cargo-telar 0.1.4

//! `cargo telar fmt` — formats a project's `.rsx` and `.rs` files.
//!
//! Two formatters behind one command, because a Telar project is two languages. `.rsx` goes through
//! [`telar_parser::format`], the same function the language server serves `textDocument/formatting` from, so a
//! file formatted from a terminal and one formatted on save come out identical. `.rs` goes to `rustfmt`, one
//! file at a time — which is the whole reason this command exists, since `cargo fmt` walks the module tree from
//! the crate root and an `auto_modules` crate declares that tree from a macro `cargo fmt` cannot expand.

use std::path::{Path, PathBuf};
use std::process::Command;

use super::cli::FmtArgs;

pub(crate) fn run_fmt_cmd(args: FmtArgs) {
    let roots = if args.paths.is_empty() {
        vec![std::env::current_dir().unwrap_or_else(|_| PathBuf::from("."))]
    } else {
        args.paths.clone()
    };

    let mut sources = Vec::new();
    for root in &roots {
        collect(root, &mut sources);
    }
    sources.sort();
    sources.dedup();

    let (mut changed, mut failed) = (Vec::new(), Vec::new());
    for path in &sources {
        match format_file(path, args.check) {
            Ok(true) => changed.push(path.clone()),
            Ok(false) => {}
            Err(e) => failed.push((path.clone(), e)),
        }
    }

    for (path, error) in &failed {
        eprintln!("[cargo-telar] {}: {error}", display(path));
    }
    if args.check {
        for path in &changed {
            println!("{}", display(path));
        }
        let verdict = match (changed.len(), failed.len()) {
            (0, 0) => return println!("[cargo-telar] {} files already formatted", sources.len()),
            (n, 0) => format!("{n} file(s) need formatting"),
            (0, f) => format!("{f} file(s) could not be read"),
            (n, f) => format!("{n} file(s) need formatting, {f} could not be read"),
        };
        eprintln!("[cargo-telar] {verdict}");
        std::process::exit(1);
    }
    println!(
        "[cargo-telar] formatted {} of {} files",
        changed.len(),
        sources.len()
    );
    if !failed.is_empty() {
        std::process::exit(1);
    }
}

/// Every `.rsx` and `.rs` file under `root`, skipping what is not source: `target/`, the generated `.telar/`
/// tree (formatting it would be undone by the next build) and any dot-directory.
fn collect(root: &Path, out: &mut Vec<PathBuf>) {
    if root.is_file() {
        if is_source(root) {
            out.push(root.to_path_buf());
        }
        return;
    }
    let Ok(entries) = std::fs::read_dir(root) else {
        return;
    };
    for entry in entries.flatten() {
        let path = entry.path();
        let name = entry.file_name();
        let name = name.to_string_lossy();
        if path.is_dir() {
            if name.starts_with('.') || name == "target" {
                continue;
            }
            collect(&path, out);
        } else if is_source(&path) {
            out.push(path);
        }
    }
}

fn is_source(path: &Path) -> bool {
    matches!(
        path.extension().and_then(|e| e.to_str()),
        Some("rsx") | Some("rs")
    )
}

/// Formats one file, reporting whether it changed. `check` reads and compares without writing.
fn format_file(path: &Path, check: bool) -> Result<bool, String> {
    let source = std::fs::read_to_string(path).map_err(|e| e.to_string())?;
    let formatted = match path.extension().and_then(|e| e.to_str()) {
        // A document that does not parse is left exactly as it is, which is what every formatter does with a
        // file it cannot read — the error belongs to the compiler, not to the formatter.
        Some("rsx") => match telar_parser::format::format_document(&source) {
            Some(formatted) => formatted,
            None => return Ok(false),
        },
        _ => rustfmt(&source)?,
    };
    if formatted == source {
        return Ok(false);
    }
    if !check {
        std::fs::write(path, &formatted).map_err(|e| e.to_string())?;
    }
    Ok(true)
}

/// Runs `rustfmt` over one file's text. Through stdin rather than by path so `--check` never writes, and so a
/// file rustfmt rejects leaves the original untouched instead of half-formatted.
fn rustfmt(source: &str) -> Result<String, String> {
    use std::io::Write;

    let mut child = Command::new("rustfmt")
        .args(["--edition", "2024", "--emit", "stdout", "--quiet"])
        .stdin(std::process::Stdio::piped())
        .stdout(std::process::Stdio::piped())
        .stderr(std::process::Stdio::piped())
        .spawn()
        .map_err(|e| format!("could not run rustfmt: {e}"))?;
    child
        .stdin
        .take()
        .ok_or("rustfmt took no stdin")?
        .write_all(source.as_bytes())
        .map_err(|e| e.to_string())?;
    let out = child.wait_with_output().map_err(|e| e.to_string())?;
    if !out.status.success() {
        return Err(String::from_utf8_lossy(&out.stderr).trim().to_string());
    }
    String::from_utf8(out.stdout).map_err(|e| e.to_string())
}

fn display(path: &Path) -> String {
    std::env::current_dir()
        .ok()
        .and_then(|cwd| path.strip_prefix(cwd).ok().map(Path::to_path_buf))
        .unwrap_or_else(|| path.to_path_buf())
        .display()
        .to_string()
}