helper/resource: Add terraform plan output to TRACE logging

.changelog/1058.txt

@@ -0,0 +1,3 @@
+```release-note:enhancement
+helper/resource: Added `terraform plan` output to `TRACE` logging
+```

internal/logging/keys.go

@@ -49,6 +49,9 @@ const (
 	// The path to the Terraform CLI used for an acceptance test.
 	KeyTestTerraformPath = "test_terraform_path"
 
+	// Terraform plan output generated during a TestStep.
+	KeyTestTerraformPlan = "test_terraform_plan"
+
 	// The working directory of the acceptance test.
 	KeyTestWorkingDirectory = "test_working_directory"
 )

internal/plugintest/working_dir.go

@@ -174,23 +174,59 @@ func (wd *WorkingDir) planFilename() string {
 func (wd *WorkingDir) CreatePlan(ctx context.Context) error {
 	logging.HelperResourceTrace(ctx, "Calling Terraform CLI plan command")
 
-	_, err := wd.tf.Plan(context.Background(), tfexec.Reattach(wd.reattachInfo), tfexec.Refresh(false), tfexec.Out(PlanFileName))
+	hasChanges, err := wd.tf.Plan(context.Background(), tfexec.Reattach(wd.reattachInfo), tfexec.Refresh(false), tfexec.Out(PlanFileName))
 
 	logging.HelperResourceTrace(ctx, "Called Terraform CLI plan command")
 
-	return err
+	if err != nil {
+		return err
+	}
+
+	if !hasChanges {
+		logging.HelperResourceTrace(ctx, "Created plan with no changes")
+
+		return nil
+	}
+
+	stdout, err := wd.SavedPlanRawStdout(ctx)
+
+	if err != nil {
+		return fmt.Errorf("error retrieving formatted plan output: %w", err)
+	}
+
+	logging.HelperResourceTrace(ctx, "Created plan with changes", map[string]any{logging.KeyTestTerraformPlan: stdout})
+
+	return nil
 }
 
 // CreateDestroyPlan runs "terraform plan -destroy" to create a saved plan
 // file, which if successful will then be used for the next call to Apply.
 func (wd *WorkingDir) CreateDestroyPlan(ctx context.Context) error {
 	logging.HelperResourceTrace(ctx, "Calling Terraform CLI plan -destroy command")
 
-	_, err := wd.tf.Plan(context.Background(), tfexec.Reattach(wd.reattachInfo), tfexec.Refresh(false), tfexec.Out(PlanFileName), tfexec.Destroy(true))
+	hasChanges, err := wd.tf.Plan(context.Background(), tfexec.Reattach(wd.reattachInfo), tfexec.Refresh(false), tfexec.Out(PlanFileName), tfexec.Destroy(true))
 
 	logging.HelperResourceTrace(ctx, "Called Terraform CLI plan -destroy command")
 
-	return err
+	if err != nil {
+		return err
+	}
+
+	if !hasChanges {
+		logging.HelperResourceTrace(ctx, "Created destroy plan with no changes")
+
+		return nil
+	}
+
+	stdout, err := wd.SavedPlanRawStdout(ctx)
+
+	if err != nil {
+		return fmt.Errorf("error retrieving formatted plan output: %w", err)
+	}
+
+	logging.HelperResourceTrace(ctx, "Created destroy plan with changes", map[string]any{logging.KeyTestTerraformPlan: stdout})
+
+	return nil
 }
 
 // Apply runs "terraform apply". If CreatePlan has previously completed