Refactor ws_service_exec.rs:handle_ws to reduce cognitive_complexity and add test coverage

[mukeshblackhat]

ws_service_exec.rs:handle_ws (line 239) has #[allow(clippy::cognitive_complexity)]. The function is ~140 lines handling a PTY-backed exec session for running commands inside a service container.

What it does

handle_ws(WebSocket, AppState, project, name, service, container_id, session_id) — WebSocket handler for interactive shell/exec sessions into a service container. If a session_id is provided and active, reconnects to that session. Otherwise creates a new session: resolves the inner container, opens a PTY via docker exec, stores a PtySession in state, spawns a reader task that pushes PTY output into a scrollback ring buffer + broadcast, sends an init message with the new session_id, and runs the bridge loop.

What to do

1. Extract session creation

Lines 260–332 set up a brand-new session: generate UUID, resolve inner container, open PTY via spawn_blocking, dup the fd, build the PtySession, insert into state. Extract:

async fn create_pty_session(
    state: &AppState,
    docker: &bollard::Docker,
    container_id: &str,
    project: &str,
    service: &str,
    composite_key: String,
    socket: &mut WebSocket,
) -> Option<(String, Arc<Mutex<VecDeque<u8>>>, broadcast::Sender<Vec<u8>>, i32, i32)>
// returns (session_id, scrollback, output_tx, read_fd, write_fd) on success

2. Extract PTY reader task spawn

Lines 334–366 spawn the background task that reads from the PTY master fd into the scrollback ring + broadcast. Extract:

fn spawn_pty_reader_task(
    state: Arc<AppState>,
    sid: String,
    read_fd: i32,
    scrollback: Arc<Mutex<VecDeque<u8>>>,
    output_tx: broadcast::Sender<Vec<u8>>,
)

3. Extract error-and-return helper

The pattern let _ = socket.send(Message::Text(...)).await; return; appears 5+ times for different error paths. Extract:

async fn send_error_and_return(
    socket: &mut WebSocket,
    message: impl Into<String>,
)

4. Add unit tests

Unit testing this handler directly is hard (requires Docker + PTY). Focus on:

• send_error_and_return — called via a mock socket to verify message format (if feasible)
• Any pure helper functions that come out of the extraction

Important

The workspace Cargo.toml sets cognitive_complexity, too_many_lines, too_many_arguments, and several other clippy lints to warn globally. Run make lint after every change and make sure the output is clean. Don't fix a suppression here only to create new warnings elsewhere.

Acceptance criteria

• create_pty_session extracted
• spawn_pty_reader_task extracted
• send_error_and_return extracted to deduplicate error paths
• handle_ws uses the new helpers
• All tests pass (make test)
• make lint passes with zero new warnings
• Remove #[allow(clippy::cognitive_complexity)] if make lint passes without it, keep if not (note why)

Related

Tracking issue pattern from previous PRs: #122, #133, #157, #158, #171, #172, #173, #174, #175