Fork patch: Probe untraced media src writes

packages/lint/src/rules/media.ts

@@ -391,6 +391,7 @@ function findRuntimeMediaSrcMutationFindings(ctx: LintContext): HyperframeLintFi
   const findings: HyperframeLintFinding[] = [];
   for (const script of ctx.scripts) {
     for (const mutation of extractMediaSrcMutations(script.content)) {
+      if (!mutation.selector) continue;
       let targets: Element[];
       try {
         const id = /^#[A-Za-z_][\w-]*$/.test(mutation.selector) ? mutation.selector.slice(1) : null;

packages/parsers/src/mediaSrcMutation.ts

@@ -2,7 +2,8 @@ import * as acorn from "acorn";
 import * as acornWalk from "acorn-walk";
 
 export interface MediaSrcMutation {
-  selector: string;
+  /** Null when the write's target is not a statically resolvable DOM lookup. */
+  selector: string | null;
   operation: "src_assignment" | "set_attribute";
   raw: string;
 }
@@ -206,7 +207,7 @@ function selectorFromDomLookup(
   return method === "getElementById" ? `#${value}` : value;
 }
 
-/** Find literal source writes whose target is a statically resolvable DOM lookup. */
+/** Find source writes, with the target's selector when it is a statically resolvable DOM lookup. */
 export function extractMediaSrcMutations(script: string): MediaSrcMutation[] {
   try {
     const ast = parseProgram(script);
@@ -220,10 +221,8 @@ export function extractMediaSrcMutations(script: string): MediaSrcMutation[] {
           memberName(node.left) !== "src"
         )
           return;
-        const selector = lookupSelector(node.left.object, scopeAt(ancestors));
-        if (!selector) return;
         mutations.push({
-          selector,
+          selector: lookupSelector(node.left.object, scopeAt(ancestors)) ?? null,
           operation: "src_assignment",
           raw: script.slice(node.start, node.end),
         });
@@ -232,10 +231,8 @@ export function extractMediaSrcMutations(script: string): MediaSrcMutation[] {
         if (node.callee.type !== "MemberExpression" || memberName(node.callee) !== "setAttribute")
           return;
         if (literalString(node.arguments[0])?.toLowerCase() !== "src") return;
-        const selector = lookupSelector(node.callee.object, scopeAt(ancestors));
-        if (!selector) return;
         mutations.push({
-          selector,
+          selector: lookupSelector(node.callee.object, scopeAt(ancestors)) ?? null,
           operation: "set_attribute",
           raw: script.slice(node.start, node.end),
         });

packages/producer/src/services/render/stages/probeStage.test.ts

@@ -1113,6 +1113,43 @@ describe("runProbeStage — forceScreenshot threading", () => {
     expect(capturedCfgs).toHaveLength(0);
   });
 
+  it("probes a src write whose target is resolved at runtime when the document has media", async () => {
+    resetRetryMocks();
+    capturedCfgs.length = 0;
+    const { runProbeStage } = await import("./probeStage.js");
+    const input = makeProbeInput({});
+    input.composition.duration = 5;
+    input.compiled.html = `<video id="clip" data-start="0" data-key="clipUrl" src="video-a.mp4"></video>
+      <script>
+        const S = { clipUrl: "video-b.mp4" };
+        document.querySelectorAll("[data-key]").forEach((el) => {
+          el.src = S[el.getAttribute("data-key")];
+        });
+      </script>`;
+
+    await runProbeStage(input);
+
+    expect(capturedCfgs.length).toBeGreaterThan(0);
+  });
+
+  it("does not probe a src write resolved at runtime when the document has no media", async () => {
+    resetRetryMocks();
+    capturedCfgs.length = 0;
+    const { runProbeStage } = await import("./probeStage.js");
+    const input = makeProbeInput({});
+    input.composition.duration = 5;
+    input.compiled.html = `<img class="logo" src="a.png">
+      <script>
+        document.querySelectorAll(".logo").forEach((el) => {
+          el.src = "b.png";
+        });
+      </script>`;
+
+    await runProbeStage(input);
+
+    expect(capturedCfgs).toHaveLength(0);
+  });
+
   it("probes when a source child of existing media is mutated", async () => {
     resetRetryMocks();
     capturedCfgs.length = 0;

packages/producer/src/services/render/stages/probeStage.ts

@@ -289,8 +289,15 @@ function hasRuntimeMediaChanges(html: string): boolean {
     if (name === "video" || name === "audio") return true;
     return name === "source" && element.closest("video, audio") !== null;
   };
+  const hasManagedMedia = document.querySelector("video, audio") !== null;
   for (const script of scriptBodies) {
     for (const mutation of extractMediaSrcMutations(script)) {
+      // A write whose target can't be resolved statically, such as one in a loop
+      // over querySelectorAll, may land on any media in the document.
+      if (!mutation.selector) {
+        if (hasManagedMedia) return true;
+        continue;
+      }
       try {
         const id = /^#[A-Za-z_][\w-]*$/.test(mutation.selector) ? mutation.selector.slice(1) : null;
         const idTarget = id ? document.getElementById(id) : null;