Fix issues with .ref in Database functions (#727)

Author: samtstern

CHANGELOG.md

@@ -1,3 +1,4 @@
 - Fixes error when last argument to logger methods is `null`. (#716)
 - Adds newly available locations `us-west3`, `europe-west6`, `northamerica-northeast1`, and `australia-southeast1`.
 - No longer throw errors for unrecognized regions (deploy will error instead).
+- Fixes error where `snap.ref` in database functions did not work when using the Emulator Suite (#726)

src/providers/database.ts

@@ -41,6 +41,7 @@ export const provider = 'google.firebase.database';
 export const service = 'firebaseio.com';
 
 const databaseURLRegex = new RegExp('^https://([^.]+).');
+const emulatorDatabaseURLRegex = new RegExp('^http://.*ns=([^&]+)');
 
 /**
  * Registers a function that triggers on events from a specific
@@ -138,14 +139,25 @@ export function _refWithOptions(
           '\n If you are unit testing, please set process.env.FIREBASE_CONFIG'
       );
     }
-    const match = databaseURL.match(databaseURLRegex);
-    if (!match) {
+
+    let instance = undefined;
+    const prodMatch = databaseURL.match(databaseURLRegex);
+    if (prodMatch) {
+      instance = prodMatch[1];
+    } else {
+      const emulatorMatch = databaseURL.match(emulatorDatabaseURLRegex);
+      if (emulatorMatch) {
+        instance = emulatorMatch[1];
+      }
+    }
+
+    if (!instance) {
       throw new Error(
         'Invalid value for config firebase.databaseURL: ' + databaseURL
       );
     }
-    const subdomain = match[1];
-    return `projects/_/instances/${subdomain}/refs/${normalized}`;
+
+    return `projects/_/instances/${instance}/refs/${normalized}`;
   };
 
   return new RefBuilder(apps(), resourceGetter, options);
@@ -350,7 +362,10 @@ export class DataSnapshot {
     private app?: firebase.app.App,
     instance?: string
   ) {
-    if (instance) {
+    if (app && app.options.databaseURL.startsWith('http:')) {
+      // In this case we're dealing with an emulator
+      this.instance = app.options.databaseURL;
+    } else if (instance) {
       // SDK always supplies instance, but user's unit tests may not
       this.instance = instance;
     } else if (app) {