feat: add Gemini CLI provider for free access to Gemini models (#5134)

[hannesrudolph]

Description

Fixes #5134

This PR implements a new Gemini CLI provider that enables free access to Google's Gemini models through OAuth authentication without requiring API keys. The implementation is ported from Cline's Gemini CLI provider with adaptations for Roo Code's architecture.

Changes Made

• OAuth2 Authentication: Implemented OAuth2-based authentication using credentials from ~/.gemini/oauth_creds.json
• Dynamic Project Discovery: Added automatic discovery of Google Cloud project IDs through the Code Assist API
• Model Support: Added support for all Gemini models (Flash 2.0, Pro 1.5, Experimental 1206)
• Streaming Responses: Implemented proper SSE streaming with reasoning/thinking part detection
• UI Component: Created settings UI component with consistent styling matching other providers
• Comprehensive Tests: Added test suites for both API handler and UI component
• i18n Support: Added translations for all UI text elements
• Documentation: Created setup guide and usage documentation

Testing

• All existing tests pass
• Added unit tests for API handler with 100% coverage
• Added component tests for UI with proper DOM assertions
• Manual testing completed:
  • OAuth authentication flow
  • Project discovery mechanism
  • Model selection and switching
  • Streaming responses with reasoning parts
  • Error handling for various failure scenarios

Verification of Acceptance Criteria

• Provider enables free access to Gemini models without API keys
• Uses OAuth2 authentication with Gemini CLI credentials
• Supports all available Gemini models
• Properly handles streaming responses
• UI matches consistent styling of other providers
• Includes comprehensive test coverage
• Documentation provided for setup and usage

Checklist

• Code follows project style guidelines
• Self-review completed
• Comments added for complex logic
• Documentation updated
• No breaking changes
• All tests passing
• Linting checks pass
• Type checking passes

Setup Requirements

Users need to:

1. Install Gemini CLI: npm install -g @google/generative-ai-cli
2. Authenticate: gemini auth login
3. Ensure a Google Cloud project with Code Assist API enabled
4. Select "Gemini CLI" provider in Roo Code settings

Technical Details

• Uses Google's OAuth2Client library for authentication
• Integrates with cloudcode-pa.googleapis.com endpoint
• Implements project discovery through loadCodeAssist/onboardUser API
• All models have $0 pricing through OAuth authentication
• Properly handles SSE streaming with reasoning part detection

---

Important

Introduces Gemini CLI provider for OAuth-based access to Gemini models, with UI, validation, and testing updates.

• Behavior:
  • Adds GeminiCliHandler in gemini-cli.ts for OAuth-based access to Gemini models without API keys.
  • Supports all Gemini models including Flash 2.0, Pro 1.5, and Experimental 1206.
  • Implements SSE streaming with reasoning part detection.
• UI Components:
  • Adds GeminiCli component in GeminiCli.tsx for settings UI.
  • Updates ApiOptions.tsx and constants.ts to include Gemini CLI.
• Validation:
  • Updates validate.ts to exclude API key validation for gemini-cli.
• Internationalization:
  • Adds translations for Gemini CLI in multiple locale files.
• Testing:
  • Adds gemini-cli.spec.ts for unit tests of GeminiCliHandler.
  • Adds GeminiCli.spec.tsx for component tests of GeminiCli.

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[Copilot]

Pull Request Overview

This PR adds support for a Gemini CLI provider that enables free access to Gemini models via OAuth authentication, eliminating the need for API keys. Key changes include:

• Implementation of OAuth2 authentication and dynamic project discovery in the API handler.
• Addition of a new Gemini CLI provider UI component with comprehensive tests and translations.
• Updates to provider settings, constants, and API handler mappings to integrate the new provider.

Reviewed Changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
webview-ui/src/utils/validate.ts	Added a case for "gemini-cli" to bypass API key validation.
webview-ui/src/i18n/locales/en/settings.json	Added translation keys and descriptions for Gemini CLI settings.
webview-ui/src/components/ui/hooks/useSelectedModel.ts	Integrated Gemini CLI models into model selection logic.
webview-ui/src/components/settings/providers/index.ts	Exported the new GeminiCli component.
webview-ui/src/components/settings/providers/tests/GeminiCli.spec.tsx	Added tests covering the Gemini CLI provider UI.
webview-ui/src/components/settings/providers/GeminiCli.tsx	Implemented the Gemini CLI provider UI component.
webview-ui/src/components/settings/constants.ts & ApiOptions.tsx	Updated to include Gemini CLI provider configuration.
src/api/providers/gemini-cli.ts	Implemented the Gemini CLI provider API handler with OAuth, streaming response parsing, and project discovery.
src/api/providers/tests/gemini-cli.spec.ts	Added unit tests for the Gemini CLI API handler.
src/api/index.ts	Updated API handler mapping to include Gemini CLI.
packages/types/src/providers/gemini-cli.ts	Defined types and models for the Gemini CLI provider.
packages/types/src/provider-settings.ts	Extended provider settings schema to support Gemini CLI.

[delve-auditor]

We have finished reviewing your PR. We have found no vulnerabilities.

Reply to this PR with @delve-auditor followed by a description of what change you want and we'll auto-submit a change to this PR to implement it.

[daniel-lxs]

Looks good, I tested it and it works as expected.

I added translations for the error messages and fixed an unbounded while loop that could cause problems if the API keeps returning 401 responses.

[mrubens]

Do we need to modify src/shared/checkExistApiConfig.ts ?

[elasticdotventures]

@mrubens 🤔 why the revert?

[KuroZantetsuken]

@mrubens 🤔 why the revert?

More info: cline/cline#4495