cargo-soothfast 0.1.3

//! `cargo soothfast spec gate` — fail on API changes that break consumers.
//!
//! A generated spec can never disagree with the code, so the drift check that
//! `spec check` performs stops being meaningful for files we generate. What
//! remains worth gating is compatibility: the spec is rebuilt from the
//! merge-base in a temporary worktree and compared against this branch's, so
//! there is no committed baseline to go stale.

use soothfast_spec::compat::Severity;

use crate::invoke::{self, CommonArgs};
use crate::spec_config;
use crate::spec_gen;

pub fn run(args: &[String]) -> i32 {
    let mut common = CommonArgs::default();
    let mut base = "origin/master".to_string();
    let mut allow_breaking = false;
    let mut it = args.iter();
    while let Some(a) = it.next() {
        match a.as_str() {
            "--base" => match it.next() {
                Some(b) => base = b.clone(),
                None => {
                    eprintln!("soothfast: --base needs a git ref");
                    return 2;
                }
            },
            // Escape hatch for a deliberate, coordinated break.
            "--allow-breaking" => allow_breaking = true,
            _ => {
                if !common.try_parse(a, &mut it) {
                    eprintln!("soothfast: unknown spec gate arg {a:?}");
                    return 2;
                }
            }
        }
    }
    let Some(pkg) = common.pkg.clone() else {
        eprintln!("soothfast: spec gate requires -p PKG");
        return 2;
    };
    match gate(&pkg, &common, &base, allow_breaking) {
        Ok(code) => code,
        Err(e) => {
            eprintln!("soothfast: {e}");
            1
        }
    }
}

fn gate(pkg: &str, common: &CommonArgs, base: &str, allow_breaking: bool) -> Result<i32, String> {
    let meta = invoke::pkg_meta(pkg).map_err(|e| e.to_string())?;
    let cfg = spec_config::load(&meta.dir)?;

    let head = spec_gen::build(pkg, common, None, &cfg, &meta)?;
    if head.docs.is_empty() {
        println!("spec gate: no generated spec files — nothing to gate");
        return Ok(0);
    }

    let base_built = invoke::with_merge_base_worktree(base, |wt| {
        spec_gen::build(pkg, common, Some(wt), &cfg, &meta)
    })?;

    let mut breaking = 0u32;
    let mut additive = 0u32;

    for (spec_file, new_doc) in &head.docs {
        let kind = cfg.dialect_of(spec_file);
        // A spec file absent from the base is entirely new, so every
        // operation in it is additive by construction.
        let empty = kind.empty();
        let old_doc = base_built.docs.get(spec_file).unwrap_or(&empty);
        let changes = kind.diff(old_doc, new_doc);

        if changes.is_empty() {
            println!(
                "spec gate: {spec_file} [{}] — no API changes vs {base}",
                kind.name()
            );
            continue;
        }
        println!("spec gate: {spec_file} [{}] — vs {base}", kind.name());
        for c in &changes {
            let tag = match c.severity {
                Severity::Breaking => {
                    breaking += 1;
                    "BREAKING"
                }
                Severity::Additive => {
                    additive += 1;
                    "additive"
                }
            };
            println!("  {tag}  {}: {}", c.at, c.detail);
        }
    }

    println!("spec gate: {breaking} breaking, {additive} additive");
    if breaking > 0 && !allow_breaking {
        println!(
            "spec gate: FAILED — pass --allow-breaking to release these \
             deliberately, after coordinating with consumers"
        );
        return Ok(1);
    }
    if breaking > 0 {
        println!("spec gate: breaking changes allowed by --allow-breaking");
    }
    Ok(0)
}