Firebase App Auto Init (#164)

Add code to read default options from the FIREBASE_CONFIG environment variable. (and make the options param to initializeApp optional)

Author: avishalom

src/firebase-app.ts

@@ -36,7 +36,6 @@ import {InstanceId} from './instance-id/instance-id';
  */
 export type AppHook = (event: string, app: FirebaseApp) => void;
 
-
 /**
  * Type representing the options object passed into initializeApp().
  */
@@ -260,7 +259,6 @@ export class FirebaseApp {
     if (!hasCredential) {
       errorMessage = 'Options must be an object containing at least a "credential" property.';
     }
-
     const credential = this.options_.credential;
     if (typeof credential !== 'object' || credential === null || typeof credential.getAccessToken !== 'function') {
       errorMessage = 'The "credential" property must be an object which implements the Credential interface.';

src/firebase-namespace.ts

@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+import fs = require('fs');
 import {deepExtend} from './utils/deep-copy';
 import {AppErrorCodes, FirebaseAppError} from './utils/error';
 import {AppHook, FirebaseApp, FirebaseAppOptions} from './firebase-app';
@@ -32,8 +33,18 @@ import {Database} from '@firebase/database';
 import {Firestore} from '@google-cloud/firestore';
 import {InstanceId} from './instance-id/instance-id';
 
+import * as validator from './utils/validator';
+
 const DEFAULT_APP_NAME = '[DEFAULT]';
 
+/**
+ * Constant holding the environment variable name with the default config.
+ * If the environmet variable contains a string that starts with '{' it will be parsed as JSON,
+ * otherwise it will be assumed to be pointing to a file.
+ */
+export const FIREBASE_CONFIG_VAR: string = 'FIREBASE_CONFIG';
+
+
 let globalAppDefaultCred: ApplicationDefaultCredential;
 let globalCertCreds: { [key: string]: CertCredential } = {};
 let globalRefreshTokenCreds: { [key: string]: RefreshTokenCredential } = {};
@@ -59,12 +70,20 @@ export class FirebaseNamespaceInternals {
   /**
    * Initializes the FirebaseApp instance.
    *
-   * @param {FirebaseAppOptions} options Options for the FirebaseApp instance.
+   * @param {FirebaseAppOptions} options Optional options for the FirebaseApp instance. If none present
+   *                             will try to initialize from the FIREBASE_CONFIG environment variable.
+   *                             If the environmet variable contains a string that starts with '{'
+   *                             it will be parsed as JSON,
+   *                             otherwise it will be assumed to be pointing to a file.
    * @param {string} [appName] Optional name of the FirebaseApp instance.
    *
    * @return {FirebaseApp} A new FirebaseApp instance.
    */
-  public initializeApp(options: FirebaseAppOptions, appName = DEFAULT_APP_NAME): FirebaseApp {
+  public initializeApp(options?: FirebaseAppOptions, appName = DEFAULT_APP_NAME): FirebaseApp {
+    if (typeof options === 'undefined') {
+      options = this.loadOptionsFromEnvVar();
+      options.credential = new ApplicationDefaultCredential();
+    }
     if (typeof appName !== 'string' || appName === '') {
       throw new FirebaseAppError(
         AppErrorCodes.INVALID_APP_NAME,
@@ -227,6 +246,36 @@ export class FirebaseNamespaceInternals {
       }
     });
   }
+
+  /**
+   * Parse the file pointed to by the FIREBASE_CONFIG_VAR, if it exists.
+   * Or if the FIREBASE_CONFIG_ENV contains a valid JSON object, parse it directly.
+   * If the environmet variable contains a string that starts with '{' it will be parsed as JSON,
+   * otherwise it will be assumed to be pointing to a file.
+   */
+  private loadOptionsFromEnvVar(): FirebaseAppOptions {
+    let config = process.env[FIREBASE_CONFIG_VAR];
+    if (!validator.isNonEmptyString(config)) {
+      return {};
+    }
+    try {
+      let contents;
+      if (config.startsWith('{')) {
+        // Assume json object.
+        contents = config;
+      } else {
+        // Assume filename.
+        contents = fs.readFileSync(config, 'utf8');
+      }
+      return JSON.parse(contents) as FirebaseAppOptions;
+    } catch (error) {
+      // Throw a nicely formed error message if the file contents cannot be parsed
+      throw new FirebaseAppError(
+        AppErrorCodes.INVALID_APP_OPTIONS,
+        'Failed to parse app options file: ' + error,
+      );
+    }
+  }
 }
 
 
@@ -354,12 +403,15 @@ export class FirebaseNamespace {
   /**
    * Initializes the FirebaseApp instance.
    *
-   * @param {FirebaseAppOptions} options Options for the FirebaseApp instance.
+   * @param {FirebaseAppOptions} [options] Optional options for the FirebaseApp instance.
+   *   If none present will try to initialize from the FIREBASE_CONFIG environment variable.
+   *   If the environmet variable contains a string that starts with '{' it will be parsed as JSON,
+   *   otherwise it will be assumed to be pointing to a file.
    * @param {string} [appName] Optional name of the FirebaseApp instance.
    *
    * @return {FirebaseApp} A new FirebaseApp instance.
    */
-  public initializeApp(options: FirebaseAppOptions, appName?: string): FirebaseApp {
+  public initializeApp(options?: FirebaseAppOptions, appName?: string): FirebaseApp {
     return this.INTERNAL.initializeApp(options, appName);
   }
 

src/index.d.ts

@@ -60,7 +60,7 @@ declare namespace admin {
   function storage(app?: admin.app.App): admin.storage.Storage;
   function firestore(app?: admin.app.App): admin.firestore.Firestore;
   function instanceId(app?: admin.app.App): admin.instanceId.InstanceId;
-  function initializeApp(options: admin.AppOptions, name?: string): admin.app.App;
+  function initializeApp(options?: admin.AppOptions, name?: string): admin.app.App;
 }
 
 declare namespace admin.app {

test/resources/firebase_config.json

@@ -0,0 +1,6 @@
+{
+  "databaseAuthVariableOverride":  { "some#key": "some#val" },
+  "databaseURL": "https://hipster-chat.firebaseio.mock",
+  "projectId": "hipster-chat-mock",
+  "storageBucket": "hipster-chat.appspot.mock"
+}

test/resources/firebase_config_bad.json

@@ -0,0 +1 @@
+baaaaad

test/resources/firebase_config_bad_key.json

@@ -0,0 +1,4 @@
+{
+  "notAValidKeyValue": "The key value here is not valid.",
+  "projectId": "hipster-chat-mock"
+}

test/resources/firebase_config_empty.json

@@ -0,0 +1,4 @@
+{
+  "databaseURL": "https://hipster-chat.firebaseio.mock",
+  "projectId": "hipster-chat-mock"
+}

test/resources/firebase_config_partial.json

@@ -45,6 +45,8 @@ export let serviceName = 'mock-service-name';
 
 export let databaseURL = 'https://databaseName.firebaseio.com';
 
+export let databaseAuthVariableOverride = { 'some#string': 'some#val' };
+
 export let storageBucket = 'bucketName.appspot.com';
 
 export let credential = new CertCredential(path.resolve(__dirname, './mock.key.json'));
@@ -55,6 +57,14 @@ export let appOptions: FirebaseAppOptions = {
   storageBucket,
 };
 
+export let appOptionsWithOverride: FirebaseAppOptions = {
+  credential,
+  databaseAuthVariableOverride,
+  databaseURL,
+  storageBucket,
+  projectId,
+};
+
 export let appOptionsNoAuth: FirebaseAppOptions = {
   databaseURL,
 };
@@ -63,6 +73,11 @@ export let appOptionsNoDatabaseUrl: FirebaseAppOptions = {
   credential,
 };
 
+export let appOptionsAuthDB: FirebaseAppOptions = {
+  credential,
+  databaseURL,
+};
+
 export class MockCredential implements Credential {
   public getAccessToken(): Promise<GoogleOAuthAccessToken> {
     return Promise.resolve({