Overwrite arrays when merging Babel config

laravel-mix · Dec 6, 2018 · 83f5052 · 83f5052
1 parent 2c90afc
commit 83f5052
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Showing 2 changed files with 32 additions and 5 deletions.
diff --git a/src/BabelConfig.js b/src/BabelConfig.js
@@ -8,11 +8,17 @@ class BabelConfig {
      * @param {String} babelRcPath
      */
     static generate(mixBabelConfig, babelRcPath) {
-        return merge.all([
-            new BabelConfig().fetchBabelRc(babelRcPath),
-            mixBabelConfig,
-            BabelConfig.default()
-        ]);
+        return merge.all(
+            [
+                BabelConfig.default(),
+                new BabelConfig().fetchBabelRc(babelRcPath),
+                mixBabelConfig
+            ],
+            {
+                arrayMerge: (destinationArray, sourceArray, options) =>
+                    sourceArray
+            }
+        );
     }
 
     /**

diff --git a/test/features/babel.js b/test/features/babel.js
@@ -45,3 +45,24 @@ test.serial('Babel reads the project .babelrc file', t => {
     // Cleanup.
     File.find(__dirname + '/.testbabelrc').delete();
 });
+
+test.serial(
+    'Values from duplicate keys in the .babelrc file override the defaults entirely.',
+    t => {
+        // Setup a test .babelrc file.
+        let babelRcPath = __dirname + '/.testbabelrc';
+
+        new File(babelRcPath).write(
+            '{ "presets": [ ["@babel/preset-env", {"useBuiltIns": "usage"}] ] }'
+        );
+
+        let babelConfig = Config.babel(babelRcPath);
+
+        t.is(1, babelConfig.presets.length);
+
+        t.deepEqual({ useBuiltIns: 'usage' }, babelConfig.presets[0][1]);
+
+        // Cleanup.
+        File.find(babelRcPath).delete();
+    }
+);