terraform: improved refactor of EvalWriteResourceState

EvalWriteResourceState finds new life as a method called WriteResourceState on NodeAbstractResource.

terraform/node_resource_abstract.go

@@ -10,6 +10,7 @@ import (
 	"github.com/hashicorp/terraform/dag"
 	"github.com/hashicorp/terraform/lang"
 	"github.com/hashicorp/terraform/states"
+	"github.com/hashicorp/terraform/tfdiags"
 )
 
 // ConcreteResourceNodeFunc is a callback type used to convert an
@@ -446,6 +447,55 @@ func (n *NodeAbstractResource) DotNode(name string, opts *dag.DotOpts) *dag.DotN
 	}
 }
 
+// WriteResourceState ensures that a suitable resource-level state record is
+// present in the state, if that's required for the "each mode" of that
+// resource.
+//å
+// This is important primarily for the situation where count = 0, since this
+// eval is the only change we get to set the resource "each mode" to list
+// in that case, allowing expression evaluation to see it as a zero-element list
+// rather than as not set at all.
+func (n *NodeAbstractResource) WriteResourceState(ctx EvalContext, addr addrs.AbsResource) error {
+	var diags tfdiags.Diagnostics
+	state := ctx.State()
+
+	// We'll record our expansion decision in the shared "expander" object
+	// so that later operations (i.e. DynamicExpand and expression evaluation)
+	// can refer to it. Since this node represents the abstract module, we need
+	// to expand the module here to create all resources.
+	expander := ctx.InstanceExpander()
+
+	switch {
+	case n.Config.Count != nil:
+		count, countDiags := evaluateCountExpression(n.Config.Count, ctx)
+		diags = diags.Append(countDiags)
+		if countDiags.HasErrors() {
+			return diags.Err()
+		}
+
+		state.SetResourceProvider(addr, n.ResolvedProvider)
+		expander.SetResourceCount(addr.Module, n.Addr.Resource, count)
+
+	case n.Config.ForEach != nil:
+		forEach, forEachDiags := evaluateForEachExpression(n.Config.ForEach, ctx)
+		diags = diags.Append(forEachDiags)
+		if forEachDiags.HasErrors() {
+			return diags.Err()
+		}
+
+		// This method takes care of all of the business logic of updating this
+		// while ensuring that any existing instances are preserved, etc.
+		state.SetResourceProvider(addr, n.ResolvedProvider)
+		expander.SetResourceForEach(addr.Module, n.Addr.Resource, forEach)
+
+	default:
+		state.SetResourceProvider(addr, n.ResolvedProvider)
+		expander.SetResourceSingle(addr.Module, n.Addr.Resource)
+	}
+
+	return nil
+}
+
 // graphNodesAreResourceInstancesInDifferentInstancesOfSameModule is an
 // annoyingly-task-specific helper function that returns true if and only if
 // the following conditions hold:

terraform/node_resource_apply.go

@@ -6,7 +6,6 @@ import (
 	"github.com/hashicorp/terraform/addrs"
 	"github.com/hashicorp/terraform/dag"
 	"github.com/hashicorp/terraform/lang"
-	"github.com/hashicorp/terraform/tfdiags"
 )
 
 // nodeExpandApplyableResource handles the first layer of resource
@@ -109,41 +108,6 @@ func (n *NodeApplyableResource) Execute(ctx EvalContext, op walkOperation) error
 		return nil
 	}
 
-	var diags tfdiags.Diagnostics
-	state := ctx.State()
-
-	// We'll record our expansion decision in the shared "expander" object
-	// so that later operations (i.e. DynamicExpand and expression evaluation)
-	// can refer to it. Since this node represents the abstract module, we need
-	// to expand the module here to create all resources.
-	expander := ctx.InstanceExpander()
-
-	switch {
-	case n.Config.Count != nil:
-		count, countDiags := evaluateCountExpression(n.Config.Count, ctx)
-		diags = diags.Append(countDiags)
-		if countDiags.HasErrors() {
-			return diags.Err()
-		}
-
-		state.SetResourceProvider(n.Addr, n.ResolvedProvider)
-		expander.SetResourceCount(n.Addr.Module, n.Addr.Resource, count)
-
-	case n.Config.ForEach != nil:
-		forEach, forEachDiags := evaluateForEachExpression(n.Config.ForEach, ctx)
-		diags = diags.Append(forEachDiags)
-		if forEachDiags.HasErrors() {
-			return diags.Err()
-		}
-
-		// This method takes care of all of the business logic of updating this
-		// while ensuring that any existing instances are preserved, etc.
-		state.SetResourceProvider(n.Addr, n.ResolvedProvider)
-		expander.SetResourceForEach(n.Addr.Module, n.Addr.Resource, forEach)
-
-	default:
-		state.SetResourceProvider(n.Addr, n.ResolvedProvider)
-		expander.SetResourceSingle(n.Addr.Module, n.Addr.Resource)
-	}
-	return nil
+	err := n.WriteResourceState(ctx, n.Addr)
+	return err
 }

terraform/node_resource_plan.go

@@ -185,43 +185,8 @@ func (n *NodePlannableResource) Execute(ctx EvalContext, op walkOperation) error
 		return nil
 	}
 
-	var diags tfdiags.Diagnostics
-	state := ctx.State()
-
-	// We'll record our expansion decision in the shared "expander" object
-	// so that later operations (i.e. DynamicExpand and expression evaluation)
-	// can refer to it. Since this node represents the abstract module, we need
-	// to expand the module here to create all resources.
-	expander := ctx.InstanceExpander()
-
-	switch {
-	case n.Config.Count != nil:
-		count, countDiags := evaluateCountExpression(n.Config.Count, ctx)
-		diags = diags.Append(countDiags)
-		if countDiags.HasErrors() {
-			return diags.Err()
-		}
-
-		state.SetResourceProvider(n.Addr, n.ResolvedProvider)
-		expander.SetResourceCount(n.Addr.Module, n.Addr.Resource, count)
-
-	case n.Config.ForEach != nil:
-		forEach, forEachDiags := evaluateForEachExpression(n.Config.ForEach, ctx)
-		diags = diags.Append(forEachDiags)
-		if forEachDiags.HasErrors() {
-			return diags.Err()
-		}
-
-		// This method takes care of all of the business logic of updating this
-		// while ensuring that any existing instances are preserved, etc.
-		state.SetResourceProvider(n.Addr, n.ResolvedProvider)
-		expander.SetResourceForEach(n.Addr.Module, n.Addr.Resource, forEach)
-
-	default:
-		state.SetResourceProvider(n.Addr, n.ResolvedProvider)
-		expander.SetResourceSingle(n.Addr.Module, n.Addr.Resource)
-	}
-	return nil
+	err := n.WriteResourceState(ctx, n.Addr)
+	return err
 }
 
 // GraphNodeDestroyerCBD