feat(language_server): introduce ServerFormatter

[Sysix]

First try on formatter integration.
The server will only tell the client, that is supports formatting when fmt.experimental is true.

It will respect the flag in initialize, did_change_configuration (changing configuration), or did_change_workspace_folders.
It will not tell the client, it does not support formatting when the configuration is changed to false.
This can be optimized but has no high priority, because the client needs to send the request and the ServerFormatter needs to be set. The last requirement is then false.

Make WorkspaceWorker.option optional, so we the servers knows when the configuration in initialize or initialized (with request_workspace_configuration). Before the server knew it, by looking at the WorkspaceWorker.server_linter instance.

[Sysix]

• refactor(langauge_server): move Backend into own file #13955
• feat(editor): add oxc.fmt.experimental flag #13923
• feat(language_server): introduce ServerFormatter #13700 👈 (View in Graphite)
• refactor(language_server): introduce LSPFileSystem #13731
• refactor(language_server): split options for linting and formatting #13627
• main

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[codspeed-hq]

CodSpeed Instrumentation Performance Report

Merging #13700 will not alter performance

_{Comparing 09-11-refactor_language_server_introduce_dummy_serverformatter_ (a21ff54) with main (6fcb0d0)}

Summary

✅ 37 untouched

[Copilot]

Pull Request Overview

This PR introduces experimental formatter support to the OXC language server, adding the ServerFormatter struct and configuring it to be enabled via the fmt.experimental configuration option. The formatter integration uses dynamic LSP capability registration to conditionally advertise formatting support to clients.

• Adds ServerFormatter with run_single method for formatting files
• Introduces fmt.experimental configuration option for enabling the formatter
• Implements dynamic capability registration for textDocument/formatting when formatter is enabled

Reviewed Changes

Copilot reviewed 12 out of 13 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
worker.rs	Adds formatter state management and configuration handling to WorkspaceWorker
main.rs	Implements LSP formatting endpoint and dynamic capability registration
formatter/server_formatter.rs	Core formatter implementation with file processing logic
formatter/options.rs	Configuration parsing for formatter experimental flag
capabilities.rs	Enables dynamic formatting capability support
options.rs	Adds test for new fmt.experimental configuration option

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[camc314]

Merge activity

• Sep 20, 6:04 PM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Sep 20, 6:04 PM UTC: camc314 added this pull request to the Graphite merge queue.
• Sep 20, 6:10 PM UTC: Merged by the Graphite merge queue.