feat(fetch): Support abort reasons in fetch

The spec PR for this (whatwg/fetch#1343) hasn't been finalized yet
because some questions regarding service worker integration are not
settled yet, but everything else seems settled, and it seems best to
not wait for another Deno version to support abort reasons in the fetch
API.

Author: Andreu Botella

cli/tests/unit/fetch_test.ts

@@ -1272,7 +1272,60 @@ Deno.test(
     } catch (error) {
       assert(error instanceof DOMException);
       assertEquals(error.name, "AbortError");
-      assertEquals(error.message, "Ongoing fetch was aborted.");
+      assertEquals(error.message, "The signal has been aborted");
+    }
+  },
+);
+
+Deno.test(
+  { permissions: { net: true } },
+  async function fetchAbortWhileUploadStreamingWithReason(): Promise<void> {
+    const abortController = new AbortController();
+    const abortReason = new Error();
+    try {
+      await fetch(
+        "http://localhost:5552/echo_server",
+        {
+          method: "POST",
+          body: new ReadableStream({
+            pull(controller) {
+              abortController.abort(abortReason);
+              controller.enqueue(new Uint8Array([1, 2, 3, 4]));
+            },
+          }),
+          signal: abortController.signal,
+        },
+      );
+      fail("Fetch didn't reject.");
+    } catch (error) {
+      assertEquals(error, abortReason);
+    }
+  },
+);
+
+Deno.test(
+  { permissions: { net: true } },
+  async function fetchAbortWhileUploadStreamingWithPrimitiveReason(): Promise<
+    void
+  > {
+    const abortController = new AbortController();
+    try {
+      await fetch(
+        "http://localhost:5552/echo_server",
+        {
+          method: "POST",
+          body: new ReadableStream({
+            pull(controller) {
+              abortController.abort("Abort reason");
+              controller.enqueue(new Uint8Array([1, 2, 3, 4]));
+            },
+          }),
+          signal: abortController.signal,
+        },
+      );
+      fail("Fetch didn't reject.");
+    } catch (error) {
+      assertEquals(error, "Abort reason");
     }
   },
 );

ext/fetch/26_fetch.js

@@ -88,10 +88,7 @@
   function createResponseBodyStream(responseBodyRid, terminator) {
     function onAbort() {
       if (readable) {
-        errorReadableStream(
-          readable,
-          new DOMException("Ongoing fetch was aborted.", "AbortError"),
-        );
+        errorReadableStream(readable, terminator.reason);
       }
       core.tryClose(responseBodyRid);
     }
@@ -121,9 +118,7 @@
         } catch (err) {
           RESOURCE_REGISTRY.unregister(readable);
           if (terminator.aborted) {
-            controller.error(
-              new DOMException("Ongoing fetch was aborted.", "AbortError"),
-            );
+            controller.error(terminator.reason);
           } else {
             // There was an error while reading a chunk of the body, so we
             // error.
@@ -155,9 +150,7 @@
       }
 
       const body = new InnerBody(req.blobUrlEntry.stream());
-      terminator[abortSignal.add](() =>
-        body.error(new DOMException("Ongoing fetch was aborted.", "AbortError"))
-      );
+      terminator[abortSignal.add](() => body.error(terminator.reason));
 
       return {
         headerList: [
@@ -328,6 +321,7 @@
   /**
    * @param {InnerRequest} request
    * @param {InnerResponse} response
+   * @param {AbortSignal} terminator
    * @returns {Promise<InnerResponse>}
    */
   function httpRedirectFetch(request, response, terminator) {
@@ -405,7 +399,7 @@
       const request = toInnerRequest(requestObject);
       // 4.
       if (requestObject.signal.aborted) {
-        reject(abortFetch(request, null));
+        reject(abortFetch(request, null, requestObject.signal.reason));
         return;
       }
 
@@ -416,7 +410,9 @@
       // 10.
       function onabort() {
         locallyAborted = true;
-        reject(abortFetch(request, responseObject));
+        reject(
+          abortFetch(request, responseObject, requestObject.signal.reason),
+        );
       }
       requestObject.signal[abortSignal.add](onabort);
 
@@ -433,7 +429,13 @@
             if (locallyAborted) return;
             // 12.2.
             if (response.aborted) {
-              reject(request, responseObject);
+              reject(
+                abortFetch(
+                  request,
+                  responseObject,
+                  requestObject.signal.reason,
+                ),
+              );
               requestObject.signal[abortSignal.remove](onabort);
               return;
             }
@@ -459,8 +461,7 @@
     });
   }
 
-  function abortFetch(request, responseObject) {
-    const error = new DOMException("Ongoing fetch was aborted.", "AbortError");
+  function abortFetch(request, responseObject, error) {
     if (request.body !== null) {
       if (WeakMapPrototypeHas(requestBodyReaders, request)) {
         WeakMapPrototypeGet(requestBodyReaders, request).cancel(error);