fix: ensure numbered list start property always present (#2241)

packages/core/src/blocks/ListItem/NumberedListItem/block.ts

@@ -51,13 +51,9 @@ export const createNumberedListItemBlockSpec = createBlockSpec(
 
         const defaultProps = parseDefaultProps(element);
 
-        if (element.previousElementSibling || startIndex === 1) {
-          return defaultProps;
-        }
-
         return {
           ...defaultProps,
-          start: startIndex,
+          start: element.previousElementSibling || startIndex === 1 ? undefined : startIndex,
         };
       }
 

tests/src/unit/core/blocks/NumberedListItem.test.ts

@@ -0,0 +1,101 @@
+import { describe, expect, it } from "vitest";
+import { createNumberedListItemBlockSpec } from "../../../../../packages/core/src/blocks/ListItem/NumberedListItem/block.js";
+
+describe("NumberedListItem parse() method", () => {
+  const blockSpec = createNumberedListItemBlockSpec();
+  const parseFunc = blockSpec.implementation.parse;
+
+  if (!parseFunc) {
+    throw new Error("parse function not found");
+  }
+
+  it("should always return an object with 'start' property - first item, startIndex=1", () => {
+    // Create mock DOM elements
+    const li = document.createElement("li");
+    const ol = document.createElement("ol");
+    ol.setAttribute("start", "1");
+    ol.appendChild(li);
+
+    const result = parseFunc(li);
+
+    // The parse function should return an object with 'start' property
+    expect(result).toBeDefined();
+    expect(result).toHaveProperty("start");
+    expect(result?.start).toBeUndefined(); // Should be undefined for first item at index 1
+  });
+
+  it("should always return an object with 'start' property - first item, startIndex=5", () => {
+    const li = document.createElement("li");
+    const ol = document.createElement("ol");
+    ol.setAttribute("start", "5");
+    ol.appendChild(li);
+
+    const result = parseFunc(li);
+
+    expect(result).toBeDefined();
+    expect(result).toHaveProperty("start");
+    expect(result?.start).toBe(5); // Should be 5 for first item at non-standard index
+  });
+
+  it("should always return an object with 'start' property - subsequent item", () => {
+    const li1 = document.createElement("li");
+    const li2 = document.createElement("li");
+    const ol = document.createElement("ol");
+    ol.setAttribute("start", "1");
+    ol.appendChild(li1);
+    ol.appendChild(li2);
+
+    const result = parseFunc(li2);
+
+    expect(result).toBeDefined();
+    expect(result).toHaveProperty("start");
+    expect(result?.start).toBeUndefined(); // Subsequent items don't need explicit start
+  });
+
+  it("should always return an object with 'start' property - subsequent item in list starting at 5", () => {
+    const li1 = document.createElement("li");
+    const li2 = document.createElement("li");
+    const ol = document.createElement("ol");
+    ol.setAttribute("start", "5");
+    ol.appendChild(li1);
+    ol.appendChild(li2);
+
+    const result = parseFunc(li2);
+
+    expect(result).toBeDefined();
+    expect(result).toHaveProperty("start");
+    expect(result?.start).toBeUndefined(); // Subsequent items get undefined
+  });
+
+  it("regression test for issue #2241 - ensures 'start' property is always present", () => {
+    // This test verifies the fix for issue #2241
+    // The old code would return defaultProps (without 'start') for certain conditions
+    // The new code always includes 'start' in the returned object
+
+    const testCases = [
+      { startAttr: "1", hasPreSibling: false, expectedStart: undefined },
+      { startAttr: "1", hasPreSibling: true, expectedStart: undefined },
+      { startAttr: "5", hasPreSibling: false, expectedStart: 5 },
+      { startAttr: "5", hasPreSibling: true, expectedStart: undefined },
+    ];
+
+    testCases.forEach(({ startAttr, hasPreSibling, expectedStart }) => {
+      const li = document.createElement("li");
+      const ol = document.createElement("ol");
+      ol.setAttribute("start", startAttr);
+
+      if (hasPreSibling) {
+        const li1 = document.createElement("li");
+        ol.appendChild(li1);
+      }
+
+      ol.appendChild(li);
+
+      const result = parseFunc(li);
+
+      // Critical assertion: 'start' property must ALWAYS be present
+      expect(result).toHaveProperty("start");
+      expect(result?.start).toBe(expectedStart);
+    });
+  });
+});

tests/src/unit/core/formatConversion/parse/__snapshots__/markdown/issue2241NumberedListStartProperty.json

@@ -0,0 +1,104 @@
+[
+  {
+    "children": [],
+    "content": [
+      {
+        "styles": {},
+        "text": "First item",
+        "type": "text",
+      },
+    ],
+    "id": "1",
+    "props": {
+      "backgroundColor": "default",
+      "textAlignment": "left",
+      "textColor": "default",
+    },
+    "type": "numberedListItem",
+  },
+  {
+    "children": [],
+    "content": [
+      {
+        "styles": {},
+        "text": "Second item",
+        "type": "text",
+      },
+    ],
+    "id": "2",
+    "props": {
+      "backgroundColor": "default",
+      "textAlignment": "left",
+      "textColor": "default",
+    },
+    "type": "numberedListItem",
+  },
+  {
+    "children": [],
+    "content": [
+      {
+        "styles": {},
+        "text": "Third item",
+        "type": "text",
+      },
+    ],
+    "id": "3",
+    "props": {
+      "backgroundColor": "default",
+      "textAlignment": "left",
+      "textColor": "default",
+    },
+    "type": "numberedListItem",
+  },
+  {
+    "children": [],
+    "content": [
+      {
+        "styles": {},
+        "text": "List starting at 5",
+        "type": "text",
+      },
+    ],
+    "id": "4",
+    "props": {
+      "backgroundColor": "default",
+      "textAlignment": "left",
+      "textColor": "default",
+    },
+    "type": "numberedListItem",
+  },
+  {
+    "children": [],
+    "content": [
+      {
+        "styles": {},
+        "text": "Second item",
+        "type": "text",
+      },
+    ],
+    "id": "5",
+    "props": {
+      "backgroundColor": "default",
+      "textAlignment": "left",
+      "textColor": "default",
+    },
+    "type": "numberedListItem",
+  },
+  {
+    "children": [],
+    "content": [
+      {
+        "styles": {},
+        "text": "Third item",
+        "type": "text",
+      },
+    ],
+    "id": "6",
+    "props": {
+      "backgroundColor": "default",
+      "textAlignment": "left",
+      "textColor": "default",
+    },
+    "type": "numberedListItem",
+  },
+]

tests/src/unit/core/formatConversion/parse/parseTestInstances.ts

@@ -1111,4 +1111,17 @@ Regular paragraph`,
     },
     executeTest: testParseMarkdown,
   },
+  {
+    testCase: {
+      name: "issue2241NumberedListStartProperty",
+      content: `1. First item
+2. Second item
+3. Third item
+
+5. List starting at 5
+6. Second item
+7. Third item`,
+    },
+    executeTest: testParseMarkdown,
+  },
 ];