uniqueSet race condition

* uniqueSet uses transaction to prevent race condition - #207

docs/roadmap.md

@@ -49,6 +49,8 @@
 #### Enhancements/Fixes
 * Return correct promise from `firebase.auth().signOut()` - [#152](https://github.com/prescottprue/react-redux-firebase/issues/152)
 * Removed `browser` field from `package.json` so that webpack will point to `main` field - [#128](https://github.com/prescottprue/react-redux-firebase/issues/128)
+* Fix `uniqueSet` race condition - [#207](https://github.com/prescottprue/react-redux-firebase/issues/207)
+* improved testing of `firebaseConnect` HOC
 
 ## Future Minor Versions (`v1.6.0 - v1.*.*`)
 
@@ -65,6 +67,7 @@
 * Setting that allows for `waitForPopulate` to be turned off (i.e. return populated data as in becomes available). As of `v1.4.0-rc.2`, populate only sets `isLoaded` to true after all children are loaded, `waitForPopulate` would make this optional - [#121](https://github.com/prescottprue/react-redux-firebase/issues/121)
 * Integration for [`react-native-google-signin`](https://github.com/devfd/react-native-google-signin) to simplify react-native authentication implementation
 * Nested populates - [#85](https://github.com/prescottprue/react-redux-firebase/issues/85)
+* Renaming a file on upload (currently does not work due to HTML 5 File element being read only)
 
 #### Enhancements/Fixes
  *None Yet Planned*

package.json

@@ -1,6 +1,6 @@
 {
   "name": "react-redux-firebase",
-  "version": "1.5.0-rc.2",
+  "version": "1.5.0-rc.3",
   "description": "Redux integration for Firebase. Comes with a Higher Order Component for use with React.",
   "main": "lib/index.js",
   "module": "es/index.js",

src/compose.js

@@ -280,7 +280,8 @@ export default (fbConfig, otherConfig) => next =>
     /**
      * @private
      * @description Sets data to Firebase only if the path does not already
-     * exist, otherwise it rejects.
+     * exist, otherwise it rejects. Internally uses a Firebase transaction to
+     * prevent a race condition between seperate clients calling uniqueSet.
      * @param {String} path - Path to location on Firebase which to set
      * @param {Object|String|Boolean|Number} value - Value to write to Firebase
      * @param {Function} onComplete - Function to run on complete (`not required`)
@@ -298,14 +299,15 @@ export default (fbConfig, otherConfig) => next =>
      */
     const uniqueSet = (path, value, onComplete) =>
       rootRef.child(path)
-        .once('value')
-        .then(snap => {
-          if (snap.val && snap.val() !== null) {
-            const err = new Error('Path already exists.')
-            if (onComplete) onComplete(err)
-            return Promise.reject(err)
+        .transaction(d => d === null ? value : undefined)
+        .then(({ commited, snapshot }) => {
+          if (!commited) {
+            const newError = new Error('Path already exists.')
+            if (onComplete) onComplete(newError)
+            return Promise.reject(newError)
           }
-          return rootRef.child(path).set(value, onComplete)
+          if (onComplete) onComplete(snapshot)
+          return snapshot
         })
 
     /**