do not create delete change for nonexistent output

If there are outputs in configuration, a destroy plan will always contain a "delete" change for each of these outputs.

This leads to meaningless delete changes being present for outputs which were not present in state and therefore cannot be deleted. Since there is a change in the plan, this plan will then be considered applyable, and the user will be presented with text instructing them to apply a plan in which there are no actual changes.

This commit stops the above from happening in the case of root module outputs.

Author: kmoe

internal/terraform/node_output.go

@@ -5,6 +5,8 @@ import (
 	"log"
 
 	"github.com/hashicorp/hcl/v2"
+	"github.com/zclconf/go-cty/cty"
+
 	"github.com/hashicorp/terraform/internal/addrs"
 	"github.com/hashicorp/terraform/internal/configs"
 	"github.com/hashicorp/terraform/internal/dag"
@@ -13,7 +15,6 @@ import (
 	"github.com/hashicorp/terraform/internal/plans"
 	"github.com/hashicorp/terraform/internal/states"
 	"github.com/hashicorp/terraform/internal/tfdiags"
-	"github.com/zclconf/go-cty/cty"
 )
 
 // nodeExpandOutput is the placeholder for a non-root module output that has
@@ -413,12 +414,14 @@ func (n *NodeDestroyableOutput) Execute(ctx EvalContext, op walkOperation) tfdia
 	before := cty.NullVal(cty.DynamicPseudoType)
 	mod := state.Module(n.Addr.Module)
 	if n.Addr.Module.IsRoot() && mod != nil {
-		for name, o := range mod.OutputValues {
-			if name == n.Addr.OutputValue.Name {
-				sensitiveBefore = o.Sensitive
-				before = o.Value
-				break
-			}
+		if o, ok := mod.OutputValues[n.Addr.OutputValue.Name]; ok {
+			sensitiveBefore = o.Sensitive
+			before = o.Value
+		} else {
+			// If the output was not in state, a delete change would
+			// be meaningless, so exit early.
+			return nil
+
 		}
 	}
 

internal/terraform/node_output_test.go

@@ -5,11 +5,12 @@ import (
 	"testing"
 
 	"github.com/hashicorp/hcl/v2"
+	"github.com/zclconf/go-cty/cty"
+
 	"github.com/hashicorp/terraform/internal/addrs"
 	"github.com/hashicorp/terraform/internal/configs"
 	"github.com/hashicorp/terraform/internal/lang/marks"
 	"github.com/hashicorp/terraform/internal/states"
-	"github.com/zclconf/go-cty/cty"
 )
 
 func TestNodeApplyableOutputExecute_knownValue(t *testing.T) {
@@ -160,3 +161,22 @@ func TestNodeDestroyableOutputExecute(t *testing.T) {
 		t.Fatal("Unexpected outputs in state after removal")
 	}
 }
+
+func TestNodeDestroyableOutputExecute_notInState(t *testing.T) {
+	outputAddr := addrs.OutputValue{Name: "foo"}.Absolute(addrs.RootModuleInstance)
+
+	state := states.NewState()
+
+	ctx := &MockEvalContext{
+		StateState: state.SyncWrapper(),
+	}
+	node := NodeDestroyableOutput{Addr: outputAddr}
+
+	diags := node.Execute(ctx, walkApply)
+	if diags.HasErrors() {
+		t.Fatalf("Unexpected error: %s", diags.Err())
+	}
+	if state.OutputValue(outputAddr) != nil {
+		t.Fatal("Unexpected outputs in state after removal")
+	}
+}