[Fizz][Float] When src or srcSet is a data URI we should not preload …

…the image (#27218) Data URI's in images can't effectively be preloaded (the URI contains the data so preloading only duplicates the data in the stream. If we encounter an image with this protocol in the src attribute we should avoid preloading it.
facebook · Aug 12, 2023 · 1a001da · 1a001da
1 parent 4e3618a
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diff --git a/packages/react-dom-bindings/src/server/ReactFizzConfigDOM.js b/packages/react-dom-bindings/src/server/ReactFizzConfigDOM.js
@@ -2392,14 +2392,32 @@ function pushImg(
   props: Object,
   resources: Resources,
 ): null {
+  const {src, srcSet} = props;
   if (
     props.loading !== 'lazy' &&
-    typeof props.src === 'string' &&
-    props.fetchPriority !== 'low'
+    (typeof src === 'string' || typeof srcSet === 'string') &&
+    props.fetchPriority !== 'low' &&
+    // We exclude data URIs in src and srcSet since these should not be preloaded
+    !(
+      typeof src === 'string' &&
+      src[4] === ':' &&
+      (src[0] === 'd' || src[0] === 'D') &&
+      (src[1] === 'a' || src[1] === 'A') &&
+      (src[2] === 't' || src[2] === 'T') &&
+      (src[3] === 'a' || src[3] === 'A')
+    ) &&
+    !(
+      typeof srcSet === 'string' &&
+      srcSet[4] === ':' &&
+      (srcSet[0] === 'd' || srcSet[0] === 'D') &&
+      (srcSet[1] === 'a' || srcSet[1] === 'A') &&
+      (srcSet[2] === 't' || srcSet[2] === 'T') &&
+      (srcSet[3] === 'a' || srcSet[3] === 'A')
+    )
   ) {
     // We have a suspensey image and ought to preload it to optimize the loading of display blocking
     // resources.
-    const {src, srcSet, sizes} = props;
+    const {sizes} = props;
     const key = getImagePreloadKey(src, srcSet, sizes);
     let resource = resources.preloadsMap.get(key);
     if (!resource) {

diff --git a/packages/react-dom/src/__tests__/ReactDOMFloat-test.js b/packages/react-dom/src/__tests__/ReactDOMFloat-test.js
@@ -3969,6 +3969,36 @@ body {
     );
   });
 
+  it('should not preload images that have a data URIs for src or srcSet', async () => {
+    function App() {
+      return (
+        <html>
+          <body>
+            <img src="data:1" />
+            <img src="data:2" srcSet="ss2" />
+            <img srcSet="data:3a, data:3b 2x" />
+            <img src="4" srcSet="data:4a, data4b 2x" />
+          </body>
+        </html>
+      );
+    }
+    await act(() => {
+      renderToPipeableStream(<App />).pipe(writable);
+    });
+
+    expect(getMeaningfulChildren(document)).toEqual(
+      <html>
+        <head />
+        <body>
+          <img src="data:1" />
+          <img src="data:2" srcset="ss2" />
+          <img srcset="data:3a, data:3b 2x" />
+          <img src="4" srcset="data:4a, data4b 2x" />
+        </body>
+      </html>,
+    );
+  });
+
   describe('ReactDOM.prefetchDNS(href)', () => {
     it('creates a dns-prefetch resource when called', async () => {
       function App({url}) {