Implement basic spec for merge.strategy

Closes #17.

lib/index.js

@@ -30,8 +30,19 @@ function mergeStrategy() {
   return function () {
     var _ref3;
 
-    return lodashMerge.apply(null, (_ref3 = [{}]).concat.apply(_ref3, arguments).concat([joinArrays() // TODO: connect rules with customizers
-    ]));
+    return lodashMerge.apply(null, (_ref3 = [{}]).concat.apply(_ref3, arguments).concat([joinArrays({
+      customizeArray: function customizeArray(a, b, key) {
+        if (rules[key]) {
+          return rules[key] === 'prepend' && b.concat(a);
+        }
+      },
+      customizeObject: function customizeObject(a, b, key) {
+        if (rules[key]) {
+          // No support for recursive checks yet - are those even needed?
+          return rules[key] === 'prepend' && lodashMerge({}, b, a, joinArrays());
+        }
+      }
+    })]));
   };
 }
 

src/index.js

@@ -25,7 +25,19 @@ function mergeStrategy(rules = {}) {
   // All default to append but you can override here
   return function () {
     return lodashMerge.apply(null, [{}].concat(...arguments).concat([
-      joinArrays() // TODO: connect rules with customizers
+      joinArrays({
+        customizeArray: (a, b, key) => {
+          if (rules[key]) {
+            return rules[key] === 'prepend' && b.concat(a);
+          }
+        },
+        customizeObject: (a, b, key) => {
+          if (rules[key]) {
+            // No support for recursive checks yet - are those even needed?
+            return rules[key] === 'prepend' && lodashMerge({}, b, a, joinArrays());
+          }
+        }
+      })
     ]));
   };
 }

tests/test-merge-strategy.js

@@ -1,4 +1,5 @@
 /* eslint-env mocha */
+const assert = require('assert');
 const webpackMerge = require('..');
 const normalMergeTests = require('./test-merge');
 const mergeTests = require('./merge-tests');
@@ -11,4 +12,91 @@ describe('Merge strategy', function () {
   normalMergeTests(merge(), 'postLoaders');
   normalMergeTests(merge(), 'rules');
   mergeTests(merge());
+  mergeStrategyTests(merge);
 });
+
+function mergeStrategyTests(merge) {
+  it('should allow setting to array append', function () {
+    const a = {
+      entry: ['foo', 'bar', 'baz']
+    };
+    const b = {
+      entry: ['zoo']
+    };
+    const result = {
+      entry: ['foo', 'bar', 'baz', 'zoo']
+    };
+
+    assert.deepEqual(merge({
+      entry: 'append'
+    })(a, b), result);
+  });
+
+  it('should allow setting to array prepend', function () {
+    const a = {
+      entry: ['foo', 'bar', 'baz']
+    };
+    const b = {
+      entry: ['zoo']
+    };
+    const result = {
+      entry: ['zoo', 'foo', 'bar', 'baz']
+    };
+
+    assert.deepEqual(merge({
+      entry: 'prepend'
+    })(a, b), result);
+  });
+
+  it('should allow setting to object append', function () {
+    const a = {
+      entry: {
+        foo: 'bar'
+      }
+    };
+    const b = {
+      entry: {
+        bar: 'baz'
+      }
+    };
+    const result = {
+      entry: {
+        foo: 'bar',
+        bar: 'baz'
+      }
+    };
+
+    assert.deepEqual(
+      Object.keys(merge({
+        entry: 'append'
+      })(a, b).entry),
+      Object.keys(result.entry)
+    );
+  });
+
+  it('should allow setting to object prepend', function () {
+    const a = {
+      entry: {
+        foo: 'bar'
+      }
+    };
+    const b = {
+      entry: {
+        bar: 'baz'
+      }
+    };
+    const result = {
+      entry: {
+        bar: 'baz',
+        foo: 'bar'
+      }
+    };
+
+    assert.deepEqual(
+      Object.keys(merge({
+        entry: 'prepend'
+      })(a, b).entry),
+      Object.keys(result.entry)
+    );
+  });
+}