fix(language_server): handle invalid root URI gracefully

[381181295]

Summary

• Server panicked on init when rootUri is invalid (e.g., file:// with no path)
• to_file_path().unwrap() failed in server_formatter.rs and server_linter.rs
• Changed ToolBuilder::build_boxed to return Option<Box<dyn Tool>>
• Worker now uses filter_map() to skip tools that fail to build
• Server responds with capabilities instead of crashing

Repro (before fix)

echo 'Content-Length: 95

{"jsonrpc":"2.0","id":0,"method":"initialize","params":{"capabilities":{},"rootUri":"file://"}}' | oxc_language_server
# Panics: called Option::unwrap() on a None value

After fix

Server returns capabilities JSON and continues running.

[Copilot]

Pull request overview

This PR fixes a panic that occurred when the language server received an invalid rootUri during initialization (e.g., file:// with no path). The fix gracefully handles URI conversion failures by making tool builders return Option and filtering out failed tool builds.

Key changes:

• Modified ToolBuilder::build_boxed to return Option<Box<dyn Tool>> instead of Box<dyn Tool>
• Updated ServerLinterBuilder::build and ServerFormatterBuilder::build to return Option and handle invalid URIs with the ? operator
• Added graceful fallback behavior in WorkspaceWorker::is_responsible_for_uri and start_worker to handle invalid root URIs

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
crates/oxc_language_server/src/tool.rs	Changed build_boxed trait method signature to return Option<Box<dyn Tool>> with updated documentation
crates/oxc_language_server/src/worker.rs	Updated is_responsible_for_uri to return false for invalid URIs and modified start_worker to filter out failed tool builds using filter_map
crates/oxc_language_server/src/linter/server_linter.rs	Changed build and build_boxed to return Option, added error logging for invalid URIs, and removed outdated panic documentation
crates/oxc_language_server/src/formatter/server_formatter.rs	Changed build and build_boxed to return Option, added error logging for invalid URIs, and removed outdated panic documentation
crates/oxc_language_server/src/tests.rs	Updated FakeToolBuilder to return Some(Box::new(FakeTool)) and adjusted test code to work with the new Option return type
crates/oxc_language_server/src/linter/tester.rs	Added .expect("test requires valid root URI") to ensure tests fail clearly if the root URI is invalid
crates/oxc_language_server/src/formatter/tester.rs	Added .expect("test requires valid root URI") to ensure tests fail clearly if the root URI is invalid

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[Sysix]

Can you explain a bit more why this is needed?
I would never expect an invalid file URI for workspace/root URI's:)

@camc314 I do not think we will support non-file URIs for a tool base.
If we are 100% sure, we should probably add a check in the initialize request and return an Err instead of panicking.

[381181295]

@Sysix I was debugging oxfmt not formatting on save in Zed, noticed an LSP crashed logand traced back to to_file_path().unwrap() in server_formatter.rs. Don't know exactly what Zed sent that triggered it originally.

[camc314]

Even if we don't know what case causes this, it seems reasonable to handle by retuning an err (over unwrapping)

[camc314]

Hmm I'm thinking the latest vscode failure isn't a flake

[381181295]

@camc314 fixed the vscode failur, is_responsible_for_uri was using string prefix matching instead of file path comparison, this was causing root_second to incorrectly match root.

reverted to path based comparison with error handling and added regression test in case it makes sense

[Sysix]

Because is_responsible_for_uri uses again for to_file_path on the workspace worker root URI, no workspace worker is responsible for a URI ⇒ No tasks are done.

this was causing root_second to incorrectly match root.
I guess we need to sort the workspace workers before setting them in Backend. Or add a trailing slash at the URI, so it does not match similar names, like root and root_xyz

After #17388 I am not sure, if this PR is needed anymore.
@camc314 your thoughts? Fix sorting/trailing or closing this PR :)?