fix(editor): notion text adapter should handle text without styles correctly (#12248)

Closes: [BS-3486](https://linear.app/affine-design/issue/BS-3486/粘贴从-notion-复制的内容出错)

<!-- This is an auto-generated comment: release notes by coderabbit.ai -->

## Summary by CodeRabbit

- **Bug Fixes**
  - Improved handling of Notion text segments with empty or invalid style arrays, ensuring plain text and styled text are both processed correctly and preventing errors from malformed input.
- **Tests**
  - Added a test case to verify correct conversion of Notion text with empty styles arrays.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

blocksuite/affine/all/src/__tests__/adapters/notion-text.unit.spec.ts

@@ -106,4 +106,65 @@ describe('notion-text to snapshot', () => {
     });
     expect(nanoidReplacement(target!)).toEqual(sliceSnapshot);
   });
+
+  test('notion text with empty styles array', () => {
+    const notionText =
+      '{"blockType":"text","editing":[["a "],["bold text",[["b"]]],[" hello world"]],"selection":{"startIndex":0,"endIndex":23},"action":"copy"}';
+
+    const sliceSnapshot: SliceSnapshot = {
+      type: 'slice',
+      content: [
+        {
+          type: 'block',
+          id: 'matchesReplaceMap[0]',
+          flavour: 'affine:note',
+          props: {
+            xywh: '[0,0,800,95]',
+            background: DefaultTheme.noteBackgrounColor,
+            index: 'a0',
+            hidden: false,
+            displayMode: 'both',
+          },
+          children: [
+            {
+              type: 'block',
+              id: 'matchesReplaceMap[1]',
+              flavour: 'affine:paragraph',
+              props: {
+                type: 'text',
+                text: {
+                  '$blocksuite:internal:text$': true,
+                  delta: [
+                    {
+                      insert: 'a ',
+                    },
+                    {
+                      insert: 'bold text',
+                      attributes: {
+                        bold: true,
+                      },
+                    },
+                    {
+                      insert: ' hello world',
+                    },
+                  ],
+                },
+              },
+              children: [],
+            },
+          ],
+        },
+      ],
+      workspaceId: '',
+      pageId: '',
+    };
+
+    const ntAdapter = new NotionTextAdapter(createJob(), provider);
+    const target = ntAdapter.toSliceSnapshot({
+      file: notionText,
+      workspaceId: '',
+      pageId: '',
+    });
+    expect(nanoidReplacement(target!)).toEqual(sliceSnapshot);
+  });
 });

blocksuite/affine/shared/src/adapters/notion-text.ts

@@ -94,28 +94,49 @@ export class NotionTextAdapter extends BaseAdapter<NotionText> {
     const notionText = JSON.parse(payload.file) as NotionTextSerialized;
     const content: SliceSnapshot['content'] = [];
     const deltas: DeltaInsert<AffineTextAttributes>[] = [];
+
+    // Check if the notionText.editing is an array
+    if (!Array.isArray(notionText.editing)) {
+      return null;
+    }
+
     for (const editing of notionText.editing) {
       const delta: DeltaInsert<AffineTextAttributes> = {
         insert: editing[0],
-        attributes: Object.create(null),
       };
-      for (const styleElement of editing[1]) {
-        switch (styleElement[0]) {
-          case 'b':
-            delta.attributes!.bold = true;
-            break;
-          case 'i':
-            delta.attributes!.italic = true;
-            break;
-          case '_':
-            delta.attributes!.underline = true;
-            break;
-          case 'c':
-            delta.attributes!.code = true;
-            break;
-          case 's':
-            delta.attributes!.strike = true;
-            break;
+
+      // Check if the stylesArray of editing[1] is an array
+      const stylesArray = editing[1];
+      if (Array.isArray(stylesArray)) {
+        for (const styleElement of stylesArray) {
+          // Skip invalid style entries
+          if (!styleElement || typeof styleElement[0] !== 'string') {
+            continue;
+          }
+
+          // Check if the delta.attributes exists, if not, create a new object
+          if (!delta.attributes) {
+            delta.attributes = Object.create(null);
+          }
+
+          // Add the style to the delta.attributes
+          switch (styleElement[0]) {
+            case 'b':
+              delta.attributes!.bold = true;
+              break;
+            case 'i':
+              delta.attributes!.italic = true;
+              break;
+            case '_':
+              delta.attributes!.underline = true;
+              break;
+            case 'c':
+              delta.attributes!.code = true;
+              break;
+            case 's':
+              delta.attributes!.strike = true;
+              break;
+          }
         }
       }
       deltas.push(delta);