Remove image preload refs without href

src/asset-inliner.mjs

@@ -206,11 +206,11 @@ export class AssetInliner {
     const rel = getAttribute(tag, "rel") || "";
     const href = getAttribute(tag, "href");
     const asValue = getAttribute(tag, "as") || "";
-    if (!href) {
-      return tag;
-    }
 
     if (/\bstylesheet\b/i.test(rel)) {
+      if (!href) {
+        return tag;
+      }
       const absolute = resolveUrl(href, baseUrl);
       if (!absolute || absolute.startsWith("data:")) {
         return "";
@@ -237,12 +237,19 @@ export class AssetInliner {
     }
     let output = tag;
     if (/\bpreload\b/i.test(rel) && /^image$/i.test(asValue)) {
+      if (!href) {
+        return "";
+      }
       const imageSrcset = getAttribute(output, "imagesrcset");
       if (imageSrcset) {
         output = setAttribute(output, "imagesrcset", await this.inlineSrcset(imageSrcset, baseUrl));
       }
     }
 
+    if (!href) {
+      return tag;
+    }
+
     const dataUri = await this.toDataUri(href, baseUrl, linkResourceType(asValue));
     if (!dataUri) {
       return "";

test/asset-inliner.test.mjs

@@ -82,6 +82,27 @@ test("external asset reporting parses srcset-like attributes without splitting U
   ]);
 });
 
+test("removes image preload srcsets when the link has no href", async () => {
+  const fetched = [];
+  const inliner = new AssetInliner();
+  inliner.fetchAsset = async (rawUrl) => {
+    fetched.push(rawUrl);
+    return {
+      bytes: Buffer.from("asset"),
+      contentType: "image/jpeg"
+    };
+  };
+
+  const output = await inliner.inlineHtml(`
+    <link rel="preload" as="image" imagesrcset="https://media.example/photos/id/master/w_120,c_limit/photo.jpg 120w, https://media.example/photos/id/master/w_240,c_limit/photo.jpg 240w">
+  `, "https://example.com/article");
+
+  assert.deepEqual(fetched, []);
+  assert.doesNotMatch(output, /https:\/\/media\.example/);
+  assert.doesNotMatch(output, /imagesrcset/);
+  assert.deepEqual(findExternalAssetRefs(output), []);
+});
+
 test("asset inliner skips URLs blocked by the filter hook", async () => {
   const blocked = [];
   const inliner = new AssetInliner({