CONTEXT: https://sourcegraph.slack.com/archives/C05ABRRGB0B/p1717790701356599

Fix an issue where a valid Gemini response ends with new lines, causing a false alert.

Issue: We are seeing *errutil.leafError: no Google response found in Sentry complaining when I run a command or chat in VS Code using google as provider.

Cause: Currently the code (added my me) would skip to the last line of the stream response and determine if the response is valid or not, which could be an issue because the stream API could ends the response with an empty new line, where our current logic would fail.

Changes included in this PR:

• Modify parseGoogleTokenUsage function to find the last non-empty line in the stream, to handle cases where the stream ends with a newline
• Add a test case to cover the scenario where the stream ends with a newline

This change modifies the behavior of the parseGoogleTokenUsage function to handle streams with trailing newlines, which would fail even if the response is valid because Gemini adds a new line to the end of their stream.

Test plan

Make a curl command to the Gemini streaming API to confirm the response ends with a new line:

curl https://generativelanguage.googleapis.com/v1beta/models/gemini-1.5-flash:streamGenerateContent\?alt=sse\&key\=$GOOGLE_API_KEY \
    -H 'Content-Type: application/json' \
    -X POST \
    -d '{
      "contents": [
        {"role":"user",
         "parts":[{
           "text": "Write the first line of a story about a magic backpack."}]},
        {"role": "model",
         "parts":[{
           "text": "In the bustling city of Meadow brook, lived a young girl named Sophie. She was a bright and curious soul with an imaginative mind."}]},
        {"role": "user",
         "parts":[{
           "text": "Can you set it in a quiet village in 1600s France?"}]},
      ]
    }' 2> /dev/null

Copied the response to the test file and confirmed our current test would fail with the same error message:

This is now handled by the newly added test with the actually stream response returned by calling the Gemini API.

Changelog