Fix collection size check in merge() (immutable-js#1521)

acusti · kozlitinaelja · commit a22ece71ec6a · 2018-05-15T12:29:11.000-04:00
Records can have a size property (`collection.size`, in this
conditional) that is independent of the Collection.size property; using
toSeq() ensures that the Collection.size property is checked instead
diff --git a/__tests__/merge.ts b/__tests__/merge.ts
@@ -15,6 +15,7 @@ import {
   merge,
   mergeDeep,
   mergeDeepWith,
+  Record,
   Set,
 } from '../';
 
@@ -229,4 +230,9 @@ describe('merge', () => {
       Map([[a, Map([[b, Map([[c, 10], [d, 2], [e, 20], [f, 30], [g, 40]])]])]])
     );
   });
+
+  it('merges records with a size property set to 0', () => {
+    const Sizable = Record({ size: 0 });
+    expect(Sizable().merge({ size: 123 }).size).toBe(123);
+  });
 });
diff --git a/src/methods/merge.js b/src/methods/merge.js
@@ -28,7 +28,11 @@ function mergeIntoKeyedWith(collection, collections, merger) {
   if (iters.length === 0) {
     return collection;
   }
-  if (collection.size === 0 && !collection.__ownerID && iters.length === 1) {
+  if (
+    collection.toSeq().size === 0 &&
+    !collection.__ownerID &&
+    iters.length === 1
+  ) {
     return collection.constructor(iters[0]);
   }
   return collection.withMutations(collection => {

Original file line number	Diff line number	Diff line change
`@@ -28,7 +28,11 @@ function mergeIntoKeyedWith(collection, collections, merger) {`
`28`	`28`	`if (iters.length === 0) {`
`29`	`29`	`return collection;`
`30`	`30`	`}`
`31`		`- if (collection.size === 0 && !collection.__ownerID && iters.length === 1) {`
	`31`	`+ if (`
	`32`	`+ collection.toSeq().size === 0 &&`
	`33`	`+ !collection.__ownerID &&`
	`34`	`+ iters.length === 1`
	`35`	`+ ) {`
`32`	`36`	`return collection.constructor(iters[0]);`
`33`	`37`	`}`
`34`	`38`	`return collection.withMutations(collection => {`