perf: handle source map as object (#35)

BREAKING CHANGE: applyTransformers returns source map as object

Author: privatenumber

package.json

@@ -51,6 +51,7 @@
 		"manten": "^0.3.0",
 		"memfs": "^3.4.7",
 		"pkgroll": "^1.4.0",
+		"source-map": "^0.6.0",
 		"tsx": "^3.9.0",
 		"typescript": "^4.8.4"
 	},

pnpm-lock.yaml

@@ -1,5 +1,6 @@
 import sourceMapSupport from 'source-map-support';
-import type { SourceMapInput } from '@ampproject/remapping';
+import type { RawSourceMap } from 'source-map';
+import type { Transformed } from './transform/apply-transformers';
 
 const inlineSourceMapPrefix = '\n//# sourceMappingURL=data:application/json;base64,';
 
@@ -25,14 +26,15 @@ export function installSourceMapSupport() {
 		process.setSourceMapsEnabled(true);
 
 		return (
-			{ code, map }: { code: string; map: SourceMapInput },
-		) => {
-			const mapString = typeof map === 'string' ? map : map.toString();
-			return code + inlineSourceMapPrefix + Buffer.from(mapString, 'utf8').toString('base64');
-		};
+			{ code, map }: Transformed,
+		) => (
+			code
+			+ inlineSourceMapPrefix
+			+ Buffer.from(JSON.stringify(map), 'utf8').toString('base64')
+		);
 	}
 
-	const sourcemaps = new Map<string, string>();
+	const sourcemaps = new Map<string, RawSourceMap>();
 
 	sourceMapSupport.install({
 		environment: 'node',
@@ -43,11 +45,10 @@ export function installSourceMapSupport() {
 	});
 
 	return (
-		{ code, map }: { code: string; map: SourceMapInput },
+		{ code, map }: Transformed,
 		filePath: string,
 	) => {
-		const mapString = typeof map === 'string' ? map : map.toString();
-		sourcemaps.set(filePath, mapString);
+		sourcemaps.set(filePath, map);
 		return code;
 	};
 }

src/source-map.ts

@@ -1,5 +1,8 @@
 import remapping from '@ampproject/remapping';
 import type { SourceMapInput } from '@ampproject/remapping';
+import type { RawSourceMap } from 'source-map';
+
+type SourceMap = SourceMapInput | RawSourceMap;
 
 type MaybePromise<T> = T | Promise<T>;
 
@@ -9,19 +12,17 @@ type IntersectionArray<T extends unknown[]> = (
 		: unknown
 );
 
-type Transformed = {
+type TransformerResult = {
 	code: string;
-	map: SourceMapInput;
-};
-
-type TransformerResult = Transformed | undefined;
+	map: SourceMap;
+} | undefined;
 
 type Transformer<
-	Result extends MaybePromise<TransformerResult>
+	ReturnType extends MaybePromise<TransformerResult>
 > = (
 	filePath: string,
 	code: string,
-) => Result;
+) => ReturnType;
 
 type Results<
 	Array_ extends Transformer<MaybePromise<TransformerResult>>[]
@@ -33,7 +34,12 @@ type Results<
 	);
 };
 
-type AddSourceMap<T> = Omit<T, 'map'> & { map: string };
+type AddSourceMap<T> = Omit<T, 'map'> & { map: RawSourceMap };
+
+export type Transformed = {
+	code: string;
+	map: RawSourceMap;
+};
 
 export function applyTransformersSync<
 	T extends Readonly<Transformer<TransformerResult>[]>,
@@ -42,11 +48,8 @@ export function applyTransformersSync<
 	code: string,
 	transformers: T,
 ) {
-	const maps: SourceMapInput[] = [];
-	const result = {
-		code,
-		map: '',
-	};
+	const maps: SourceMap[] = [];
+	const result = { code };
 
 	for (const transformer of transformers) {
 		const transformed = transformer(filePath, result.code);
@@ -57,13 +60,10 @@ export function applyTransformersSync<
 		}
 	}
 
-	result.map = (
-		maps.length > 1
-			? remapping(maps, () => null).toString()
-			: maps[0].toString()
-	);
-
-	return result as unknown as AddSourceMap<IntersectionArray<Results<[...T]>>>;
+	return {
+		...result,
+		map: remapping(maps as SourceMapInput[], () => null),
+	} as unknown as AddSourceMap<IntersectionArray<Results<[...T]>>>;
 }
 
 export async function applyTransformers<
@@ -73,11 +73,8 @@ export async function applyTransformers<
 	code: string,
 	transformers: T,
 ) {
-	const maps: SourceMapInput[] = [];
-	const result = {
-		code,
-		map: '',
-	};
+	const maps: SourceMap[] = [];
+	const result = { code };
 
 	for (const transformer of transformers) {
 		const transformed = await transformer(filePath, result.code);
@@ -88,11 +85,8 @@ export async function applyTransformers<
 		}
 	}
 
-	result.map = (
-		maps.length > 1
-			? remapping(maps, () => null).toString()
-			: maps[0].toString()
-	);
-
-	return result as unknown as AddSourceMap<IntersectionArray<Results<[...T]>>>;
+	return {
+		...result,
+		map: remapping(maps as SourceMapInput[], () => null),
+	} as unknown as AddSourceMap<IntersectionArray<Results<[...T]>>>;
 }

src/transform/apply-transformers.ts

@@ -1,12 +1,12 @@
 import fs from 'fs';
 import path from 'path';
 import os from 'os';
-import type { TransformResult } from 'esbuild';
 import { readJsonFile } from '../utils/read-json-file';
+import type { Transformed } from './apply-transformers';
 
 const getTime = () => Math.floor(Date.now() / 1e8);
 
-class FileCache extends Map<string, TransformResult> {
+class FileCache<ReturnType> extends Map<string, ReturnType> {
 	/**
 	 * By using tmpdir, the expectation is for the OS to clean any files
 	 * that haven't been read for a while.
@@ -56,7 +56,7 @@ class FileCache extends Map<string, TransformResult> {
 		}
 
 		const cacheFilePath = path.join(this.cacheDirectory, diskCacheHit.fileName);
-		const cachedResult = readJsonFile<TransformResult>(cacheFilePath);
+		const cachedResult = readJsonFile<ReturnType>(cacheFilePath);
 
 		if (!cachedResult) {
 			// Remove broken cache file
@@ -77,7 +77,7 @@ class FileCache extends Map<string, TransformResult> {
 		return cachedResult;
 	}
 
-	set(key: string, value: TransformResult) {
+	set(key: string, value: ReturnType) {
 		super.set(key, value);
 
 		if (value) {
@@ -116,6 +116,6 @@ class FileCache extends Map<string, TransformResult> {
 
 export default (
 	process.env.ESBK_DISABLE_CACHE
-		? new Map<string, TransformResult>()
-		: new FileCache()
+		? new Map<string, Transformed>()
+		: new FileCache<Transformed>()
 );

src/transform/cache.ts

@@ -8,16 +8,15 @@ import {
 import { sha1 } from '../utils/sha1';
 import { transformDynamicImport } from './transform-dynamic-import';
 import cache from './cache';
-import { applyTransformersSync, applyTransformers } from './apply-transformers';
+import {
+	applyTransformersSync,
+	applyTransformers,
+	type Transformed,
+} from './apply-transformers';
 import { getEsbuildOptions } from './get-esbuild-options';
 
 export { transformDynamicImport } from './transform-dynamic-import';
 
-type Transformed = {
-	code: string;
-	map: string;
-};
-
 // Used by cjs-loader
 export function transformSync(
 	code: string,

src/transform/index.ts

@@ -1,10 +1,7 @@
 import MagicString from 'magic-string';
-import type { EncodedSourceMap } from '@ampproject/remapping';
+import type { RawSourceMap } from 'source-map';
 import { parseEsm } from '../utils/es-module-lexer';
 
-// Necessary for types to build correctly
-export type { EncodedSourceMap };
-
 const checkEsModule = `.then((mod)=>{
 	const exports = Object.keys(mod);
 	if(
@@ -41,6 +38,6 @@ export function transformDynamicImport(
 		map: magicString.generateMap({
 			source: filePath,
 			hires: true,
-		}) as EncodedSourceMap,
+		}) as unknown as RawSourceMap,
 	};
 }