feat: Add support for babel.config.js (#32)

src/index.js

@@ -6,13 +6,19 @@ const pathExists = require('path-exists');
 const INFINITY = 1 / 0;
 const BABELRC_FILENAME = '.babelrc';
 const BABELRC_JS_FILENAME = '.babelrc.js';
+const BABEL_CONFIG_JS_FILENAME = 'babel.config.js';
 const PACKAGE_FILENAME = 'package.json';
 
 const nullConf = { file: null, config: null };
 
 function getBabelJsConfig(file) {
     // eslint-disable-next-line global-require, import/no-dynamic-require
     const configModule = require(file);
+
+    if (typeof configModule === 'function') {
+        return configModule();
+    }
+
     // eslint-disable-next-line no-underscore-dangle
     return configModule && configModule.__esModule ? configModule.default : configModule;
 }
@@ -72,6 +78,22 @@ function asyncFind(resolve, dir, depth) {
         }
         return exists;
     })
+    .then((exists) => {
+        if (!exists) {
+            const babelConfigJSrc = path.join(dir, BABEL_CONFIG_JS_FILENAME);
+            return pathExists(babelConfigJSrc).then((ex) => {
+                if (ex) {
+                    const config = getBabelJsConfig(babelConfigJSrc);
+                    resolve({
+                        file: babelConfigJSrc,
+                        config,
+                    });
+                }
+            });
+        }
+        return exists;
+    })
+
     .then((exists) => {
         if (!exists) {
             const nextDir = path.dirname(dir);
@@ -129,6 +151,15 @@ module.exports.sync = function findBabelConfigSync(start, depth = INFINITY) {
             };
         }
 
+        const babelConfigJSrc = path.join(dir, BABEL_CONFIG_JS_FILENAME);
+        if (pathExists.sync(babelConfigJSrc)) {
+            const config = getBabelJsConfig(babelConfigJSrc);
+            return {
+                file: babelConfigJSrc,
+                config,
+            };
+        }
+
         const packageFile = path.join(dir, PACKAGE_FILENAME);
         if (pathExists.sync(packageFile)) {
             const packageContent = fs.readFileSync(packageFile, 'utf8');

test/data/babelconfigjs/babel.config.js

@@ -0,0 +1,9 @@
+module.exports = function config() {
+    const presets = ['fake-preset-babel-config-js'];
+    const plugins = ['fake-plugin-babel-config-js'];
+
+    return {
+        presets,
+        plugins,
+    };
+};

test/data/babelconfigjs/dir1/dir2/dir3/babel.config.js

@@ -0,0 +1,9 @@
+module.exports = function config() {
+    const presets = ['fake-preset-dir3-babel-config-js'];
+    const plugins = ['fake-plugin-dir3-babel-config-js'];
+
+    return {
+        presets,
+        plugins,
+    };
+};

test/index.test.js

@@ -96,6 +96,29 @@ describe('find-babel-config', () => {
             );
         });
 
+        describe('babel.config.js', () => {
+            it('should return the config in the direct directory', () =>
+                findBabelConfig('test/data/babelconfigjs').then(({ file, config }) => {
+                    expect(file).toBe(path.join(process.cwd(), 'test/data/babelconfigjs/babel.config.js'));
+                    expect(config).toEqual({ presets: ['fake-preset-babel-config-js'], plugins: ['fake-plugin-babel-config-js'] });
+                }),
+            );
+
+            it('should return the config in the parent directory', () =>
+                findBabelConfig(path.join(process.cwd(), 'test/data/babelconfigjs/dir1')).then(({ file, config }) => {
+                    expect(file).toBe(path.join(process.cwd(), 'test/data/babelconfigjs/babel.config.js'));
+                    expect(config).toEqual({ presets: ['fake-preset-babel-config-js'], plugins: ['fake-plugin-babel-config-js'] });
+                }),
+            );
+
+            it('should return the first config found in the parents', () =>
+                findBabelConfig('test/data/babelconfigjs/dir1/dir2/dir3/dir4/dir5').then(({ file, config }) => {
+                    expect(file).toBe(path.join(process.cwd(), 'test/data/babelconfigjs/dir1/dir2/dir3/babel.config.js'));
+                    expect(config).toEqual({ presets: ['fake-preset-dir3-babel-config-js'], plugins: ['fake-plugin-dir3-babel-config-js'] });
+                }),
+            );
+        });
+
         describe('with depth', () => {
             it('should check only the direct directory with a depth 0', () =>
                 findBabelConfig('test/data/babelrc/dir1/dir2/dir3/dir4', 0).then(({ file, config }) => {
@@ -204,6 +227,26 @@ describe('find-babel-config', () => {
             });
         });
 
+        describe('babel.config.js', () => {
+            it('should return the config in the specified directory', () => {
+                const { file, config } = findBabelConfig.sync('test/data/babelconfigjs');
+                expect(file).toBe(path.join(process.cwd(), 'test/data/babelconfigjs/babel.config.js'));
+                expect(config).toEqual({ presets: ['fake-preset-babel-config-js'], plugins: ['fake-plugin-babel-config-js'] });
+            });
+
+            it('should return the config in the parent directory', () => {
+                const { file, config } = findBabelConfig.sync(path.join(process.cwd(), 'test/data/babelconfigjs/dir1'));
+                expect(file).toBe(path.join(process.cwd(), 'test/data/babelconfigjs/babel.config.js'));
+                expect(config).toEqual({ presets: ['fake-preset-babel-config-js'], plugins: ['fake-plugin-babel-config-js'] });
+            });
+
+            it('should return the first config found in the parents', () => {
+                const { file, config } = findBabelConfig.sync('test/data/babelconfigjs/dir1/dir2/dir3/dir4/dir5');
+                expect(file).toBe(path.join(process.cwd(), 'test/data/babelconfigjs/dir1/dir2/dir3/babel.config.js'));
+                expect(config).toEqual({ presets: ['fake-preset-dir3-babel-config-js'], plugins: ['fake-plugin-dir3-babel-config-js'] });
+            });
+        });
+
         describe('both files', () => {
             it('should return the first babel config in package.json', () => {
                 const { file, config } = findBabelConfig.sync('test/data/both/dir1/dir2/dir3');