Fix source maps generation for the UMD build.

packages/ckeditor5-dev-build-tools/src/build.ts

@@ -9,8 +9,9 @@ import util from 'util';
 import chalk from 'chalk';
 import path from 'upath';
 import { rollup, type RollupOutput, type GlobalsOption } from 'rollup';
+import { loadSourcemaps } from './plugins/loadSourcemaps.js';
 import { getRollupConfig } from './config.js';
-import { getCwdPath, camelizeObjectKeys, removeWhitespace } from './utils.js';
+import { getCwdPath, camelizeObjectKeys, removeWhitespace, getOptionalPlugin } from './utils.js';
 
 export interface BuildOptions {
 	input: string;
@@ -104,19 +105,33 @@ async function generateUmdBuild( args: BuildOptions, bundle: RollupOutput ): Pro
 
 	const { dir, name } = path.parse( args.output );
 	const { plugins, ...config } = await getRollupConfig( args );
-	const build = await rollup( config );
-	const globals = {
-		...CKEDITOR_GLOBALS,
-		...args.globals as GlobalsOption
-	};
+
+	/**
+	 * Ignore the plugins we used for the ESM build. Instead, add a new plugin to not only
+	 * load the source code of the dependencies (which is the default in Rollup for better
+	 * performance), but also their source maps to generate a proper final source map for
+	 * the UMD bundle.
+	 */
+	const build = await rollup( {
+		...config,
+		plugins: [
+			getOptionalPlugin(
+				args.sourceMap,
+				loadSourcemaps()
+			)
+		]
+	} );
 
 	const umdBundle = await build.write( {
 		format: 'umd',
 		file: path.join( dir, `${ name }.umd.js` ),
 		assetFileNames: '[name][extname]',
 		sourcemap: args.sourceMap,
 		name: args.name,
-		globals
+		globals: {
+			...CKEDITOR_GLOBALS,
+			...args.globals as GlobalsOption
+		}
 	} );
 
 	return {

packages/ckeditor5-dev-build-tools/src/config.ts

@@ -5,9 +5,9 @@
 
 import path from 'upath';
 import { existsSync } from 'fs';
-import { getUserDependency } from './utils.js';
+import { getOptionalPlugin, getUserDependency } from './utils.js';
 import type { PackageJson } from 'type-fest';
-import type { InputPluginOption, Plugin, RollupOptions } from 'rollup';
+import type { Plugin, RollupOptions } from 'rollup';
 import type { BuildOptions } from './build.js';
 
 /**
@@ -272,13 +272,6 @@ export async function getRollupConfig( options: BuildOptions ) {
 	} as const satisfies RollupOptions;
 }
 
-/**
- * Returns plugin if condition is truthy. This is used only to get the types right.
- */
-function getOptionalPlugin<T extends InputPluginOption>( condition: unknown, plugin: T ): T | undefined {
-	return condition ? plugin : undefined;
-}
-
 /**
  * Returns a list of keys in `package.json` file of a given dependency.
  */

packages/ckeditor5-dev-build-tools/src/index.ts

@@ -6,6 +6,7 @@
 export { build } from './build.js';
 export { addBanner, type RollupBannerOptions } from './plugins/banner.js';
 export { emitCss, type RollupEmitCssOptions } from './plugins/emitCss.js';
+export { loadSourcemaps } from './plugins/loadSourcemaps.js';
 export { replaceImports, type RollupReplaceOptions } from './plugins/replace.js';
 export { splitCss, type RollupSplitCssOptions } from './plugins/splitCss.js';
 export { translations, type RollupTranslationsOptions } from './plugins/translations.js';

packages/ckeditor5-dev-build-tools/src/plugins/loadSourcemaps.ts

@@ -0,0 +1,25 @@
+/**
+ * @license Copyright (c) 2003-2024, CKSource Holding sp. z o.o. All rights reserved.
+ * For licensing, see LICENSE.md.
+ */
+
+import fs from 'fs';
+import type { Plugin } from 'rollup';
+
+export function loadSourcemaps(): Plugin {
+	return {
+		name: 'cke5-load-sourcemaps',
+		load( id: string ) {
+			const sourceMapId = id + '.map';
+
+			if ( !fs.existsSync( sourceMapId ) ) {
+				return;
+			}
+
+			return {
+				code: fs.readFileSync( id, 'utf-8' ),
+				map: fs.readFileSync( sourceMapId, 'utf-8' )
+			};
+		}
+	};
+}

packages/ckeditor5-dev-build-tools/src/utils.ts

@@ -6,6 +6,7 @@
 import { createRequire } from 'module';
 import path from 'upath';
 import type { CamelCase, CamelCasedProperties } from 'type-fest';
+import type { InputPluginOption } from 'rollup';
 
 const require = createRequire( import.meta.url );
 
@@ -60,3 +61,10 @@ export function getUserDependency( name: string ): any {
 
 	return require( path );
 }
+
+/**
+ * Returns plugin if condition is truthy. This is used only to get the types right.
+ */
+export function getOptionalPlugin<T extends InputPluginOption>( condition: unknown, plugin: T ): T | undefined {
+	return condition ? plugin : undefined;
+}

packages/ckeditor5-dev-build-tools/tests/_utils/utils.ts

@@ -4,7 +4,8 @@
  */
 
 import { expect, vi } from 'vitest';
-import type { RollupOutput, OutputChunk, OutputAsset } from 'rollup';
+import swc from '@rollup/plugin-swc';
+import type { RollupOutput, OutputChunk, OutputAsset, Plugin } from 'rollup';
 import * as utils from '../../src/utils';
 
 /**
@@ -71,3 +72,20 @@ export async function mockGetUserDependency( path: string, cb: () => any ): Prom
 			return actualImport( url );
 		} );
 }
+
+/**
+ * Helper function for getting a preconfigured `swc` plugin.
+ */
+export function swcPlugin(): Plugin {
+	return swc( {
+		include: [ '**/*.[jt]s' ],
+		swc: {
+			jsc: {
+				target: 'es2019'
+			},
+			module: {
+				type: 'es6'
+			}
+		}
+	} );
+}

packages/ckeditor5-dev-build-tools/tests/plugins/banner/banner.test.ts

@@ -5,10 +5,9 @@
 
 import { join } from 'path';
 import { test, expect } from 'vitest';
-import swc from '@rollup/plugin-swc';
 import styles from 'rollup-plugin-styles';
 import { rollup, type RollupOutput, type OutputAsset } from 'rollup';
-import { verifyAsset, verifyChunk } from '../../_utils/utils.js';
+import { swcPlugin, verifyAsset, verifyChunk } from '../../_utils/utils.js';
 
 import { addBanner, type RollupBannerOptions } from '../../../src/index.js';
 
@@ -19,17 +18,7 @@ async function generateBundle( options: RollupBannerOptions, sourcemap: boolean
 	const bundle = await rollup( {
 		input: join( import.meta.dirname, './fixtures/input.ts' ),
 		plugins: [
-			swc( {
-				include: [ '**/*.[jt]s' ],
-				swc: {
-					jsc: {
-						target: 'es2019'
-					},
-					module: {
-						type: 'es6'
-					}
-				}
-			} ),
+			swcPlugin,
 
 			// eslint-disable-next-line @typescript-eslint/ban-ts-comment
 			// @ts-ignore

packages/ckeditor5-dev-build-tools/tests/plugins/emitCss/emitCss.test.ts

@@ -5,28 +5,17 @@
 
 import { join } from 'path';
 import { test } from 'vitest';
-import swc from '@rollup/plugin-swc';
 import styles from 'rollup-plugin-styles';
 import { rollup, type RollupOutput } from 'rollup';
-import { verifyAsset } from '../../_utils/utils.js';
+import { swcPlugin, verifyAsset } from '../../_utils/utils.js';
 
 import { emitCss } from '../../../src/index.js';
 
 async function generateBundle( input: string ): Promise<RollupOutput['output']> {
 	const bundle = await rollup( {
 		input: join( import.meta.dirname, input ),
 		plugins: [
-			swc( {
-				include: [ '**/*.[jt]s' ],
-				swc: {
-					jsc: {
-						target: 'es2019'
-					},
-					module: {
-						type: 'es6'
-					}
-				}
-			} ),
+			swcPlugin,
 
 			// eslint-disable-next-line @typescript-eslint/ban-ts-comment
 			// @ts-ignore

packages/ckeditor5-dev-build-tools/tests/plugins/loadSourcemaps/fixtures/input.ts

@@ -0,0 +1,7 @@
+/**
+ * @license Copyright (c) 2003-2024, CKSource Holding sp. z o.o. All rights reserved.
+ * For licensing, see LICENSE.md.
+ */
+
+// The `magic-string` package is used because it contains source maps.
+export { default as MagicString } from 'magic-string';

packages/ckeditor5-dev-build-tools/tests/plugins/loadSourcemaps/fixtures/tsconfig.json

@@ -0,0 +1,17 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "lib": [
+      "ES2022",
+      "DOM",
+      "DOM.Iterable"
+    ],
+    "module": "NodeNext",
+    "moduleResolution": "NodeNext",
+    "skipLibCheck": true,
+    "resolveJsonModule": true
+  },
+  "include": [
+    "**/*"
+  ]
+}

packages/ckeditor5-dev-build-tools/tests/plugins/loadSourcemaps/loadSourcemaps.test.ts

@@ -0,0 +1,46 @@
+/**
+ * @license Copyright (c) 2003-2024, CKSource Holding sp. z o.o. All rights reserved.
+ * For licensing, see LICENSE.md.
+ */
+
+import { join } from 'path';
+import { test, expect } from 'vitest';
+import { rollup, type RollupOutput, type OutputAsset } from 'rollup';
+import { nodeResolve } from '@rollup/plugin-node-resolve';
+import { swcPlugin } from '../../_utils/utils.js';
+
+import { loadSourcemaps } from '../../../src/index.js';
+import { getOptionalPlugin } from '../../../src/utils.js';
+
+async function generateBundle( input: string, sourcemap: boolean = false ): Promise<RollupOutput[ 'output' ]> {
+	const bundle = await rollup( {
+		input: join( import.meta.dirname, input ),
+		plugins: [
+			nodeResolve(),
+			swcPlugin,
+			getOptionalPlugin( sourcemap, loadSourcemaps() )
+		]
+	} );
+
+	const { output } = await bundle.generate( {
+		format: 'esm',
+		file: 'input.js',
+		assetFileNames: '[name][extname]',
+		sourcemap
+	} );
+
+	return output;
+}
+
+test( 'Emits source maps combined with source maps of dependencies', async () => {
+	const output = await generateBundle( './fixtures/input.ts', true );
+	const sourceMap = output.find( asset => asset.fileName === 'input.js.map' ) as OutputAsset;
+
+	/**
+	 * The resulting source map will only contain the `/magic-string/src/` string if the source map
+	 * of the `magic-string` dependency was loaded and combined with the source map of the input file.
+	 * Otherwise, the source map will contain the `/magic-string/dist/` string, which is the bundled
+	 * build of the `magic-string` dependency.
+	 */
+	expect( sourceMap.source ).toContain( '/magic-string/src/' );
+} );