: cty.ObjectVal(map[string]cty.Value{
+			"id": cty.StringVal("bar"),
+		}),
+	}
+	ctx := &MockEvalContext{
+		StateState:       state.SyncWrapper(),
+		ProviderProvider: p,
+		ProviderSchemaSchema: &ProviderSchema{
+			ResourceTypes: map[string]*configschema.Block{
+				"test_instance": {
+					Attributes: map[string]*configschema.Attribute{
+						"id": {
+							Type:     cty.String,
+							Computed: true,
+						},
+					},
+				},
+			},
+		},
+		ChangesChanges: plans.NewChanges().SyncWrapper(),
+	}
+
+	node := NodePlanDeposedResourceInstanceObject{
+		NodeAbstractResourceInstance: &NodeAbstractResourceInstance{
+			Addr: absResource,
+			NodeAbstractResource: NodeAbstractResource{
+				ResolvedProvider: mustProviderConfig(`provider["registry.terraform.io/hashicorp/test"]`),
+			},
+		},
+		DeposedKey: deposedKey,
+	}
+	err := node.Execute(ctx, walkPlan)
+
+	if err != nil {
+		t.Fatalf("unexpected error: %s", err)
+	}
+
+	change := ctx.Changes().GetResourceInstanceChange(absResource, deposedKey)
+	if change.ChangeSrc.Action != plans.Delete {
+		t.Fatalf("delete change not planned")
+	}
+
+}
+
+func TestNodeDestroyDeposedResourceInstanceObject_Execute(t *testing.T) {
+	deposedKey := states.NewDeposedKey()
+	state := states.NewState()
+	absResource := mustResourceInstanceAddr("test_instance.foo")
+	state.Module(addrs.RootModuleInstance).SetResourceInstanceDeposed(
+		absResource.Resource,
+		deposedKey,
+		&states.ResourceInstanceObjectSrc{
+			Status:    states.ObjectTainted,
+			AttrsJSON: []byte(`{"id":"bar"}`),
+		},
+		mustProviderConfig(`provider["registry.terraform.io/hashicorp/test"]`),
+	)
+
+	p := testProvider("test")
+	p.UpgradeResourceStateResponse = providers.UpgradeResourceStateResponse{
+		UpgradedState: cty.ObjectVal(map[string]cty.Value{
+			"id": cty.StringVal("bar"),
+		}),
+	}
+	ctx := &MockEvalContext{
+		StateState:       state.SyncWrapper(),
+		ProviderProvider: p,
+		ProviderSchemaSchema: &ProviderSchema{
+			ResourceTypes: map[string]*configschema.Block{
+				"test_instance": {
+					Attributes: map[string]*configschema.Attribute{
+						"id": {
+							Type:     cty.String,
+							Computed: true,
+						},
+					},
+				},
+			},
+		},
+		ChangesChanges: plans.NewChanges().SyncWrapper(),
+	}
+
+	node := NodeDestroyDeposedResourceInstanceObject{
+		NodeAbstractResourceInstance: &NodeAbstractResourceInstance{
+			Addr: absResource,
+			NodeAbstractResource: NodeAbstractResource{
+				ResolvedProvider: mustProviderConfig(`provider["registry.terraform.io/hashicorp/test"]`),
+			},
+		},
+		DeposedKey: deposedKey,
+	}
+	err := node.Execute(ctx, walkApply)
+
+	if err != nil {
+		t.Fatalf("unexpected error: %s", err)
+	}
+
+	if !state.Empty() {
+		t.Fatalf("resources left in state after destroy")
+	}
+}

terraform/node_resource_plan_destroy.go

@@ -1,12 +1,8 @@
 package terraform
 
 import (
-	"fmt"
-
 	"github.com/hashicorp/terraform/addrs"
-	"github.com/hashicorp/terraform/dag"
 	"github.com/hashicorp/terraform/plans"
-	"github.com/hashicorp/terraform/providers"
 	"github.com/hashicorp/terraform/states"
 )
 
@@ -25,7 +21,7 @@ var (
 	_ GraphNodeResourceInstance     = (*NodePlanDestroyableResourceInstance)(nil)
 	_ GraphNodeAttachResourceConfig = (*NodePlanDestroyableResourceInstance)(nil)
 	_ GraphNodeAttachResourceState  = (*NodePlanDestroyableResourceInstance)(nil)
-	_ GraphNodeEvalable             = (*NodePlanDestroyableResourceInstance)(nil)
+	_ GraphNodeExecutable           = (*NodePlanDestroyableResourceInstance)(nil)
 	_ GraphNodeProviderConsumer     = (*NodePlanDestroyableResourceInstance)(nil)
 )
 
@@ -36,53 +32,46 @@ func (n *NodePlanDestroyableResourceInstance) DestroyAddr() *addrs.AbsResourceIn
 }
 
 // GraphNodeEvalable
-func (n *NodePlanDestroyableResourceInstance) EvalTree() EvalNode {
+func (n *NodePlanDestroyableResourceInstance) Execute(ctx EvalContext, op walkOperation) error {
 	addr := n.ResourceInstanceAddr()
 
 	// Declare a bunch of variables that are used for state during
 	// evaluation. These are written to by address in the EvalNodes we
 	// declare below.
-	var provider providers.Interface
-	var providerSchema *ProviderSchema
 	var change *plans.ResourceInstanceChange
 	var state *states.ResourceInstanceObject
 
-	if n.ResolvedProvider.Provider.Type == "" {
+	_, providerSchema, err := GetProvider(ctx, n.ResolvedProvider)
-		// Should never happen; indicates that the graph was not constructed
+	if err != nil {
-		// correctly since we didn't get our provider attached.
+		return err
-		panic(fmt.Sprintf("%T %q was not assigned a resolved provider", n, dag.VertexName(n)))
 	}
 
-	return &EvalSequence{
+	state, err = n.ReadResourceInstanceState(ctx, addr)
-		Nodes: []EvalNode{
+	if err != nil {
-			&EvalGetProvider{
+		return err
-				Addr:   n.ResolvedProvider,
-				Output: &provider,
-				Schema: &providerSchema,
-			},
-			&EvalReadState{
-				Addr:           addr.Resource,
-				Provider:       &provider,
-				ProviderSchema: &providerSchema,
-
-				Output: &state,
-			},
-			&EvalDiffDestroy{
-				Addr:         addr.Resource,
-				ProviderAddr: n.ResolvedProvider,
-				State:        &state,
-				Output:       &change,
-			},
-			&EvalCheckPreventDestroy{
-				Addr:   addr.Resource,
-				Config: n.Config,
-				Change: &change,
-			},
-			&EvalWriteDiff{
-				Addr:           addr.Resource,
-				ProviderSchema: &providerSchema,
-				Change:         &change,
-			},
-		},
 	}
+
+	diffDestroy := &EvalDiffDestroy{
+		Addr:         addr.Resource,
+		ProviderAddr: n.ResolvedProvider,
+		State:        &state,
+		Output:       &change,
+	}
+	_, err = diffDestroy.Eval(ctx)
+	if err != nil {
+		return err
+	}
+
+	err = n.checkPreventDestroy(change)
+	if err != nil {
+		return err
+	}
+
+	writeDiff := &EvalWriteDiff{
+		Addr:           addr.Resource,
+		ProviderSchema: &providerSchema,
+		Change:         &change,
+	}
+	_, err = writeDiff.Eval(ctx)
+	return err
 }

terraform/node_resource_plan_instance.go

@@ -4,7 +4,6 @@ import (
 	"fmt"
 
 	"github.com/hashicorp/terraform/plans"
-	"github.com/hashicorp/terraform/providers"
 	"github.com/hashicorp/terraform/states"
 
 	"github.com/hashicorp/terraform/addrs"
@@ -27,183 +26,211 @@ var (
 	_ GraphNodeResourceInstance     = (*NodePlannableResourceInstance)(nil)
 	_ GraphNodeAttachResourceConfig = (*NodePlannableResourceInstance)(nil)
 	_ GraphNodeAttachResourceState  = (*NodePlannableResourceInstance)(nil)
-	_ GraphNodeEvalable             = (*NodePlannableResourceInstance)(nil)
+	_ GraphNodeExecutable           = (*NodePlannableResourceInstance)(nil)
 )
 
 // GraphNodeEvalable
-func (n *NodePlannableResourceInstance) EvalTree() EvalNode {
+func (n *NodePlannableResourceInstance) Execute(ctx EvalContext, op walkOperation) error {
 	addr := n.ResourceInstanceAddr()
 
 	// Eval info is different depending on what kind of resource this is
 	switch addr.Resource.Resource.Mode {
 	case addrs.ManagedResourceMode:
-		return n.evalTreeManagedResource(addr)
+		return n.managedResourceExecute(ctx, n.skipRefresh)
 	case addrs.DataResourceMode:
-		return n.evalTreeDataResource(addr)
+		return n.dataResourceExecute(ctx)
 	default:
 		panic(fmt.Errorf("unsupported resource mode %s", n.Config.Mode))
 	}
 }
 
-func (n *NodePlannableResourceInstance) evalTreeDataResource(addr addrs.AbsResourceInstance) EvalNode {
+func (n *NodePlannableResourceInstance) dataResourceExecute(ctx EvalContext) error {
 	config := n.Config
-	var provider providers.Interface
+	addr := n.ResourceInstanceAddr()
-	var providerSchema *ProviderSchema
+
 	var change *plans.ResourceInstanceChange
 	var state *states.ResourceInstanceObject
 
-	return &EvalSequence{
+	provider, providerSchema, err := GetProvider(ctx, n.ResolvedProvider)
-		Nodes: []EvalNode{
+	if err != nil {
-			&EvalGetProvider{
+		return err
-				Addr:   n.ResolvedProvider,
+	}
-				Output: &provider,
-				Schema: &providerSchema,
-			},
 
-			&EvalReadState{
+	state, err = n.ReadResourceInstanceState(ctx, addr)
-				Addr:           addr.Resource,
+	if err != nil {
-				Provider:       &provider,
+		return err
-				ProviderSchema: &providerSchema,
+	}
-				Output:         &state,
-			},
 
-			&EvalValidateSelfRef{
+	validateSelfRef := &EvalValidateSelfRef{
-				Addr:           addr.Resource,
+		Addr:           addr.Resource,
-				Config:         config.Config,
+		Config:         config.Config,
-				ProviderSchema: &providerSchema,
+		ProviderSchema: &providerSchema,
-			},
+	}
+	_, err = validateSelfRef.Eval(ctx)
+	if err != nil {
+		return err
+	}
 
-			&evalReadDataPlan{
+	readDataPlan := &evalReadDataPlan{
-				evalReadData: evalReadData{
+		evalReadData: evalReadData{
-					Addr:           addr.Resource,
+			Addr:           addr.Resource,
-					Config:         n.Config,
+			Config:         n.Config,
-					Provider:       &provider,
+			Provider:       &provider,
-					ProviderAddr:   n.ResolvedProvider,
+			ProviderAddr:   n.ResolvedProvider,
-					ProviderMetas:  n.ProviderMetas,
+			ProviderMetas:  n.ProviderMetas,
-					ProviderSchema: &providerSchema,
+			ProviderSchema: &providerSchema,
-					OutputChange:   &change,
+			OutputChange:   &change,
-					State:          &state,
+			State:          &state,
-					dependsOn:      n.dependsOn,
+			dependsOn:      n.dependsOn,
-				},
-			},
-
-			// write the data source into both the refresh state and the
-			// working state
-			&EvalWriteState{
-				Addr:           addr.Resource,
-				ProviderAddr:   n.ResolvedProvider,
-				ProviderSchema: &providerSchema,
-				State:          &state,
-				targetState:    refreshState,
-			},
-
-			&EvalWriteState{
-				Addr:           addr.Resource,
-				ProviderAddr:   n.ResolvedProvider,
-				ProviderSchema: &providerSchema,
-				State:          &state,
-			},
-
-			&EvalWriteDiff{
-				Addr:           addr.Resource,
-				ProviderSchema: &providerSchema,
-				Change:         &change,
-			},
 		},
 	}
+	_, err = readDataPlan.Eval(ctx)
+	if err != nil {
+		return err
+	}
+
+	// write the data source into both the refresh state and the
+	// working state
+	writeRefreshState := &EvalWriteState{
+		Addr:           addr.Resource,
+		ProviderAddr:   n.ResolvedProvider,
+		ProviderSchema: &providerSchema,
+		State:          &state,
+		targetState:    refreshState,
+	}
+	_, err = writeRefreshState.Eval(ctx)
+	if err != nil {
+		return err
+	}
+
+	writeState := &EvalWriteState{
+		Addr:           addr.Resource,
+		ProviderAddr:   n.ResolvedProvider,
+		ProviderSchema: &providerSchema,
+		State:          &state,
+	}
+	_, err = writeState.Eval(ctx)
+	if err != nil {
+		return err
+	}
+
+	writeDiff := &EvalWriteDiff{
+		Addr:           addr.Resource,
+		ProviderSchema: &providerSchema,
+		Change:         &change,
+	}
+	_, err = writeDiff.Eval(ctx)
+	return err
 }
 
-func (n *NodePlannableResourceInstance) evalTreeManagedResource(addr addrs.AbsResourceInstance) EvalNode {
+func (n *NodePlannableResourceInstance) managedResourceExecute(ctx EvalContext, skipRefresh bool) error {
 	config := n.Config
-	var provider providers.Interface
+	addr := n.ResourceInstanceAddr()
-	var providerSchema *ProviderSchema
+
 	var change *plans.ResourceInstanceChange
 	var instanceRefreshState *states.ResourceInstanceObject
 	var instancePlanState *states.ResourceInstanceObject
 
-	return &EvalSequence{
+	provider, providerSchema, err := GetProvider(ctx, n.ResolvedProvider)
-		Nodes: []EvalNode{
+	if err != nil {
-			&EvalGetProvider{
+		return err
-				Addr:   n.ResolvedProvider,
-				Output: &provider,
-				Schema: &providerSchema,
-			},
-
-			&EvalValidateSelfRef{
-				Addr:           addr.Resource,
-				Config:         config.Config,
-				ProviderSchema: &providerSchema,
-			},
-
-			&EvalIf{
-				If: func(ctx EvalContext) (bool, error) {
-					return !n.skipRefresh, nil
-				},
-				Then: &EvalSequence{
-					Nodes: []EvalNode{
-						// Refresh the instance
-						&EvalReadState{
-							Addr:           addr.Resource,
-							Provider:       &provider,
-							ProviderSchema: &providerSchema,
-							Output:         &instanceRefreshState,
-						},
-						&EvalRefreshLifecycle{
-							Addr:                     addr,
-							Config:                   n.Config,
-							State:                    &instanceRefreshState,
-							ForceCreateBeforeDestroy: n.ForceCreateBeforeDestroy,
-						},
-						&EvalRefresh{
-							Addr:           addr.Resource,
-							ProviderAddr:   n.ResolvedProvider,
-							Provider:       &provider,
-							ProviderMetas:  n.ProviderMetas,
-							ProviderSchema: &providerSchema,
-							State:          &instanceRefreshState,
-							Output:         &instanceRefreshState,
-						},
-						&EvalWriteState{
-							Addr:           addr.Resource,
-							ProviderAddr:   n.ResolvedProvider,
-							State:          &instanceRefreshState,
-							ProviderSchema: &providerSchema,
-							targetState:    refreshState,
-							Dependencies:   &n.Dependencies,
-						},
-					},
-				},
-			},
-
-			// Plan the instance
-			&EvalDiff{
-				Addr:                addr.Resource,
-				Config:              n.Config,
-				CreateBeforeDestroy: n.ForceCreateBeforeDestroy,
-				Provider:            &provider,
-				ProviderAddr:        n.ResolvedProvider,
-				ProviderMetas:       n.ProviderMetas,
-				ProviderSchema:      &providerSchema,
-				State:               &instanceRefreshState,
-				OutputChange:        &change,
-				OutputState:         &instancePlanState,
-			},
-			&EvalCheckPreventDestroy{
-				Addr:   addr.Resource,
-				Config: n.Config,
-				Change: &change,
-			},
-			&EvalWriteState{
-				Addr:           addr.Resource,
-				ProviderAddr:   n.ResolvedProvider,
-				State:          &instancePlanState,
-				ProviderSchema: &providerSchema,
-			},
-			&EvalWriteDiff{
-				Addr:           addr.Resource,
-				ProviderSchema: &providerSchema,
-				Change:         &change,
-			},
-		},
 	}
+
+	validateSelfRef := &EvalValidateSelfRef{
+		Addr:           addr.Resource,
+		Config:         config.Config,
+		ProviderSchema: &providerSchema,
+	}
+	_, err = validateSelfRef.Eval(ctx)
+	if err != nil {
+		return err
+	}
+
+	// Refresh, maybe
+	if !skipRefresh {
+		instanceRefreshState, err = n.ReadResourceInstanceState(ctx, addr)
+		if err != nil {
+			return err
+		}
+
+		refreshLifecycle := &EvalRefreshLifecycle{
+			Addr:                     addr,
+			Config:                   n.Config,
+			State:                    &instanceRefreshState,
+			ForceCreateBeforeDestroy: n.ForceCreateBeforeDestroy,
+		}
+		_, err = refreshLifecycle.Eval(ctx)
+		if err != nil {
+			return err
+		}
+
+		refresh := &EvalRefresh{
+			Addr:           addr.Resource,
+			ProviderAddr:   n.ResolvedProvider,
+			Provider:       &provider,
+			ProviderMetas:  n.ProviderMetas,
+			ProviderSchema: &providerSchema,
+			State:          &instanceRefreshState,
+			Output:         &instanceRefreshState,
+		}
+		_, err = refresh.Eval(ctx)
+		if err != nil {
+			return err
+		}
+
+		writeRefreshState := &EvalWriteState{
+			Addr:           addr.Resource,
+			ProviderAddr:   n.ResolvedProvider,
+			ProviderSchema: &providerSchema,
+			State:          &instanceRefreshState,
+			targetState:    refreshState,
+			Dependencies:   &n.Dependencies,
+		}
+		_, err = writeRefreshState.Eval(ctx)
+		if err != nil {
+			return err
+		}
+	}
+
+	// Plan the instance
+	diff := &EvalDiff{
+		Addr:                addr.Resource,
+		Config:              n.Config,
+		CreateBeforeDestroy: n.ForceCreateBeforeDestroy,
+		Provider:            &provider,
+		ProviderAddr:        n.ResolvedProvider,
+		ProviderMetas:       n.ProviderMetas,
+		ProviderSchema:      &providerSchema,
+		State:               &instanceRefreshState,
+		OutputChange:        &change,
+		OutputState:         &instancePlanState,
+	}
+	_, err = diff.Eval(ctx)
+	if err != nil {
+		return err
+	}
+
+	err = n.checkPreventDestroy(change)
+	if err != nil {
+		return err
+	}
+
+	writeState := &EvalWriteState{
+		Addr:           addr.Resource,
+		ProviderAddr:   n.ResolvedProvider,
+		State:          &instancePlanState,
+		ProviderSchema: &providerSchema,
+	}
+	_, err = writeState.Eval(ctx)
+	if err != nil {
+		return err
+	}
+
+	writeDiff := &EvalWriteDiff{
+		Addr:           addr.Resource,
+		ProviderSchema: &providerSchema,
+		Change:         &change,
+	}
+	_, err = writeDiff.Eval(ctx)
+	return err
 }

terraform/node_resource_plan_orphan.go

@@ -57,7 +57,7 @@ func (n *NodePlannableResourceInstanceOrphan) Execute(ctx EvalContext, op walkOp
 		return err
 	}
 
-	err = n.CheckPreventDestroy(addr, change)
+	err = n.checkPreventDestroy(change)
 	if err != nil {
 		return err
 	}