refactor(script-rs): idiomatic Rust, better error handling, doc comments, SIGINT cleanup

[Copilot]

The script-rs CLI had several code-quality issues: &String params, empty-string sentinels, repeated env::args() reads per call, bare unwrap() on I/O, and String::from("x") + &y concatenation.

src/main.rs

• Serial number extracted once in main as Option<&str> and threaded through all helpers; serial_checked_command now accepts serial: Option<&str> instead of re-reading env::args() on every invocation
• locate_apk_path → Option<String> — replaces the empty-string sentinel with a proper None return
• &String → &str in all function signatures
• open_browser(port, serial) — accepts parameters instead of re-reading args
• format! everywhere — replaces String::from("x") + &y and the redundant println!("{}", format!(…))
• split_once(':') — replaces the fragile .split(":").last()
• Descriptive expect messages on every I/O .unwrap()
• /// doc comments added to every top-level function
• Removed the redundant use webbrowser; bare import
• SIGINT handler cleans up port forward exclusively — setup_signal_handler accepts port: String and serial: Option<String>, moves them into a dedicated background thread, and invokes unforward_connection on Ctrl-C. The handler is registered in main after forward_connection (to avoid spurious cleanup on early exits) and is the sole place unforward_connection is called. The thread processes exactly one SIGINT via signals.forever().next() and then returns. setup_signal_handler returns (thread::JoinHandle<()>, Handle) — after startup_service_and_wait, main calls signals_close.close() to unblock the thread on a normal exit and then signal_handle.join() to wait for cleanup in both the SIGINT and clean-exit paths.

// Before
fn forward_connection(port: &String) {
    let grp = String::from("tcp:") + &port;
    serial_checked_command().args(…).output().expect(…);
}

// After
fn forward_connection(port: &str, serial: Option<&str>) {
    let grp = format!("tcp:{}", port);
    serial_checked_command(serial).args(…).output().expect(…);
}

Cargo.toml

• Added description and repository fields; dropped the vacuous authors = []

Original prompt

Overview

Refine the Rust script located in the script-rs/ directory (script-rs/src/main.rs and script-rs/Cargo.toml). The goal is to improve code quality, idiomatic Rust usage, error handling, and maintainability without changing the core behavior of the program.

Current code

The current script-rs/src/main.rs has these issues:

1. Clippy / idiomatic Rust warnings:

   • port.trim().parse::<u32>().expect(...) — the parsed value is discarded; it should validate via a proper error message or be stored.
   • Functions take port: &String instead of the idiomatic port: &str.
   • raw_path.split(":").last() — use splitn or direct strip_prefix for clarity.
   • String::from("tcp:") + &port — use format! consistently.
   • String::from("CLASSPATH=") + &(raw_path.to_string()) — use format!.
   • use webbrowser; at the top is an unnecessary bare use (the crate is invoked as webbrowser::open).
   • The open_browser function re-reads env::args() instead of accepting the needed values as parameters.
   • count_connected_devices uses .unwrap() without any error context.
   • Inline format string in println!("{}", format!(...)) — should be println!("{}", ...) directly.

2. Error handling:

   • Many .unwrap() calls in I/O paths (adb command output, UTF-8 conversion) should use expect with a descriptive message or be propagated via Result.
   • locate_apk_path returns an empty String as a sentinel for failure; this should return Option<String> or Result<String, ...>.

3. Code organisation / readability:

   • serial_checked_command() reads env::args() on every call; the serial number should be extracted once in main and passed around.
   • The startup_service_and_wait function name is slightly misleading; it also spawns the process. A doc comment would help.
   • Add brief doc comments (///) to each public/top-level function explaining what it does.

4. Cargo.toml:

   • Add description, authors (can be left empty [] as a placeholder), and repository fields to the [package] section to silence cargo publish warnings and improve discoverability.
   • Consider whether edition = "2021" deps are up-to-date (bump webbrowser and signal-hook to their latest compatible versions if newer ones exist).

Expected changes

• Refactor functions to accept &str instead of &String where appropriate.
• Replace sentinel empty-string returns with Option<String>.
• Extract the serial-number argument into main and pass it to helper functions rather than re-reading env::args() each time.
• Replace String::from("x") + &y patterns with format!("x{}", y).
• Remove the redundant use webbrowser; statement (keep the call site webbrowser::open).
• Add expect messages to .unwrap() calls that touch external process output.
• Add brief /// doc comments to each function.
• Update Cargo.toml with description and tidy up formatting.

Please make all these refinements in a single commit on a new branch and open a pull request against master.

The following is the prior conversation context from the user's chat exploration (may be truncated):

User: Create a PR to refine the Rust script under the folder script-rs in the repo DroidCast

Assistant: Now I have a thorough understanding of the Rust code. Let me create a PR with meaningful refinements.

Assistant: We're waiting for your response to the tool call dialog to continue — please accept or reject the request to let me proceed with creating the pull request.

This pull request was created from Copilot chat.

[rayworks]

The main thread should be interrupted at this time. So can you call unforward_connection method when receiving the SIGINT signal ?
@copilot

[Copilot]

Done in f0b9cb1. setup_signal_handler now accepts port: String and serial: Option<String>, moves them into the handler thread, and calls unforward_connection on SIGINT. The call is placed in main right after forward_connection, so the handler only runs cleanup for a forward that was actually established.

[rayworks]

This redundant call should be removed since it will be called in the signal handler.

[Copilot]

Removed in 629c813. Cleanup is now exclusively the signal handler's responsibility.

[rayworks]

Once received the SIGINT, the thread should return, with a JoinHandle waiting for the thread exit.

[Copilot]

Done in 629c813. setup_signal_handler now returns (thread::JoinHandle<()>, Handle). The thread uses signals.forever().next() — it processes one SIGINT and then returns. In main, after startup_service_and_wait, signals_close.close() is called (unblocks the thread on a normal exit) and signal_handle.join() waits for it to finish in both the SIGINT and normal-exit paths.