Issue/3607 rollup watch only one config in exported array (#3620)

* Added watch: false as a way to exclude certain configs from watch mode (#3607)

* updated types (#3607)

* updated cli documentation (#3607)

* updated big list of all options (#3607)

* fixed types (#3607)

* throws an error if no config has to be watched (#3607)

* added example config to the 999-big-list-of-options.md file (#3607)
for excluding some configs from the watch mode

* Add tests

* Polish docs

Co-authored-by: Lukas Taegert-Atkinson <lukas.taegert-atkinson@tngtech.com>
Co-authored-by: Lukas Taegert-Atkinson <lukastaegert@users.noreply.github.com>

cli/run/watch-cli.ts

@@ -81,7 +81,11 @@ export async function watch(command: any) {
 	const resetScreen = getResetScreen(configs!, isTTY);
 
 	function start(configs: MergedRollupOptions[]) {
-		watcher = rollup.watch(configs as any);
+		try {
+			watcher = rollup.watch(configs as any);
+		} catch (err) {
+			return handleError(err);
+		}
 
 		watcher.on('event', event => {
 			switch (event.code) {

docs/01-command-line-reference.md

@@ -104,7 +104,7 @@ export default { // can be an array (for multiple inputs)
     skipWrite,
     exclude,
     include
-  }
+  } | false
 };
 ```
 

docs/999-big-list-of-options.md

@@ -1279,6 +1279,26 @@ For each key, the first number represents the elapsed time while the second repr
 
 ### Watch options
 
+Type: `{ buildDelay?: number, chokidar?: ChokidarOptions, clearScreen?: boolean, exclude?: string, include?: string, skipWrite?: boolean } | false`<br>
+Default: `{}`<br>
+
+Specify options for watch mode or prevent this configuration from being watched. Specifying `false` is only really useful when an array of configurations is used. In that case, this configuration will not be built or rebuilt on change in watch mode, but it will be built when running Rollup regularly:
+
+```js
+// rollup.config.js
+export default [
+  {
+    input: 'main.js',
+    output: { file: 'bundle.cjs.js', format: 'cjs' }
+  },
+  {
+    input: 'main.js',
+    watch: false,
+    output: { file: 'bundle.es.js', format: 'es' }
+  }
+]
+```
+
 These options only take effect when running Rollup with the `--watch` flag, or using `rollup.watch`.
 
 #### watch.buildDelay
@@ -1300,13 +1320,6 @@ Default: `true`
 
 Whether to clear the screen when a rebuild is triggered.
 
-#### watch.skipWrite
-Type: `boolean`<br>
-CLI: `--watch.skipWrite`/`--no-watch.skipWrite`<br>
-Default: `false`
-
-Whether to skip the `bundle.write()` step when a rebuild is triggered.
-
 #### watch.exclude
 Type: `string`<br>
 CLI: `--watch.exclude <files>`
@@ -1339,6 +1352,13 @@ export default {
 };
 ```
 
+#### watch.skipWrite
+Type: `boolean`<br>
+CLI: `--watch.skipWrite`/`--no-watch.skipWrite`<br>
+Default: `false`
+
+Whether to skip the `bundle.write()` step when a rebuild is triggered.
+
 ### Deprecated options
 
 ☢️ These options have been deprecated and may be removed in a future Rollup version.

src/rollup/types.d.ts

@@ -503,7 +503,7 @@ export interface InputOptions {
 	shimMissingExports?: boolean;
 	strictDeprecations?: boolean;
 	treeshake?: boolean | TreeshakingOptions;
-	watch?: WatcherOptions;
+	watch?: WatcherOptions | false;
 }
 
 export interface NormalizedInputOptions {
@@ -740,7 +740,7 @@ export interface WatcherOptions {
 
 export interface RollupWatchOptions extends InputOptions {
 	output?: OutputOptions | OutputOptions[];
-	watch?: WatcherOptions;
+	watch?: WatcherOptions | false;
 }
 
 interface TypedEventEmitter<T> {

src/utils/options/mergeOptions.ts

@@ -116,7 +116,7 @@ function mergeInputOptions(
 		shimMissingExports: getOption('shimMissingExports'),
 		strictDeprecations: getOption('strictDeprecations'),
 		treeshake: getObjectOption(config, overrides, 'treeshake'),
-		watch: getObjectOption(config, overrides, 'watch')
+		watch: getWatch(config, overrides, 'watch')
 	};
 
 	warnUnknownOptions(
@@ -161,6 +161,9 @@ const getObjectOption = (
 	return configOption;
 };
 
+const getWatch = (config: GenericConfigObject, overrides: GenericConfigObject, name: string) =>
+	config.watch !== false && getObjectOption(config, overrides, name);
+
 export const normalizeObjectOptionValue = (optionValue: any) => {
 	if (!optionValue) {
 		return optionValue;

src/watch/watch-proxy.ts

@@ -1,5 +1,7 @@
 import { EventEmitter } from 'events';
 import { RollupWatcher } from '../rollup/types';
+import { ensureArray } from '../utils/ensureArray';
+import { errInvalidOption, error } from '../utils/error';
 import { GenericConfigObject } from '../utils/options/options';
 import { loadFsEvents } from './fsevents-importer';
 
@@ -16,8 +18,18 @@ class WatchEmitter extends EventEmitter {
 
 export default function watch(configs: GenericConfigObject[] | GenericConfigObject): RollupWatcher {
 	const emitter = new WatchEmitter() as RollupWatcher;
+	const configArray = ensureArray(configs);
+	const watchConfigs = configArray.filter(config => config.watch !== false);
+	if (watchConfigs.length === 0) {
+		throw error(
+			errInvalidOption(
+				'watch',
+				'there must be at least one config where "watch" is not set to "false"'
+			)
+		);
+	}
 	loadFsEvents()
 		.then(() => import('./watch'))
-		.then(({ Watcher }) => new Watcher(configs, emitter));
+		.then(({ Watcher }) => new Watcher(watchConfigs, emitter));
 	return emitter;
 }

src/watch/watch.ts

@@ -9,7 +9,6 @@ import {
 	RollupWatcher,
 	WatcherOptions
 } from '../rollup/types';
-import { ensureArray } from '../utils/ensureArray';
 import { mergeOptions } from '../utils/options/mergeOptions';
 import { GenericConfigObject } from '../utils/options/options';
 import { FileWatcher } from './fileWatcher';
@@ -24,12 +23,11 @@ export class Watcher {
 	private running: boolean;
 	private tasks: Task[];
 
-	constructor(configs: GenericConfigObject[] | GenericConfigObject, emitter: RollupWatcher) {
+	constructor(configs: GenericConfigObject[], emitter: RollupWatcher) {
 		this.emitter = emitter;
 		emitter.close = this.close.bind(this);
-		const configArray = ensureArray(configs);
-		this.tasks = configArray.map(config => new Task(this, config));
-		this.buildDelay = configArray.reduce(
+		this.tasks = configs.map(config => new Task(this, config));
+		this.buildDelay = configs.reduce(
 			(buildDelay, { watch }: any) =>
 				watch && typeof watch.buildDelay === 'number'
 					? Math.max(buildDelay, (watch as WatcherOptions).buildDelay!)

test/cli/samples/watch/no-watched-config/_config.js

@@ -0,0 +1,13 @@
+const { assertStderrIncludes } = require('../../../../utils.js');
+
+module.exports = {
+	description: 'throws if no config is watched',
+	command: 'rollup -cw',
+	error: () => true,
+	stderr(stderr) {
+		assertStderrIncludes(
+			stderr,
+			'[!] Error: Invalid value for option "watch" - there must be at least one config where "watch" is not set to "false".'
+		);
+	}
+};

test/cli/samples/watch/no-watched-config/main.js

@@ -0,0 +1 @@
+assert.equal( 1 + 1, 2 );

test/cli/samples/watch/no-watched-config/rollup.config.js

@@ -0,0 +1,18 @@
+export default [
+	{
+		input: 'main.js',
+		watch: false,
+		output: {
+			dir: '_actual/es',
+			format: 'es'
+		}
+	},
+	{
+		input: 'main.js',
+		watch: false,
+		output: {
+			dir: '_actual/cjs',
+			format: 'cjs'
+		}
+	}
+];

test/watch/index.js

@@ -796,6 +796,50 @@ describe('rollup.watch', () => {
 			});
 	});
 
+	it('allows watching only some configs', () => {
+		return sander
+			.copydir('test/watch/samples/multiple')
+			.to('test/_tmp/input')
+			.then(() => wait(100))
+			.then(() => {
+				watcher = rollup.watch([
+					{
+						input: 'test/_tmp/input/main1.js',
+						watch: false,
+						output: {
+							file: 'test/_tmp/output/bundle1.js',
+							format: 'cjs'
+						}
+					},
+					{
+						input: 'test/_tmp/input/main2.js',
+						output: {
+							file: 'test/_tmp/output/bundle2.js',
+							format: 'cjs'
+						}
+					}
+				]);
+
+				return sequence(watcher, [
+					'START',
+					'BUNDLE_START',
+					'BUNDLE_END',
+					'END',
+					() => {
+						assert.strictEqual(
+							sander.existsSync(path.resolve(__dirname, '../_tmp/output/bundle1.js')),
+							false
+						);
+						assert.strictEqual(
+							sander.existsSync(path.resolve(__dirname, '../_tmp/output/bundle2.js')),
+							true
+						);
+						assert.deepStrictEqual(run('../_tmp/output/bundle2.js'), 43);
+					}
+				]);
+			});
+	});
+
 	it('respects output.globals', () => {
 		return sander
 			.copydir('test/watch/samples/globals')