package.json

@@ -75,11 +75,13 @@
 		"eslint": "^8.49.0",
 		"execa": "^8.0.1",
 		"fs-fixture": "^1.2.0",
+		"fs-require": "^1.6.0",
 		"get-node": "^14.2.1",
 		"kolorist": "^1.8.0",
 		"lint-staged": "^14.0.1",
 		"magic-string": "^0.30.3",
 		"manten": "^1.2.0",
+		"memfs": "^4.6.0",
 		"node-pty": "^1.0.0",
 		"outdent": "^0.8.0",
 		"pkgroll": "^1.11.1",

src/cjs/index.ts

@@ -8,7 +8,7 @@ import {
 	createFilesMatcher,
 } from 'get-tsconfig';
 import type { TransformOptions } from 'esbuild';
-import { installSourceMapSupport, shouldStripSourceMap, stripSourceMap } from '../source-map';
+import { installSourceMapSupport } from '../source-map';
 import { transformSync } from '../utils/transform';
 import { transformDynamicImport } from '../utils/transform/transform-dynamic-import';
 import { resolveTsPath } from '../utils/resolve-ts-path';
@@ -69,11 +69,6 @@ const transformer = (
 
 	let code = fs.readFileSync(filePath, 'utf8');
 
-	// Strip source maps if originally disabled
-	if (shouldStripSourceMap) {
-		code = stripSourceMap(code);
-	}
-
 	if (filePath.endsWith('.cjs')) {
 		// Contains native ESM check
 		const transformed = transformDynamicImport(filePath, code);

src/esm/loaders.ts

@@ -8,7 +8,7 @@ import type { TransformOptions } from 'esbuild';
 import { transform } from '../utils/transform';
 import { transformDynamicImport } from '../utils/transform/transform-dynamic-import';
 import { resolveTsPath } from '../utils/resolve-ts-path';
-import { installSourceMapSupport, shouldStripSourceMap, stripSourceMap } from '../source-map';
+import { installSourceMapSupport } from '../source-map';
 import { importAttributes } from '../utils/node-features';
 import {
 	tsconfigPathsMatcher,
@@ -281,12 +281,7 @@ export const load: LoadHook = async function (
 	}
 
 	const filePath = url.startsWith('file://') ? fileURLToPath(url) : url;
-	let code = loaded.source.toString();
-
-	// Strip source maps if originally disabled
-	if (shouldStripSourceMap) {
-		code = stripSourceMap(code);
-	}
+	const code = loaded.source.toString();
 
 	if (
 		// Support named imports in JSON modules

src/source-map.ts

@@ -10,26 +10,7 @@ type PortMessage = {
 	map: RawSourceMap;
 };
 
-// If Node.js has source map disabled, we should strip source maps to speed up processing
-export const shouldStripSourceMap = (
-	('sourceMapsEnabled' in process)
-	&& process.sourceMapsEnabled === false
-);
-
-const sourceMapPrefix = '\n//# sourceMappingURL=';
-
-export const stripSourceMap = (code: string) => {
-	const sourceMapIndex = code.indexOf(sourceMapPrefix);
-	if (sourceMapIndex === -1) {
-		return code;
-	}
-
-	const nextNewLine = code.indexOf('\n', sourceMapIndex + sourceMapPrefix.length);
-	const afterSourceMap = nextNewLine === -1 ? '' : code.slice(nextNewLine);
-	return code.slice(0, sourceMapIndex) + afterSourceMap;
-};
-
-const inlineSourceMapPrefix = `${sourceMapPrefix}data:application/json;base64,`;
+const inlineSourceMapPrefix = '\n//# sourceMappingURL=data:application/json;base64,';
 
 export const installSourceMapSupport = (
 	/**

src/utils/transform/get-esbuild-options.ts

@@ -1,50 +1,66 @@
 import path from 'path';
-import type { TransformOptions } from 'esbuild';
+import type { TransformOptions, TransformResult } from 'esbuild';
 
-const nodeVersion = process.versions.node;
+export const baseConfig = Object.freeze({
+	target: `node${process.versions.node}`,
 
-export const getEsbuildOptions = (
-	extendOptions: TransformOptions,
+	// "default" tells esbuild to infer loader from file name
+	// https://github.com/evanw/esbuild/blob/4a07b17adad23e40cbca7d2f8931e8fb81b47c33/internal/bundler/bundler.go#L158
+	loader: 'default',
+});
+
+export const cacheConfig = {
+	...baseConfig,
+
+	sourcemap: true,
+
+	/**
+	 * Smaller output for cache and marginal performance improvement:
+	 * https://twitter.com/evanwallace/status/1396336348366180359?s=20
+	 *
+	 * minifyIdentifiers is disabled because debuggers don't use the
+	 * `names` property from the source map
+	 *
+	 * minifySyntax is disabled because it does some tree-shaking
+	 * eg. unused try-catch error variable
+	 */
+	minifyWhitespace: true,
+
+	/**
+	 * esbuild renames variables even if minification is not enabled
+	 * https://esbuild.github.io/try/#dAAwLjE5LjUAAGNvbnN0IGEgPSAxOwooZnVuY3Rpb24gYSgpIHt9KTs
+	 */
+	keepNames: true,
+};
+
+export const patchOptions = (
+	options: TransformOptions,
 ) => {
-	const options: TransformOptions = {
-		target: `node${nodeVersion}`,
-
-		// "default" tells esbuild to infer loader from file name
-		// https://github.com/evanw/esbuild/blob/4a07b17adad23e40cbca7d2f8931e8fb81b47c33/internal/bundler/bundler.go#L158
-		loader: 'default',
-
-		sourcemap: true,
-
-		/**
-		 * Smaller output for cache and marginal performance improvement:
-		 * https://twitter.com/evanwallace/status/1396336348366180359?s=20
-		 *
-		 * minifyIdentifiers is disabled because debuggers don't use the
-		 * `names` property from the source map
-		 *
-		 * minifySyntax is disabled because it does some tree-shaking
-		 * eg. unused try-catch error variable
-		 */
-		minifyWhitespace: true,
-		keepNames: true,
-
-		...extendOptions,
-	};
+	const originalSourcefile = options.sourcefile;
 
-	if (options.sourcefile) {
-		const { sourcefile } = options;
-		const extension = path.extname(sourcefile);
+	if (originalSourcefile) {
+		const extension = path.extname(originalSourcefile);
 
 		if (extension) {
 			// https://github.com/evanw/esbuild/issues/1932
 			if (extension === '.cts' || extension === '.mts') {
-				options.sourcefile = `${sourcefile.slice(0, -3)}ts`;
+				options.sourcefile = `${originalSourcefile.slice(0, -3)}ts`;
 			}
 		} else {
 			// esbuild errors to detect loader when a file doesn't have an extension
 			options.sourcefile += '.js';
 		}
 	}
 
-	return options;
+	return (
+		result: TransformResult,
+	) => {
+		if (options.sourcefile !== originalSourcefile) {
+			result.map = result.map.replace(
+				JSON.stringify(options.sourcefile),
+				JSON.stringify(originalSourcefile),
+			);
+		}
+		return result;
+	};
 };