fix(utils): support numerical keys in walkSet

Fixes #195

Author: posva

Diff for: src/utils.js

@@ -74,6 +74,6 @@ export function walkSet (obj, path, value) {
   const target = keys.reduce((target, key) => target[key], obj)
   // global isFinite is different from Number.isFinite
   // it converts values to numbers
-  if (isFinite(key)) target.splice(key, 1, value)
+  if (isFinite(key) && Array.isArray(target)) target.splice(key, 1, value)
   else target[key] = value
 }

Diff for: test/utils.spec.js

@@ -1,4 +1,4 @@
-import { createSnapshot, extractRefs } from '../src/utils'
+import { createSnapshot, extractRefs, walkSet } from '../src/utils'
 import { Key, db, _id, DocumentReference, GeoPoint, DocumentSnapshot, Timestamp } from './helpers'
 
 let id, doc, snapshot, collection, docRef
@@ -139,3 +139,11 @@ test('extracts refs from array', async () => {
     'arr.2': docRef
   })
 })
+
+test('supports numbers as keys in objects', () => {
+  const obj = {
+    '0': 'foo'
+  }
+  expect(() => walkSet(obj, '0', 'bar')).not.toThrow()
+  expect(obj['0']).toBe('bar')
+})