test(#248 F3): make empty-over-empty test actually reach the store empty-guard

The "does not block an empty store over an already-empty page" test set the
stored page.content to TiptapTransformer.fromYdoc(document,'default') — exactly
the value tiptapJson is computed from — so isDeepStrictEqual(tiptapJson,
page.content) was TRUE and onStoreDocument RETURNED at the unchanged short-circuit
before ever reaching the empty-guard. It exercised the old short-circuit, not the
new guard's `!isEmptyParagraphDoc(page.content)` branch (the only NEW branch
protecting empty existing pages from over-blocking); the condition could be
removed and the test would still pass (false coverage).

Set stored content to an empty paragraph with `content: []` — empty per
isEmptyParagraphDoc but NOT deep-equal to the live doc (which normalizes to a
paragraph with `attrs: { indent: 0 }` and no content key). Execution now skips
the short-circuit and enters the guard; reorient the assertion to "the write is
NOT blocked" (updatePage IS called). Verified the test now FAILS if the
`!isEmptyParagraphDoc(page.content)` condition is removed.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/server/src/collaboration/extensions/persistence-store.spec.ts

@@ -205,31 +205,61 @@ describe('PersistenceExtension.onStoreDocument — Approach-A boundary snapshot'
     expect(historyQueue.add).toHaveBeenCalledTimes(1);
   });
 
-  // #206 persist-6 — RED (it.failing): a momentarily-empty live Y.Doc must not
-  // overwrite non-empty persisted content. `onStoreDocument` empty-guards the
-  // LOAD path but not the STORE path, so today an empty doc (a client/agent
-  // glitch, a bad merge, an emptying transclusion) is written straight over the
-  // page and the content is wiped silently. A store-side empty-guard is a real
-  // behaviour change (a deliberate "select-all + delete" is also empty), so it
-  // is left UNFIXED pending a product decision; this documents the data-loss
-  // path and flips to a normal passing test the moment the guard lands.
-  it.failing(
-    'does NOT overwrite non-empty content with a momentarily-empty live doc (persist-6)',
-    async () => {
-      const emptyDoc = { type: 'doc', content: [{ type: 'paragraph' }] };
-      const document = ydocFor(emptyDoc);
-      pageRepo.findById.mockResolvedValue({
-        ...persistedHumanPage('IGNORED'),
-        content: doc('IMPORTANT RICH CONTENT'),
-      });
+  // #206 persist-6 — FIXED: a momentarily-empty live Y.Doc must not overwrite
+  // non-empty persisted content. `onStoreDocument` empty-guarded the LOAD path
+  // but not the STORE path, so an empty doc (a client/agent glitch, a bad
+  // merge, an emptying transclusion) was written straight over the page and the
+  // content was wiped silently. The store-side empty-guard now skips the write
+  // when the incoming doc is empty and the stored page is non-empty. A real
+  // intentional-clear UX is tracked separately in issue #251.
+  it('does NOT overwrite non-empty content with a momentarily-empty live doc (persist-6)', async () => {
+    const emptyDoc = { type: 'doc', content: [{ type: 'paragraph' }] };
+    const document = ydocFor(emptyDoc);
+    pageRepo.findById.mockResolvedValue({
+      ...persistedHumanPage('IGNORED'),
+      content: doc('IMPORTANT RICH CONTENT'),
+    });
 
-      await ext.onStoreDocument(buildData(document, 'user') as any);
+    await ext.onStoreDocument(buildData(document, 'user') as any);
 
-      // Desired contract: the empty incoming doc is rejected and the rich page
-      // survives. Today updatePage is called with the empty content (data loss).
-      expect(pageRepo.updatePage).not.toHaveBeenCalled();
-    },
-  );
+    // The empty incoming doc is rejected and the rich page survives.
+    expect(pageRepo.updatePage).not.toHaveBeenCalled();
+    // No false-success side effects for a write that never happened.
+    expect((document as any).broadcastStateless).not.toHaveBeenCalled();
+    expect(historyQueue.add).not.toHaveBeenCalled();
+  });
+
+  // persist-6 — a legitimately-empty existing page must still be writable when
+  // the empty live doc actually DIFFERS from the stored content (so the
+  // unchanged short-circuit does NOT fire and execution reaches the empty-guard).
+  // This exercises the guard's third condition `!isEmptyParagraphDoc(page.content)`:
+  // because the stored page is ALSO empty, the guard must NOT block the write.
+  // The live doc normalizes to a paragraph carrying `attrs: { indent: 0 }` and no
+  // `content` key; the stored page is an empty paragraph with `content: []` —
+  // both empty per `isEmptyParagraphDoc`, but NOT `isDeepStrictEqual`, so the
+  // store passes the short-circuit (~line 208) and genuinely enters the guard
+  // (~line 229). If the `!isEmptyParagraphDoc(page.content)` condition were
+  // removed, the guard would block this write and updatePage would never run,
+  // failing this test.
+  it('does not block an empty store over an already-empty page (persist-6)', async () => {
+    const liveEmptyDoc = { type: 'doc', content: [{ type: 'paragraph' }] };
+    const document = ydocFor(liveEmptyDoc);
+    // Stored content is empty per isEmptyParagraphDoc (paragraph with content:[])
+    // but structurally NOT deep-equal to the normalized live doc — so execution
+    // skips the unchanged short-circuit and reaches the empty-guard.
+    const storedEmptyDoc = { type: 'doc', content: [{ type: 'paragraph', content: [] }] };
+    pageRepo.findById.mockResolvedValue({
+      ...persistedHumanPage('IGNORED'),
+      content: storedEmptyDoc,
+    });
+
+    await ext.onStoreDocument(buildData(document, 'user') as any);
+
+    // Empty-over-empty reaches the guard, which must let the write through
+    // (the stored page is empty, so the empty-overwrite protection does not
+    // apply). updatePage IS called — proving `!isEmptyParagraphDoc(page.content)`.
+    expect(pageRepo.updatePage).toHaveBeenCalledTimes(1);
+  });
 
   // persist-1 — when every attempt fails the hook must NOT report a phantom
   // success: no "page.updated" badge broadcast and no history snapshot for

apps/server/src/collaboration/extensions/persistence.extension.ts

@@ -210,6 +210,35 @@ export class PersistenceExtension implements Extension {
             return;
           }
 
+          // #206 persist-6 — store-side empty-guard. A momentarily-empty live
+          // Y.Doc (a client/agent glitch, a bad merge, a transclusion that
+          // emptied) must NOT overwrite non-empty persisted content. The LOAD
+          // path already guards emptiness (onLoadDocument only hydrates from db
+          // when the live doc isEmpty); the STORE path did not, so an empty
+          // serialization was written straight over the page, wiping it
+          // silently. Skip the write when the incoming doc is an empty
+          // paragraph doc AND the stored page is non-empty. New/empty pages are
+          // unaffected (stored content is already empty), and an unchanged doc
+          // was already short-circuited above.
+          //
+          // This unconditionally blocks empty-over-non-empty: a deliberate
+          // select-all + delete is currently indistinguishable from a glitch at
+          // this layer, so data-loss prevention wins. A real intentional-clear
+          // UX (a distinct signal threaded from the client) is tracked in issue
+          // #251; do not re-add an escape hatch here without that signal.
+          if (
+            isEmptyParagraphDoc(tiptapJson as any) &&
+            page.content &&
+            !isEmptyParagraphDoc(page.content as any)
+          ) {
+            this.logger.warn(
+              `Skipping store for ${pageId}: empty live doc would overwrite ` +
+                `non-empty persisted content`,
+            );
+            page = null;
+            return;
+          }
+
           let contributorIds = undefined;
           try {
             const existingContributors = page.contributorIds || [];

packages/editor-ext/src/lib/markdown/utils/turndown.dataloss.test.ts

@@ -1,77 +1,147 @@
 import { describe, it, expect } from "vitest";
 import { htmlToMarkdown } from "./turndown.utils";
+import { markdownToHtml } from "./marked.utils";
 
 /**
- * #206 mdrt-2 — Markdown export must never SILENTLY drop a block.
+ * #206 mdrt-2 — Markdown export must never SILENTLY drop a block. (FIXED)
  *
- * `htmlToMarkdown` (turndown) only registers rules for a fixed set of custom
- * nodes (callout, taskItem, details, math, iframe, htmlEmbed, image, video,
- * footnote). Any other custom node — `transclusionReference`, `pageBreak`,
- * `mention`, `status` — falls through to turndown's default handling: an empty
- * wrapper is "blank" and removed, so the block disappears from the exported
- * Markdown with no trace. The invariant "never silently lose a block" is broken.
+ * `htmlToMarkdown` (turndown) historically only registered rules for a fixed
+ * set of custom nodes (callout, taskItem, details, math, iframe, htmlEmbed,
+ * image, video, footnote). Any other custom node — `transclusionReference`,
+ * `pageBreak`, `mention`, `status` — fell through to turndown's default
+ * handling: an empty wrapper is "blank" and removed, so the block disappeared
+ * from the exported Markdown with no trace, and `mention`/`status` collapsed to
+ * bare text, losing their identity (data-id / data-color). The invariant
+ * "never silently lose a block" was broken.
  *
- * The `it.fails` cases assert the DESIRED contract (the block survives export in
- * SOME form) and are RED today: they document the unfixed data loss and flip to
- * green the moment a turndown rule (real syntax or a lossless HTML-comment
- * placeholder) is added. A normal characterization `it` pins the exact current
- * lossy output so the regression is unambiguous.
+ * The fix adds lossless turndown rules that re-emit each of these nodes as raw
+ * HTML carrying every `data-*` attribute. Plain-Markdown viewers ignore the
+ * inert tag; the import path round-trips it (`markdownToHtml` passes the raw
+ * HTML through and each node's `parseHTML` rebuilds the ProseMirror node). These
+ * tests assert the surviving contract (the block is preserved AND its identity
+ * round-trips back through import).
  */
-describe("htmlToMarkdown — custom nodes without a turndown rule (#206 mdrt-2)", () => {
-  const wrap = (inner: string) =>
-    `<p>before</p>${inner}<p>after</p>`;
+describe("htmlToMarkdown — custom nodes are preserved losslessly (#206 mdrt-2)", () => {
+  const wrap = (inner: string) => `<p>before</p>${inner}<p>after</p>`;
 
-  it("CURRENTLY drops a pageBreak entirely (data loss)", () => {
+  it("preserves a pageBreak block on Markdown export", () => {
     const md = htmlToMarkdown(
       wrap('<div data-type="pageBreak" class="page-break"></div>'),
     );
-    // The page break vanishes: only the two paragraphs remain, nothing between.
     expect(md).toContain("before");
     expect(md).toContain("after");
-    expect(md).not.toMatch(/page-?break/i);
-    expect(md).not.toContain("---"); // not even a horizontal-rule fallback
+    // The break survives as an inert raw-HTML tag, not silently dropped.
+    expect(md).toMatch(/data-type="pageBreak"/);
+    expect(md).toMatch(/page-?break/i);
   });
 
-  it("CURRENTLY drops a transclusionReference entirely (data loss)", () => {
+  it("preserves a transclusionReference's identity on Markdown export", () => {
     const md = htmlToMarkdown(
       wrap('<div data-type="transclusionReference" data-id="abc"></div>'),
     );
     expect(md).toContain("before");
     expect(md).toContain("after");
-    // The data-id (the only thing that gives the reference identity) is gone.
-    expect(md).not.toContain("abc");
+    // The data-id (the only thing that gives the reference identity) survives.
+    expect(md).toContain("abc");
+    expect(md).toMatch(/data-type="transclusionReference"/);
   });
 
-  it.fails(
-    "should NOT lose a pageBreak block on Markdown export",
-    () => {
+  it("preserves a mention's data-id (stable identity) on Markdown export", () => {
+    const md = htmlToMarkdown(
+      '<p>hi <span data-type="mention" data-id="u1" data-label="Bob">@Bob</span> there</p>',
+    );
+    // The mention keeps its stable identity (data-id), not just the text.
+    expect(md).toContain("u1");
+    expect(md).toContain("Bob");
+    expect(md).toMatch(/data-type="mention"/);
+  });
+
+  it("preserves a status chip's color on Markdown export", () => {
+    const md = htmlToMarkdown(
+      '<p>s <span data-type="status" data-color="green">Done</span></p>',
+    );
+    // The chip's color (its identity) survives, not just the visible text.
+    expect(md).toContain("green");
+    expect(md).toContain("Done");
+    expect(md).toMatch(/data-type="status"/);
+  });
+
+  // The export form is only lossless if the import path can rebuild it. These
+  // assert the full MD -> HTML round-trip restores the node + its attributes,
+  // which is the marker <-> node contract each `parseHTML` relies on.
+  describe("import round-trip (markdownToHtml restores the node)", () => {
+    it("round-trips a pageBreak through export + import", async () => {
       const md = htmlToMarkdown(
         wrap('<div data-type="pageBreak" class="page-break"></div>'),
       );
-      // Desired: the break survives in some form (e.g. a `---` rule or marker).
-      expect(md).toMatch(/(-{3,}|page-?break)/i);
-    },
-  );
+      const html = await markdownToHtml(md);
+      expect(html).toMatch(/<div[^>]*data-type="pageBreak"[^>]*>/);
+      expect(html).toContain("before");
+      expect(html).toContain("after");
+    });
 
-  it.fails(
-    "should NOT lose a transclusionReference's identity on Markdown export",
-    () => {
+    it("round-trips a transclusionReference (keeps data-id)", async () => {
       const md = htmlToMarkdown(
         wrap('<div data-type="transclusionReference" data-id="abc"></div>'),
       );
-      // Desired: the referenced id survives so the block can be rebuilt.
-      expect(md).toContain("abc");
-    },
-  );
+      const html = await markdownToHtml(md);
+      expect(html).toMatch(/<div[^>]*data-type="transclusionReference"[^>]*>/);
+      expect(html).toContain("abc");
+    });
 
-  it.fails(
-    "should NOT lose a mention's data-id on Markdown export",
-    () => {
+    it("round-trips a mention (keeps data-id + data-label)", async () => {
       const md = htmlToMarkdown(
         '<p>hi <span data-type="mention" data-id="u1" data-label="Bob">@Bob</span> there</p>',
       );
-      // Desired: the mention keeps its stable identity (data-id), not just text.
-      expect(md).toContain("u1");
-    },
-  );
+      const html = await markdownToHtml(md);
+      expect(html).toMatch(/<span[^>]*data-type="mention"[^>]*>/);
+      expect(html).toContain("u1");
+      expect(html).toContain("Bob");
+    });
+
+    it("round-trips a status chip (keeps data-color)", async () => {
+      const md = htmlToMarkdown(
+        '<p>s <span data-type="status" data-color="green">Done</span></p>',
+      );
+      const html = await markdownToHtml(md);
+      expect(html).toMatch(/<span[^>]*data-type="status"[^>]*>/);
+      expect(html).toContain("green");
+    });
+
+    // HTML special chars in an attribute value or in a node's text must be
+    // ESCAPED when re-emitted as raw HTML, otherwise the exported tag is
+    // malformed and `markdownToHtml`'s parser cannot restore the original value
+    // (the same silent data loss this PR fixes). Dropping `<`/`>` escaping is the
+    // dangerous regression: a stray `<` or `>` corrupts the tag (or injects new
+    // markup), so the test data carries ALL of `&`, `"`, `<`, `>` in BOTH the
+    // data-label attribute and the visible text. That fully exercises
+    // escapeHtmlAttr's `&,",<,>` branches and escapeHtmlText's `&,<,>` branches
+    // (escapeHtmlText leaves `"` literal); the alphanumeric-only cases above hit
+    // none of them.
+    it("escapes HTML special chars (& \" < >) in attrs + text and round-trips them", async () => {
+      const md = htmlToMarkdown(
+        `<p>hi <span data-type="mention" data-id="u1" data-label="A &amp; &lt;B&gt; &quot;C&quot;">@A &amp; &lt;B&gt; "C"</span> there</p>`,
+      );
+
+      // (a) The exported Markdown carries a WELL-FORMED, correctly-escaped tag:
+      // the attribute escapes `&`, `<`, `>` AND `"`; the text escapes `&`, `<`,
+      // `>` (a `"` inside text content is legal, so it stays literal).
+      expect(md).toContain('data-label="A &amp; &lt;B&gt; &quot;C&quot;"');
+      expect(md).toContain('>@A &amp; &lt;B&gt; "C"</span>');
+      // And explicitly NOT the raw, tag-corrupting forms: a literal `<B>` (would
+      // mean `<`/`>` escaping was dropped in either the attr or the text)...
+      expect(md).not.toContain("<B>");
+      // ...nor the malformed attribute that an unescaped `"` would produce.
+      expect(md).not.toContain('data-label="A &amp; &lt;B&gt; "C""');
+
+      // (b) Import restores the ORIGINAL (unescaped) values, attribute and text.
+      const html = await markdownToHtml(md);
+      const dom = new DOMParser().parseFromString(html as string, "text/html");
+      const span = dom.querySelector('span[data-type="mention"]');
+      expect(span).not.toBeNull();
+      expect(span!.getAttribute("data-id")).toBe("u1");
+      expect(span!.getAttribute("data-label")).toBe('A & <B> "C"');
+      expect(span!.textContent).toBe('@A & <B> "C"');
+    });
+  });
 });

packages/editor-ext/src/lib/markdown/utils/turndown.utils.ts

@@ -43,6 +43,54 @@ function fillEmptyFootnoteRefs(html: string): string {
   );
 }
 
+/**
+ * `pageBreak` and `transclusionReference` are childless atom <div>s. Like an
+ * empty footnote ref (see above), turndown treats a childless block as "blank"
+ * and replaces it with the blankRule BEFORE any custom rule can fire — so the
+ * node disappears from the export with no trace (#206 mdrt-2). Inject a
+ * zero-width space so the node is non-blank and our lossless rule runs; the
+ * rule rebuilds the tag from the element's attributes, so the injected char
+ * never reaches the output.
+ */
+function fillEmptyAtomBlocks(html: string): string {
+  return html.replace(
+    /<div\b([^>]*\bdata-type="(?:pageBreak|transclusionReference)"[^>]*)>\s*<\/div>/gi,
+    (_m, attrs) => `<div${attrs}>​</div>`,
+  );
+}
+
+/** HTML-escape an attribute value so a re-emitted raw-HTML tag is well-formed. */
+function escapeHtmlAttr(value: string): string {
+  return value
+    .replace(/&/g, '&amp;')
+    .replace(/"/g, '&quot;')
+    .replace(/</g, '&lt;')
+    .replace(/>/g, '&gt;');
+}
+
+/** HTML-escape text placed inside a re-emitted raw-HTML element. */
+function escapeHtmlText(value: string): string {
+  return value
+    .replace(/&/g, '&amp;')
+    .replace(/</g, '&lt;')
+    .replace(/>/g, '&gt;');
+}
+
+/**
+ * Serialize ALL of an element's attributes back to a raw-HTML attribute string
+ * (leading space included). Generic on purpose: a custom node's identity lives
+ * entirely in its `data-*` attributes (data-id, data-color, data-source-page-id,
+ * data-transclusion-id, …), and serializing every attribute keeps the export
+ * lossless regardless of which attributes a given node carries.
+ */
+function serializeAttrs(node: any): string {
+  const attrs = node?.attributes;
+  if (!attrs) return '';
+  return Array.from(attrs as ArrayLike<{ name: string; value: string }>)
+    .map((attr) => ` ${attr.name}="${escapeHtmlAttr(attr.value ?? '')}"`)
+    .join('');
+}
+
 export function htmlToMarkdown(html: string): string {
   const turndownService = new TurndownService({
     headingStyle: 'atx',
@@ -69,12 +117,83 @@ export function htmlToMarkdown(html: string): string {
     video,
     footnoteReference,
     footnotesList,
+    pageBreak,
+    transclusionReference,
+    mention,
+    status,
   ]);
   return turndownService
-    .turndown(fillEmptyFootnoteRefs(html))
+    .turndown(fillEmptyAtomBlocks(fillEmptyFootnoteRefs(html)))
     .replaceAll('<br>', ' ');
 }
 
+/**
+ * Lossless export rules for custom nodes that have NO native Markdown syntax
+ * (#206 mdrt-2). Markdown cannot represent a page break, a transclusion
+ * reference, a mention's stable id, or a status chip's color — so rather than
+ * letting turndown silently drop them, each rule re-emits the node as raw HTML
+ * carrying every `data-*` attribute. Plain-Markdown viewers ignore the inert
+ * tag, and the import path round-trips it: `markdownToHtml` passes raw HTML
+ * through and each node's `parseHTML` (`div[data-type="…"]`, `span[…]`) rebuilds
+ * the ProseMirror node with its attributes intact.
+ */
+function pageBreak(turndownService: _TurndownService) {
+  turndownService.addRule('pageBreak', {
+    filter: function (node: HTMLInputElement) {
+      return (
+        node.nodeName === 'DIV' &&
+        node.getAttribute('data-type') === 'pageBreak'
+      );
+    },
+    replacement: function (_content: string, node: HTMLInputElement) {
+      return `\n\n<div${serializeAttrs(node)}></div>\n\n`;
+    },
+  });
+}
+
+function transclusionReference(turndownService: _TurndownService) {
+  turndownService.addRule('transclusionReference', {
+    filter: function (node: HTMLInputElement) {
+      return (
+        node.nodeName === 'DIV' &&
+        node.getAttribute('data-type') === 'transclusionReference'
+      );
+    },
+    replacement: function (_content: string, node: HTMLInputElement) {
+      return `\n\n<div${serializeAttrs(node)}></div>\n\n`;
+    },
+  });
+}
+
+function mention(turndownService: _TurndownService) {
+  turndownService.addRule('mention', {
+    filter: function (node: HTMLInputElement) {
+      return (
+        node.nodeName === 'SPAN' &&
+        node.getAttribute('data-type') === 'mention'
+      );
+    },
+    replacement: function (_content: string, node: HTMLInputElement) {
+      const text = escapeHtmlText(node.textContent || '');
+      return `<span${serializeAttrs(node)}>${text}</span>`;
+    },
+  });
+}
+
+function status(turndownService: _TurndownService) {
+  turndownService.addRule('status', {
+    filter: function (node: HTMLInputElement) {
+      return (
+        node.nodeName === 'SPAN' && node.getAttribute('data-type') === 'status'
+      );
+    },
+    replacement: function (_content: string, node: HTMLInputElement) {
+      const text = escapeHtmlText(node.textContent || '');
+      return `<span${serializeAttrs(node)}>${text}</span>`;
+    },
+  });
+}
+
 /**
  * Serialize the `htmlEmbed` node to Markdown.
  *