refactor(editor): refactor page note empty checker (#9570)

Close [BS-2320](https://linear.app/affine-design/issue/BS-2320/内容为空的状态判断)

blocksuite/affine/model/src/blocks/note/note-model.ts

@@ -111,6 +111,17 @@ export class NoteBlockModel
     if (!this._isSelectable()) return false;
     return super.intersectsBound(bound);
   }
+
+  override isEmpty(): boolean {
+    if (this.children.length === 0) return true;
+    if (this.children.length === 1) {
+      const firstChild = this.children[0];
+      if (firstChild.flavour === 'affine:paragraph') {
+        return firstChild.isEmpty();
+      }
+    }
+    return false;
+  }
 }
 
 declare global {

blocksuite/affine/model/src/blocks/paragraph/paragraph-model.ts

@@ -41,6 +41,10 @@ export class ParagraphBlockModel extends BlockModel<ParagraphProps> {
   override flavour!: 'affine:paragraph';
 
   override text!: Text;
+
+  override isEmpty(): boolean {
+    return this.text$.value.length === 0 && this.children.length === 0;
+  }
 }
 
 declare global {

blocksuite/affine/model/src/blocks/root/root-block-model.ts

@@ -22,6 +22,22 @@ export class RootBlockModel extends BlockModel<RootBlockProps> {
       });
     });
   }
+
+  /**
+   * A page is empty if it only contains one empty note and the canvas is empty
+   */
+  override isEmpty() {
+    let numNotes = 0;
+    let empty = true;
+    for (const child of this.children) {
+      empty = empty && child.isEmpty();
+
+      if (child.flavour === 'affine:note') numNotes++;
+      if (numNotes > 1) return false;
+    }
+
+    return empty;
+  }
 }
 
 export const RootBlockSchema = defineBlockSchema({

blocksuite/affine/shared/src/utils/dnd/get-drop-rect-by-point.ts

@@ -33,7 +33,7 @@ export function getDropRectByPoint(
     }
 
     let bounds = table.getBoundingClientRect();
-    if (model.isEmpty.value) {
+    if (model.children.length === 0) {
       result.flag = DropFlags.EmptyDatabase;
 
       if (point.y < bounds.top) return result;

blocksuite/blocks/src/root-block/page/page-root-block.ts

@@ -112,6 +112,10 @@ export class PageRootBlockComponent extends BlockComponent<
 
   clipboardController = new PageClipboard(this);
 
+  /**
+   * Focus the first paragraph in the default note block.
+   * If there is no paragraph, create one.
+   */
   focusFirstParagraph = () => {
     const defaultNote = this._getDefaultNoteBlock();
     const firstText = defaultNote?.children.find(block =>

blocksuite/framework/block-std/src/gfx/model/surface/surface-model.ts

@@ -103,6 +103,10 @@ export class SurfaceBlockModel extends BlockModel<SurfaceBlockProps> {
     return Object.keys(this._elementCtorMap);
   }
 
+  override isEmpty(): boolean {
+    return this._elementModels.size === 0 && this.children.length === 0;
+  }
+
   constructor() {
     super();
     this.created.once(() => this._init());

blocksuite/framework/store/src/model/block/block-model.ts

@@ -70,9 +70,9 @@ export class BlockModel<
 
   id!: string;
 
-  isEmpty = computed(() => {
-    return this._children.value.length === 0;
-  });
+  isEmpty() {
+    return this.children.length === 0;
+  }
 
   keys!: string[];
 

blocksuite/framework/store/src/model/blocks/blocks.ts

@@ -192,7 +192,7 @@ export class Blocks {
   }
 
   get isEmpty() {
-    return Object.values(this._blocks.peek()).length === 0;
+    return this.root?.isEmpty() ?? true;
   }
 
   get loaded() {

blocksuite/presets/src/__tests__/edgeless/basic.spec.ts

@@ -1,6 +1,8 @@
-import { beforeEach, expect, test } from 'vitest';
+import { LocalShapeElementModel } from '@blocksuite/affine-model';
+import { Text } from '@blocksuite/store';
+import { beforeEach, describe, expect, test } from 'vitest';
 
-import { getSurface } from '../utils/edgeless.js';
+import { addNote, getSurface } from '../utils/edgeless.js';
 import { setupEditor } from '../utils/setup.js';
 
 beforeEach(async () => {
@@ -16,3 +18,136 @@ test('basic assert', () => {
 
   expect(getSurface(window.doc, window.editor)).toBeDefined();
 });
+
+describe('doc / note empty checker', () => {
+  test('a paragraph is empty if it dose not contain text and child blocks', () => {
+    const noteId = addNote(doc);
+    const paragraphId = doc.addBlock('affine:paragraph', {}, noteId);
+    const paragraph = doc.getBlock(paragraphId)?.model;
+    expect(paragraph?.isEmpty()).toBe(true);
+  });
+
+  test('a paragraph is not empty if it contains text', () => {
+    const noteId = addNote(doc);
+    const paragraphId = doc.addBlock(
+      'affine:paragraph',
+      {
+        text: new Text('hello'),
+      },
+      noteId
+    );
+    const paragraph = doc.getBlock(paragraphId)?.model;
+    expect(paragraph?.isEmpty()).toBe(false);
+  });
+
+  test('a paragraph is not empty if it contains children blocks', () => {
+    const noteId = addNote(doc);
+    const paragraphId = doc.addBlock('affine:paragraph', {}, noteId);
+    const paragraph = doc.getBlock(paragraphId)?.model;
+
+    // sub paragraph
+    doc.addBlock('affine:paragraph', {}, paragraphId);
+    expect(paragraph?.isEmpty()).toBe(false);
+  });
+
+  test('a note is empty if it dose not contain any blocks', () => {
+    const noteId = addNote(doc);
+    const note = doc.getBlock(noteId)!.model;
+    note.children.forEach(child => {
+      doc.deleteBlock(child);
+    });
+    expect(note.children.length).toBe(0);
+    expect(note.isEmpty()).toBe(true);
+  });
+
+  test('a note is empty if it only contains a empty paragraph', () => {
+    // `addNote` will create a empty paragraph
+    const noteId = addNote(doc);
+    const note = doc.getBlock(noteId)!.model;
+    expect(note.isEmpty()).toBe(true);
+  });
+
+  test('a note is not empty if it contains multi blocks', () => {
+    const noteId = addNote(doc);
+    const note = doc.getBlock(noteId)!.model;
+    doc.addBlock('affine:paragraph', {}, noteId);
+    expect(note.isEmpty()).toBe(false);
+  });
+
+  test('a surface is empty if it dose not contains any element or blocks', () => {
+    const surface = getSurface(doc, editor).model;
+    expect(surface.isEmpty()).toBe(true);
+
+    const shapeId = surface.addElement({
+      type: 'shape',
+    });
+    expect(surface.isEmpty()).toBe(false);
+    surface.deleteElement(shapeId);
+    expect(surface.isEmpty()).toBe(true);
+
+    const frameId = doc.addBlock('affine:frame', {}, surface.id);
+    const frame = doc.getBlock(frameId)!.model;
+    expect(surface.isEmpty()).toBe(false);
+    doc.deleteBlock(frame);
+    expect(surface.isEmpty()).toBe(true);
+  });
+
+  test('a surface is empty if it only contains local elements', () => {
+    const surface = getSurface(doc, editor).model;
+    const localShape = new LocalShapeElementModel(surface);
+    surface.addLocalElement(localShape);
+    expect(surface.isEmpty()).toBe(true);
+  });
+
+  test('a just initialized doc is empty', () => {
+    expect(doc.isEmpty).toBe(true);
+    expect(editor.rootModel.isEmpty()).toBe(true);
+  });
+
+  test('a doc is empty if it only contains a note', () => {
+    addNote(doc);
+    expect(doc.isEmpty).toBe(true);
+
+    addNote(doc);
+    expect(
+      doc.isEmpty,
+      'a doc is not empty if it contains multi-notes'
+    ).toBeFalsy();
+  });
+
+  test('a note is empty if its children array is empty', () => {
+    const noteId = addNote(doc);
+    const note = doc.getBlock(noteId)?.model;
+    note?.children.forEach(child => doc.deleteBlock(child));
+    expect(note?.children.length === 0).toBe(true);
+    expect(note?.isEmpty()).toBe(true);
+  });
+
+  test('a doc is empty if its only contains an empty note and an empty surface', () => {
+    const noteId = addNote(doc);
+    const note = doc.getBlock(noteId)!.model;
+    expect(doc.isEmpty).toBe(true);
+
+    const newNoteId = addNote(doc);
+    const newNote = doc.getBlock(newNoteId)!.model;
+    expect(doc.isEmpty).toBe(false);
+    doc.deleteBlock(newNote);
+    expect(doc.isEmpty).toBe(true);
+
+    const newParagraphId = doc.addBlock('affine:paragraph', {}, note);
+    const newParagraph = doc.getBlock(newParagraphId)!.model;
+    expect(doc.isEmpty).toBe(false);
+    doc.deleteBlock(newParagraph);
+    expect(doc.isEmpty).toBe(true);
+
+    const surface = getSurface(doc, editor).model;
+    expect(doc.isEmpty).toBe(true);
+
+    const shapeId = surface.addElement({
+      type: 'shape',
+    });
+    expect(doc.isEmpty).toBe(false);
+    surface.deleteElement(shapeId);
+    expect(doc.isEmpty).toBe(true);
+  });
+});

blocksuite/presets/src/fragments/doc-title/doc-title.ts

@@ -61,9 +61,8 @@ export class DocTitle extends WithDisposable(ShadowlessElement) {
 
   private readonly _onTitleKeyDown = (event: KeyboardEvent) => {
     if (event.isComposing || this.doc.readonly) return;
-    const hasContent = !this.doc.isEmpty;
 
-    if (event.key === 'Enter' && hasContent && !event.isComposing) {
+    if (event.key === 'Enter' && this._pageRoot) {
       event.preventDefault();
       event.stopPropagation();
 
@@ -73,10 +72,10 @@ export class DocTitle extends WithDisposable(ShadowlessElement) {
         const rightText = this._rootModel.title.split(inlineRange.index);
         this._pageRoot.prependParagraphWithText(rightText);
       }
-    } else if (event.key === 'ArrowDown' && hasContent) {
+    } else if (event.key === 'ArrowDown') {
       event.preventDefault();
       event.stopPropagation();
-      this._pageRoot.focusFirstParagraph();
+      this._pageRoot?.focusFirstParagraph();
     } else if (event.key === 'Tab') {
       event.preventDefault();
       event.stopPropagation();
@@ -94,9 +93,7 @@ export class DocTitle extends WithDisposable(ShadowlessElement) {
   }
 
   private get _pageRoot() {
-    const pageRoot = this._viewport.querySelector('affine-page-root');
-    assertExists(pageRoot);
-    return pageRoot;
+    return this._viewport.querySelector('affine-page-root');
   }
 
   private get _rootModel() {

blocksuite/presets/src/fragments/outline/card/outline-card.ts

@@ -9,7 +9,7 @@ import {
 import { SignalWatcher, WithDisposable } from '@blocksuite/global/utils';
 import type { BlockModel, Blocks } from '@blocksuite/store';
 import { baseTheme } from '@toeverything/theme';
-import { css, html, LitElement, nothing, unsafeCSS } from 'lit';
+import { css, html, LitElement, unsafeCSS } from 'lit';
 import { property, query, state } from 'lit/decorators.js';
 import { classMap } from 'lit/directives/class-map.js';
 
@@ -286,7 +286,7 @@ export class OutlineNoteCard extends SignalWatcher(WithDisposable(LitElement)) {
     }
   }
 
-  override firstUpdated() {
+  override updated() {
     this._displayModePopper = createButtonPopper(
       this._displayModeButtonGroup,
       this._displayModePanel,
@@ -303,8 +303,6 @@ export class OutlineNoteCard extends SignalWatcher(WithDisposable(LitElement)) {
   }
 
   override render() {
-    if (this.note.isEmpty.peek()) return nothing;
-
     const { children, displayMode } = this.note;
     const currentMode = this._getCurrentModeLabel(displayMode);
     const cardHeaderClasses = classMap({