Allow merging invalid changesets (#74)

README.md

@@ -380,7 +380,7 @@ changeset.rollback(); // returns changeset
 
 #### `merge`
 
-Merges 2 valid changesets and returns a new changeset with the same underlying content and validator as the origin. Both changesets must point to the same underlying object. For example:
+Merges 2 changesets and returns a new changeset with the same underlying content and validator as the origin. Both changesets must point to the same underlying object. For example:
 
 ```js
 let changesetA = new Changeset(user, validatorFn);

addon/index.js

@@ -4,6 +4,7 @@ import isEmptyObject from 'ember-changeset/utils/computed/is-empty-object';
 import isPromise from 'ember-changeset/utils/is-promise';
 import isObject from 'ember-changeset/utils/is-object';
 import pureAssign from 'ember-changeset/utils/assign';
+import objectWithout from 'ember-changeset/utils/object-without';
 import { CHANGESET, isChangeset } from 'ember-changeset/-private/internals';
 
 const {
@@ -211,18 +212,24 @@ export function changeset(obj, validateFn = defaultValidatorFn, validationMap =
       let content = get(this, CONTENT);
       assert('Cannot merge with a non-changeset', isChangeset(changeset));
       assert('Cannot merge with a changeset of different content', get(changeset, CONTENT) === content);
-      assert('Cannot merge invalid changesets', get(this, 'isValid') && get(changeset, 'isValid'));
 
       if (get(this, 'isPristine') && get(changeset, 'isPristine')) {
         return this;
       }
 
       let changesA = get(this, CHANGES);
       let changesB = get(changeset, CHANGES);
-      let mergedChanges = pureAssign(changesA, changesB);
+      let errorsA = get(this, ERRORS);
+      let errorsB = get(changeset, ERRORS);
       let newChangeset = new Changeset(content, get(this, VALIDATOR));
+      let newErrors = objectWithout(keys(changesB), errorsA);
+      let newChanges = objectWithout(keys(errorsB), changesA);
+      let mergedChanges = pureAssign(newChanges, changesB);
+      let mergedErrors = pureAssign(newErrors, errorsB);
+
       newChangeset[CHANGES] = mergedChanges;
-      newChangeset.notifyPropertyChange(CHANGES);
+      newChangeset[ERRORS] = mergedErrors;
+      newChangeset._notifyVirtualProperties();
 
       return newChangeset;
     },

addon/utils/object-without.js

@@ -0,0 +1,18 @@
+const { keys } = Object;
+
+/**
+ * Merges all sources together, excluding keys in excludedKeys.
+ *
+ * @param  {Array[String]}    excludedKeys
+ * @param  {...Object}        sources
+ *
+ * @return {Object}
+ */
+export default function objectWithout(excludedKeys, ...sources) {
+  return sources.reduce((acc, source) => {
+    keys(source)
+      .filter((key) => excludedKeys.indexOf(key) === -1 || !source.hasOwnProperty(key))
+      .forEach((key) => acc[key] = source[key]);
+    return acc;
+  }, {});
+}

app/utils/object-without.js

@@ -0,0 +1 @@
+export { default } from 'ember-changeset/utils/object-without';

tests/unit/changeset-test.js

@@ -227,15 +227,27 @@ test('#merge merges 2 valid changesets', function(assert) {
   assert.deepEqual(get(dummyChangesetB, 'changes'), [{ key: 'lastName', value: 'Bob' }], 'should not mutate second changeset');
 });
 
-test('#merge does not merge invalid changesets', function(assert) {
+test('#merge merges invalid changesets', function(assert) {
   let dummyChangesetA = new Changeset(dummyModel, dummyValidator);
   let dummyChangesetB = new Changeset(dummyModel, dummyValidator);
+  let dummyChangesetC = new Changeset(dummyModel, dummyValidator);
+  dummyChangesetA.set('age', 21);
   dummyChangesetA.set('name', 'a');
-  dummyChangesetB.set('name', 'b');
+  dummyChangesetB.set('name', 'Tony Stark');
+  dummyChangesetC.set('name', 'b');
 
-  assert.throws(() => dummyChangesetA.merge(dummyChangesetB), ({ message }) => {
-    return message === 'Assertion Failed: Cannot merge invalid changesets';
-  }, 'should throw error');
+  let dummyChangesetD = dummyChangesetA.merge(dummyChangesetB);
+  dummyChangesetD = dummyChangesetD.merge(dummyChangesetC);
+
+  let expectedChanges = [{ key: 'age', value: 21 }];
+  let expectedErrors = [{ key: 'name', 'validation': 'too short', value: 'b' }];
+
+  assert.deepEqual(get(dummyChangesetA, 'isInvalid'), true, 'changesetA is not valid becuase of name');
+  assert.deepEqual(get(dummyChangesetB, 'isValid'), true, 'changesetB should be invalid');
+  assert.deepEqual(get(dummyChangesetC, 'isInvalid'), true, 'changesetC should be invalid');
+  assert.deepEqual(get(dummyChangesetD, 'isInvalid'), true, 'changesetD should be invalid');
+  assert.deepEqual(get(dummyChangesetD, 'changes'), expectedChanges, 'should not merge invalid changes');
+  assert.deepEqual(get(dummyChangesetD, 'errors'), expectedErrors, 'should assign errors from both changesets');
 });
 
 test('#merge does not merge a changeset with a non-changeset', function(assert) {

tests/unit/utils/object-without-test.js

@@ -0,0 +1,15 @@
+import objectWithout from 'dummy/utils/object-without';
+import { module, test } from 'qunit';
+
+module('Unit | Utility | object without');
+
+test('it exludes the given keys from all merged objects', function(assert) {
+  let objA = { name: 'Ivan' };
+  let objB = { name: 'John' };
+  let objC = { age: 27 };
+  let objD = objectWithout([ 'age' ], objA, objB, objC);
+
+  assert.deepEqual(objD, { name: 'John' }, 'result only contains name');
+  assert.deepEqual(objA.name, 'Ivan', 'does not mutate original object');
+  assert.deepEqual(objC.age, 27, 'does not mutate original object');
+});