test: add stream map tests

Add more tests to check and enforce the behavior of the map method.

Co-Authored-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
PR-URL: nodejs#41642
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Robert Nagy <ronagy@icloud.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>

test/parallel/test-stream-map.js

@@ -5,16 +5,14 @@ const {
   Readable,
 } = require('stream');
 const assert = require('assert');
+const { once } = require('events');
 const { setTimeout } = require('timers/promises');
 
 {
   // Map works on synchronous streams with a synchronous mapper
   const stream = Readable.from([1, 2, 3, 4, 5]).map((x) => x + x);
-  const result = [2, 4, 6, 8, 10];
   (async () => {
-    for await (const item of stream) {
-      assert.strictEqual(item, result.shift());
-    }
+    assert.deepStrictEqual(await stream.toArray(), [2, 4, 6, 8, 10]);
   })().then(common.mustCall());
 }
 
@@ -24,7 +22,49 @@ const { setTimeout } = require('timers/promises');
     await Promise.resolve();
     return x + x;
   });
-  const result = [2, 4, 6, 8, 10];
+  (async () => {
+    assert.deepStrictEqual(await stream.toArray(), [2, 4, 6, 8, 10]);
+  })().then(common.mustCall());
+}
+
+{
+  // Map works on asynchronous streams with a asynchronous mapper
+  const stream = Readable.from([1, 2, 3, 4, 5]).map(async (x) => {
+    return x + x;
+  }).map((x) => x + x);
+  (async () => {
+    assert.deepStrictEqual(await stream.toArray(), [4, 8, 12, 16, 20]);
+  })().then(common.mustCall());
+}
+
+{
+  // Map works on an infinite stream
+  const stream = Readable.from(async function* () {
+    while (true) yield 1;
+  }()).map(common.mustCall(async (x) => {
+    return x + x;
+  }, 5));
+  (async () => {
+    let i = 1;
+    for await (const item of stream) {
+      assert.strictEqual(item, 2);
+      if (++i === 5) break;
+    }
+  })().then(common.mustCall());
+}
+
+{
+  // Map works on non-objectMode streams
+  const stream = new Readable({
+    read() {
+      this.push(Uint8Array.from([1]));
+      this.push(Uint8Array.from([2]));
+      this.push(null);
+    }
+  }).map(async ([x]) => {
+    return x + x;
+  }).map((x) => x + x);
+  const result = [4, 8];
   (async () => {
     for await (const item of stream) {
       assert.strictEqual(item, result.shift());
@@ -33,39 +73,88 @@ const { setTimeout } = require('timers/promises');
 }
 
 {
-  // Map works on asynchronous streams with a asynchronous mapper
-  const stream = Readable.from([1, 2, 3, 4, 5]).map(async (x) => {
+  // Does not care about data events
+  const source = new Readable({
+    read() {
+      this.push(Uint8Array.from([1]));
+      this.push(Uint8Array.from([2]));
+      this.push(null);
+    }
+  });
+  setImmediate(() => stream.emit('data', Uint8Array.from([1])));
+  const stream = source.map(async ([x]) => {
     return x + x;
   }).map((x) => x + x);
-  const result = [4, 8, 12, 16, 20];
+  const result = [4, 8];
   (async () => {
     for await (const item of stream) {
       assert.strictEqual(item, result.shift());
     }
   })().then(common.mustCall());
 }
 
+{
+  // Emitting an error during `map`
+  const stream = Readable.from([1, 2, 3, 4, 5]).map(async (x) => {
+    if (x === 3) {
+      stream.emit('error', new Error('boom'));
+    }
+    return x + x;
+  });
+  assert.rejects(
+    stream.map((x) => x + x).toArray(),
+    /boom/,
+  ).then(common.mustCall());
+}
+
+{
+  // Throwing an error during `map` (sync)
+  const stream = Readable.from([1, 2, 3, 4, 5]).map((x) => {
+    if (x === 3) {
+      throw new Error('boom');
+    }
+    return x + x;
+  });
+  assert.rejects(
+    stream.map((x) => x + x).toArray(),
+    /boom/,
+  ).then(common.mustCall());
+}
+
+
+{
+  // Throwing an error during `map` (async)
+  const stream = Readable.from([1, 2, 3, 4, 5]).map(async (x) => {
+    if (x === 3) {
+      throw new Error('boom');
+    }
+    return x + x;
+  });
+  assert.rejects(
+    stream.map((x) => x + x).toArray(),
+    /boom/,
+  ).then(common.mustCall());
+}
+
 {
   // Concurrency + AbortSignal
   const ac = new AbortController();
-  let calls = 0;
-  const stream = Readable.from([1, 2, 3, 4, 5]).map(async (_, { signal }) => {
-    calls++;
-    await setTimeout(100, { signal });
-  }, { signal: ac.signal, concurrency: 2 });
+  const range = Readable.from([1, 2, 3, 4, 5]);
+  const stream = range.map(common.mustCall(async (_, { signal }) => {
+    await once(signal, 'abort');
+    throw signal.reason;
+  }, 2), { signal: ac.signal, concurrency: 2 });
   // pump
   assert.rejects(async () => {
     for await (const item of stream) {
-      // nope
-      console.log(item);
+      assert.fail('should not reach here, got ' + item);
     }
   }, {
     name: 'AbortError',
   }).then(common.mustCall());
 
   setImmediate(() => {
     ac.abort();
-    assert.strictEqual(calls, 2);
   });
 }