Rewrite syntactic refactoring actions in sourcekitd using swift-syntax

[ahoppen]

Implementing refactoring actions in swift-syntax instead of in sourcekitd makes them more robust and easier to maintain going forward. A full list of refactoring actions implemented in sourcekitd is at https://github.com/swiftlang/swift/blob/9b452820367ccc7b5d9effbc1565bcd945c81768/include/swift/Refactoring/RefactoringKinds.def#L21-L92. Only refactoring actions that don’t require (too much) semantic knowledge about types can be implemented in swift-syntax. I think the following can be implemented in swift-syntax. Once these are implemented in swift-syntax, we should suppress the corresponding sourcekitd refactoring in SourceKit-LSP based on its ID. The original implementation of these refactoring actions can be found in https://github.com/swiftlang/swift by searching for the refactoring’s name.

No type information required (easier to implement):

• ConvertToComputedProperty (Add new features to ConvertStoredPropertyToComputed swift-syntax#3229)
• CollapseNestedIfStmt
• ConvertToSwitchStmt
• ConvertToTernaryExpr (Refactor ConvertToTernaryExpr swift-syntax#3252)
• ExpandTernaryExpr (Implement ExpandTernaryExpr mirroring sourcekitd implementation swift-syntax#3247)
• MoveMembersToExtension

Require type information that can be retrived using a cursor info (harder to implement because we don’t have a blueprint for this at the moment):

• ExtractExpr
• ExtractFunction
• ExtractRepeatedExpr
• MemberwiseInitLocalRefactoring

If you are interested in working on this, please open a separate PR for each refactoring action.

[Clemo97]

Hey @ahoppen

Thanks for your earlier guidance, it significantly improved my understanding of sourcekit-lsp.
I’m interested in taking on this issue and would love to work on it.

[ahoppen]

Just comment which refactoring action you want to work on so others can start on others.

[Clemo97]

Just comment which refactoring action you want to work on so others can start on others.

I'll start working on ConvertToDoCatch.

Just to confirm my understanding of the process:

1. Study the original implementation in swiftlang/swift (sourcekitd's RefactoringActionConvertToDoCatch)
2. Implement the refactoring in swiftlang/swift-syntax as a pure syntax transformation.
3. Add it as a code action in swiftlang/sourcekit-lsp and suppress the sourcekitd version.

So basically, this involves code changes in two repositories: swift-syntax and sourcekit-lsp? Correct me if I'm wrong.

I'll open a separate PR for this as you mentioned.

[myaumura]

Hi, @ahoppen. Can I take the ConvertToComputedProperty part of the issue to work on?

[ahoppen]

Can I take the ConvertToComputedProperty part of the issue to work on?

Absolutely. Looking forward to your PR.

[ahoppen]

So basically, this involves code changes in two repositories: swift-syntax and sourcekit-lsp? Correct me if I'm wrong.

Yes. That’s correct.

[Viditgupta-official]

I’d like to start working on this by implementing the “collapse nested if” refactoring using SwiftSyntax, since it’s a purely syntax-based transformation and seems like a good first step to migrate out of sourcekitd.

Plan is to do this as a small, self-contained PR (as suggested), and suppress the existing sourcekitd action once the SwiftSyntax version is in place.

Please let me know if that sounds reasonable or if there’s any guidance before I begin.

[ahoppen]

That sounds great. Looking forward to your PR @Viditgupta-official.