Aligned DataSnapshot methods to @firebase/database counterpart

Author: rhodgkins

src/v1/providers/database.ts

@@ -108,7 +108,7 @@ export function _instanceWithOptions(
  */
 export class InstanceBuilder {
   /** @hidden */
-  constructor(private instance: string, private options: DeploymentOptions) {}
+  constructor(private instance: string, private options: DeploymentOptions) { }
 
   /**
    * @return Firebase Realtime Database reference builder interface.
@@ -134,9 +134,9 @@ export function _refWithOptions(
     if (!databaseURL) {
       throw new Error(
         'Missing expected firebase config value databaseURL, ' +
-          'config is actually' +
-          JSON.stringify(firebaseConfig()) +
-          '\n If you are unit testing, please set process.env.FIREBASE_CONFIG'
+        'config is actually' +
+        JSON.stringify(firebaseConfig()) +
+        '\n If you are unit testing, please set process.env.FIREBASE_CONFIG'
       );
     }
 
@@ -174,7 +174,7 @@ export class RefBuilder {
     private apps: apps.Apps,
     private triggerResource: () => string,
     private options: DeploymentOptions
-  ) {}
+  ) { }
 
   /**
    * Event handler that fires every time a Firebase Realtime Database write
@@ -325,7 +325,7 @@ export function extractInstanceAndPath(
   if (!match) {
     throw new Error(
       `Unexpected resource string for Firebase Realtime Database event: ${resource}. ` +
-        'Expected string in the format of "projects/_/instances/{firebaseioSubdomain}/refs/{ref=**}"'
+      'Expected string in the format of "projects/_/instances/{firebaseioSubdomain}/refs/{ref=**}"'
     );
   }
   const [, project, dbInstanceName, path] = match;
@@ -396,7 +396,7 @@ export class DataSnapshot {
       // may be unpopulated in user's unit tests
       throw new Error(
         'Please supply a Firebase app in the constructor for DataSnapshot' +
-          ' in order to use the .ref method.'
+        ' in order to use the .ref method.'
       );
     }
     if (!this._ref) {
@@ -471,7 +471,16 @@ export class DataSnapshot {
    * @return `true` if this `DataSnapshot` contains any data; otherwise, `false`.
    */
   exists(): boolean {
-    return !_.isNull(this.val());
+    const val = this.val();
+    if (_.isNull(val)) {
+      // Null value
+      return false;
+    }
+    if ((_.isObjectLike(val) || _.isArray(val)) && _.isEmpty(val)) {
+      // Empty object/array
+      return false;
+    }
+    return true
   }
 
   /**
@@ -512,7 +521,7 @@ export class DataSnapshot {
    */
   forEach(action: (a: DataSnapshot) => boolean | void): boolean {
     const val = this.val();
-    if (_.isPlainObject(val)) {
+    if (_.isObjectLike(val) || _.isArray(val)) {
       return _.some(
         val,
         (value, key: string) => action(this.child(key)) === true
@@ -546,7 +555,7 @@ export class DataSnapshot {
    */
   hasChildren(): boolean {
     const val = this.val();
-    return _.isPlainObject(val) && _.keys(val).length > 0;
+    return (_.isObjectLike(val) || _.isArray(val)) && !_.isEmpty(val);
   }
 
   /**
@@ -556,7 +565,7 @@ export class DataSnapshot {
    */
   numChildren(): number {
     const val = this.val();
-    return _.isPlainObject(val) ? Object.keys(val).length : 0;
+    return (_.isObjectLike(val) || _.isArray(val)) ? _.keys(val).length : 0;
   }
 
   /**
@@ -588,7 +597,12 @@ export class DataSnapshot {
         continue;
       }
       const childNode = node[key];
-      obj[key] = this._checkAndConvertToArray(childNode);
+      const v = this._checkAndConvertToArray(childNode);
+      if (v === null) {
+        // Empty child node
+        continue;
+      }
+      obj[key] = v;
       numKeys++;
       const integerRegExp = /^(0|[1-9]\d*)$/;
       if (allIntegerKeys && integerRegExp.test(key)) {
@@ -598,6 +612,11 @@ export class DataSnapshot {
       }
     }
 
+    if (numKeys === 0) {
+      // Empty node
+      return null;
+    }
+
     if (allIntegerKeys && maxKey < 2 * numKeys) {
       // convert to array.
       const array: any = [];