refactor(events): Introduce and use event type predicates (#8538)

* refactor(events): Introduce type predicates for event classes

  Introduce predicates for testing Abstract event subclasses based on
  their .type properties.  These are useful because there are places
  where it is not possible to use instanceof <ClassConstructor> tests
  for type narrowing due to load ordering issues that would be caused
  by the need to import (rather than just import type) the class
  constructors in question.

* refactor(events): Use event type predicates

  Simplify several sections of code by using type predicates for
  type narrowing and thereby avoiding the need for explicit casts.

* chore(events): Fix copyright date of recently-added files

* chore: Remove unused import

core/bump_objects.ts

@@ -13,7 +13,7 @@ import type {BlockMove} from './events/events_block_move.js';
 import type {CommentCreate} from './events/events_comment_create.js';
 import type {CommentMove} from './events/events_comment_move.js';
 import type {CommentResize} from './events/events_comment_resize.js';
-import type {ViewportChange} from './events/events_viewport.js';
+import {isViewportChange} from './events/predicates.js';
 import {BUMP_EVENTS, EventType} from './events/type.js';
 import * as eventUtils from './events/utils.js';
 import type {IBoundedElement} from './interfaces/i_bounded_element.js';
@@ -128,13 +128,8 @@ export function bumpIntoBoundsHandler(
         );
       }
       eventUtils.setGroup(existingGroup);
-    } else if (e.type === EventType.VIEWPORT_CHANGE) {
-      const viewportEvent = e as ViewportChange;
-      if (
-        viewportEvent.scale &&
-        viewportEvent.oldScale &&
-        viewportEvent.scale > viewportEvent.oldScale
-      ) {
+    } else if (isViewportChange(e)) {
+      if (e.scale && e.oldScale && e.scale > e.oldScale) {
         bumpTopObjectsIntoBounds(workspace);
       }
     }

core/events/predicates.ts

@@ -0,0 +1,172 @@
+/**
+ * @license
+ * Copyright 2024 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @file Predicates for testing Abstract event subclasses based on
+ * their .type properties.  These are useful because there are places
+ * where it is not possible to use instanceof <ClassConstructor> tests
+ * for type narrowing due to load ordering issues that would be caused
+ * by the need to import (rather than just import type) the class
+ * constructors in question.
+ */
+
+import type {Abstract} from './events_abstract.js';
+import type {BlockChange} from './events_block_change.js';
+import type {BlockCreate} from './events_block_create.js';
+import type {BlockDelete} from './events_block_delete.js';
+import type {BlockDrag} from './events_block_drag.js';
+import type {BlockFieldIntermediateChange} from './events_block_field_intermediate_change.js';
+import type {BlockMove} from './events_block_move.js';
+import type {BubbleOpen} from './events_bubble_open.js';
+import type {Click} from './events_click.js';
+import type {CommentChange} from './events_comment_change.js';
+import type {CommentCollapse} from './events_comment_collapse.js';
+import type {CommentCreate} from './events_comment_create.js';
+import type {CommentDelete} from './events_comment_delete.js';
+import type {CommentDrag} from './events_comment_drag.js';
+import type {CommentMove} from './events_comment_move.js';
+import type {CommentResize} from './events_comment_resize.js';
+import type {MarkerMove} from './events_marker_move.js';
+import type {Selected} from './events_selected.js';
+import type {ThemeChange} from './events_theme_change.js';
+import type {ToolboxItemSelect} from './events_toolbox_item_select.js';
+import type {TrashcanOpen} from './events_trashcan_open.js';
+import type {VarCreate} from './events_var_create.js';
+import type {VarDelete} from './events_var_delete.js';
+import type {VarRename} from './events_var_rename.js';
+import type {ViewportChange} from './events_viewport.js';
+import type {FinishedLoading} from './workspace_events.js';
+
+import {EventType} from './type.js';
+
+/** @returns true iff event.type is EventType.BLOCK_CREATE */
+export function isBlockCreate(event: Abstract): event is BlockCreate {
+  return event.type === EventType.BLOCK_CREATE;
+}
+
+/** @returns true iff event.type is EventType.BLOCK_DELETE */
+export function isBlockDelete(event: Abstract): event is BlockDelete {
+  return event.type === EventType.BLOCK_DELETE;
+}
+
+/** @returns true iff event.type is EventType.BLOCK_CHANGE */
+export function isBlockChange(event: Abstract): event is BlockChange {
+  return event.type === EventType.BLOCK_CHANGE;
+}
+
+/** @returns true iff event.type is EventType.BLOCK_FIELD_INTERMEDIATE_CHANGE */
+export function isBlockFieldIntermediateChange(
+  event: Abstract,
+): event is BlockFieldIntermediateChange {
+  return event.type === EventType.BLOCK_FIELD_INTERMEDIATE_CHANGE;
+}
+
+/** @returns true iff event.type is EventType.BLOCK_MOVE */
+export function isBlockMove(event: Abstract): event is BlockMove {
+  return event.type === EventType.BLOCK_MOVE;
+}
+
+/** @returns true iff event.type is EventType.VAR_CREATE */
+export function isVarCreate(event: Abstract): event is VarCreate {
+  return event.type === EventType.VAR_CREATE;
+}
+
+/** @returns true iff event.type is EventType.VAR_DELETE */
+export function isVarDelete(event: Abstract): event is VarDelete {
+  return event.type === EventType.VAR_DELETE;
+}
+
+/** @returns true iff event.type is EventType.VAR_RENAME */
+export function isVarRename(event: Abstract): event is VarRename {
+  return event.type === EventType.VAR_RENAME;
+}
+
+/** @returns true iff event.type is EventType.BLOCK_DRAG */
+export function isBlockDrag(event: Abstract): event is BlockDrag {
+  return event.type === EventType.BLOCK_DRAG;
+}
+
+/** @returns true iff event.type is EventType.SELECTED */
+export function isSelected(event: Abstract): event is Selected {
+  return event.type === EventType.SELECTED;
+}
+
+/** @returns true iff event.type is EventType.CLICK */
+export function isClick(event: Abstract): event is Click {
+  return event.type === EventType.CLICK;
+}
+
+/** @returns true iff event.type is EventType.MARKER_MOVE */
+export function isMarkerMove(event: Abstract): event is MarkerMove {
+  return event.type === EventType.MARKER_MOVE;
+}
+
+/** @returns true iff event.type is EventType.BUBBLE_OPEN */
+export function isBubbleOpen(event: Abstract): event is BubbleOpen {
+  return event.type === EventType.BUBBLE_OPEN;
+}
+
+/** @returns true iff event.type is EventType.TRASHCAN_OPEN */
+export function isTrashcanOpen(event: Abstract): event is TrashcanOpen {
+  return event.type === EventType.TRASHCAN_OPEN;
+}
+
+/** @returns true iff event.type is EventType.TOOLBOX_ITEM_SELECT */
+export function isToolboxItemSelect(
+  event: Abstract,
+): event is ToolboxItemSelect {
+  return event.type === EventType.TOOLBOX_ITEM_SELECT;
+}
+
+/** @returns true iff event.type is EventType.THEME_CHANGE */
+export function isThemeChange(event: Abstract): event is ThemeChange {
+  return event.type === EventType.THEME_CHANGE;
+}
+
+/** @returns true iff event.type is EventType.VIEWPORT_CHANGE */
+export function isViewportChange(event: Abstract): event is ViewportChange {
+  return event.type === EventType.VIEWPORT_CHANGE;
+}
+
+/** @returns true iff event.type is EventType.COMMENT_CREATE */
+export function isCommentCreate(event: Abstract): event is CommentCreate {
+  return event.type === EventType.COMMENT_CREATE;
+}
+
+/** @returns true iff event.type is EventType.COMMENT_DELETE */
+export function isCommentDelete(event: Abstract): event is CommentDelete {
+  return event.type === EventType.COMMENT_DELETE;
+}
+
+/** @returns true iff event.type is EventType.COMMENT_CHANGE */
+export function isCommentChange(event: Abstract): event is CommentChange {
+  return event.type === EventType.COMMENT_CHANGE;
+}
+
+/** @returns true iff event.type is EventType.COMMENT_MOVE */
+export function isCommentMove(event: Abstract): event is CommentMove {
+  return event.type === EventType.COMMENT_MOVE;
+}
+
+/** @returns true iff event.type is EventType.COMMENT_RESIZE */
+export function isCommentResize(event: Abstract): event is CommentResize {
+  return event.type === EventType.COMMENT_RESIZE;
+}
+
+/** @returns true iff event.type is EventType.COMMENT_DRAG */
+export function isCommentDrag(event: Abstract): event is CommentDrag {
+  return event.type === EventType.COMMENT_DRAG;
+}
+
+/** @returns true iff event.type is EventType.COMMENT_COLLAPSE */
+export function isCommentCollapse(event: Abstract): event is CommentCollapse {
+  return event.type === EventType.COMMENT_COLLAPSE;
+}
+
+/** @returns true iff event.type is EventType.FINISHED_LOADING */
+export function isFinishedLoading(event: Abstract): event is FinishedLoading {
+  return event.type === EventType.FINISHED_LOADING;
+}

core/events/type.ts

@@ -1,6 +1,6 @@
 /**
  * @license
- * Copyright 2021 Google LLC
+ * Copyright 2024 Google LLC
  * SPDX-License-Identifier: Apache-2.0
  */
 

core/events/utils.ts

@@ -13,13 +13,19 @@ import * as idGenerator from '../utils/idgenerator.js';
 import type {Workspace} from '../workspace.js';
 import type {WorkspaceSvg} from '../workspace_svg.js';
 import type {Abstract} from './events_abstract.js';
-import type {BlockChange} from './events_block_change.js';
 import type {BlockCreate} from './events_block_create.js';
 import type {BlockMove} from './events_block_move.js';
 import type {CommentCreate} from './events_comment_create.js';
 import type {CommentMove} from './events_comment_move.js';
 import type {CommentResize} from './events_comment_resize.js';
-import type {ViewportChange} from './events_viewport.js';
+import {
+  isBlockChange,
+  isBlockCreate,
+  isBlockMove,
+  isBubbleOpen,
+  isClick,
+  isViewportChange,
+} from './predicates.js';
 import {EventType} from './type.js';
 
 /** Group ID for new events.  Grouped events are indivisible. */
@@ -188,46 +194,35 @@ export function filter(queueIn: Abstract[], forward: boolean): Abstract[] {
         // move events.
         hash[key] = {event, index: i};
         mergedQueue.push(event);
-      } else if (
-        event.type === EventType.BLOCK_MOVE &&
-        lastEntry.index === i - 1
-      ) {
-        const moveEvent = event as BlockMove;
+      } else if (isBlockMove(event) && lastEntry.index === i - 1) {
         // Merge move events.
-        lastEvent.newParentId = moveEvent.newParentId;
-        lastEvent.newInputName = moveEvent.newInputName;
-        lastEvent.newCoordinate = moveEvent.newCoordinate;
-        if (moveEvent.reason) {
+        lastEvent.newParentId = event.newParentId;
+        lastEvent.newInputName = event.newInputName;
+        lastEvent.newCoordinate = event.newCoordinate;
+        if (event.reason) {
           if (lastEvent.reason) {
             // Concatenate reasons without duplicates.
-            const reasonSet = new Set(
-              moveEvent.reason.concat(lastEvent.reason),
-            );
+            const reasonSet = new Set(event.reason.concat(lastEvent.reason));
             lastEvent.reason = Array.from(reasonSet);
           } else {
-            lastEvent.reason = moveEvent.reason;
+            lastEvent.reason = event.reason;
           }
         }
         lastEntry.index = i;
       } else if (
-        event.type === EventType.BLOCK_CHANGE &&
-        (event as BlockChange).element === lastEvent.element &&
-        (event as BlockChange).name === lastEvent.name
+        isBlockChange(event) &&
+        event.element === lastEvent.element &&
+        event.name === lastEvent.name
       ) {
-        const changeEvent = event as BlockChange;
         // Merge change events.
-        lastEvent.newValue = changeEvent.newValue;
-      } else if (event.type === EventType.VIEWPORT_CHANGE) {
-        const viewportEvent = event as ViewportChange;
+        lastEvent.newValue = event.newValue;
+      } else if (isViewportChange(event)) {
         // Merge viewport change events.
-        lastEvent.viewTop = viewportEvent.viewTop;
-        lastEvent.viewLeft = viewportEvent.viewLeft;
-        lastEvent.scale = viewportEvent.scale;
-        lastEvent.oldScale = viewportEvent.oldScale;
-      } else if (
-        event.type === EventType.CLICK &&
-        lastEvent.type === EventType.BUBBLE_OPEN
-      ) {
+        lastEvent.viewTop = event.viewTop;
+        lastEvent.viewLeft = event.viewLeft;
+        lastEvent.scale = event.scale;
+        lastEvent.oldScale = event.oldScale;
+      } else if (isClick(event) && isBubbleOpen(lastEvent)) {
         // Drop click events caused by opening/closing bubbles.
       } else {
         // Collision: newer events should merge into this event to maintain
@@ -381,10 +376,7 @@ export function get(
  * @param event Custom data for event.
  */
 export function disableOrphans(event: Abstract) {
-  if (
-    event.type === EventType.BLOCK_MOVE ||
-    event.type === EventType.BLOCK_CREATE
-  ) {
+  if (isBlockMove(event) || isBlockCreate(event)) {
     const blockEvent = event as BlockMove | BlockCreate;
     if (!blockEvent.workspaceId) {
       return;

core/icons/mutator_icon.ts

@@ -11,6 +11,7 @@ import type {BlocklyOptions} from '../blockly_options.js';
 import {MiniWorkspaceBubble} from '../bubbles/mini_workspace_bubble.js';
 import type {Abstract} from '../events/events_abstract.js';
 import {BlockChange} from '../events/events_block_change.js';
+import {isBlockChange, isBlockCreate} from '../events/predicates.js';
 import {EventType} from '../events/type.js';
 import * as eventUtils from '../events/utils.js';
 import type {IHasBubble} from '../interfaces/i_has_bubble.js';
@@ -308,9 +309,8 @@ export class MutatorIcon extends Icon implements IHasBubble {
   static isIgnorableMutatorEvent(e: Abstract) {
     return (
       e.isUiEvent ||
-      e.type === EventType.BLOCK_CREATE ||
-      (e.type === EventType.BLOCK_CHANGE &&
-        (e as BlockChange).element === 'disabled')
+      isBlockCreate(e) ||
+      (isBlockChange(e) && e.element === 'disabled')
     );
   }
 

core/procedures.ts

@@ -15,6 +15,13 @@ import {Blocks} from './blocks.js';
 import * as common from './common.js';
 import type {Abstract} from './events/events_abstract.js';
 import type {BubbleOpen} from './events/events_bubble_open.js';
+import {
+  isBlockChange,
+  isBlockCreate,
+  isBlockDelete,
+  isBlockFieldIntermediateChange,
+  isBubbleOpen,
+} from './events/predicates.js';
 import {EventType} from './events/type.js';
 import * as eventUtils from './events/utils.js';
 import {Field, UnattachedFieldError} from './field.js';
@@ -355,9 +362,8 @@ function updateMutatorFlyout(workspace: WorkspaceSvg) {
  * @internal
  */
 export function mutatorOpenListener(e: Abstract) {
-  if (e.type !== EventType.BUBBLE_OPEN) {
-    return;
-  }
+  if (!isBubbleOpen(e)) return;
+
   const bubbleEvent = e as BubbleOpen;
   if (
     !(bubbleEvent.bubbleType === 'mutator' && bubbleEvent.isOpen) ||
@@ -387,10 +393,10 @@ export function mutatorOpenListener(e: Abstract) {
  */
 function mutatorChangeListener(e: Abstract) {
   if (
-    e.type !== EventType.BLOCK_CREATE &&
-    e.type !== EventType.BLOCK_DELETE &&
-    e.type !== EventType.BLOCK_CHANGE &&
-    e.type !== EventType.BLOCK_FIELD_INTERMEDIATE_CHANGE
+    !isBlockCreate(e) &&
+    !isBlockDelete(e) &&
+    !isBlockChange(e) &&
+    !isBlockFieldIntermediateChange(e)
   ) {
     return;
   }

core/trashcan.ts

@@ -17,8 +17,8 @@ import * as browserEvents from './browser_events.js';
 import {ComponentManager} from './component_manager.js';
 import {DeleteArea} from './delete_area.js';
 import type {Abstract} from './events/events_abstract.js';
-import type {BlockDelete} from './events/events_block_delete.js';
 import './events/events_trashcan_open.js';
+import {isBlockDelete} from './events/predicates.js';
 import {EventType} from './events/type.js';
 import * as eventUtils from './events/utils.js';
 import type {IAutoHideable} from './interfaces/i_autohideable.js';
@@ -604,30 +604,22 @@ export class Trashcan
   private onDelete(event: Abstract) {
     if (
       this.workspace.options.maxTrashcanContents <= 0 ||
-      event.type !== EventType.BLOCK_DELETE
+      !isBlockDelete(event) ||
+      event.wasShadow
     ) {
       return;
     }
-    const deleteEvent = event as BlockDelete;
-    if (event.type === EventType.BLOCK_DELETE && !deleteEvent.wasShadow) {
-      if (!deleteEvent.oldJson) {
-        throw new Error('Encountered a delete event without proper oldJson');
-      }
-      const cleanedJson = JSON.stringify(
-        this.cleanBlockJson(deleteEvent.oldJson),
-      );
-      if (this.contents.includes(cleanedJson)) {
-        return;
-      }
-      this.contents.unshift(cleanedJson);
-      while (
-        this.contents.length > this.workspace.options.maxTrashcanContents
-      ) {
-        this.contents.pop();
-      }
-
-      this.setMinOpenness(HAS_BLOCKS_LID_ANGLE);
+    if (!event.oldJson) {
+      throw new Error('Encountered a delete event without proper oldJson');
     }
+    const cleanedJson = JSON.stringify(this.cleanBlockJson(event.oldJson));
+    if (this.contents.includes(cleanedJson)) return;
+    this.contents.unshift(cleanedJson);
+    while (this.contents.length > this.workspace.options.maxTrashcanContents) {
+      this.contents.pop();
+    }
+
+    this.setMinOpenness(HAS_BLOCKS_LID_ANGLE);
   }
 
   /**