🐛Fix SRA in no signing exp (#30037)

* move body check to 204

* return real response from sra

* sraBlockCallbackHandler test

extensions/amp-a4a/0.1/amp-a4a.js

@@ -883,7 +883,7 @@ export class AmpA4A extends AMP.BaseElement {
    * @return {Promise<?./head-validation.ValidatedHeadDef>}
    */
   streamResponse_(httpResponse, checkStillCurrent) {
-    if (!httpResponse.body) {
+    if (httpResponse.status === 204) {
       this.forceCollapse();
       return Promise.reject(NO_CONTENT_RESPONSE);
     }

extensions/amp-ad-network-doubleclick-impl/0.1/amp-ad-network-doubleclick-impl.js

@@ -1714,7 +1714,8 @@ export class AmpAdNetworkDoubleclickImpl extends AmpA4A {
                         headersObj,
                         done,
                         sraRequestAdUrlResolvers,
-                        sraUrl
+                        sraUrl,
+                        this.isInNoSigningExp()
                       );
                     }
                   );

extensions/amp-ad-network-doubleclick-impl/0.1/sra-utils.js

@@ -399,13 +399,15 @@ function serializeItem_(key, value) {
  * @param {boolean} done
  * @param {!Array<function(?Response)>} sraRequestAdUrlResolvers
  * @param {string} sraUrl url of SRA request for error reporting
+ * @param {boolean=} isNoSigning
  */
 export function sraBlockCallbackHandler(
   creative,
   headersObj,
   done,
   sraRequestAdUrlResolvers,
-  sraUrl
+  sraUrl,
+  isNoSigning
 ) {
   const headerNames = Object.keys(headersObj);
   if (headerNames.length == 1 && isObject(headersObj[headerNames[0]])) {
@@ -435,12 +437,20 @@ export function sraBlockCallbackHandler(
       },
       has: (name) => !!headersObj[name.toLowerCase()],
     });
-  const fetchResponse =
-    /** @type {?Response} */
-    ({
-      headers,
-      arrayBuffer: () => tryResolve(() => utf8Encode(creative)),
-    });
+
+  let fetchResponse;
+  if (isNoSigning) {
+    const stringifiedHeaders = stringifyHeaderValues(headersObj);
+    fetchResponse = new Response(creative, {headers: stringifiedHeaders});
+  } else {
+    fetchResponse =
+      /** @type {?Response} */
+      ({
+        headers,
+        arrayBuffer: () => tryResolve(() => utf8Encode(creative)),
+      });
+  }
+
   // Pop head off of the array of resolvers as the response
   // should match the order of blocks declared in the ad url.
   // This allows the block to start rendering while the SRA
@@ -457,3 +467,21 @@ export function sraBlockCallbackHandler(
     );
   }
 }
+
+/**
+ * Takes any parsed header values from the object that are not strings and
+ * converts them back to the orginal stringified version.
+ * TODO above indicates this might get fixed upstream at some point.
+ * @param {!Object} headersObj
+ * @return {!Object<string, string>}
+ */
+function stringifyHeaderValues(headersObj) {
+  return Object.keys(headersObj).reduce((stringifiedHeaders, headerName) => {
+    let headerValue = headersObj[headerName];
+    if (headerValue && typeof headerValue != 'string') {
+      headerValue = JSON.stringify(headerValue);
+    }
+    stringifiedHeaders[headerName] = headerValue;
+    return stringifiedHeaders;
+  }, {});
+}

extensions/amp-ad-network-doubleclick-impl/0.1/test/test-doubleclick-sra.js

@@ -800,6 +800,40 @@ describes.realWin('Doubleclick SRA', config, (env) => {
       });
     });
 
+    it('should return a real response in no-siging exp', async () => {
+      const headerObj = {a: 'b', c: 123};
+      const slotDeferred = new Deferred();
+      const sraRequestAdUrlResolvers = [
+        slotDeferred.resolve,
+        {
+          resolve: () => {
+            throw new Error();
+          },
+        },
+      ];
+      sraBlockCallbackHandler(
+        creative,
+        headerObj,
+        /* done */ false,
+        sraRequestAdUrlResolvers,
+        /* sraUrl */ 'http://www.example.com',
+        /* isNoSigning */ true
+      );
+      expect(sraRequestAdUrlResolvers.length).to.equal(1);
+      const fetchResponse = await slotDeferred.promise;
+      expect(fetchResponse).to.be.an.instanceof(Response);
+      expect(fetchResponse.body).to.be.an.instanceof(ReadableStream);
+      expect(fetchResponse.headers.get('a')).to.equal('b');
+      expect(fetchResponse.headers.get('c')).to.equal('123');
+      expect(
+        fetchResponse.headers.get(RENDERING_TYPE_HEADER.toLowerCase())
+      ).to.equal(XORIGIN_MODE.SAFEFRAME);
+      expect(fetchResponse.headers.has('unknown')).to.be.false;
+
+      const text = await fetchResponse.text();
+      expect(text).to.equal(creative);
+    });
+
     it('should handle multiple blocks', () => {
       const blocks = [
         {