fix(markdown): keep the first image reference definition

packages/app/src/components/markdown/renderer.test.ts

@@ -302,3 +302,12 @@ it("preserves angle-bracket image destinations and authored link titles during H
     '![shot](<blob:shot>) and [open](<my file.png> "<b>literal title</b>")',
   );
 });
+
+it("uses the first repeated image reference definition", () => {
+  const source = "![chart][image]\n\n[image]: first.png\n[image]: second.png";
+  const prepared = prepareMarkdownSource(source);
+  expect(prepared.images.map((image) => image.source)).toEqual(["first.png"]);
+  expect(prepared.render(new Map([["first.png", "blob:first"]]))).toBe(
+    "![chart](<blob:first>)\n\n[image]: first.png\n[image]: second.png",
+  );
+});

packages/app/src/components/markdown/source.ts

@@ -74,7 +74,8 @@ export function prepareMarkdownSource(
 
   const definitions = new Map<string, { url: string; title?: string | null }>();
   function definitionsIn(node: Nodes) {
-    if (node.type === "definition") definitions.set(node.identifier, node);
+    if (node.type === "definition" && !definitions.has(node.identifier))
+      definitions.set(node.identifier, node);
     if ("children" in node) node.children.forEach(definitionsIn);
   }
   definitionsIn(getTree());