Added a transpile-only ESM loader (#1101) (#1102)

* Added a transpile-only ESM loader (#1101)

* feat: Added transpile-only ESM loader to package.json exports and resolve tests

* feat: Added success/failure tests for transpile-only ESM loader

* fix: Fix transpile-only ESM loader tests
Fixed ESM tests being executed under node 13.0.0
Fixed error message matching criteria

* fix: Fix erroneous quotations in transpile-only ESM loader tests

* feat: Removed imports on tests for esm-transpile-only tests

* feat: Renamed and restructured esm-transpile-only tests

esm/transpile-only.mjs

@@ -0,0 +1,7 @@
+import {fileURLToPath} from 'url'
+import {createRequire} from 'module'
+const require = createRequire(fileURLToPath(import.meta.url))
+
+/** @type {import('../dist/esm')} */
+const esm = require('../dist/esm')
+export const {resolve, getFormat, transformSource} = esm.registerAndCreateEsmHooks({transpileOnly: true})

package.json

@@ -18,7 +18,9 @@
     "./register/transpile-only": "./register/transpile-only.js",
     "./register/type-check": "./register/type-check.js",
     "./esm": "./esm.mjs",
-    "./esm.mjs": "./esm.mjs"
+    "./esm.mjs": "./esm.mjs",
+    "./esm/transpile-only": "./esm/transpile-only.mjs",
+    "./esm/transpile-only.mjs": "./esm/transpile-only.mjs"
   },
   "types": "dist/index.d.ts",
   "bin": {
@@ -31,6 +33,7 @@
     "dist/",
     "dist-raw/",
     "register/",
+    "esm/",
     "esm.mjs",
     "LICENSE",
     "tsconfig.schema.json",

src/index.spec.ts

@@ -72,6 +72,8 @@ describe('ts-node', function () {
     // `node --loader ts-node/esm`
     testsDirRequire.resolve('ts-node/esm')
     testsDirRequire.resolve('ts-node/esm.mjs')
+    testsDirRequire.resolve('ts-node/esm/transpile-only')
+    testsDirRequire.resolve('ts-node/esm/transpile-only.mjs')
   })
 
   describe('cli', function () {
@@ -821,6 +823,29 @@ describe('ts-node', function () {
           return done()
         })
       })
+
+      it('should support transpile only mode via dedicated loader entrypoint', (done) => {
+        exec(`${cmd}/transpile-only index.ts`, { cwd: join(__dirname, '../tests/esm-transpile-only') }, function (err, stdout) {
+          expect(err).to.equal(null)
+          expect(stdout).to.equal('')
+
+          return done()
+        })
+      })
+      it('should throw type errors without transpile-only enabled', (done) => {
+        exec(`${cmd} index.ts`, { cwd: join(__dirname, '../tests/esm-transpile-only') }, function (err, stdout) {
+          if (err === null) {
+            return done('Command was expected to fail, but it succeeded.')
+          }
+
+          expect(err.message).to.contain('Unable to compile TypeScript')
+          expect(err.message).to.match(new RegExp('TS2345: Argument of type \'(?:number|1101)\' is not assignable to parameter of type \'string\'\\.'))
+          expect(err.message).to.match(new RegExp('TS2322: Type \'(?:"hello world"|string)\' is not assignable to type \'number\'\\.'))
+          expect(stdout).to.equal('')
+
+          return done()
+        })
+      })
     }
 
     it('executes ESM as CJS, ignoring package.json "types" field (for backwards compatibility; should be changed in next major release to throw ERR_REQUIRE_ESM)', function (done) {

tests/esm-transpile-only/index.ts

@@ -0,0 +1,5 @@
+if (typeof module !== 'undefined') throw new Error('module should not exist in ESM')
+
+// intentional type errors to check transpile-only ESM loader skips type checking
+parseInt(1101, 2)
+const x: number = 'hello world'

tests/esm-transpile-only/package.json

@@ -0,0 +1,3 @@
+{
+  "type": "module"
+}

tests/esm-transpile-only/tsconfig.json

@@ -0,0 +1,7 @@
+{
+  "compilerOptions": {
+    "module": "ESNext",
+    "allowJs": true,
+    "jsx": "react"
+  }
+}