test(streams): improve test coverage (denoland#5078)

* tests(streams): improve test coverage

* tweak

* work

* work

* work

* work

* revert

* revert

Author: iuioiua

streams/concat_readable_streams_test.ts

@@ -93,3 +93,24 @@ Deno.test("concatStreams() handles errors", async () => {
     ],
   );
 });
+
+Deno.test("concatReadableStreams cancels all streams when concatenated stream is cancelled", async () => {
+  const reasons: string[] = [];
+  const createMockStream = () =>
+    new ReadableStream({
+      start(controller) {
+        controller.enqueue("data");
+      },
+      cancel(error) {
+        reasons.push(error);
+      },
+    });
+
+  const stream1 = createMockStream();
+  const stream2 = createMockStream();
+  const concatenatedStream = concatReadableStreams(stream1, stream2);
+
+  await concatenatedStream.cancel("Test cancel");
+
+  assertEquals(reasons, ["Test cancel", "Test cancel"]);
+});

streams/early_zip_readable_streams_test.ts

@@ -1,7 +1,7 @@
 // Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
 
 import { earlyZipReadableStreams } from "./early_zip_readable_streams.ts";
-import { assertEquals } from "@std/assert";
+import { assertEquals, assertRejects } from "@std/assert";
 
 Deno.test("earlyZipReadableStreams() handles short first", async () => {
   const textStream = ReadableStream.from(["1", "2", "3"]);
@@ -60,3 +60,24 @@ Deno.test("earlyZipReadableStreams() can zip three streams", async () => {
     "3",
   ]);
 });
+
+Deno.test("earlyZipReadableStreams() controller error", async () => {
+  const errorMsg = "Test error";
+  const stream = new ReadableStream({
+    start(controller) {
+      controller.enqueue("This will succeed");
+    },
+    pull() {
+      throw new Error(errorMsg);
+    },
+  });
+
+  const zippedStream = earlyZipReadableStreams(stream);
+  const reader = zippedStream.getReader();
+
+  assertEquals(await reader.read(), {
+    value: "This will succeed",
+    done: false,
+  });
+  await assertRejects(async () => await reader.read(), Error, errorMsg);
+});

streams/text_delimiter_stream.ts

@@ -86,7 +86,7 @@ export class TextDelimiterStream extends TransformStream<string, string> {
    */
   constructor(
     delimiter: string,
-    options: DelimiterStreamOptions = { disposition: "discard" },
+    options?: DelimiterStreamOptions,
   ) {
     super({
       transform: (chunk, controller) => {
@@ -99,7 +99,7 @@ export class TextDelimiterStream extends TransformStream<string, string> {
 
     this.#delimiter = delimiter;
     this.#delimLPS = createLPS(new TextEncoder().encode(delimiter));
-    this.#disp = options.disposition ?? "discard";
+    this.#disp = options?.disposition ?? "discard";
   }
 
   #handle(

streams/zip_readable_streams_test.ts

@@ -1,6 +1,6 @@
 // Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
 
-import { assertEquals } from "@std/assert";
+import { assertEquals, assertRejects } from "@std/assert";
 import { zipReadableStreams } from "./zip_readable_streams.ts";
 
 Deno.test("zipReadableStreams()", async () => {
@@ -29,3 +29,25 @@ Deno.test("zipReadableStreams()", async () => {
     "qwertzuiopasq123d",
   ]);
 });
+
+Deno.test("zipReadableStreams handles errors by closing the stream with an error", async () => {
+  const errorStream = new ReadableStream({
+    start(controller) {
+      controller.enqueue("Initial data");
+    },
+    pull() {
+      throw new Error("Test error during read");
+    },
+  });
+  const normalStream = ReadableStream.from(["Normal data"]);
+  const zippedStream = zipReadableStreams(errorStream, normalStream);
+  const reader = zippedStream.getReader();
+
+  assertEquals(await reader.read(), { value: "Initial data", done: false });
+  assertEquals(await reader.read(), { value: "Normal data", done: false });
+  await assertRejects(
+    async () => await reader.read(),
+    Error,
+    "Test error during read",
+  );
+});