Add hook for modifying OutputOptions

docs/05-plugins.md

@@ -149,6 +149,12 @@ Kind: `sync, sequential`
 
 Reads and replaces or manipulates the options object passed to `rollup.rollup`. Returning `null` does not replace anything. This is the only hook that does not have access to most [plugin context](guide/en#plugin-context) utility functions as it is run before rollup is fully configured.
 
+#### `outputOptions`
+Type: `(outputOptions: OutputOptions) => OutputOptions | null`<br>
+Kind: `sync, sequential`
+
+Reads and replaces or manipulates the output options object passed to `bundle.generate`. Returning `null` does not replace anything.
+
 #### `outro`
 Type: `string | (() => string)`<br>
 Kind: `async, parallel`

src/rollup/index.ts

@@ -11,6 +11,7 @@ import { writeFile } from '../utils/fs';
 import getExportMode from '../utils/getExportMode';
 import mergeOptions, { GenericConfigObject } from '../utils/mergeOptions';
 import { basename, dirname, isAbsolute, resolve } from '../utils/path';
+import { PluginDriver } from '../utils/pluginDriver';
 import { SOURCEMAPPING_URL } from '../utils/sourceMappingURL';
 import { getTimings, initialiseTimers, timeEnd, timeStart } from '../utils/timers';
 import {
@@ -174,7 +175,8 @@ export default function rollup(rawInputOptions: GenericConfigObject): Promise<Ro
 					const outputOptions = normalizeOutputOptions(
 						inputOptions,
 						rawOutputOptions,
-						chunks.length > 1
+						chunks.length > 1,
+						graph.pluginDriver
 					);
 
 					timeStart('GENERATE', 1);
@@ -413,7 +415,8 @@ function writeOutputFile(
 function normalizeOutputOptions(
 	inputOptions: GenericConfigObject,
 	rawOutputOptions: GenericConfigObject,
-	hasMultipleChunks: boolean
+	hasMultipleChunks: boolean,
+	pluginDriver: PluginDriver
 ): OutputOptions {
 	if (!rawOutputOptions) {
 		throw new Error('You must supply an options object');
@@ -427,7 +430,15 @@ function normalizeOutputOptions(
 	if (mergedOptions.optionError) throw new Error(mergedOptions.optionError);
 
 	// now outputOptions is an array, but rollup.rollup API doesn't support arrays
-	const outputOptions = mergedOptions.outputOptions[0];
+	const mergedOutputOptions = mergedOptions.outputOptions[0];
+	const outputOptionsReducer = (outputOptions: OutputOptions, result: OutputOptions) => {
+		return result || outputOptions;
+	};
+	const outputOptions = pluginDriver.hookReduceArg0Sync(
+		'outputOptions',
+		[mergedOutputOptions],
+		outputOptionsReducer
+	);
 
 	checkOutputOptions(outputOptions);
 

src/rollup/types.d.ts

@@ -237,6 +237,7 @@ export interface Plugin {
 		chunk: OutputChunk
 	) => void | Promise<void>;
 	options?: (this: MinimalPluginContext, options: InputOptions) => InputOptions | void | null;
+	outputOptions?: (this: PluginContext, options: OutputOptions) => OutputOptions | void | null;
 	outro?: AddonHook;
 	renderChunk?: RenderChunkHook;
 	renderError?: (this: PluginContext, err?: Error) => Promise<void> | void;

src/utils/pluginDriver.ts

@@ -29,6 +29,12 @@ export interface PluginDriver {
 		reduce: Reduce<R, T>,
 		hookContext?: HookContext
 	): Promise<T>;
+	hookReduceArg0Sync<R = any, T = any>(
+		hook: string,
+		args: any[],
+		reduce: Reduce<R, T>,
+		hookContext?: HookContext
+	): T;
 	hookReduceValue<R = any, T = any>(
 		hook: string,
 		value: T | Promise<T>,
@@ -307,6 +313,14 @@ export function createPluginDriver(
 			}
 			return promise;
 		},
+		// chains, synchronically reduces returns of type R, to type T, handling the reduced value as the first hook argument
+		hookReduceArg0Sync(name, [arg0, ...args], reduce, hookContext) {
+			for (let i = 0; i < plugins.length; i++) {
+				const result = runHookSync(name, [arg0, ...args], i, false, hookContext);
+				arg0 = reduce.call(pluginContexts[i], arg0, result, plugins[i]);
+			}
+			return arg0;
+		},
 		// chains, reduces returns of type R, to type T, handling the reduced value separately. permits hooks as values.
 		hookReduceValue(name, initial, args, reduce, hookContext) {
 			let promise = Promise.resolve(initial);

test/hooks/index.js

@@ -29,6 +29,38 @@ describe('hooks', () => {
 			.then(bundle => {});
 	});
 
+	it('allows to read and modify output options in the outputOptions hook', () => {
+		return rollup
+			.rollup({
+				input: 'input',
+				treeshake: false,
+				plugins: [
+					loader({ input: `alert('hello')` }),
+					{
+						renderChunk(code, chunk, options) {
+							assert.strictEqual(options.banner, 'new banner');
+							assert.strictEqual(options.format, 'cjs');
+						},
+						outputOptions(options) {
+							assert.strictEqual(options.banner, 'banner');
+							assert.strictEqual(options.format, 'cjs');
+							assert.ok(/^\d+\.\d+\.\d+/.test(this.meta.rollupVersion));
+							return Object.assign({}, options, { banner: 'new banner' });
+						}
+					}
+				]
+			})
+			.then(bundle => {
+				return bundle.generate({
+					format: 'cjs',
+					banner: 'banner'
+				});
+			})
+			.then(({ output }) => {
+				assert.equal(output[0].code, `new banner\n'use strict';\n\nalert('hello');\n`);
+			});
+	});
+
 	it('supports buildStart and buildEnd hooks', () => {
 		let buildStartCnt = 0;
 		let buildEndCnt = 0;