Support --prefer-ts-exts flag (#837)

README.md

@@ -136,6 +136,7 @@ _Environment variable denoted in parentheses._
 * `--skip-project` Skip project config resolution and loading (`TS_NODE_SKIP_PROJECT`, default: `false`)
 * `--skip-ignore` Skip ignore checks (`TS_NODE_SKIP_IGNORE`, default: `false`)
 * `--log-error` Logs errors of types instead of exit the process (`TS_NODE_LOG_ERROR`, default: `false`)
+* `--prefer-ts-exts` Changes the order of file extensions used when matching file imports so that `.ts` files are preferred over `.js` (`TS_PREFER_TS_EXTS`, default: `false`)
 
 ### Programmatic Only Options
 

src/bin.ts

@@ -32,6 +32,7 @@ const args = arg({
   '--pretty': Boolean,
   '--skip-project': Boolean,
   '--skip-ignore': Boolean,
+  '--prefer-ts-exts': Boolean,
   '--log-error': Boolean,
 
   // Aliases.
@@ -64,6 +65,7 @@ const {
   '--pretty': pretty = DEFAULTS.pretty,
   '--skip-project': skipProject = DEFAULTS.skipProject,
   '--skip-ignore': skipIgnore = DEFAULTS.skipIgnore,
+  '--prefer-ts-exts': preferTsExts = DEFAULTS.preferTsExts,
   '--log-error': logError = DEFAULTS.logError
 } = args
 
@@ -91,6 +93,7 @@ Options:
   --pretty                       Use pretty diagnostic formatter
   --skip-project                 Skip reading \`tsconfig.json\`
   --skip-ignore                  Skip \`--ignore\` checks
+  --prefer-ts-exts               Prefer importing TypeScript files over JavaScript files
 `)
 
   process.exit(0)
@@ -115,6 +118,7 @@ const service = register({
   ignore,
   project,
   skipIgnore,
+  preferTsExts,
   logError,
   skipProject,
   compiler,

src/index.spec.ts

@@ -269,6 +269,33 @@ describe('ts-node', function () {
         return done()
       })
     })
+
+    it('should import js before ts by default', function (done) {
+      exec(`${BIN_EXEC} tests/import-order/compiled`, function (err, stdout) {
+        expect(err).to.equal(null)
+        expect(stdout).to.equal('Hello, JavaScript!\n')
+
+        return done()
+      })
+    })
+
+    it('should import ts before js when --prefer-ts-exts flag is present', function (done) {
+      exec(`${BIN_EXEC} --prefer-ts-exts tests/import-order/compiled`, function (err, stdout) {
+        expect(err).to.equal(null)
+        expect(stdout).to.equal('Hello, TypeScript!\n')
+
+        return done()
+      })
+    })
+
+    it('should ignore .d.ts files', function (done) {
+      exec(`${BIN_EXEC} tests/import-order/importer`, function (err, stdout) {
+        expect(err).to.equal(null)
+        expect(stdout).to.equal('Hello, World!\n')
+
+        return done()
+      })
+    })
   })
 
   describe('register', function () {

src/index.ts

@@ -66,6 +66,7 @@ export interface Options {
   project?: string
   skipIgnore?: boolean | null
   skipProject?: boolean | null
+  preferTsExts?: boolean | null
   compilerOptions?: object
   ignoreDiagnostics?: Array<number | string>
   readFile?: (path: string) => string | undefined
@@ -105,6 +106,7 @@ export const DEFAULTS: Options = {
   project: process.env['TS_NODE_PROJECT'],
   skipIgnore: yn(process.env['TS_NODE_SKIP_IGNORE']),
   skipProject: yn(process.env['TS_NODE_SKIP_PROJECT']),
+  preferTsExts: yn(process.env['TS_NODE_PREFER_TS_EXTS']),
   ignoreDiagnostics: split(process.env['TS_NODE_IGNORE_DIAGNOSTICS']),
   typeCheck: yn(process.env['TS_NODE_TYPE_CHECK']),
   transpileOnly: yn(process.env['TS_NODE_TRANSPILE_ONLY']),
@@ -399,9 +401,7 @@ export function register (opts: Options = {}): Register {
   const register: Register = { cwd, compile, getTypeInfo, extensions, ts }
 
   // Register the extensions.
-  extensions.forEach(extension => {
-    registerExtension(extension, ignore, register, originalJsHandler)
-  })
+  registerExtensions(opts, extensions, ignore, register, originalJsHandler)
 
   return register
 }
@@ -415,6 +415,44 @@ function shouldIgnore (filename: string, ignore: RegExp[]) {
   return ignore.some(x => x.test(relname))
 }
 
+/**
+ * "Refreshes" an extension on `require.extentions`.
+ *
+ * @param {string} ext
+ */
+function refreshRequireExtension (ext: string) {
+  const old = require.extensions[ext] // tslint:disable-line
+  delete require.extensions[ext] // tslint:disable-line
+  require.extensions[ext] = old // tslint:disable-line
+}
+
+/**
+ * Register the extensions to support when importing files.
+ */
+function registerExtensions (
+  opts: Options,
+  extensions: string[],
+  ignore: RegExp[],
+  register: Register,
+  originalJsHandler: (m: NodeModule, filename: string) => any
+) {
+  if (opts.preferTsExts) {
+    extensions.unshift(
+      '.ts',
+      '.tsx',
+      ...Object.keys(require.extensions), // tslint:disable-line
+    )
+  }
+
+  // @todo a better way with options
+  Array.from(new Set(extensions))
+       .forEach(ext => {
+         registerExtension(ext, ignore, register, originalJsHandler)
+
+         if (ext in require.extensions) refreshRequireExtension(ext) // tslint:disable-line
+       })
+}
+
 /**
  * Register the extension for node.
  */

tests/import-order/compiled.js

@@ -0,0 +1 @@
+console.log('Hello, JavaScript!');

tests/import-order/compiled.ts

@@ -0,0 +1 @@
+console.log('Hello, TypeScript!')

tests/import-order/defined.d.ts

@@ -0,0 +1,3 @@
+declare const v = 'Hello, World!'
+
+export default v

tests/import-order/defined.js

@@ -0,0 +1 @@
+module.exports = 'Hello, World!';

tests/import-order/importer.ts

@@ -0,0 +1,3 @@
+const v = require('./defined')
+
+console.log(v)