feat: add is_app_initialized function (#701)

firebase_admin/__init__.py

@@ -65,7 +65,7 @@ def initialize_app(credential=None, options=None, name=_DEFAULT_APP_NAME):
         credential = credentials.ApplicationDefault()
     app = App(name, credential, options)
     with _apps_lock:
-        if app.name not in _apps:
+        if not is_app_initialized(app.name):
             _apps[app.name] = app
             return app
 
@@ -85,6 +85,17 @@ def initialize_app(credential=None, options=None, name=_DEFAULT_APP_NAME):
         'you call initialize_app().').format(name))
 
 
+def is_app_initialized(name=_DEFAULT_APP_NAME):
+    """Returns True if the App instance for the specified name is initialized.
+    Args:
+      name: Name of the App instance to retrieve (optional).
+    Returns:
+      bool: True if the App instance is initialized, False otherwise.
+    """
+    with _apps_lock:
+        return name in _apps
+
+
 def delete_app(app):
     """Gracefully deletes an App instance.
 
@@ -129,9 +140,8 @@ def get_app(name=_DEFAULT_APP_NAME):
     if not isinstance(name, str):
         raise ValueError('Illegal app name argument type: "{}". App name '
                          'must be a string.'.format(type(name)))
-    with _apps_lock:
-        if name in _apps:
-            return _apps[name]
+    if is_app_initialized(name):
+        return _apps[name]
 
     if name == _DEFAULT_APP_NAME:
         raise ValueError(

tests/test_app.py

@@ -285,6 +285,24 @@ def test_app_init_with_default_config(self, env_test_case):
         app = firebase_admin.initialize_app(CREDENTIAL, options=env_test_case.init_options)
         assert app.options._options == env_test_case.want_options
 
+    def test_default_app_is_initialized(self, app_credential):
+        firebase_admin.initialize_app(app_credential)
+        assert firebase_admin.is_app_initialized()
+
+    def test_no_app_is_initialized(self):
+        assert firebase_admin.is_app_initialized() is False
+
+    def test_correct_app_is_initialized(self):
+        app_name = 'myApp'
+        firebase_admin.initialize_app(CREDENTIAL, name=app_name)
+        assert firebase_admin.is_app_initialized(app_name)
+
+    def test_correct_app_is_not_initialized(self):
+        app_name = 'myApp'
+        other_app_name = 'otherApp'
+        firebase_admin.initialize_app(CREDENTIAL, name=app_name)
+        assert firebase_admin.is_app_initialized(other_app_name) is False
+
     def test_project_id_from_options(self, app_credential):
         app = firebase_admin.initialize_app(
             app_credential, options={'projectId': 'test-project'}, name='myApp')