feat: Edit option in block context menu

src/actions/clipboard.ts

@@ -27,7 +27,7 @@ const createSerializedKey = ShortcutRegistry.registry.createSerializedKey.bind(
  * menu; changing individual weights relative to base weight can change
  * the order within the clipboard group.
  */
-const BASE_WEIGHT = 11;
+const BASE_WEIGHT = 12;
 
 /**
  * Logic and state for cut/copy/paste actions as both keyboard shortcuts

src/actions/delete.ts

@@ -132,7 +132,7 @@ export class DeleteAction {
       },
       scopeType: ContextMenuRegistry.ScopeType.BLOCK,
       id: 'blockDeleteFromContextMenu',
-      weight: 10,
+      weight: 11,
     };
 
     ContextMenuRegistry.registry.register(deleteItem);

src/actions/edit.ts

@@ -0,0 +1,87 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import {
+  Connection,
+  ContextMenuRegistry,
+  ShortcutRegistry,
+  comments,
+  utils as BlocklyUtils,
+} from 'blockly';
+import * as Constants from '../constants';
+import type {BlockSvg, WorkspaceSvg} from 'blockly';
+import {LineCursor} from '../line_cursor';
+import {NavigationController} from '../navigation_controller';
+
+const KeyCodes = BlocklyUtils.KeyCodes;
+
+/**
+ * Action to edit a block.  This just moves the cursor to the first
+ * field or input (if there is one), and exists as an aid to
+ * navigational discoverability:
+ *
+ * Any time there is a cursor position that can be accessed by
+ * pressing the right-arrow key, which isn't accessible by pressing
+ * the down-arrow key (these positions are typically fields and value
+ * inputs), a context menu item "Edit Block contents (→︎)" will be
+ * shown in the block context menu.
+ *
+ * N.B.: This item is shown any time the cursor is on a block and not
+ * in the rightmost position 'on the current line'; that means that
+ * sometimes the label ("Edit block contents") is possibly misleading,
+ * because it might not be the contents of the _current_ block that's
+ * being edited, but rather that of a sibling or parent block.
+ *
+ * This action registers itself only as a context menu item, as there
+ * is already a corresponding "right" shortcut item.
+ */
+export class EditAction {
+  constructor(private canCurrentlyNavigate: (ws: WorkspaceSvg) => boolean) {}
+
+  /**
+   * Install this action as a context menu item.
+   */
+  install() {
+    this.registerContextMenuAction();
+  }
+
+  /**
+   * Uninstall this action as both a keyboard shortcut and a context menu item.
+   * Reinstall the original context menu action if possible.
+   */
+  uninstall() {
+    ContextMenuRegistry.registry.unregister('edit');
+  }
+
+  /**
+   * Register the edit block action as a context menu item on blocks.
+   */
+  private registerContextMenuAction() {
+    const editAboveItem: ContextMenuRegistry.RegistryItem = {
+      displayText: 'Edit Block contents (→︎)',
+      preconditionFn: (scope: ContextMenuRegistry.Scope) => {
+        const workspace = scope.block?.workspace;
+        if (!workspace || !this.canCurrentlyNavigate(workspace)) {
+          return 'disabled';
+        }
+        const cursor = workspace.getCursor() as LineCursor | null;
+        if (!cursor) return 'disabled';
+        return cursor.atEndOfLine() ? 'hidden' : 'enabled';
+      },
+      callback: (scope: ContextMenuRegistry.Scope) => {
+        const workspace = scope.block?.workspace;
+        if (!workspace) return false;
+        workspace.getCursor()?.in();
+        return true;
+      },
+      scopeType: ContextMenuRegistry.ScopeType.BLOCK,
+      id: 'edit',
+      weight: 10,
+    };
+
+    ContextMenuRegistry.registry.register(editAboveItem);
+  }
+}

src/line_cursor.ts

@@ -175,6 +175,22 @@ export class LineCursor extends Marker {
     return newNode;
   }
 
+  /**
+   * Returns true iff the node to which we would navigate if in() were
+   * called, which will be a validInLineNode, is also a validLineNode
+   * - in effect, if the LineCursor is at the end of the 'current
+   * line' of the program.
+   */
+  public atEndOfLine(): boolean {
+    const curNode = this.getCurNode();
+    if (!curNode) return false;
+    const rightNode = this.getNextNode(
+      curNode,
+      this.validInLineNode.bind(this),
+    );
+    return this.validLineNode(rightNode);
+  }
+
   /**
    * Returns true iff the given node represents the "beginning of a
    * new line of code" (and thus can be visited by pressing the

src/navigation_controller.ts

@@ -22,13 +22,14 @@ import {
 } from 'blockly/core';
 
 import * as Constants from './constants';
-import {Navigation} from './navigation';
 import {Announcer} from './announcer';
-import {LineCursor} from './line_cursor';
-import {ShortcutDialog} from './shortcut_dialog';
+import {Clipboard} from './actions/clipboard';
 import {DeleteAction} from './actions/delete';
+import {EditAction} from './actions/edit';
 import {InsertAction} from './actions/insert';
-import {Clipboard} from './actions/clipboard';
+import {LineCursor} from './line_cursor';
+import {Navigation} from './navigation';
+import {ShortcutDialog} from './shortcut_dialog';
 import {WorkspaceMovement} from './actions/ws_movement';
 
 const KeyCodes = BlocklyUtils.KeyCodes;
@@ -50,6 +51,9 @@ export class NavigationController {
     this.canCurrentlyEdit.bind(this),
   );
 
+  /** Context menu and keyboard action for deletion. */
+  editAction: EditAction = new EditAction(this.canCurrentlyEdit.bind(this));
+
   /** Context menu and keyboard action for insertion. */
   insertAction: InsertAction = new InsertAction(
     this.navigation,
@@ -678,6 +682,7 @@ export class NavigationController {
       ShortcutRegistry.registry.register(shortcut);
     }
     this.deleteAction.install();
+    this.editAction.install();
     this.insertAction.install();
     this.workspaceMovement.install();
 
@@ -698,6 +703,7 @@ export class NavigationController {
     }
 
     this.deleteAction.uninstall();
+    this.editAction.uninstall();
     this.insertAction.uninstall();
     this.clipboard.uninstall();
     this.workspaceMovement.uninstall();