Add test cases for multiple mapper errors with stop on error (#49)

Co-authored-by: Sindre Sorhus <sindresorhus@gmail.com>

index.d.ts

@@ -9,7 +9,11 @@ export interface Options {
 	readonly concurrency?: number;
 
 	/**
-	When set to `false`, instead of stopping when a promise rejects, it will wait for all the promises to settle and then reject with an [aggregated error](https://github.com/sindresorhus/aggregate-error) containing all the errors from the rejected promises.
+	When `true`, the first mapper rejection will be rejected back to the consumer.
+
+	When `false`, instead of stopping when a promise rejects, it will wait for all the promises to settle and then reject with an [aggregated error](https://github.com/sindresorhus/aggregate-error) containing all the errors from the rejected promises.
+
+	Caveat: When `true`, any already-started async mappers will continue to run until they resolve or reject. In the case of infinite concurrency with sync iterables, *all* mappers are invoked on startup and will continue after the first rejection. [Issue #51](https://github.com/sindresorhus/p-map/issues/51) can be implemented for abort control.
 
 	@default true
 	*/

readme.md

@@ -72,7 +72,11 @@ Number of concurrently pending promises returned by `mapper`.
 Type: `boolean`\
 Default: `true`
 
-When set to `false`, instead of stopping when a promise rejects, it will wait for all the promises to settle and then reject with an [aggregated error](https://github.com/sindresorhus/aggregate-error) containing all the errors from the rejected promises.
+When `true`, the first mapper rejection will be rejected back to the consumer.
+
+When `false`, instead of stopping when a promise rejects, it will wait for all the promises to settle and then reject with an [aggregated error](https://github.com/sindresorhus/aggregate-error) containing all the errors from the rejected promises.
+
+Caveat: When `true`, any already-started async mappers will continue to run until they resolve or reject. In the case of infinite concurrency with sync iterables, *all* mappers are invoked on startup and will continue after the first rejection. [Issue #51](https://github.com/sindresorhus/p-map/issues/51) can be implemented for abort control.
 
 ### pMapSkip
 

test.js

@@ -378,3 +378,35 @@ test('incorrect input type', async t => {
 	await t.throwsAsync(task, {message: 'Expected `input` to be either an `Iterable` or `AsyncIterable`, got (number)'});
 	t.false(mapperCalled);
 });
+
+test('no unhandled rejected promises from mapper throws - infinite concurrency', async t => {
+	const input = [1, 2, 3];
+	const mappedValues = [];
+	await t.throwsAsync(
+		pMap(input, async value => {
+			mappedValues.push(value);
+			await delay(100);
+			throw new Error(`Oops! ${value}`);
+		}),
+		{message: 'Oops! 1'}
+	);
+	// Note: All 3 mappers get invoked, all 3 throw, even with `{stopOnError: true}` this
+	// should raise an AggregateError with all 3 exceptions instead of throwing 1
+	// exception and hiding the other 2.
+	t.deepEqual(mappedValues, [1, 2, 3]);
+});
+
+test('no unhandled rejected promises from mapper throws - concurrency 1', async t => {
+	const input = [1, 2, 3];
+	const mappedValues = [];
+	await t.throwsAsync(
+		pMap(input, async value => {
+			mappedValues.push(value);
+			await delay(100);
+			throw new Error(`Oops! ${value}`);
+		},
+		{concurrency: 1}),
+		{message: 'Oops! 1'}
+	);
+	t.deepEqual(mappedValues, [1]);
+});