get_diagnostics can abort stdio server for file paths containing URI-reserved chars

[dergachoff]

Summary

get_diagnostics can abort the mcpls stdio server when the target file path contains URI-reserved characters such as [ and ].

This happens with common framework route filenames like:

routes/api/[...].ts

The client then sees the MCP transport close instead of receiving an error response.

Reproduction

Call get_diagnostics for an existing file whose path contains brackets, for example:

/tmp/project/routes/api/[...].ts

Using an MCP stdio probe against mcpls, the process aborts before returning a tool response.

Observed behavior

mcpls panics while converting the filesystem path to an LSP URI:

thread 'tokio-rt-worker' panicked at crates/mcpls-core/src/bridge/state.rs:
failed to create URI from path: ParseError { ... kind: UnexpectedChar }

From the MCP client side this appears as a closed stdio transport.

Expected behavior

mcpls should create a valid percent-encoded LSP file:// URI, return diagnostics normally, or return a structured tool error without aborting the server.

Suspected root cause

path_to_uri formats file URIs directly as file://{path}. That leaves URI-reserved path characters raw. lsp_types::Uri::from_str rejects the raw brackets, and the following expect panics.

Local validation

A local patch that builds the file URL with Url::from_file_path, percent-encodes the remaining RFC3986-invalid path characters, and adds bracketed-path round-trip coverage fixes the crash.

Validated locally with:

cargo +nightly fmt --check
cargo +1.95 test -p mcpls-core path_to_uri
cargo +1.95 test -p mcpls-core
cargo +1.95 clippy -p mcpls-core --all-targets --all-features -- -D warnings

A post-fix MCP stdio probe against the same bracketed path returned a normal get_diagnostics response instead of aborting.