Provide `if`, `for`, `while`, etc. as snippets instead of plain keywords

[notfirefox]

Description

Other language servers, e.g. clangd, provide snippets for control structures such as if, for, while, etc. Accepting a suggestion for one of those keywords then will insert the following text:

if expression {
    |
}

The cursor will first be on expression, allowing the user to enter the expression that controls the if statement. Pressing the tab key will move the cursor to the next location, i.e. | - where the user can write the code that shall be executed when the expression is true.

[Wilfred]

FWIW this is usually a feature of the VS Code extension rather than the LSP. I think this would need to be fixed in https://github.com/swiftlang/vscode-swift?

[notfirefox]

FWIW this is usually a feature of the VS Code extension rather than the LSP. I think this would need to be fixed in https://github.com/swiftlang/vscode-swift?

That's an option as well, will not work with other code editors then though

[ahoppen]

I think it’s reasonable for SourceKit-LSP to provide snippets for general purpose Swift snippets like control flow constructs.

[DPrakashh]

Hi @ahoppen, - from Swift Forum
I'd like to take on issue #2118: Implement keyword snippets for control-flow keywords.
I have completed the implementation and verification locally, and the solution is ready for a pull request.

Summary of Key Changes
1-The solution involved updating CodeCompletionSession.swift to identify control-flow keyword completions (.keyword) and overwrite their insertText and textEdit with the correct LSP snippet string, setting insertTextFormat = .snippet.

2-This ensures that keywords like if, for, while, guard, switch, and repeat now contain placeholders (e.g., ${1:condition} and $0) required by LSP clients.

Verification
1-Test: Added unit tests (in SwiftCompletionSnippetTests.swift) to explicitly check for insertTextFormat == .snippet and the presence of placeholders.

2-Result: The focused test, swift test --filter SwiftCompletionSnippetTests/testKeywordIfProvidesSnippet, passed successfully locally.

Please assign this issue to me.

[ahoppen]

@DPrakashh That’s great. Please just open a pull request. With your comment and the PR being linked from the issue, people will know that you’re working on it without me assigning the issue to you – we have had quite a few cases in the past where issues were assigned to contributors who never opened a PR and thus nobody else tackled them and I’d like to avoid that going forward.

[DPrakashh]

Hi @ahoppen,

I wanted to check in on the status of my pull request, submitted about a week ago. Given that it touches core completion, I understand it requires careful review.

Just confirming that I have run the full local test suite and all checks passed on my end. Would it be possible to get the automated CI tests triggered when you or another maintainer has a chance to look at it?
@swift-ci Please test

I am eager to continue contributing. Should I wait for the review on this PR, or is it better to move ahead and start work on another small issue while this one is in the queue?

If there are any issues or required changes, please give me a review, and I will immediately work to address them.
Thanks for your time and guidance!