feat: add topgrade configuration management plugin

[AdityaM-IITH]

Related Issue

Closes #186

Proposed Changes

• Added a new Python plugin to manage the topgrade system-wide upgrade configuration (topgrade.toml).
• Implemented the config_provider capability using tomlkit to safely merge incoming settings while perfectly preserving existing user comments and TOML formatting.
• Set up inline script metadata (PEP 723) so uv automatically handles dependencies without manual pip installs.
• Created plugins/topgrade/plugin.yaml manifest.
• Created plugins/topgrade/src/plugin.py containing the core config parsing and merging logic.
• Created plugins/topgrade/test/test_topgrade.py for automated tests of the new plugin.

Type of Change

• 🐛 Bug fix
• ✨ New feature
• 📖 Documentation
• 🧪 Testing
• 🛠️ Refactoring
• 🚀 DevOps/CI

Screenshots / Logs (if applicable)

============================= test session starts =============================
platform win32 -- Python 3.12.13, pytest-9.0.3, pluggy-1.6.0
rootdir: C:\Users\hp\.gemini\antigravity\scratch\WinHome
configfile: pyproject.toml
collected 3 items

plugins\topgrade\test\test_topgrade.py ...                               [100%]

============================== 3 passed in 0.42s ==============================

Testing & Verification

• I have run dotnet test and all 60+ cross-platform tests passed.
• I have verified the changes on a Windows environment (if applicable).
• I have added new unit tests to cover my changes.

GSSOC 2026 Checklist

• I have read the Contribution Guidelines.
• My code is formatted correctly (I have run dotnet format, uv tool run ruff format plugins/, and bun x prettier --write plugins/).
• I have linked the PR to an approved issue.
• I understand that a maintainer must apply the gssoc:approved label for this PR to count for points.

[AdityaM-IITH]

Hi maintainers, just a heads-up the ruff check CI failure on plugins/everything/src/plugin.py (I001 unsorted imports) is a pre-existing issue on main and is not introduced by this PR.

You can verify by running:

git checkout main
uv tool run ruff check plugins/everything/src/plugin.py

[DotDev262]

Thanks for the PR. Several issues to fix:

1. CRITICAL: Empty stdin causes silent exit (host hangs)

if not raw_input: return returns nothing to stdout. Must return a JSON error response:

{"requestId": "unknown", "error": "No input received"}

2. CRITICAL: JSON parse error has no stdout response

Writing to stderr only and returning silently still leaves the host hanging. Must print a JSON error to stdout.

3. check_installed must return bare bool

Returns {"data": {"installed": bool}}. Must return bare bool, and main() wraps it:

result = handle_check_installed()
response = {"requestId": req_id, "installed": result}

4. dryRun must come from args, not context

dry_run = context.get("dryRun", False) should be args.get("dryRun", False).

5. requestId must use .get("requestId") or "unknown"

request.get("requestId") returns None when key exists but is null.

6. Non-standard response fields

"success" and "changed" are not standard. Use only requestId, error, and action-specific fields.

7. response.update() merge pattern

The response.update(res) pattern breaks when functions return non-dict values. Design each handler to return data, and let main() construct the response.

Please reference existing merged plugins (e.g., plugins/pnpm/) for correct patterns.

[DotDev262]

@AdityaM-IITH — Thanks for addressing the review feedback! The PR needs a rebase before I can do a final review. Please rebase onto latest main.

[DotDev262]

@AdityaM-IITH — please rebase on latest main (6 commits behind) so I can re-review. Let me know if you need help.

[DotDev262]

@AdityaM-IITH Please rebase onto latest main before review. Let me know when done.

[DotDev262]

@AdityaM-IITH Please rebase onto latest main. Let me know when done.

[AdityaM-IITH]

@DotDev262 Rebased onto latest main. I also fixed the pre-existing linting errors that were failing CI, so everything should pass cleanly now.

[DotDev262]

Hi @AdityaM-IITH,

Thank you for rebasing this PR and updating the format!

However, the plugin does not yet comply with the repository's updated JSON-RPC protocol contract and guidelines. Please address the following issues:

1. check_installed Return Type:

   • Per the repository guidelines, check_installed must return a bare bool. It is the responsibility of main() to wrap it into the standard JSON response format: {"requestId": request_id, "installed": result}.
   • Currently, check_installed returns a dictionary including success and data fields.

2. Banned Response Fields (success and data):

   • The "success" field and "data" wrapper are banned from all JSON-RPC responses.
   • Currently, they are used across all responses in check_installed, apply_config, and the error handlers. Please remove them and return flat response objects containing only the required fields (e.g. requestId, changed, installed, error).

3. Non-Atomic File Writes:

   • In apply_config (lines 113–114), the file is written to directly using open(config_path, "w").
   • The repository requires atomic writes using tempfile.mkstemp() and os.replace() to prevent configuration corruption.

4. Test Refactoring:

   • Once the response schema is updated to remove success and data and wrap check_installed properly, the unit tests in plugins/topgrade/test/test_topgrade.py must be updated to match the new schema (i.e. assert on installed directly and remove success/data assertions).

5. Rebase Required:

   • The branch is 1 commit behind main due to a recent merge. Please rebase your branch on the latest main.

Thank you!

[DotDev262]

Hi @AdityaM-IITH! Just a friendly reminder — this PR is 10 commits behind main and has outstanding protocol issues (check_installed bare bool, success/data fields). Could you please rebase and address the remaining feedback? Thanks!

[DotDev262]

Your branch is behind main. Please rebase onto latest main and force-push so we can proceed with the review. Thanks!

[AdityaM-IITH]

@DotDev262 Rebase is complete. I've also fully addressed the protocol issues:

check_installed now returns a bare bool, which main() handles.
Removed success and data wrappers everywhere to ensure flat responses.
Implemented atomic file writes via tempfile and os.replace for config generation.
Fixed the empty stdin / bad JSON parsing edge cases so the plugin correctly returns an error instead of hanging.
Updated tests to match the new schema.
Let me know if anything else is needed.