fix: Add support for file URIs in LiteLLM content conversion to fix issue #3131

changed the LiteLLM content conversion so Part.file_data.file_uri (like the gs://…) becomes a file object with file_id, making sure GCS-backed files reach LiteLLM proxies instead of being dropped add unit tests covering both _get_content and _content_to_message_param paths for file URIs

PiperOrigin-RevId: 817658432

tests/unittests/models/test_litellm.py

@@ -1005,6 +1005,47 @@ def test_content_to_message_param_user_message():
   assert message["content"] == "Test prompt"
 
 
+def test_content_to_message_param_user_message_with_file_uri():
+  file_part = types.Part.from_uri(
+      file_uri="gs://bucket/document.pdf", mime_type="application/pdf"
+  )
+  content = types.Content(
+      role="user",
+      parts=[
+          types.Part.from_text(text="Summarize this file."),
+          file_part,
+      ],
+  )
+
+  message = _content_to_message_param(content)
+  assert message["role"] == "user"
+  assert isinstance(message["content"], list)
+  assert message["content"][0]["type"] == "text"
+  assert message["content"][0]["text"] == "Summarize this file."
+  assert message["content"][1]["type"] == "file"
+  assert message["content"][1]["file"]["file_id"] == "gs://bucket/document.pdf"
+  assert message["content"][1]["file"]["format"] == "application/pdf"
+
+
+def test_content_to_message_param_user_message_file_uri_only():
+  file_part = types.Part.from_uri(
+      file_uri="gs://bucket/only.pdf", mime_type="application/pdf"
+  )
+  content = types.Content(
+      role="user",
+      parts=[
+          file_part,
+      ],
+  )
+
+  message = _content_to_message_param(content)
+  assert message["role"] == "user"
+  assert isinstance(message["content"], list)
+  assert message["content"][0]["type"] == "file"
+  assert message["content"][0]["file"]["file_id"] == "gs://bucket/only.pdf"
+  assert message["content"][0]["file"]["format"] == "application/pdf"
+
+
 def test_content_to_message_param_multi_part_function_response():
   part1 = types.Part.from_function_response(
       name="function_one",
@@ -1183,6 +1224,19 @@ def test_get_content_pdf():
   assert content[0]["file"]["format"] == "application/pdf"
 
 
+def test_get_content_file_uri():
+  parts = [
+      types.Part.from_uri(
+          file_uri="gs://bucket/document.pdf",
+          mime_type="application/pdf",
+      )
+  ]
+  content = _get_content(parts)
+  assert content[0]["type"] == "file"
+  assert content[0]["file"]["file_id"] == "gs://bucket/document.pdf"
+  assert content[0]["file"]["format"] == "application/pdf"
+
+
 def test_get_content_audio():
   parts = [
       types.Part.from_bytes(data=b"test_audio_data", mime_type="audio/mpeg")