[dart_mcp_server] Support refactorings

[dcharkes]

Gemini CLI takes quite a lot of time to rename private members to public members with text replacements. It would be much better to expose refactoring tools to in the MCP:

• Rename symbol
• Change modifiers of classes
• Extract method (though then Gemini must provide the correct range selected)

Likely we'd need a separate tool for each refactoring in an MCP? (E.g. there are no sub-tools in MCP servers.) It looks like pub is set up with a command parameter. I have no idea whether LLMs perform better or worse with sub-commands. 🙃

And we'd need to specify in the tool-description that the refactoring tools likely only work if dart_analyze tool doesn't report any errors.

@jakemac53 Have we considered adding support for refactorings in the Dart MCP?

[jakemac53]

It is certainly something that has been considered yes, and I do think it would be generally quite useful. Not sure when anybody can/will get around to it.

We probably want to do one tool with the type of refactoring as an option, in order to keep down the total number of top level tools available (similar to flutter_driver, pub).

We need evals to really confirm that actually helps, right now we are just going off of other recommendations/anecdotes that it works better to use these "meta" tools.

[bwilkerson]

I'll note that the MCP server already has a connection to the analysis server, which has a fairly large number of refactors implemented already. It shouldn't be too hard to make those available to the model.

[jakemac53]

Yeah, I agree that hooking it up is easy. Evaluating that it actually works, getting the prompting right so the model will actually use the tools, etc is harder.

[jakemac53]

(there is a larger issue at play here that we don't have any sort of eval framework set up so its very ad-hoc right now and requires a lot of manual testing)

[bwilkerson]

@jwren has started thinking about testing and eval

[jpeiffer]

Oh, this would be awesome. I miss Eclipse's right-click -> refactor -> rename ability in Java where you could quickly rename any method or variable and every instance of it's actual usage would be updated. That kind of ability for Dart would be wonderful.

[bwilkerson]

There's already support in VS Code (and other LSP-based clients) as well as IntelliJ and Android Studio for this rename functionality in Dart, and the MCP server has access to the same LSP server as is used by the IDEs, so it's at least theoretically possible.

And we'd need to specify in the tool-description that the refactoring tools likely only work if dart_analyze tool doesn't report any errors.

I missed this the first time I read through this issue, but that isn't strictly true. It depends on the nature of the diagnostics, but most of our refactors work in the presence of diagnostics. They kind of have to or they'd be no help in getting the user back to a diagnostic-free state.

We would need a way to let the model know if the refactor couldn't be applied for some reason, hopefully with enough information to allow the model to try to solve the blocking problem first and then retry the refactor.