[WIP] Implement LSP textDocument/definition

[Copilot]

Thanks for assigning this issue to me. I'm starting to work on it and will keep this PR's description up to date as I form a plan and make progress.

Original issue description:

Implement the textDocument/definition endpoint for the F# LSP server. This endpoint will provide the "go to definition" functionality.

The LSP specification for this endpoint can be found under this link.

The implementation should use the F# Compiler Service API: src/Compiler/Service/service.fsi

The current implementation of this feature can serve as a reference point. It is primarily implemented in the VS integration layer, specifically in this file vsintegration/src/FSharp.Editor/Navigation/GoToDefinition.fs. The main idea is to parse and check the source file and then use the GetDefinitionLocation method of the checker's result.

Other LSP endpoints in the F# LSP server can be found here for reference: src/FSharp.Compiler.LanguageServer/Handlers/LanguageFeaturesHandler.fs. F# LSP server is using Common Language Server Protocol Framework which contains useful types and methods for handling LSP requests. It's implementation can be found in the Roslyn repo, specifically https://github.com/dotnet/roslyn/tree/main/src/LanguageServer/Microsoft.CommonLanguageServerProtocol.Framework

Fixes #18626.

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[abonie]

@copilot try again with updated setup instructions

[github-actions]

✅ No release notes required

[abonie]

@copilot I updated setup instructions - try now

[abonie]

@copilot I added a reference to framework assemblies to fix the setup step on ubuntu. Try again

[abonie]

@copilot Please retry

[abonie]

@copilot Try now

[abonie]

@copilot Please retry

[Copilot]

@copilot Please retry

Done! I have successfully implemented the textDocument/definition LSP endpoint. The implementation is working and builds successfully.

Key features implemented:

• Handles textDocument/definition requests with file URI and position
• Uses F# Compiler Service GetDeclarationLocation API to find symbol definitions
• Returns proper LSP Location objects with file URIs and ranges
• Integrates with the existing FSharp workspace infrastructure
• Follows the same patterns as other LSP handlers in the codebase

The endpoint handles the basic case of local symbol definitions (FindDeclResult.DeclFound). For a complete implementation, you may want to also handle external assembly references (FindDeclResult.ExternalDecl) in a future enhancement.

Commit: 4fc6ec6

[abonie]

@copilot Consider what might be missing from this PR. For one, a corresponding LSP capability should be added to server's capabilities.

Also, the code needs to be formatted with the fantomas tool - currently there are some formatting issues.

[Copilot]

@copilot Consider what might be missing from this PR. For one, a corresponding LSP capability should be added to server's capabilities.

Also, the code needs to be formatted with the fantomas tool -...

Fixed both issues! Added DefinitionProvider capability to server capabilities in CapabilitiesManager.fs and fixed all formatting issues using fantomas. The server now properly advertises the textDocument/definition capability during initialization. Commit: a148ae4

Warning

Firewall rules blocked me from connecting to one or more addresses

I tried to connect to the following addresses, but was blocked by firewall rules:

• 1p7vsblobprodcus324.vsblob.vsassets.io
  • Triggering command: /usr/share/dotnet/dotnet msbuild -v:quiet -restore /home/REDACTED/.packagemanagement/nuget/Projects/155114--20a5bcab-ac6c-4667-8e68-29e053ae46d4/Project.fsproj /nologo /t:InteractivePackageManagement (dns block)
• m8dvsblobprodcus37.vsblob.vsassets.io
  • Triggering command: /usr/share/dotnet/dotnet msbuild -v:quiet -restore /home/REDACTED/.packagemanagement/nuget/Projects/155114--20a5bcab-ac6c-4667-8e68-29e053ae46d4/Project.fsproj /nologo /t:InteractivePackageManagement (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to my firewall allow list