fix: Correctly catch DefaultCredentialsError when looking up project_id (#720)

* Added additional exception catching with unit tests

* lint: fixed spacing

* fix: explicitly force exception raise in unit test

Author: jonathanedey

firebase_admin/__init__.py

@@ -18,6 +18,7 @@
 import os
 import threading
 
+from google.auth.exceptions import DefaultCredentialsError
 from firebase_admin import credentials
 from firebase_admin.__about__ import __version__
 
@@ -257,7 +258,7 @@ def _lookup_project_id(self):
         if not project_id:
             try:
                 project_id = self._credential.project_id
-            except AttributeError:
+            except (AttributeError, DefaultCredentialsError):
                 pass
         if not project_id:
             project_id = os.environ.get('GOOGLE_CLOUD_PROJECT',

tests/test_app.py

@@ -17,6 +17,7 @@
 import os
 
 import pytest
+from google.auth.exceptions import DefaultCredentialsError
 
 import firebase_admin
 from firebase_admin import credentials
@@ -315,6 +316,27 @@ def evaluate():
             assert app.project_id is None
         testutils.run_without_project_id(evaluate)
 
+    def test_no_project_id_from_environment(self, app_credential):
+        default_env = 'GOOGLE_APPLICATION_CREDENTIALS'
+        gcloud_env = 'CLOUDSDK_CONFIG'
+        def evaluate():
+            app = firebase_admin.initialize_app(app_credential, name='myApp')
+            app._credential._g_credential = None
+            old_gcloud_var = os.environ.get(gcloud_env)
+            os.environ[gcloud_env] = ''
+            old_default_var = os.environ.get(default_env)
+            if old_default_var:
+                del os.environ[default_env]
+            with pytest.raises((AttributeError, DefaultCredentialsError)):
+                project_id = app._credential.project_id
+            project_id = app.project_id
+            if old_default_var:
+                os.environ[default_env] = old_default_var
+            if old_gcloud_var:
+                os.environ[gcloud_env] = old_gcloud_var
+            assert project_id is None
+        testutils.run_without_project_id(evaluate)
+
     def test_non_string_project_id(self):
         options = {'projectId': {'key': 'not a string'}}
         with pytest.raises(ValueError):