feat: add cdf dev function serve command

[trygveu]

Summary

• Adds cdf dev function serve command that starts a local uvicorn dev server for testing Function App handlers
• Interactive function discovery — when no path argument is given, scans the project for Function App handlers and prompts the user to pick one
• Landing page at / with function info, CDF project warning banner, tracing status, link to Swagger docs, and live log viewer with severity toggle (Warnings+ / All)
• Safety controls — bans prod validation-type configs entirely; prompts user to acknowledge full read/write CDF access for dev/staging
• Validation-type from config — reads validation-type from config.{env}.yaml (same as build/deploy), not from env vars
• Classical function guard — rejects plain def handle(client, data) handlers; only Function Apps supported
• Toolkit auth — monkey-patches cognite_function_apps to use the toolkit's EnvironmentVariables auth path, so all toolkit auth flows work
• Log streaming via SSE at /api/logs with severity toggle, status JSON at /api/status
• Tracing detection — detects TracingApp in the handler's middleware chain and displays tracing status on the landing page
• Auto-opens browser on server start

Changes

• pyproject.toml — new serve optional dependency group
• commands/serve.py — ServeFunctionCommand with:
  • _discover_function_dirs() / _prompt_function_selection() for interactive handler discovery
  • _load_validation_type() reading from BuildConfigYAML config files
  • _check_build_type() blocking prod, prompting for dev/staging
  • _validate_handler_is_function_app() rejecting classical functions
  • _detect_tracing() inspecting the handler's ASGI middleware chain
  • _patch_cognite_client_factory() for toolkit auth integration
  • Reload/no-reload server startup with graceful shutdown timeout
• commands/_landing_page.py — Pure ASGI middleware: landing page HTML with warning banner, tracing row, log severity toggle, SSE log streaming, status API
• apps/_dev_function_app.py — DevFunctionApp typer with optional path argument, --host, --port, --reload/--no-reload, --log-level
• apps/_dev_app.py — wires DevFunctionApp under cdf dev function
• tests/test_serve.py — 22 unit tests covering validation, auth patching, build type checks, and all middleware routes

Test plan

• cdf dev function serve (no args) — discovers handlers, prompts selection
• cdf dev function serve <path> — starts uvicorn, opens browser to landing page
• Landing page shows function name, CDF project warning, tracing status, link to /docs, live log stream with toggle
• /docs link opens Swagger UI
• With --reload: editing handler.py triggers reload visible in logs
• Prod config blocked with clear error message
• Dev/staging config prompts for acknowledgement
• Classical function handler rejected with clear error
• Without cognite-function-apps[cli] installed, prints helpful install message
• Unit tests pass (22/22)

🤖 Generated with Claude Code

[gemini-code-assist]

Using Gemini Code Assist

The full guide for Gemini Code Assist can be found on our documentation page, here are some quick tips.

Invoking Gemini

You can request assistance from Gemini at any point by creating a comment using either /gemini <command> or @gemini-code-assist <command>. Below is a summary of the supported commands on the current page.

Feature	Command	Description

Customization

To customize Gemini Code Assist for GitHub experience, repository maintainers can create a configuration file and/or provide a custom code review style guide (such as PEP-8 for Python) by creating and adding files to a .gemini/ folder in the base of the repository. Detailed instructions can be found here.

Limitations & Feedback

Gemini Code Assist may make mistakes. Please leave feedback on any instances where its feedback is incorrect or counter productive. You can react with 👍 and 👎 on @gemini-code-assist comments. If you're interested in giving your feedback about your experience with Gemini Code Assist for GitHub and other Google products, sign up here.

[github-actions]

☂️ Python Coverage

current status: ✅

Overall Coverage

Lines	Covered	Coverage	Threshold	Status
37581	31979	85%	80%	🟢

New Files

File	Coverage	Status
cognite_toolkit/_cdf_tk/commands/_landing_page.py	91%	🟢
cognite_toolkit/_cdf_tk/commands/serve.py	32%	🟢
TOTAL	62%	🟢

Modified Files

File	Coverage	Status
cognite_toolkit/_cdf_tk/commands/init.py	100%	🟢
TOTAL	100%	🟢

updated for commit: 8f04f83 by action🐍

[codecov]

Codecov Report

❌ Patch coverage is 49.22118% with 163 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.09%. Comparing base (e0415f3) to head (8f04f83).
⚠️ Report is 15 commits behind head on main.

Files with missing lines	Patch %	Lines
cognite_toolkit/_cdf_tk/commands/serve.py	32.31%	155 Missing ⚠️
cognite_toolkit/_cdf_tk/commands/_landing_page.py	91.20%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2667      +/-   ##
==========================================
+ Coverage   84.89%   85.09%   +0.19%     
==========================================
  Files         436      440       +4     
  Lines       37014    37581     +567     
==========================================
+ Hits        31423    31979     +556     
- Misses       5591     5602      +11     

Files with missing lines	Coverage Δ
cognite_toolkit/_cdf_tk/commands/__init__.py	100.00% <100.00%> (ø)
cognite_toolkit/_cdf_tk/commands/_landing_page.py	91.20% <91.20%> (ø)
cognite_toolkit/_cdf_tk/commands/serve.py	32.31% <32.31%> (ø)

... and 62 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.