feat: support ESM configuration files

README.md

@@ -188,9 +188,9 @@ You can configure `commit-and-tag-version` either by:
    > Note for users who have migrated to
    > `commit-and-tag-version` from `standard-version`: the previous package.json configuration key of `standard-version` will still work.
 
-2. Creating a `.versionrc`, `.versionrc.json` or `.versionrc.js`.
+2. Creating a `.versionrc`, `.versionrc.json`, `.versionrc.js`, `.versionrc.cjs` or `.versionrc.mjs`.
 
-- If you are using a `.versionrc.js` your default export must be a configuration object, or a function returning a configuration object.
+- If you are using a `.versionrc.js`, `.versionrc.cjs` or `.versionrc.mjs` your default export must be a configuration object, or a function returning a configuration object. Both CommonJS and ES module configs are supported (ES module configs require Node.js >= 22.12).
 
 Any of the command line parameters accepted by `commit-and-tag-version` can instead
 be provided via configuration. Please refer to the [conventional-changelog-config-spec](https://github.com/conventional-changelog/conventional-changelog-config-spec/) for details on available configuration options.
@@ -342,7 +342,7 @@ commit-and-tag-version -c ./path/to/.versionrc.js
 All config file formats can be used:
 
 ```sh
-commit-and-tag-version -c ./path/to/.versionrc[.js|.cjs|.json]
+commit-and-tag-version -c ./path/to/.versionrc[.js|.cjs|.mjs|.json]
 ```
 
 ### Signing Commits and Tags

lib/configuration.js

@@ -8,6 +8,7 @@ const require = createRequire(import.meta.url);
 const CONFIGURATION_FILES = [
   '.versionrc',
   '.versionrc.cjs',
+  '.versionrc.mjs',
   '.versionrc.json',
   '.versionrc.js',
 ];
@@ -23,8 +24,17 @@ export function getConfiguration(configFile) {
     return config;
   }
   const ext = path.extname(configPath);
-  if (ext === '.js' || ext === '.cjs') {
-    const jsConfiguration = require(configPath);
+  if (ext === '.js' || ext === '.cjs' || ext === '.mjs') {
+    let jsConfiguration = require(configPath);
+    // ES modules arrive as a namespace wrapper (via Node's `require(esm)`,
+    // available since 22.12); the configuration is its default export.
+    if (
+      jsConfiguration != null &&
+      (jsConfiguration.__esModule ||
+        jsConfiguration[Symbol.toStringTag] === 'Module')
+    ) {
+      jsConfiguration = jsConfiguration.default;
+    }
     if (typeof jsConfiguration === 'function') {
       config = jsConfiguration();
     } else {

test/esm-config.integration-test.js

@@ -0,0 +1,97 @@
+import shell from 'shelljs';
+import fs from 'fs';
+import { execFileSync } from 'child_process';
+import { fileURLToPath } from 'url';
+
+const CLI = fileURLToPath(new URL('../bin/cli.js', import.meta.url));
+
+/**
+ * These tests spawn the real CLI in a child process instead of using the usual
+ * in-process harness. That is deliberate: `getConfiguration` loads ESM config
+ * files through Node's `require(esm)` (available since 22.12), and under vitest
+ * that require is intercepted by the module runner, which throws a Babel
+ * SyntaxError on ESM sources — a failure mode that does not exist in
+ * production. Only a child process observes the real behavior.
+ */
+
+function setupTestDirectory() {
+  shell.rm('-rf', 'esm-config-temp');
+  shell.config.silent = true;
+  shell.mkdir('esm-config-temp');
+  shell.cd('esm-config-temp');
+  shell.exec('git init');
+  shell.exec('git config commit.gpgSign false');
+  shell.exec('git config core.autocrlf false');
+  shell.exec('git commit --allow-empty -m"root-commit"');
+}
+
+function resetShell() {
+  shell.cd('../');
+  shell.rm('-rf', 'esm-config-temp');
+}
+
+function runCli() {
+  return execFileSync(process.execPath, [CLI, '--dry-run'], {
+    encoding: 'utf-8',
+  });
+}
+
+describe('ESM config files', function () {
+  beforeEach(function () {
+    setupTestDirectory();
+
+    fs.writeFileSync(
+      'package.json',
+      JSON.stringify({ version: '1.0.0' }),
+      'utf-8',
+    );
+  });
+
+  afterEach(function () {
+    resetShell();
+  });
+
+  it('reads an ES module config-object from .versionrc.js', function () {
+    fs.writeFileSync(
+      '.versionrc.js',
+      'export default { tagPrefix: "custom-" }',
+      'utf-8',
+    );
+
+    const output = runCli();
+    expect(output).toContain('tagging release custom-1.0.1');
+  });
+
+  it('reads an ES module config from .versionrc.mjs', function () {
+    fs.writeFileSync(
+      '.versionrc.mjs',
+      'export default { tagPrefix: "custom-" }',
+      'utf-8',
+    );
+
+    const output = runCli();
+    expect(output).toContain('tagging release custom-1.0.1');
+  });
+
+  it('evaluates an ES module config-function', function () {
+    fs.writeFileSync(
+      '.versionrc.mjs',
+      'export default function () { return { tagPrefix: "custom-" }; }',
+      'utf-8',
+    );
+
+    const output = runCli();
+    expect(output).toContain('tagging release custom-1.0.1');
+  });
+
+  it('applies the same configuration when written as CommonJS', function () {
+    fs.writeFileSync(
+      '.versionrc.js',
+      'module.exports = { tagPrefix: "custom-" }',
+      'utf-8',
+    );
+
+    const output = runCli();
+    expect(output).toContain('tagging release custom-1.0.1');
+  });
+});