refactor(language_server): move tools definitions to Backend

[Sysix]

This PR refactors the language server architecture by moving tool definitions (linter and formatter) from individual workers to the Backend. The ToolBuilder trait is redesigned to use a method that returns boxed trait objects, and builder structs are simplified to stateless types.

Now it should be easy to implement something like Backend::new(vec![ServerLinterBuilder]);

[Sysix]

• refactor(language_server): move tools definitions to Backend #15563 : 2 dependent PRs (#15608 , #15609 ) 👈 (View in Graphite)
• refactor(language_server): make tools inside WorkspaceWorker more generic #15505
• perf(language_server): pass file content as a referenced String #15568
• main

---

How to use the Graphite Merge Queue

Add either label to this PR to merge it via the merge queue:

• 0-merge - adds this PR to the back of the merge queue
• hotfix - for urgent hot fixes, skip the queue and merge this PR next

You must have a Graphite account in order to use the merge queue. Sign up using this link.

An organization admin has enabled the Graphite Merge Queue in this repository.

Please do not merge from GitHub as this will restart CI on PRs being processed by the merge queue.

This stack of pull requests is managed by Graphite. Learn more about stacking.

[Copilot]

Pull Request Overview

This PR refactors the language server architecture by moving tool definitions (linter and formatter) from individual workers to the Backend. The ToolBuilder trait is redesigned to use a method that returns boxed trait objects, and builder structs are simplified to stateless types.

• Redesigned ToolBuilder trait with a build_boxed method that takes parameters by reference
• Simplified ServerLinterBuilder and ServerFormatterBuilder to stateless structs with static-like build methods
• Centralized tool builder instantiation in Backend::new() and passed them to workers during initialization

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
crates/oxc_language_server/src/tool.rs	Simplified ToolBuilder trait to return boxed trait objects with references
crates/oxc_language_server/src/linter/server_linter.rs	Refactored ServerLinterBuilder to a stateless struct with separate build and build_boxed methods
crates/oxc_language_server/src/formatter/server_formatter.rs	Refactored ServerFormatterBuilder to a stateless struct with separate build and build_boxed methods
crates/oxc_language_server/src/backend.rs	Added tool_builders field and centralized tool builder instantiation
crates/oxc_language_server/src/worker.rs	Updated start_worker to accept tool builders as parameters
crates/oxc_language_server/src/linter/tester.rs	Updated test code to use new builder pattern
crates/oxc_language_server/src/formatter/tester.rs	Updated test code to use new builder pattern

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[camc314]

Merge activity

• Nov 12, 9:23 PM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Nov 12, 9:42 PM UTC: camc314 added this pull request to the Graphite merge queue.
• Nov 12, 9:48 PM UTC: Merged by the Graphite merge queue.