feat: introduce the virtualDirname option to customize the virtual directory name (#5602)

Author: TrickyPi

docs/configuration-options/index.md

@@ -1472,7 +1472,7 @@ define(['https://d3js.org/d3.v4.min'], function (d3) {
 |     CLI: | `--preserveModules`/`--no-preserveModules` |
 | Default: | `false`                                    |
 
-Instead of creating as few chunks as possible, this mode will create separate chunks for all modules using the original module names as file names. Requires the [`output.dir`](#output-dir) option. Tree-shaking will still be applied, suppressing files that are not used by the provided entry points or do not have side effects when executed and removing unused exports of files that are not entry points. On the other hand, if plugins (like `@rollup/plugin-commonjs`) emit additional "virtual" files to achieve certain results, those files will be emitted as actual files using a pattern `_virtual/fileName.js`.
+Instead of creating as few chunks as possible, this mode will create separate chunks for all modules using the original module names as file names. Requires the [`output.dir`](#output-dir) option. Tree-shaking will still be applied, suppressing files that are not used by the provided entry points or do not have side effects when executed and removing unused exports of files that are not entry points. On the other hand, if plugins (like `@rollup/plugin-commonjs`) emit additional "virtual" files to achieve certain results, those files will be emitted as actual files using a pattern [`${output.virtualDirname}/fileName.js`](#output-virtualdirname).
 
 It is therefore not recommended to blindly use this option to transform an entire file structure to another format if you directly want to import from those files as expected exports may be missing. In that case, you should rather designate all files explicitly as entry points by adding them to the [`input` option object](#input), see the example there for how to do that.
 
@@ -1682,6 +1682,16 @@ Re-parses each generated chunk to detect if the generated code is valid JavaScri
 
 If the code is invalid, a warning will be issued. Note that no error is thrown so that you can still inspect the generated output. To promote this warning to an error, you can watch for it in an [`onwarn`](#onwarn) handler.
 
+### output.virtualDirname
+
+|          |                              |
+| -------: | :--------------------------- |
+|    Type: | `string`                     |
+|     CLI: | `--virtualDirname <dirname>` |
+| Default: | `_virtual`                   |
+
+This option specifies the directory name for "virtual" files that might be emitted by plugins (like `@rollup/plugin-commonjs`). It is only validated when [`output.preserveModules`](#output-preservemodules) is enabled.
+
 ### preserveEntrySignatures
 
 |  |  |

src/Chunk.ts

@@ -1075,7 +1075,9 @@ export default class Chunk {
 				? idWithoutExtension.slice(preserveModulesRoot.length).replace(/^[/\\]/, '')
 				: relative(this.inputBase, idWithoutExtension);
 		} else {
-			return `_virtual/${basename(idWithoutExtension)}`;
+			return (
+				this.outputOptions.virtualDirname.replace(/\/$/, '') + '/' + basename(idWithoutExtension)
+			);
 		}
 	}
 

src/rollup/types.d.ts

@@ -756,6 +756,7 @@ export interface OutputOptions {
 	strict?: boolean;
 	systemNullSetters?: boolean;
 	validate?: boolean;
+	virtualDirname?: string;
 }
 
 export interface NormalizedOutputOptions {
@@ -809,6 +810,7 @@ export interface NormalizedOutputOptions {
 	strict: boolean;
 	systemNullSetters: boolean;
 	validate: boolean;
+	virtualDirname: string;
 }
 
 export type WarningHandlerWithDefault = (

src/utils/options/mergeOptions.ts

@@ -279,7 +279,8 @@ async function mergeOutputOptions(
 		sourcemapPathTransform: getOption('sourcemapPathTransform'),
 		strict: getOption('strict'),
 		systemNullSetters: getOption('systemNullSetters'),
-		validate: getOption('validate')
+		validate: getOption('validate'),
+		virtualDirname: getOption('virtualDirname')
 	};
 
 	warnUnknownOptions(config, Object.keys(outputOptions), 'output options', log);

src/utils/options/normalizeOutputOptions.ts

@@ -108,7 +108,8 @@ export async function normalizeOutputOptions(
 			| undefined,
 		strict: config.strict ?? true,
 		systemNullSetters: config.systemNullSetters ?? true,
-		validate: config.validate || false
+		validate: config.validate || false,
+		virtualDirname: config.virtualDirname || '_virtual'
 	};
 
 	warnUnknownOptions(config, Object.keys(outputOptions), 'output options', inputOptions.onLog);

test/chunking-form/samples/option-virtual-dirname/_config.js

@@ -0,0 +1,9 @@
+const commonjs = require('@rollup/plugin-commonjs');
+
+module.exports = defineTest({
+	description: 'expect the directory name for "virtual" files to be rollup_virtual',
+	options: {
+		plugins: [commonjs()],
+		output: { preserveModules: true, virtualDirname: 'rollup_virtual' }
+	}
+});

test/chunking-form/samples/option-virtual-dirname/_expected/amd/main.js

@@ -0,0 +1,7 @@
+define(['./main2'], (function (main) { 'use strict';
+
+
+
+	return main;
+
+}));

test/chunking-form/samples/option-virtual-dirname/_expected/amd/main2.js

@@ -0,0 +1,9 @@
+define(['./rollup_virtual/_commonjsHelpers'], (function (_commonjsHelpers) { 'use strict';
+
+	var main = true;
+
+	var main$1 = /*@__PURE__*/_commonjsHelpers.getDefaultExportFromCjs(main);
+
+	return main$1;
+
+}));

test/chunking-form/samples/option-virtual-dirname/_expected/amd/rollup_virtual/_commonjsHelpers.js

@@ -0,0 +1,9 @@
+define(['exports'], (function (exports) { 'use strict';
+
+	function getDefaultExportFromCjs (x) {
+		return x.__esModule && Object.prototype.hasOwnProperty.call(x, 'default') ? x['default'] : x;
+	}
+
+	exports.getDefaultExportFromCjs = getDefaultExportFromCjs;
+
+}));

test/chunking-form/samples/option-virtual-dirname/_expected/cjs/main.js

@@ -0,0 +1,7 @@
+'use strict';
+
+var main = require('./main2.js');
+
+
+
+module.exports = main;