feat: support tsconfig-paths (#21)

Author: hanayashiki

loader.mjs

@@ -1,12 +1,20 @@
 import { URL, pathToFileURL, fileURLToPath } from 'url'
 import fs from 'fs'
 import { transformSync } from 'esbuild'
+import { createMatchPath, loadConfig } from 'tsconfig-paths'
 
 const baseURL = pathToFileURL(`${process.cwd()}/`).href
 const isWindows = process.platform === 'win32'
 
-const extensionsRegex = /\.(tsx?|json)$/
+const extensionsRegex = /\.(m?tsx?|json)$/
 const excludeRegex = /^\w+:/
+const tsExtensions = ['.mts', '.ts', '.cts', '.tsx'] // https://www.typescriptlang.org/docs/handbook/release-notes/typescript-4-5.html
+const jsExtensions = ['.mjs', '.js', '.cjs', '.jsx']
+const extensions = [...tsExtensions, ...jsExtensions]
+
+const tsconfig = loadConfig()
+
+const matchPath = tsconfig.resultType === 'success' ? createMatchPath(tsconfig.absoluteBaseUrl, tsconfig.paths) : undefined
 
 function esbuildTransformSync(rawSource, filename, url, format) {
   const {
@@ -31,7 +39,29 @@ function esbuildTransformSync(rawSource, filename, url, format) {
   return { js, jsSourceMap }
 }
 
+export const tryPathWithExtensions = (path) => {
+  for (const ext of extensions) {
+    const p = `${path}${ext}`
+    if (fs.existsSync(p))
+      return p
+  }
+  return null
+}
+
 export function resolve(specifier, context, defaultResolve) {
+  // baseUrl & paths takes the highest precedence, as TypeScript behaves.
+  if (matchPath) {
+    const nodePath = matchPath(specifier, undefined, undefined, extensions)
+
+    if (nodePath) {
+      const foundPath = tryPathWithExtensions(nodePath)
+      return {
+        url: pathToFileURL(foundPath).href,
+        format: extensionsRegex.test(foundPath) && 'module',
+      }
+    }
+  }
+
   const { parentURL = baseURL } = context
   const url = new URL(specifier, parentURL)
   if (extensionsRegex.test(url.pathname))
@@ -40,15 +70,14 @@ export function resolve(specifier, context, defaultResolve) {
   // ignore `data:` and `node:` prefix etc.
   if (!excludeRegex.test(specifier)) {
     // Try to resolve extension
-    const pathname = url.pathname
-    for (const ext of ['ts', 'tsx']) {
-      url.pathname = `${pathname}.${ext}`
-      const path = fileURLToPath(url.href)
-      if (fs.existsSync(path))
-        return {
-          url: url.href,
-          format: extensionsRegex.test(url.pathname) && 'module',
-        }
+    const path = fileURLToPath(url.href)
+    const foundPath = tryPathWithExtensions(path)
+    if (foundPath) {
+      url.pathname = foundPath
+      return {
+        url: url.href,
+        format: extensionsRegex.test(url.pathname) && 'module',
+      }
     }
   }
 

package.json

@@ -33,7 +33,8 @@
     "test": "node --experimental-loader ./loader.mjs test/entry.ts"
   },
   "dependencies": {
-    "esbuild": "^0.13.3"
+    "esbuild": "^0.13.3",
+    "tsconfig-paths": "^3.11.0"
   },
   "devDependencies": {
     "@antfu/eslint-config": "^0.9.0",

pnpm-lock.yaml

@@ -4,8 +4,8 @@ import { test } from 'uvu'
 import execa from 'execa'
 
 const cwd = process.cwd()
-function relativize(path: string) {
-  return `./${relative(cwd, path)}`
+function relativize(path: string, curCwd = cwd) {
+  return `./${relative(curCwd, path)}`
 }
 
 test('register', async() => {
@@ -107,4 +107,16 @@ test('import json', async() => {
   assert(stdout === 'esbuild-node-loader')
 })
 
+test('tsconfig-paths', async() => {
+  const cwd2 = `${cwd}/test/tsconfig-paths`;
+  const { stdout } = await execa('node', [
+    '--experimental-loader',
+    relativize(`${cwd}/loader.mjs`, cwd2),
+    relativize(`${cwd}/test/tsconfig-paths/src/utils/fixture.ts`, cwd2),
+  ], {
+    cwd: cwd2,
+  })
+  assert.equal(stdout, 'foo\nfoo')
+})
+
 test.run()

test/entry.ts

@@ -0,0 +1,3 @@
+export const foo = () => {
+  console.info('foo')
+}

test/tsconfig-paths/node_modules/@apis/foo.ts

@@ -0,0 +1,3 @@
+export const index = () => {
+  console.info('index')
+}

test/tsconfig-paths/src/apis/foo.ts

@@ -0,0 +1,5 @@
+import { foo as foo2 } from 'src/apis/foo'
+import { foo } from '@apis/foo'
+
+foo()
+foo2()

test/tsconfig-paths/src/apis/index.ts

@@ -0,0 +1,18 @@
+{
+  "compilerOptions": {
+    "target": "esnext",
+    "module": "esnext",                               /* Allow JavaScript files to be a part o
+    "esModuleInterop": true,                             /* Emit additional JavaScript to ease support for importing CommonJS modules. This enables `allowSyntheticDefaultImports` for type compatibility. */
+    "forceConsistentCasingInFileNames": true,            /* Ensure that casing is correct in imports. */
+
+    /* Type Checking */
+    "strict": true,
+    "skipLibCheck": true,                                /* Skip type checking all .d.ts files. */
+    "noEmit": true,
+    "baseUrl": ".",
+    "paths": {
+      "@apis/*": ["src/apis/*"],
+      "@utils/*": ["src/utils/*"]
+    }
+  }
+}