fix(lsp): fix workspace worker selection for nested and similar-named workspaces

[Copilot]

The language server incorrectly routed files to workspace workers when multiple workspaces existed. With [workspace, workspace/deeper], files in the nested workspace could be handled by the parent worker because the code used .find() which returns the first match rather than the most specific one.

Changes

• Added optimized find_worker_for_uri helper that selects the worker with the longest matching path instead of first match
• Inlined path matching logic directly into the helper, removing the intermediate is_responsible_for_uri method
• Updated 11 worker lookups across LSP operations (did_open, did_change, diagnostics, etc.) to use the new helper
• Fixed workspace option matching during initialization to use exact URI comparison instead of path prefix matching

Implementation

fn find_worker_for_uri<'a>(
    workers: &'a [WorkspaceWorker],
    uri: &Uri,
) -> Option<&'a WorkspaceWorker> {
    let file_path = uri.to_file_path()?;

    workers
        .iter()
        .filter_map(|worker| {
            let root_path = worker.get_root_uri().to_file_path()?;
            if file_path.starts_with(&root_path) {
                Some((worker, root_path.as_os_str().len()))
            } else {
                None
            }
        })
        .max_by_key(|(_, len)| *len)
        .map(|(worker, _)| worker)
}

For nested workspaces like /workspace and /workspace/deeper, both match files in the deeper path via starts_with, but the helper now selects the longer (more specific) path. The implementation uses filter_map to compute path lengths once per worker, avoiding redundant to_file_path() calls for better performance.

Tests

Added unit tests in backend.rs:

• Nested workspace routing (workspace vs workspace/deeper)
• Similar-named workspace routing (workspace vs workspace-2)
• Single workspace edge case
• Empty workers edge case
• Non-file URI edge case

Original prompt

inside crates/oxc_language_server there are multiple checks for detecting which WorkspaceWorker is responsible for a given URI. Fix the logic so workspaces like: [workspace, workspace-2] or [workspace, workspace/deeper] are handeled correctly.

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[Sysix]

@copilot Remove worker.is_responsible_for_uri implementation, it is no longer needed because it only checked for the start of a URI

[Copilot]

@copilot Remove worker.is_responsible_for_uri implementation, it is no longer needed because it only checked for the start of a URI

Done in 74c1c61. Removed is_responsible_for_uri and inlined the starts_with check directly into find_worker_for_uri. Also removed the 3 unit tests that were testing that method since the functionality is now fully covered by the integration tests.

[Sysix]

@copilot do not write integration tests, unit tests are enough. Write them inside Backend.rs as a own testblock, you can check worker.rs for inspiration. Try to optimize find_worker_for_uri

[Copilot]

@copilot do not write integration tests, unit tests are enough. Write them inside Backend.rs as a own testblock, you can check worker.rs for inspiration. Try to optimize find_worker_for_uri

Done in 0682bc0. Replaced integration tests with 5 unit tests in backend.rs test module. Also optimized find_worker_for_uri to use filter_map with tuples, computing path lengths once per worker instead of twice (once in filter, once in max_by_key).

[Copilot]

Pull request overview

This PR fixes incorrect workspace worker selection in the LSP server when multiple workspaces exist, particularly for nested workspaces (e.g., workspace and workspace/deeper) or similarly-named workspaces (e.g., workspace and workspace-2). The previous implementation used .find() which returned the first matching worker rather than the most specific one.

Changes:

• Added find_worker_for_uri helper function that selects workers based on longest matching path instead of first match
• Removed is_responsible_for_uri method from WorkspaceWorker and centralized the logic
• Updated 11 worker lookup locations across LSP operations to use the new helper or exact URI comparison where appropriate
• Added comprehensive unit tests covering nested workspaces, similar-named workspaces, and edge cases

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
crates/oxc_language_server/src/worker.rs	Removed is_responsible_for_uri method and its test, centralizing workspace matching logic
crates/oxc_language_server/src/backend.rs	Added find_worker_for_uri helper with longest-path matching; updated 11 call sites to use new helper or exact URI comparison; added 5 comprehensive unit tests

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