refactor(language_server): Pass ToolBuilder reference to Tool trait methods

[Copilot]

The current architecture requires ServerFormatter and ServerLinter to call static builder methods (ServerFormatterBuilder::build()) when rebuilding, preventing builders from holding and reusing state across rebuilds.

Changes

Tool trait (tool.rs)

• Added builder: &dyn ToolBuilder parameter to handle_configuration_change and handle_watched_file_change

Tool implementations (server_formatter.rs, server_linter.rs)

• Replaced static ServerFormatterBuilder::build() / ServerLinterBuilder::build() calls with builder.build_boxed()
• Both tools now receive and use the builder reference for rebuilding

WorkspaceWorker (worker.rs)

• Stores Arc<Vec<Box<dyn ToolBuilder>>> alongside tools
• Constructor accepts builders parameter; start_worker() uses stored builders
• Passes appropriate builder reference to each tool during handle_configuration_change and handle_watched_file_change

Backend (backend.rs)

• Wraps tool_builders in Arc for shared ownership across workers
• Updated all WorkspaceWorker instantiations to pass builder Arc

Example

Before:

fn handle_configuration_change(&self, root_uri: &Uri, ...) -> ToolRestartChanges {
    let new_formatter = ServerFormatterBuilder::build(root_uri, new_options);
    // ...
}

After:

fn handle_configuration_change(&self, builder: &dyn ToolBuilder, root_uri: &Uri, ...) -> ToolRestartChanges {
    let new_formatter = builder.build_boxed(root_uri, new_options);
    // ...
}

This enables ToolBuilder implementations to hold state without further API changes.

Original prompt

Problem Statement

Currently, ServerFormatter and ServerLinter rebuild themselves in handle_configuration_change and handle_watched_file_change by calling static methods like ServerFormatterBuilder::build(). This prevents the ToolBuilder from holding and reusing state during tool rebuilds.

Goal

Refactor the architecture so that:

1. The ToolBuilder can hold its own data/state
2. The Tool trait methods handle_configuration_change and handle_watched_file_change receive a reference to the ToolBuilder (&dyn ToolBuilder)
3. Tools can use the builder reference to rebuild themselves, allowing the builder to utilize its stored data

Required Changes

1. Update the Tool trait in crates/oxc_language_server/src/tool.rs

Modify the trait methods to accept a builder parameter:

fn handle_configuration_change(
    &self,
    builder: &dyn ToolBuilder,
    root_uri: &Uri,
    old_options_json: &serde_json::Value,
    new_options_json: serde_json::Value,
) -> ToolRestartChanges;

fn handle_watched_file_change(
    &self,
    builder: &dyn ToolBuilder,
    changed_uri: &Uri,
    root_uri: &Uri,
    options: serde_json::Value,
) -> ToolRestartChanges;

2. Update ServerFormatter implementation in crates/oxc_language_server/src/formatter/server_formatter.rs

Update the Tool trait implementation to use the builder reference:

fn handle_configuration_change(
    &self,
    builder: &dyn ToolBuilder,
    root_uri: &Uri,
    old_options_json: &serde_json::Value,
    new_options_json: serde_json::Value,
) -> ToolRestartChanges {
    // ... existing comparison logic ...
    
    let new_formatter = builder.build_boxed(root_uri, new_options_json.clone());
    let watch_patterns = new_formatter.get_watcher_patterns(new_options_json);
    ToolRestartChanges {
        tool: Some(new_formatter),
        watch_patterns: Some(watch_patterns),
    }
}

fn handle_watched_file_change(
    &self,
    builder: &dyn ToolBuilder,
    _changed_uri: &Uri,
    root_uri: &Uri,
    options: serde_json::Value,
) -> ToolRestartChanges {
    let new_formatter = builder.build_boxed(root_uri, options);
    ToolRestartChanges {
        tool: Some(new_formatter),
        watch_patterns: None,
    }
}

3. Update ServerLinter implementation in crates/oxc_language_server/src/linter/server_linter.rs

Similar changes to use the builder reference instead of static ServerLinterBuilder::build() calls.

4. Update WorkspaceWorker in crates/oxc_language_server/src/worker.rs

Update the code that calls these trait methods to pass the builder:

• Store the builder alongside each tool
• Pass the builder reference when calling handle_configuration_change and handle_watched_file_change

5. Update backend initialization in crates/oxc_language_server/src/backend.rs

Ensure builders are properly stored and accessible when creating workspace workers.

6. Update test code

• Update FakeTool in crates/oxc_language_server/src/tests.rs
• Update test helpers in crates/oxc_language_server/src/formatter/tester.rs
• Update test helpers in crates/oxc_language_server/src/linter/tester.rs

Implementation Notes

• The ToolBuilder trait doesn't need changes to its interface
• ServerFormatterBuilder and ServerLinterBuilder can remain zero-sized structs for now, but this change enables them to hold state in the future
• Ensure all call sites are updated to maintain existing behavior
• The refactoring should not change external behavior, only internal architecture

Success Criteria

• All existing tests pass
• The code compiles without errors
• handle_configuration_change and handle_watched_file_change use builder.build_boxed() instead of static method calls
• The architecture supports ToolBuilder holding state for future enhancements

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Pull request overview

This PR refactors the Tool trait architecture to pass ToolBuilder references to handle_configuration_change and handle_watched_file_change methods, enabling builders to hold and reuse state across tool rebuilds.

Key Changes:

• Added builder: &dyn ToolBuilder parameter to Tool trait methods
• Updated all Tool implementations to use builder.build_boxed() instead of static builder method calls
• Modified WorkspaceWorker to store builders alongside tools and pass appropriate builder references during tool operations

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
crates/oxc_language_server/src/tool.rs	Added builder parameter to handle_configuration_change and handle_watched_file_change trait methods
crates/oxc_language_server/src/formatter/server_formatter.rs	Updated ServerFormatter to use builder.build_boxed() instead of static ServerFormatterBuilder::build() calls
crates/oxc_language_server/src/linter/server_linter.rs	Updated ServerLinter to use builder.build_boxed() instead of static ServerLinterBuilder::build() calls
crates/oxc_language_server/src/worker.rs	Added builders: Arc<[Box<dyn ToolBuilder>]> field, updated constructor and start_worker() to use stored builders, modified handle_tool_changes() to pass builder references
crates/oxc_language_server/src/backend.rs	Wrapped tool_builders in Arc and updated all WorkspaceWorker instantiations to pass cloned Arc references
crates/oxc_language_server/src/tests.rs	Updated FakeTool implementation to use builder parameter in trait methods
crates/oxc_language_server/src/formatter/tester.rs	Updated test helper to instantiate builder and pass it to handle_configuration_change()
crates/oxc_language_server/src/linter/tester.rs	Updated test helper to instantiate builder and pass it to handle_configuration_change()

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