feat: support loading TypeScript files

src/get-env-vars.ts

@@ -1,6 +1,7 @@
 import type { GetEnvVarOptions, Environment } from './types.ts'
 import { getRCFileVars } from './parse-rc-file.js'
 import { getEnvFileVars } from './parse-env-file.js'
+import { isLoaderError } from './utils.js'
 
 const RC_FILE_DEFAULT_LOCATIONS = ['./.env-cmdrc', './.env-cmdrc.js', './.env-cmdrc.json']
 const ENV_FILE_DEFAULT_LOCATIONS = ['./.env', './.env.js', './.env.json']
@@ -34,7 +35,11 @@ export async function getEnvFile(
       }
       return env
     }
-    catch {
+    catch (error) {
+      if (isLoaderError(error)) {
+        throw error
+      }
+
       if (verbose === true) {
         console.info(`Failed to find .env file at path: ${filePath}`)
       }

src/loaders/typescript.ts

@@ -0,0 +1,11 @@
+export function checkIfTypescriptSupported() {
+  if (!process.features.typescript) {
+    const error = new Error(
+      'To load typescript files with env-cmd, you need to enable ' +
+        'node’s --experimental-strip-types option, or upgrade to node ' +
+        'v23.6 or later. See https://nodejs.org/en/learn/typescript/run-natively',
+    );
+    Object.assign(error, { code: 'ERR_UNKNOWN_FILE_EXTENSION' });
+    throw error;
+  }
+}

src/parse-env-file.ts

@@ -3,6 +3,7 @@ import { extname } from 'node:path'
 import { pathToFileURL } from 'node:url'
 import { resolveEnvFilePath, IMPORT_HOOK_EXTENSIONS, isPromise, importAttributesKeyword } from './utils.js'
 import type { Environment } from './types.ts'
+import { checkIfTypescriptSupported } from './loaders/typescript.js'
 
 /**
  * Gets the environment vars from an env file
@@ -19,6 +20,8 @@ export async function getEnvFileVars(envFilePath: string): Promise<Environment>
   const ext = extname(absolutePath).toLowerCase()
   let env: Environment = {}
   if (IMPORT_HOOK_EXTENSIONS.includes(ext)) {
+    if (/tsx?$/.test(ext)) checkIfTypescriptSupported();
+
     // For some reason in ES Modules, only JSON file types need to be specifically delinated when importing them
     let attributeTypes = {}
     if (ext === '.json') {

src/parse-rc-file.ts

@@ -4,6 +4,7 @@ import { extname } from 'node:path'
 import { pathToFileURL } from 'node:url'
 import { resolveEnvFilePath, IMPORT_HOOK_EXTENSIONS, isPromise, importAttributesKeyword } from './utils.js'
 import type { Environment, RCEnvironment } from './types.ts'
+import { checkIfTypescriptSupported } from './loaders/typescript.js'
 
 const statAsync = promisify(stat)
 const readFileAsync = promisify(readFile)
@@ -30,6 +31,8 @@ export async function getRCFileVars(
   let parsedData: Partial<RCEnvironment> = {}
   try {
     if (IMPORT_HOOK_EXTENSIONS.includes(ext)) {
+      if (/tsx?$/.test(ext)) checkIfTypescriptSupported()
+
       // For some reason in ES Modules, only JSON file types need to be specifically delinated when importing them
       let attributeTypes = {}
       if (ext === '.json') {

src/utils.ts

@@ -3,7 +3,16 @@ import { homedir } from 'node:os'
 import { cwd } from 'node:process'
 
 // Special file extensions that node can natively import
-export const IMPORT_HOOK_EXTENSIONS = ['.json', '.js', '.cjs', '.mjs']
+export const IMPORT_HOOK_EXTENSIONS = [
+  '.json',
+  '.js',
+  '.cjs',
+  '.mjs',
+  '.ts',
+  '.mts',
+  '.cts',
+  '.tsx',
+];
 
 /**
  * A simple function for resolving the path the user entered
@@ -33,6 +42,15 @@ export function isPromise<T>(value?: T | PromiseLike<T>): value is PromiseLike<T
     && typeof value.then === 'function'
 }
 
+/** @returns true if the error is `ERR_UNKNOWN_FILE_EXTENSION` */
+export function isLoaderError(error: unknown): error is Error {
+  return (
+    error instanceof Error &&
+    'code' in error &&
+    error.code === 'ERR_UNKNOWN_FILE_EXTENSION'
+  );
+}
+
 
 // "Import Attributes" are only supported since node v18.20 and v20.10.
 // For older node versions, we have to use "Import Assertions".

test/parse-env-file.spec.ts

@@ -192,6 +192,32 @@ describe('getEnvFileVars', (): void => {
       THANKS: 'FOR ALL THE FISH',
       ANSWER: 0,
     })
+  });
+
+  (process.features.typescript ? describe : describe.skip)('TS', () => {
+    it('should parse a .ts file', async () => {
+      const env = await getEnvFileVars('./test/test-files/ts-test.ts');
+      assert.deepEqual(env, {
+        THANKS: 'FOR ALL THE FISH',
+        ANSWER: 1,
+      });
+    });
+
+    it('should parse a .cts file', async () => {
+      const env = await getEnvFileVars('./test/test-files/cts-test.cts');
+      assert.deepEqual(env, {
+        THANKS: 'FOR ALL THE FISH',
+        ANSWER: 0,
+      });
+    });
+
+    it('should parse a .tsx file', async () => {
+      const env = await getEnvFileVars('./test/test-files/tsx-test.tsx');
+      assert.deepEqual(env, {
+        THANKS: 'FOR ALL THE FISH',
+        ANSWER: 2,
+      });
+    });
   })
 
   it('should parse an env file', async (): Promise<void> => {

test/test-files/cts-test.cts

@@ -0,0 +1,5 @@
+const env: unknown = {
+  THANKS: 'FOR ALL THE FISH',
+  ANSWER: 0,
+};
+export default env;

test/test-files/ts-test.ts

@@ -0,0 +1,7 @@
+import type { Environment } from '../../src/types.js';
+
+const env: Environment = {
+  THANKS: 'FOR ALL THE FISH',
+  ANSWER: 1,
+};
+export default env;

test/test-files/tsx-test.tsx

@@ -0,0 +1,8 @@
+import type { Environment } from '../../src/types.js';
+
+const env: Environment = {
+  THANKS: 'FOR ALL THE FISH',
+  ANSWER: 2,
+};
+
+export default env;