Treat dropped download connections as status 0 again

Since HTTP.download() switched to fetch() in 10.0, a connection that
dropped mid-download threw a TypeError ("Error in input stream"), so
ZFS sync no longer retried interrupted S3 downloads and failed the file
sync immediately.

https://forums.zotero.org/discussion/134446/sync-error

(cherry picked from commit d85ec125be)

chrome/content/zotero/xpcom/http.js

@@ -727,6 +727,14 @@ Zotero.HTTP = new function () {
 			}, timeout);
 		}
 
+		// Report a dropped connection as status 0, as request() does, so that callers and
+		// _retryOnServerError() handle it the same way
+		function connectionError(e) {
+			let msg = "HTTP GET " + ctx.dispURL + " failed: " + e;
+			Zotero.debug(msg, 1);
+			return new Zotero.HTTP.UnexpectedStatusException({ status: 0 }, url, msg);
+		}
+
 		let response;
 		try {
 			response = await fetch(url, fetchOptions);
@@ -737,7 +745,7 @@ Zotero.HTTP = new function () {
 			if (controller.signal.aborted) {
 				throw new Zotero.HTTP.TimeoutException(timeout);
 			}
-			throw e;
+			throw connectionError(e);
 		}
 		clearTimeout(connectTimerID);
 
@@ -777,7 +785,9 @@ Zotero.HTTP = new function () {
 			await IOUtils.write(path, new Uint8Array());
 			while (true) {
 				resetInactivityTimer();
-				let { done, value } = await reader.read();
+				let { done, value } = await reader.read().catch((e) => {
+					throw connectionError(e);
+				});
 				if (done) break;
 				await IOUtils.write(path, value, { mode: 'append' });
 				totalBytes += value.byteLength;

test/tests/httpTest.js

@@ -424,6 +424,20 @@ describe("Zotero.HTTP", function () {
 					}
 				}
 			);
+			httpd.registerPathHandler(
+				'/download/truncated',
+				{
+					handle: function (request, response) {
+						response.seizePower();
+						response.write("HTTP/1.1 200 OK\r\n"
+							+ "Content-Type: application/octet-stream\r\n"
+							+ "Content-Length: 10000\r\n"
+							+ "\r\n"
+							+ "x".repeat(100));
+						response.finish();
+					}
+				}
+			);
 			httpd.registerPathHandler(
 				'/download/redirect-to-file',
 				{
@@ -564,6 +578,24 @@ describe("Zotero.HTTP", function () {
 			assert.isFalse(await IOUtils.exists(dest));
 		});
 
+		it("should throw UnexpectedStatusException with status 0 if the connection is refused", async function () {
+			let dest = PathUtils.join(tmpDir, "refused.bin");
+			let e = await getPromiseError(
+				Zotero.HTTP.download("http://127.0.0.1:1/", dest)
+			);
+			assert.instanceOf(e, Zotero.HTTP.UnexpectedStatusException);
+			assert.equal(e.status, 0);
+		});
+
+		it("should throw UnexpectedStatusException with status 0 if the connection drops during the download", async function () {
+			let dest = PathUtils.join(tmpDir, "truncated.bin");
+			let e = await getPromiseError(
+				Zotero.HTTP.download(baseURL + "download/truncated", dest)
+			);
+			assert.instanceOf(e, Zotero.HTTP.UnexpectedStatusException);
+			assert.equal(e.status, 0);
+		});
+
 		it("should allow non-success status with successCodes", async function () {
 			let dest = PathUtils.join(tmpDir, "404.bin");
 			let req = await Zotero.HTTP.download(