core: targeted operations

Add `-target=resource` flag to core operations, allowing users to
target specific resources in their infrastructure. When `-target` is
used, the operation will only apply to that resource and its
dependencies.

The calculated dependencies are different depending on whether we're
running a normal operation or a `terraform destroy`.

Generally, "dependencies" refers to ancestors: resources falling
_before_ the target in the graph, because their changes are required to
accurately act on the target.

For destroys, "dependencies" are descendents: those resources which fall
_after_ the target. These resources depend on our target, which is going
to be destroyed, so they should also be destroyed.

command/apply.go

@@ -93,6 +93,7 @@ func (c *ApplyCommand) Run(args []string) int {
 
 	// Build the context based on the arguments given
 	ctx, planned, err := c.Context(contextOpts{
+		Destroy:   c.Destroy,
 		Path:      configPath,
 		StatePath: c.Meta.statePath,
 	})
@@ -140,12 +141,7 @@ func (c *ApplyCommand) Run(args []string) int {
 			}
 		}
 
-		var opts terraform.PlanOpts
+		if _, err := ctx.Plan(); err != nil {
-		if c.Destroy {
-			opts.Destroy = true
-		}
-
-		if _, err := ctx.Plan(&opts); err != nil {
 			c.Ui.Error(fmt.Sprintf(
 				"Error creating plan: %s", err))
 			return 1
@@ -319,6 +315,10 @@ Options:
                          "-state". This can be used to preserve the old
                          state.
 
+  -target=resource       Resource to target. Operation will be limited to this
+                         resource and its dependencies. This flag can be used
+                         multiple times.
+
   -var 'foo=bar'         Set a variable in the Terraform configuration. This
                          flag can be set multiple times.
 
@@ -357,6 +357,10 @@ Options:
                          "-state". This can be used to preserve the old
                          state.
 
+  -target=resource       Resource to target. Operation will be limited to this
+                         resource and its dependencies. This flag can be used
+                         multiple times.
+
   -var 'foo=bar'         Set a variable in the Terraform configuration. This
                          flag can be set multiple times.
 

command/apply_destroy_test.go

@@ -116,6 +116,96 @@ func TestApply_destroyPlan(t *testing.T) {
 	}
 }
 
+func TestApply_destroyTargeted(t *testing.T) {
+	originalState := &terraform.State{
+		Modules: []*terraform.ModuleState{
+			&terraform.ModuleState{
+				Path: []string{"root"},
+				Resources: map[string]*terraform.ResourceState{
+					"test_instance.foo": &terraform.ResourceState{
+						Type: "test_instance",
+						Primary: &terraform.InstanceState{
+							ID: "i-ab123",
+						},
+					},
+					"test_load_balancer.foo": &terraform.ResourceState{
+						Type: "test_load_balancer",
+						Primary: &terraform.InstanceState{
+							ID: "lb-abc123",
+						},
+					},
+				},
+			},
+		},
+	}
+
+	statePath := testStateFile(t, originalState)
+
+	p := testProvider()
+	ui := new(cli.MockUi)
+	c := &ApplyCommand{
+		Destroy: true,
+		Meta: Meta{
+			ContextOpts: testCtxConfig(p),
+			Ui:          ui,
+		},
+	}
+
+	// Run the apply command pointing to our existing state
+	args := []string{
+		"-force",
+		"-target", "test_instance.foo",
+		"-state", statePath,
+		testFixturePath("apply-destroy-targeted"),
+	}
+	if code := c.Run(args); code != 0 {
+		t.Fatalf("bad: %d\n\n%s", code, ui.ErrorWriter.String())
+	}
+
+	// Verify a new state exists
+	if _, err := os.Stat(statePath); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	f, err := os.Open(statePath)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	defer f.Close()
+
+	state, err := terraform.ReadState(f)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	if state == nil {
+		t.Fatal("state should not be nil")
+	}
+
+	actualStr := strings.TrimSpace(state.String())
+	expectedStr := strings.TrimSpace(testApplyDestroyStr)
+	if actualStr != expectedStr {
+		t.Fatalf("bad:\n\n%s\n\n%s", actualStr, expectedStr)
+	}
+
+	// Should have a backup file
+	f, err = os.Open(statePath + DefaultBackupExtention)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	backupState, err := terraform.ReadState(f)
+	f.Close()
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	actualStr = strings.TrimSpace(backupState.String())
+	expectedStr = strings.TrimSpace(originalState.String())
+	if actualStr != expectedStr {
+		t.Fatalf("bad:\n\nactual:\n%s\n\nexpected:\nb%s", actualStr, expectedStr)
+	}
+}
+
 const testApplyDestroyStr = `
 <no state>
 `

command/flag_kv.go

@@ -85,3 +85,17 @@ func loadKVFile(rawPath string) (map[string]string, error) {
 
 	return result, nil
 }
+
+// FlagStringSlice is a flag.Value implementation for parsing targets from the
+// command line, e.g. -target=aws_instance.foo -target=aws_vpc.bar
+
+type FlagStringSlice []string
+
+func (v *FlagStringSlice) String() string {
+	return ""
+}
+func (v *FlagStringSlice) Set(raw string) error {
+	*v = append(*v, raw)
+
+	return nil
+}

command/meta.go

@@ -38,6 +38,9 @@ type Meta struct {
 	input         bool
 	variables     map[string]string
 
+	// Targets for this context (private)
+	targets []string
+
 	color bool
 	oldUi cli.Ui
 
@@ -126,6 +129,9 @@ func (m *Meta) Context(copts contextOpts) (*terraform.Context, bool, error) {
 		m.statePath = copts.StatePath
 	}
 
+	// Tell the context if we're in a destroy plan / apply
+	opts.Destroy = copts.Destroy
+
 	// Store the loaded state
 	state, err := m.State()
 	if err != nil {
@@ -267,6 +273,7 @@ func (m *Meta) contextOpts() *terraform.ContextOpts {
 		vs[k] = v
 	}
 	opts.Variables = vs
+	opts.Targets = m.targets
 	opts.UIInput = m.UIInput()
 
 	return &opts
@@ -278,6 +285,7 @@ func (m *Meta) flagSet(n string) *flag.FlagSet {
 	f.BoolVar(&m.input, "input", true, "input")
 	f.Var((*FlagKV)(&m.variables), "var", "variables")
 	f.Var((*FlagKVFile)(&m.variables), "var-file", "variable file")
+	f.Var((*FlagStringSlice)(&m.targets), "target", "resource to target")
 
 	if m.autoKey != "" {
 		f.Var((*FlagKVFile)(&m.autoVariables), m.autoKey, "variable file")
@@ -388,4 +396,7 @@ type contextOpts struct {
 
 	// GetMode is the module.GetMode to use when loading the module tree.
 	GetMode module.GetMode
+
+	// Set to true when running a destroy plan/apply.
+	Destroy bool
 }

command/plan.go

@@ -53,6 +53,7 @@ func (c *PlanCommand) Run(args []string) int {
 	}
 
 	ctx, _, err := c.Context(contextOpts{
+		Destroy:   destroy,
 		Path:      path,
 		StatePath: c.Meta.statePath,
 	})
@@ -86,7 +87,7 @@ func (c *PlanCommand) Run(args []string) int {
 		}
 	}
 
-	plan, err := ctx.Plan(&terraform.PlanOpts{Destroy: destroy})
+	plan, err := ctx.Plan()
 	if err != nil {
 		c.Ui.Error(fmt.Sprintf("Error running plan: %s", err))
 		return 1
@@ -168,6 +169,10 @@ Options:
                       up Terraform-managed resources. By default it will
                       use the state "terraform.tfstate" if it exists.
 
+  -target=resource    Resource to target. Operation will be limited to this
+                      resource and its dependencies. This flag can be used
+                      multiple times.
+
   -var 'foo=bar'      Set a variable in the Terraform configuration. This
                       flag can be set multiple times.
 

command/refresh.go

@@ -135,6 +135,10 @@ Options:
   -state-out=path     Path to write updated state file. By default, the
                       "-state" path will be used.
 
+  -target=resource    Resource to target. Operation will be limited to this
+                      resource and its dependencies. This flag can be used
+                      multiple times.
+
   -var 'foo=bar'      Set a variable in the Terraform configuration. This
                       flag can be set multiple times.
 

command/test-fixtures/apply-destroy-targeted/main.tf

@@ -0,0 +1,7 @@
+resource "test_instance" "foo" {
+  count = 3
+}
+
+resource "test_load_balancer" "foo" {
+  instances = ["${test_instance.foo.*.id}"]
+}

dag/dag.go

@@ -17,6 +17,40 @@ type AcyclicGraph struct {
 // WalkFunc is the callback used for walking the graph.
 type WalkFunc func(Vertex) error
 
+// Returns a Set that includes every Vertex yielded by walking down from the
+// provided starting Vertex v.
+func (g *AcyclicGraph) Ancestors(v Vertex) (*Set, error) {
+	s := new(Set)
+	start := asVertexList(g.DownEdges(v))
+	memoFunc := func(v Vertex) error {
+		s.Add(v)
+		return nil
+	}
+
+	if err := g.depthFirstWalk(start, memoFunc); err != nil {
+		return nil, err
+	}
+
+	return s, nil
+}
+
+// Returns a Set that includes every Vertex yielded by walking up from the
+// provided starting Vertex v.
+func (g *AcyclicGraph) Descendents(v Vertex) (*Set, error) {
+	s := new(Set)
+	start := asVertexList(g.UpEdges(v))
+	memoFunc := func(v Vertex) error {
+		s.Add(v)
+		return nil
+	}
+
+	if err := g.reverseDepthFirstWalk(start, memoFunc); err != nil {
+		return nil, err
+	}
+
+	return s, nil
+}
+
 // Root returns the root of the DAG, or an error.
 //
 // Complexity: O(V)
@@ -61,15 +95,11 @@ func (g *AcyclicGraph) TransitiveReduction() {
 
 	for _, u := range g.Vertices() {
 		uTargets := g.DownEdges(u)
-		vs := make([]Vertex, uTargets.Len())
+		vs := asVertexList(g.DownEdges(u))
-		for i, vRaw := range uTargets.List() {
-			vs[i] = vRaw.(Vertex)
-		}
 
 		g.depthFirstWalk(vs, func(v Vertex) error {
 			shared := uTargets.Intersection(g.DownEdges(v))
-			for _, raw := range shared.List() {
+			for _, vPrime := range asVertexList(shared) {
-				vPrime := raw.(Vertex)
 				g.RemoveEdge(BasicEdge(u, vPrime))
 			}
 
@@ -145,12 +175,10 @@ func (g *AcyclicGraph) Walk(cb WalkFunc) error {
 	for _, v := range vertices {
 		// Build our list of dependencies and the list of channels to
 		// wait on until we start executing for this vertex.
-		depsRaw := g.DownEdges(v).List()
+		deps := asVertexList(g.DownEdges(v))
-		deps := make([]Vertex, len(depsRaw))
 		depChs := make([]<-chan struct{}, len(deps))
-		for i, raw := range depsRaw {
+		for i, dep := range deps {
-			deps[i] = raw.(Vertex)
+			depChs[i] = vertMap[dep]
-			depChs[i] = vertMap[deps[i]]
 		}
 
 		// Get our channel so that we can close it when we're done
@@ -200,6 +228,16 @@ func (g *AcyclicGraph) Walk(cb WalkFunc) error {
 	return errs
 }
 
+// simple convenience helper for converting a dag.Set to a []Vertex
+func asVertexList(s *Set) []Vertex {
+	rawList := s.List()
+	vertexList := make([]Vertex, len(rawList))
+	for i, raw := range rawList {
+		vertexList[i] = raw.(Vertex)
+	}
+	return vertexList
+}
+
 // depthFirstWalk does a depth-first walk of the graph starting from
 // the vertices in start. This is not exported now but it would make sense
 // to export this publicly at some point.
@@ -233,3 +271,36 @@ func (g *AcyclicGraph) depthFirstWalk(start []Vertex, cb WalkFunc) error {
 
 	return nil
 }
+
+// reverseDepthFirstWalk does a depth-first walk _up_ the graph starting from
+// the vertices in start.
+func (g *AcyclicGraph) reverseDepthFirstWalk(start []Vertex, cb WalkFunc) error {
+	seen := make(map[Vertex]struct{})
+	frontier := make([]Vertex, len(start))
+	copy(frontier, start)
+	for len(frontier) > 0 {
+		// Pop the current vertex
+		n := len(frontier)
+		current := frontier[n-1]
+		frontier = frontier[:n-1]
+
+		// Check if we've seen this already and return...
+		if _, ok := seen[current]; ok {
+			continue
+		}
+		seen[current] = struct{}{}
+
+		// Visit the current node
+		if err := cb(current); err != nil {
+			return err
+		}
+
+		// Visit targets of this in reverse order.
+		targets := g.UpEdges(current).List()
+		for i := len(targets) - 1; i >= 0; i-- {
+			frontier = append(frontier, targets[i].(Vertex))
+		}
+	}
+
+	return nil
+}

dag/dag_test.go

@@ -126,6 +126,68 @@ func TestAcyclicGraphValidate_cycleSelf(t *testing.T) {
 	}
 }
 
+func TestAcyclicGraphAncestors(t *testing.T) {
+	var g AcyclicGraph
+	g.Add(1)
+	g.Add(2)
+	g.Add(3)
+	g.Add(4)
+	g.Add(5)
+	g.Connect(BasicEdge(0, 1))
+	g.Connect(BasicEdge(1, 2))
+	g.Connect(BasicEdge(2, 3))
+	g.Connect(BasicEdge(3, 4))
+	g.Connect(BasicEdge(4, 5))
+
+	actual, err := g.Ancestors(2)
+	if err != nil {
+		t.Fatalf("err: %#v", err)
+	}
+
+	expected := []Vertex{3, 4, 5}
+
+	if actual.Len() != len(expected) {
+		t.Fatalf("bad length! expected %#v to have len %d", actual, len(expected))
+	}
+
+	for _, e := range expected {
+		if !actual.Include(e) {
+			t.Fatalf("expected: %#v to include: %#v", expected, actual)
+		}
+	}
+}
+
+func TestAcyclicGraphDescendents(t *testing.T) {
+	var g AcyclicGraph
+	g.Add(1)
+	g.Add(2)
+	g.Add(3)
+	g.Add(4)
+	g.Add(5)
+	g.Connect(BasicEdge(0, 1))
+	g.Connect(BasicEdge(1, 2))
+	g.Connect(BasicEdge(2, 3))
+	g.Connect(BasicEdge(3, 4))
+	g.Connect(BasicEdge(4, 5))
+
+	actual, err := g.Descendents(2)
+	if err != nil {
+		t.Fatalf("err: %#v", err)
+	}
+
+	expected := []Vertex{0, 1}
+
+	if actual.Len() != len(expected) {
+		t.Fatalf("bad length! expected %#v to have len %d", actual, len(expected))
+	}
+
+	for _, e := range expected {
+		if !actual.Include(e) {
+			t.Fatalf("expected: %#v to include: %#v", expected, actual)
+		}
+	}
+}
+
 func TestAcyclicGraphWalk(t *testing.T) {
 	var g AcyclicGraph
 	g.Add(1)

helper/resource/testing.go

@@ -190,6 +190,7 @@ func testStep(
 	// Build the context
 	opts.Module = mod
 	opts.State = state
+	opts.Destroy = step.Destroy
 	ctx := terraform.NewContext(&opts)
 	if ws, es := ctx.Validate(); len(ws) > 0 || len(es) > 0 {
 		estrs := make([]string, len(es))
@@ -209,7 +210,7 @@ func testStep(
 	}
 
 	// Plan!
-	if p, err := ctx.Plan(&terraform.PlanOpts{Destroy: step.Destroy}); err != nil {
+	if p, err := ctx.Plan(); err != nil {
 		return state, fmt.Errorf(
 			"Error planning: %s", err)
 	} else {

terraform/context.go

@@ -33,6 +33,7 @@ const (
 // ContextOpts are the user-configurable options to create a context with
 // NewContext.
 type ContextOpts struct {
+	Destroy      bool
 	Diff         *Diff
 	Hooks        []Hook
 	Module       *module.Tree
@@ -40,6 +41,7 @@ type ContextOpts struct {
 	State        *State
 	Providers    map[string]ResourceProviderFactory
 	Provisioners map[string]ResourceProvisionerFactory
+	Targets      []string
 	Variables    map[string]string
 
 	UIInput UIInput
@@ -49,6 +51,7 @@ type ContextOpts struct {
 // perform operations on infrastructure. This structure is built using
 // NewContext. See the documentation for that.
 type Context struct {
+	destroy      bool
 	diff         *Diff
 	diffLock     sync.RWMutex
 	hooks        []Hook
@@ -58,6 +61,7 @@ type Context struct {
 	sh           *stopHook
 	state        *State
 	stateLock    sync.RWMutex
+	targets      []string
 	uiInput      UIInput
 	variables    map[string]string
 
@@ -95,12 +99,14 @@ func NewContext(opts *ContextOpts) *Context {
 	}
 
 	return &Context{
+		destroy:      opts.Destroy,
 		diff:         opts.Diff,
 		hooks:        hooks,
 		module:       opts.Module,
 		providers:    opts.Providers,
 		provisioners: opts.Provisioners,
 		state:        state,
+		targets:      opts.Targets,
 		uiInput:      opts.UIInput,
 		variables:    opts.Variables,
 
@@ -135,6 +141,8 @@ func (c *Context) GraphBuilder() GraphBuilder {
 		Providers:    providers,
 		Provisioners: provisioners,
 		State:        c.state,
+		Targets:      c.targets,
+		Destroy:      c.destroy,
 	}
 }
 
@@ -253,7 +261,7 @@ func (c *Context) Apply() (*State, error) {
 //
 // Plan also updates the diff of this context to be the diff generated
 // by the plan, so Apply can be called after.
-func (c *Context) Plan(opts *PlanOpts) (*Plan, error) {
+func (c *Context) Plan() (*Plan, error) {
 	v := c.acquireRun()
 	defer c.releaseRun(v)
 
@@ -264,7 +272,7 @@ func (c *Context) Plan(opts *PlanOpts) (*Plan, error) {
 	}
 
 	var operation walkOperation
-	if opts != nil && opts.Destroy {
+	if c.destroy {
 		operation = walkPlanDestroy
 	} else {
 		// Set our state to be something temporary. We do this so that

terraform/context_test.go

@@ -24,7 +24,7 @@ func TestContext2Plan(t *testing.T) {
 		},
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -57,7 +57,7 @@ func TestContext2Plan_emptyDiff(t *testing.T) {
 		},
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -80,7 +80,7 @@ func TestContext2Plan_minimal(t *testing.T) {
 		},
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -103,7 +103,7 @@ func TestContext2Plan_modules(t *testing.T) {
 		},
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -126,7 +126,7 @@ func TestContext2Plan_moduleInput(t *testing.T) {
 		},
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -149,7 +149,7 @@ func TestContext2Plan_moduleInputComputed(t *testing.T) {
 		},
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -175,7 +175,7 @@ func TestContext2Plan_moduleInputFromVar(t *testing.T) {
 		},
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -198,7 +198,7 @@ func TestContext2Plan_moduleMultiVar(t *testing.T) {
 		},
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -237,7 +237,7 @@ func TestContext2Plan_moduleOrphans(t *testing.T) {
 		State: s,
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -282,7 +282,7 @@ func TestContext2Plan_moduleProviderInherit(t *testing.T) {
 		},
 	})
 
-	_, err := ctx.Plan(nil)
+	_, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -332,7 +332,7 @@ func TestContext2Plan_moduleProviderDefaults(t *testing.T) {
 		},
 	})
 
-	_, err := ctx.Plan(nil)
+	_, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -385,7 +385,7 @@ func TestContext2Plan_moduleProviderDefaultsVar(t *testing.T) {
 		},
 	})
 
-	_, err := ctx.Plan(nil)
+	_, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -410,7 +410,7 @@ func TestContext2Plan_moduleVar(t *testing.T) {
 		},
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -433,7 +433,7 @@ func TestContext2Plan_moduleVarComputed(t *testing.T) {
 		},
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -471,7 +471,7 @@ func TestContext2Plan_nil(t *testing.T) {
 		},
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -491,7 +491,7 @@ func TestContext2Plan_computed(t *testing.T) {
 		},
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -514,7 +514,7 @@ func TestContext2Plan_computedList(t *testing.T) {
 		},
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -537,7 +537,7 @@ func TestContext2Plan_count(t *testing.T) {
 		},
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -564,7 +564,7 @@ func TestContext2Plan_countComputed(t *testing.T) {
 		},
 	})
 
-	_, err := ctx.Plan(nil)
+	_, err := ctx.Plan()
 	if err == nil {
 		t.Fatal("should error")
 	}
@@ -581,7 +581,7 @@ func TestContext2Plan_countIndex(t *testing.T) {
 		},
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -604,7 +604,7 @@ func TestContext2Plan_countIndexZero(t *testing.T) {
 		},
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -630,7 +630,7 @@ func TestContext2Plan_countVar(t *testing.T) {
 		},
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -653,7 +653,7 @@ func TestContext2Plan_countZero(t *testing.T) {
 		},
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -676,7 +676,7 @@ func TestContext2Plan_countOneIndex(t *testing.T) {
 		},
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -731,7 +731,7 @@ func TestContext2Plan_countDecreaseToOne(t *testing.T) {
 		State: s,
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -774,7 +774,7 @@ func TestContext2Plan_countIncreaseFromNotSet(t *testing.T) {
 		State: s,
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -817,7 +817,7 @@ func TestContext2Plan_countIncreaseFromOne(t *testing.T) {
 		State: s,
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -875,7 +875,7 @@ func TestContext2Plan_countIncreaseFromOneCorrupted(t *testing.T) {
 		State: s,
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -918,9 +918,10 @@ func TestContext2Plan_destroy(t *testing.T) {
 			"aws": testProviderFuncFixed(p),
 		},
 		State:   s,
+		Destroy: true,
 	})
 
-	plan, err := ctx.Plan(&PlanOpts{Destroy: true})
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -972,9 +973,10 @@ func TestContext2Plan_moduleDestroy(t *testing.T) {
 			"aws": testProviderFuncFixed(p),
 		},
 		State:   s,
+		Destroy: true,
 	})
 
-	plan, err := ctx.Plan(&PlanOpts{Destroy: true})
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -1021,9 +1023,10 @@ func TestContext2Plan_moduleDestroyMultivar(t *testing.T) {
 			"aws": testProviderFuncFixed(p),
 		},
 		State:   s,
+		Destroy: true,
 	})
 
-	plan, err := ctx.Plan(&PlanOpts{Destroy: true})
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -1051,7 +1054,7 @@ func TestContext2Plan_pathVar(t *testing.T) {
 		},
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -1118,7 +1121,7 @@ func TestContext2Plan_diffVar(t *testing.T) {
 		}, nil
 	}
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -1143,7 +1146,7 @@ func TestContext2Plan_hook(t *testing.T) {
 		},
 	})
 
-	_, err := ctx.Plan(nil)
+	_, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -1183,7 +1186,7 @@ func TestContext2Plan_orphan(t *testing.T) {
 		State: s,
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -1221,7 +1224,7 @@ func TestContext2Plan_state(t *testing.T) {
 		State: s,
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -1273,7 +1276,7 @@ func TestContext2Plan_taint(t *testing.T) {
 		State: s,
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -1324,7 +1327,7 @@ func TestContext2Plan_multiple_taint(t *testing.T) {
 		State: s,
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -1357,7 +1360,7 @@ func TestContext2Plan_provider(t *testing.T) {
 		},
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -1377,7 +1380,7 @@ func TestContext2Plan_varMultiCountOne(t *testing.T) {
 		},
 	})
 
-	plan, err := ctx.Plan(nil)
+	plan, err := ctx.Plan()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -1399,7 +1402,7 @@ func TestContext2Plan_varListErr(t *testing.T) {
 		},
 	})
 
-	_, err := ctx.Plan(nil)
+	_, err := ctx.Plan()
 	if err == nil {
 		t.Fatal("should error")
 	}
@@ -2468,7 +2471,7 @@ func TestContext2Input(t *testing.T) {
 		t.Fatalf("err: %s", err)
 	}
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -2513,7 +2516,7 @@ func TestContext2Input_provider(t *testing.T) {
 		t.Fatalf("err: %s", err)
 	}
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -2590,7 +2593,7 @@ func TestContext2Input_providerId(t *testing.T) {
 		t.Fatalf("err: %s", err)
 	}
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -2638,7 +2641,7 @@ func TestContext2Input_providerOnly(t *testing.T) {
 		t.Fatalf("err: %s", err)
 	}
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -2693,7 +2696,7 @@ func TestContext2Input_providerVars(t *testing.T) {
 		t.Fatalf("err: %s", err)
 	}
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -2741,7 +2744,7 @@ func TestContext2Input_varOnly(t *testing.T) {
 		t.Fatalf("err: %s", err)
 	}
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -2787,7 +2790,7 @@ func TestContext2Input_varOnlyUnset(t *testing.T) {
 		t.Fatalf("err: %s", err)
 	}
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -2815,7 +2818,7 @@ func TestContext2Apply(t *testing.T) {
 		},
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -2848,7 +2851,7 @@ func TestContext2Apply_emptyModule(t *testing.T) {
 		},
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -2896,7 +2899,7 @@ func TestContext2Apply_createBeforeDestroy(t *testing.T) {
 		State: state,
 	})
 
-	if p, err := ctx.Plan(nil); err != nil {
+	if p, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	} else {
 		t.Logf(p.String())
@@ -2950,7 +2953,7 @@ func TestContext2Apply_createBeforeDestroyUpdate(t *testing.T) {
 		State: state,
 	})
 
-	if p, err := ctx.Plan(nil); err != nil {
+	if p, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	} else {
 		t.Logf(p.String())
@@ -2985,7 +2988,7 @@ func TestContext2Apply_minimal(t *testing.T) {
 		},
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -3013,7 +3016,7 @@ func TestContext2Apply_badDiff(t *testing.T) {
 		},
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -3071,7 +3074,7 @@ func TestContext2Apply_cancel(t *testing.T) {
 		}, nil
 	}
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -3112,7 +3115,7 @@ func TestContext2Apply_compute(t *testing.T) {
 		},
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -3181,7 +3184,7 @@ func TestContext2Apply_countDecrease(t *testing.T) {
 		State: s,
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -3241,7 +3244,7 @@ func TestContext2Apply_countDecreaseToOne(t *testing.T) {
 		State: s,
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -3303,7 +3306,7 @@ func TestContext2Apply_countDecreaseToOneCorrupted(t *testing.T) {
 		State: s,
 	})
 
-	if p, err := ctx.Plan(nil); err != nil {
+	if p, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	} else {
 		testStringMatch(t, p, testTerraformApplyCountDecToOneCorruptedPlanStr)
@@ -3354,7 +3357,7 @@ func TestContext2Apply_countTainted(t *testing.T) {
 		State: s,
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -3382,7 +3385,7 @@ func TestContext2Apply_countVariable(t *testing.T) {
 		},
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -3410,7 +3413,7 @@ func TestContext2Apply_module(t *testing.T) {
 		},
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -3439,9 +3442,10 @@ func TestContext2Apply_moduleVarResourceCount(t *testing.T) {
 		Variables: map[string]string{
 			"count": "2",
 		},
+		Destroy: true,
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -3459,7 +3463,7 @@ func TestContext2Apply_moduleVarResourceCount(t *testing.T) {
 		},
 	})
 
-	if _, err := ctx.Plan(&PlanOpts{Destroy: true}); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -3481,7 +3485,7 @@ func TestContext2Apply_moduleBool(t *testing.T) {
 		},
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -3515,7 +3519,7 @@ func TestContext2Apply_multiProvider(t *testing.T) {
 		},
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -3548,7 +3552,7 @@ func TestContext2Apply_nilDiff(t *testing.T) {
 		},
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -3588,7 +3592,7 @@ func TestContext2Apply_Provisioner_compute(t *testing.T) {
 		},
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -3633,7 +3637,7 @@ func TestContext2Apply_provisionerCreateFail(t *testing.T) {
 		},
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -3672,7 +3676,7 @@ func TestContext2Apply_provisionerCreateFailNoId(t *testing.T) {
 		},
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -3712,7 +3716,7 @@ func TestContext2Apply_provisionerFail(t *testing.T) {
 		},
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -3767,7 +3771,7 @@ func TestContext2Apply_provisionerFail_createBeforeDestroy(t *testing.T) {
 		State: state,
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -3816,7 +3820,7 @@ func TestContext2Apply_error_createBeforeDestroy(t *testing.T) {
 	}
 	p.DiffFn = testDiffFn
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -3874,7 +3878,7 @@ func TestContext2Apply_errorDestroy_createBeforeDestroy(t *testing.T) {
 	}
 	p.DiffFn = testDiffFn
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -3931,7 +3935,7 @@ func TestContext2Apply_multiDepose_createBeforeDestroy(t *testing.T) {
 		}
 	}
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -3955,7 +3959,7 @@ aws_instance.web: (1 deposed)
 		State:     state,
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -3983,7 +3987,7 @@ aws_instance.web: (2 deposed)
 	}
 
 	createdInstanceId = "qux"
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 	state, err = ctx.Apply()
@@ -4005,7 +4009,7 @@ aws_instance.web: (1 deposed)
 	}
 
 	createdInstanceId = "quux"
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 	state, err = ctx.Apply()
@@ -4045,7 +4049,7 @@ func TestContext2Apply_provisionerResourceRef(t *testing.T) {
 		},
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -4091,7 +4095,7 @@ func TestContext2Apply_provisionerSelfRef(t *testing.T) {
 		},
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -4144,7 +4148,7 @@ func TestContext2Apply_provisionerMultiSelfRef(t *testing.T) {
 		},
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -4192,7 +4196,7 @@ func TestContext2Apply_Provisioner_Diff(t *testing.T) {
 		},
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -4229,7 +4233,7 @@ func TestContext2Apply_Provisioner_Diff(t *testing.T) {
 		State: state,
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -4300,7 +4304,7 @@ func TestContext2Apply_outputDiffVars(t *testing.T) {
 		}, nil
 	}
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 	if _, err := ctx.Apply(); err != nil {
@@ -4363,7 +4367,7 @@ func TestContext2Apply_Provisioner_ConnInfo(t *testing.T) {
 		},
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -4399,22 +4403,32 @@ func TestContext2Apply_destroy(t *testing.T) {
 	})
 
 	// First plan and apply a create operation
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
-	if _, err := ctx.Apply(); err != nil {
+	state, err := ctx.Apply()
+	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
 	// Next, plan and apply a destroy operation
-	if _, err := ctx.Plan(&PlanOpts{Destroy: true}); err != nil {
+	h.Active = true
+	ctx = testContext2(t, &ContextOpts{
+		Destroy: true,
+		State:   state,
+		Module:  m,
+		Hooks:   []Hook{h},
+		Providers: map[string]ResourceProviderFactory{
+			"aws": testProviderFuncFixed(p),
+		},
+	})
+
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
-	h.Active = true
+	state, err = ctx.Apply()
-
-	state, err := ctx.Apply()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -4430,7 +4444,7 @@ func TestContext2Apply_destroy(t *testing.T) {
 	expected2 := []string{"aws_instance.bar", "aws_instance.foo"}
 	actual2 := h.IDs
 	if !reflect.DeepEqual(actual2, expected2) {
-		t.Fatalf("bad: %#v", actual2)
+		t.Fatalf("expected: %#v\n\ngot:%#v", expected2, actual2)
 	}
 }
 
@@ -4449,22 +4463,33 @@ func TestContext2Apply_destroyOutputs(t *testing.T) {
 	})
 
 	// First plan and apply a create operation
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
-	if _, err := ctx.Apply(); err != nil {
+	state, err := ctx.Apply()
+
+	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
 	// Next, plan and apply a destroy operation
-	if _, err := ctx.Plan(&PlanOpts{Destroy: true}); err != nil {
+	h.Active = true
+	ctx = testContext2(t, &ContextOpts{
+		Destroy: true,
+		State:   state,
+		Module:  m,
+		Hooks:   []Hook{h},
+		Providers: map[string]ResourceProviderFactory{
+			"aws": testProviderFuncFixed(p),
+		},
+	})
+
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
-	h.Active = true
+	state, err = ctx.Apply()
-
-	state, err := ctx.Apply()
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -4520,7 +4545,7 @@ func TestContext2Apply_destroyOrphan(t *testing.T) {
 		}, nil
 	}
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -4578,9 +4603,10 @@ func TestContext2Apply_destroyTaintedProvisioner(t *testing.T) {
 			"shell": testProvisionerFuncFixed(pr),
 		},
 		State:   s,
+		Destroy: true,
 	})
 
-	if _, err := ctx.Plan(&PlanOpts{Destroy: true}); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -4638,7 +4664,7 @@ func TestContext2Apply_error(t *testing.T) {
 		}, nil
 	}
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -4705,7 +4731,7 @@ func TestContext2Apply_errorPartial(t *testing.T) {
 		}, nil
 	}
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -4740,7 +4766,7 @@ func TestContext2Apply_hook(t *testing.T) {
 		},
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -4788,7 +4814,7 @@ func TestContext2Apply_idAttr(t *testing.T) {
 		}, nil
 	}
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -4822,7 +4848,7 @@ func TestContext2Apply_output(t *testing.T) {
 		},
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -4850,7 +4876,7 @@ func TestContext2Apply_outputInvalid(t *testing.T) {
 		},
 	})
 
-	_, err := ctx.Plan(nil)
+	_, err := ctx.Plan()
 	if err == nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -4871,7 +4897,7 @@ func TestContext2Apply_outputList(t *testing.T) {
 		},
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -4899,7 +4925,7 @@ func TestContext2Apply_outputMulti(t *testing.T) {
 		},
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -4927,7 +4953,7 @@ func TestContext2Apply_outputMultiIndex(t *testing.T) {
 		},
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -4992,7 +5018,7 @@ func TestContext2Apply_taint(t *testing.T) {
 		State: s,
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -5057,7 +5083,7 @@ func TestContext2Apply_taintDep(t *testing.T) {
 		State: s,
 	})
 
-	if p, err := ctx.Plan(nil); err != nil {
+	if p, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	} else {
 		t.Logf("plan: %s", p)
@@ -5120,7 +5146,7 @@ func TestContext2Apply_taintDepRequiresNew(t *testing.T) {
 		State: s,
 	})
 
-	if p, err := ctx.Plan(nil); err != nil {
+	if p, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	} else {
 		t.Logf("plan: %s", p)
@@ -5150,7 +5176,7 @@ func TestContext2Apply_unknownAttribute(t *testing.T) {
 		},
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -5190,7 +5216,7 @@ func TestContext2Apply_vars(t *testing.T) {
 		t.Fatalf("bad: %s", e)
 	}
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -5248,7 +5274,7 @@ func TestContext2Apply_createBefore_depends(t *testing.T) {
 		State: state,
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
@@ -5357,7 +5383,7 @@ func TestContext2Apply_singleDestroy(t *testing.T) {
 		State: state,
 	})
 
-	if _, err := ctx.Plan(nil); err != nil {
+	if _, err := ctx.Plan(); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 

terraform/graph_builder.go

@@ -65,6 +65,13 @@ type BuiltinGraphBuilder struct {
 
 	// Provisioners is the list of provisioners supported.
 	Provisioners []string
+
+	// Targets is the user-specified list of resources to target.
+	Targets []string
+
+	// Destroy is set to true when we're in a `terraform destroy` or a
+	// `terraform plan -destroy`
+	Destroy bool
 }
 
 // Build builds the graph according to the steps returned by Steps.
@@ -104,6 +111,10 @@ func (b *BuiltinGraphBuilder) Steps() []GraphTransformer {
 			},
 		},
 
+		// Optionally reduces the graph to a user-specified list of targets and
+		// their dependencies.
+		&TargetsTransformer{Targets: b.Targets, Destroy: b.Destroy},
+
 		// Create the destruction nodes
 		&DestroyTransformer{},
 		&CreateBeforeDestroyTransformer{},

terraform/plan.go

@@ -18,15 +18,6 @@ func init() {
 	gob.Register(make(map[string]string))
 }
 
-// PlanOpts are the options used to generate an execution plan for
-// Terraform.
-type PlanOpts struct {
-	// If set to true, then the generated plan will destroy all resources
-	// that are created. Otherwise, it will move towards the desired state
-	// specified in the configuration.
-	Destroy bool
-}
-
 // Plan represents a single Terraform execution plan, which contains
 // all the information necessary to make an infrastructure change.
 type Plan struct {

terraform/test-fixtures/transform-targets-basic/main.tf

@@ -0,0 +1,16 @@
+resource "aws_vpc" "me" {}
+
+resource "aws_subnet" "me" {
+  vpc_id = "${aws_vpc.me.id}"
+}
+
+resource "aws_instance" "me" {
+  subnet_id = "${aws_subnet.me.id}"
+}
+
+resource "aws_vpc" "notme" {}
+resource "aws_subnet" "notme" {}
+resource "aws_instance" "notme" {}
+resource "aws_instance" "notmeeither" {
+  name = "${aws_instance.me.id}"
+}

terraform/test-fixtures/transform-targets-destroy/main.tf

@@ -0,0 +1,18 @@
+resource "aws_vpc" "notme" {}
+
+resource "aws_subnet" "notme" {
+  vpc_id = "${aws_vpc.notme.id}"
+}
+
+resource "aws_instance" "me" {
+  subnet_id = "${aws_subnet.notme.id}"
+}
+
+resource "aws_instance" "notme" {}
+resource "aws_instance" "metoo" {
+  name = "${aws_instance.me.id}"
+}
+
+resource "aws_elb" "me" {
+  instances = "${aws_instance.me.*.id}"
+}

terraform/transform_targets.go

@@ -0,0 +1,77 @@
+package terraform
+
+import "github.com/hashicorp/terraform/dag"
+
+// TargetsTransformer is a GraphTransformer that, when the user specifies a
+// list of resources to target, limits the graph to only those resources and
+// their dependencies.
+type TargetsTransformer struct {
+	// List of targeted resource names specified by the user
+	Targets []string
+
+	// Set to true when we're in a `terraform destroy` or a
+	// `terraform plan -destroy`
+	Destroy bool
+}
+
+func (t *TargetsTransformer) Transform(g *Graph) error {
+	if len(t.Targets) > 0 {
+		targetedNodes, err := t.selectTargetedNodes(g)
+		if err != nil {
+			return err
+		}
+
+		for _, v := range g.Vertices() {
+			if !targetedNodes.Include(v) {
+				g.Remove(v)
+			}
+		}
+	}
+	return nil
+}
+
+func (t *TargetsTransformer) selectTargetedNodes(g *Graph) (*dag.Set, error) {
+	targetedNodes := new(dag.Set)
+	for _, v := range g.Vertices() {
+		// Keep all providers; they'll be pruned later if necessary
+		if r, ok := v.(GraphNodeProvider); ok {
+			targetedNodes.Add(r)
+			continue
+		}
+
+		// For the remaining filter, we only care about Resources and their deps
+		r, ok := v.(*GraphNodeConfigResource)
+		if !ok {
+			continue
+		}
+
+		if t.resourceIsTarget(r) {
+			targetedNodes.Add(r)
+
+			var deps *dag.Set
+			var err error
+			if t.Destroy {
+				deps, err = g.Descendents(r)
+			} else {
+				deps, err = g.Ancestors(r)
+			}
+			if err != nil {
+				return nil, err
+			}
+
+			for _, d := range deps.List() {
+				targetedNodes.Add(d)
+			}
+		}
+	}
+	return targetedNodes, nil
+}
+
+func (t *TargetsTransformer) resourceIsTarget(r *GraphNodeConfigResource) bool {
+	for _, target := range t.Targets {
+		if target == r.Name() {
+			return true
+		}
+	}
+	return false
+}

terraform/transform_targets_test.go

@@ -0,0 +1,71 @@
+package terraform
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestTargetsTransformer(t *testing.T) {
+	mod := testModule(t, "transform-targets-basic")
+
+	g := Graph{Path: RootModulePath}
+	{
+		tf := &ConfigTransformer{Module: mod}
+		if err := tf.Transform(&g); err != nil {
+			t.Fatalf("err: %s", err)
+		}
+	}
+
+	{
+		transform := &TargetsTransformer{Targets: []string{"aws_instance.me"}}
+		if err := transform.Transform(&g); err != nil {
+			t.Fatalf("err: %s", err)
+		}
+	}
+
+	actual := strings.TrimSpace(g.String())
+	expected := strings.TrimSpace(`
+aws_instance.me
+  aws_subnet.me
+aws_subnet.me
+  aws_vpc.me
+aws_vpc.me
+	`)
+	if actual != expected {
+		t.Fatalf("bad:\n\nexpected:\n%s\n\ngot:\n%s\n", expected, actual)
+	}
+}
+
+func TestTargetsTransformer_destroy(t *testing.T) {
+	mod := testModule(t, "transform-targets-destroy")
+
+	g := Graph{Path: RootModulePath}
+	{
+		tf := &ConfigTransformer{Module: mod}
+		if err := tf.Transform(&g); err != nil {
+			t.Fatalf("err: %s", err)
+		}
+	}
+
+	{
+		transform := &TargetsTransformer{
+			Targets: []string{"aws_instance.me"},
+			Destroy: true,
+		}
+		if err := transform.Transform(&g); err != nil {
+			t.Fatalf("err: %s", err)
+		}
+	}
+
+	actual := strings.TrimSpace(g.String())
+	expected := strings.TrimSpace(`
+aws_elb.me
+  aws_instance.me
+aws_instance.me
+aws_instance.metoo
+  aws_instance.me
+	`)
+	if actual != expected {
+		t.Fatalf("bad:\n\nexpected:\n%s\n\ngot:\n%s\n", expected, actual)
+	}
+}