Enable Google TTS with application default credentials (#721)

.changeset/tender-bikes-dream.md

@@ -0,0 +1,5 @@
+---
+"livekit-plugins-google": minor
+---
+
+Enable use of Google STT with Application Default Credentials.

livekit-plugins/livekit-plugins-google/README.md

@@ -10,4 +10,4 @@ pip install livekit-plugins-google
 
 ## Pre-requisites
 
-For credentials, you'll need a Google Cloud account and obtain the correct credentials. Credentials can be passed directly or set as [GOOGLE_APPLICATION_CREDENTIALS](https://cloud.google.com/docs/authentication/application-default-credentials) environment variable.
+For credentials, you'll need a Google Cloud account and obtain the correct credentials. Credentials can be passed directly or via Application Default Credentials as specified in [How Application Default Credentials works](https://cloud.google.com/docs/authentication/application-default-credentials).

livekit-plugins/livekit-plugins-google/livekit/plugins/google/stt.py

@@ -23,6 +23,8 @@
 from livekit import agents, rtc
 from livekit.agents import stt, utils
 
+from google.auth import default as gauth_default
+from google.auth.exceptions import DefaultCredentialsError
 from google.cloud.speech_v2 import SpeechAsyncClient
 from google.cloud.speech_v2.types import cloud_speech
 
@@ -61,8 +63,8 @@ def __init__(
         Create a new instance of Google STT.
 
         Credentials must be provided, either by using the ``credentials_info`` dict, or reading
-        from the file specified in ``credentials_file`` or the ``GOOGLE_APPLICATION_CREDENTIALS``
-        environmental variable.
+        from the file specified in ``credentials_file`` or via Application Default Credentials as
+        described in https://cloud.google.com/docs/authentication/application-default-credentials
         """
         super().__init__(
             capabilities=stt.STTCapabilities(streaming=True, interim_results=True)
@@ -73,10 +75,13 @@ def __init__(
         self._credentials_file = credentials_file
 
         if credentials_file is None and credentials_info is None:
-            creds = os.environ.get("GOOGLE_APPLICATION_CREDENTIALS")
-            if not creds:
+            try:
+                gauth_default()
+            except DefaultCredentialsError:
                 raise ValueError(
-                    "GOOGLE_APPLICATION_CREDENTIALS must be set if no credentials is provided"
+                    "Application default credentials must be available "
+                    "when using Google STT without explicitly passing "
+                    "credentials through credentials_info or credentials_file."
                 )
 
         if isinstance(languages, str):
@@ -112,7 +117,11 @@ def _recognizer(self) -> str:
         # recognizers may improve latency https://cloud.google.com/speech-to-text/v2/docs/recognizers#understand_recognizers
 
         # TODO(theomonnom): find a better way to access the project_id
-        project_id = self._ensure_client().transport._credentials.project_id  # type: ignore
+        try:
+            project_id = self._ensure_client().transport._credentials.project_id  # type: ignore
+        except AttributeError:
+            from google.auth import default as ga_default
+            _, project_id = ga_default()
         return f"projects/{project_id}/locations/global/recognizers/_"
 
     def _sanitize_options(self, *, language: str | None = None) -> STTOptions:

livekit-plugins/livekit-plugins-google/setup.py

@@ -48,6 +48,7 @@
     packages=setuptools.find_namespace_packages(include=["livekit.*"]),
     python_requires=">=3.9.0",
     install_requires=[
+        "google-auth >= 2, < 3",
         "google-cloud-speech >= 2, < 3",
         "google-cloud-texttospeech >= 2, < 3",
         "livekit-agents>=0.8.0.dev0",