feat(sgterraform): add support for "forget" action in terraform summary

Terraform is able to forget about resources (meaning remove from state
but leave real resource untouched) so we add support for this action.

Author: alethenorio

tools/sgterraform/tfplan.go

@@ -45,6 +45,9 @@ const (
 
 	// ActionDelete denotes a delete operation.
 	ActionDelete Action = "delete"
+
+	// ActionForget denotes a forget operation.
+	ActionForget Action = "forget"
 )
 
 // Actions denotes a valid change type.
@@ -124,3 +127,12 @@ func (a Actions) CreateBeforeDestroy() bool {
 func (a Actions) Replace() bool {
 	return a.DestroyBeforeCreate() || a.CreateBeforeDestroy()
 }
+
+// Forget is true if this set of Actions denotes a forget operation.
+func (a Actions) Forget() bool {
+	if len(a) != 1 {
+		return false
+	}
+
+	return a[0] == ActionForget
+}

tools/sgterraform/tools.go

@@ -181,6 +181,7 @@ func getCommentSummary(ctx context.Context, planFilePath string) (statusIcon, su
 	destroy := TfChange{actionName: "Destroy", changes: make(map[string]int), actionCount: 0}
 	update := TfChange{actionName: "Update", changes: make(map[string]int), actionCount: 0}
 	replace := TfChange{actionName: "Replace", changes: make(map[string]int), actionCount: 0}
+	forget := TfChange{actionName: "Forget", changes: make(map[string]int), actionCount: 0}
 	for _, res := range jsonPlan.ResourceChanges {
 		actions := res.Change.Actions
 		resourceType := res.Type
@@ -193,13 +194,17 @@ func getCommentSummary(ctx context.Context, planFilePath string) (statusIcon, su
 			update.add(resourceType)
 		case actions.Replace():
 			replace.add(resourceType)
+		case actions.Forget():
+			forget.add(resourceType)
 		case
 			actions.NoOp(),
 			actions.Read():
 			// Do nothing
 			continue
 		default:
-			sg.Logger(ctx).Fatal(fmt.Errorf("unable to determine resource operation: %v", res))
+			sg.Logger(ctx).Fatal(
+				fmt.Errorf("unable to build a terraform plan summary due to unknown actions (%v) on resource: %v", actions, res),
+			)
 		}
 	}
 
@@ -212,14 +217,15 @@ func getCommentSummary(ctx context.Context, planFilePath string) (statusIcon, su
 	}
 
 	summary = fmt.Sprintf(`
-Plan Summary: %d to create, %d to update, %d to replace, %d to destroy.
+Plan Summary: %d to create, %d to update, %d to replace, %d to destroy, %d to forget.
 <br/>
 %s
 `,
 		create.actionCount,
 		update.actionCount,
 		replace.actionCount,
 		destroy.actionCount,
+		forget.actionCount,
 		mapToHTMLList([]TfChange{create, destroy, update, replace}),
 	)