fix(export): skip placeholder text for empty file blocks (#434)

Empty image/video/audio/file blocks (no url set) previously leaked
their "Add image"/"Add video"/etc. UI text into HTML and markdown
exports. Each block's toExternalHTML now emits the bare element
(<img>, <video>, <audio>, <embed>) with no src, so the placeholder
text is gone from exports while the block still round-trips back to
an empty block on re-import via the existing tag-name parsers.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: nperez0111

packages/core/src/api/exporters/markdown/htmlToMarkdown.ts

@@ -84,6 +84,8 @@ function serializeNode(node: Node, ctx: SerializeContext): string {
       return serializeVideo(el, ctx);
     case "audio":
       return serializeAudio(el, ctx);
+    case "embed":
+      return serializeEmbed(el, ctx);
     case "figure":
       return serializeFigure(el, ctx);
     case "a":
@@ -501,29 +503,33 @@ function formatSeparatorRow(colWidths: number[], colCount: number): string {
 function serializeImage(el: HTMLElement, ctx: SerializeContext): string {
   const src = el.getAttribute("src") || "";
   const alt = el.getAttribute("alt") || "";
-  if (!src) {
-    return ctx.indent + "Add image\n\n";
-  }
+  // Empty placeholder — preserve the block-level break, matching how
+  // serializeParagraph/serializeHeading emit `\n\n` for empty content.
+  if (!src) {return "\n\n";}
   return ctx.indent + `![${alt}](${src})\n\n`;
 }
 
 function serializeVideo(el: HTMLElement, ctx: SerializeContext): string {
   const src =
     el.getAttribute("src") || el.getAttribute("data-url") || "";
   const name = el.getAttribute("data-name") || el.getAttribute("title") || "";
-  if (!src) {
-    return ctx.indent + "Add video\n\n";
-  }
+  if (!src) {return "\n\n";}
   return ctx.indent + `![${name}](${src})\n\n`;
 }
 
 function serializeAudio(el: HTMLElement, ctx: SerializeContext): string {
   const src = el.getAttribute("src") || "";
-  if (!src) {return "";}
+  if (!src) {return "\n\n";}
   // Audio has no visible representation in markdown; output as link with empty text
   return ctx.indent + `[](${src})\n\n`;
 }
 
+function serializeEmbed(el: HTMLElement, ctx: SerializeContext): string {
+  const src = el.getAttribute("src") || "";
+  if (!src) {return "\n\n";}
+  return ctx.indent + `[](${src})\n\n`;
+}
+
 function serializeFigure(el: HTMLElement, ctx: SerializeContext): string {
   let result = "";
 

packages/core/src/blocks/Audio/block.ts

@@ -129,11 +129,8 @@ export const audioToExternalHTML =
     >,
   ) => {
     if (!block.props.url) {
-      const div = document.createElement("p");
-      div.textContent = "Add audio";
-
       return {
-        dom: div,
+        dom: document.createElement("audio"),
       };
     }
 

packages/core/src/blocks/File/block.ts

@@ -75,11 +75,8 @@ export const createFileBlockSpec = createBlockSpec(createFileBlockConfig, {
   },
   toExternalHTML(block) {
     if (!block.props.url) {
-      const div = document.createElement("p");
-      div.textContent = "Add file";
-
       return {
-        dom: div,
+        dom: document.createElement("embed"),
       };
     }
 

packages/core/src/blocks/Image/block.ts

@@ -141,11 +141,8 @@ export const imageToExternalHTML =
     >,
   ) => {
     if (!block.props.url) {
-      const div = document.createElement("p");
-      div.textContent = "Add image";
-
       return {
-        dom: div,
+        dom: document.createElement("img"),
       };
     }
 

packages/core/src/blocks/Video/block.ts

@@ -105,11 +105,8 @@ export const createVideoBlockSpec = createBlockSpec(
     },
     toExternalHTML(block) {
       if (!block.props.url) {
-        const div = document.createElement("p");
-        div.textContent = "Add video";
-
         return {
-          dom: div,
+          dom: document.createElement("video"),
         };
       }
 

tests/src/unit/core/clipboard/copy/__snapshots__/text/html/basicBlocks.html

@@ -46,6 +46,6 @@ <h1>Heading 1</h1>
     </td>
   </tr>
 </table>
-<p>Add image</p>
+<img />
 <hr />
 <p>Paragraph 2</p>

tests/src/unit/core/formatConversion/export/__snapshots__/html/audio/button.html

@@ -1 +1 @@
-<p>Add audio</p>
+<audio></audio>

tests/src/unit/core/formatConversion/export/__snapshots__/html/file/button.html

@@ -1 +1 @@
-<p>Add file</p>
+<embed />

tests/src/unit/core/formatConversion/export/__snapshots__/html/image/button.html

@@ -1 +1 @@
-<p>Add image</p>
+<img />

tests/src/unit/core/formatConversion/export/__snapshots__/markdown/audio/button.md

@@ -1 +1 @@
-Add audio
+