lernie 0.0.3

A git-backed agent harness
Documentation 
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//! The composed side-effect contract: what a tool writes lands in the
//! calling agent's worktree (ARCH §3.3 *Working directory*) and rides
//! the same commit as its `tool_result` entry (§2.3, §3.3
//! commit-per-side-effect — [`super::transcript::commit_tool`] stages
//! `-A`).
//!
//! The two halves are what [`super::run_tool_calls`] pairs for every
//! call; asserting them over the *production* executor and real git is
//! the only way to see that the pairing actually captures the write —
//! a tool left in the harness's inherited cwd wrote its file outside
//! every worktree, where `git add -A` could never see it (bl-2503).

use super::transcript::commit_tool;
use crate::prompt::clock::SystemClock;
use crate::prompt::tool::spawn::PathLookup;
use crate::prompt::tool::{SpawnTool, ToolCall, ToolExecutor};
use crate::template::{GitRunner, RealGit};
use brazen::Content;
use serde_json::json;
use std::path::PathBuf;
use std::sync::atomic::AtomicBool;
use tempfile::TempDir;

/// Force the §3.3 second hop to miss so `bash` resolves at the third —
/// the cargo-built `lernie` binary as the injected driver target.
struct NoPath;

impl PathLookup for NoPath {
    fn which_on_path(&self, _prefixed_name: &str) -> Option<PathBuf> {
        None
    }
}

#[test]
fn a_bash_write_lands_in_the_worktree_and_rides_the_tool_commit() {
    let agent_id = "agent-2503";
    let ws = TempDir::new().unwrap();
    let worktree = crate::workspace::agent_worktree(ws.path(), agent_id);
    std::fs::create_dir_all(&worktree).unwrap();
    let git = RealGit::new();
    let branch = crate::workspace::agent_ref(agent_id);
    git.run(&worktree, &["init", "-b", &branch]).unwrap();
    git.run(&worktree, &["config", "user.email", "t@t"])
        .unwrap();
    git.run(&worktree, &["config", "user.name", "t"]).unwrap();
    git.run(&worktree, &["config", "core.hooksPath", "/dev/null"])
        .unwrap();
    std::fs::create_dir_all(worktree.join("messages")).unwrap();
    std::fs::write(worktree.join("messages/001-model.json"), b"[]").unwrap();
    git.run(&worktree, &["add", "-A"]).unwrap();
    git.run(&worktree, &["commit", "-m", "dispatch"]).unwrap();

    // Steps sit at the workspace root, outside every worktree (§2.2).
    let step_dir = ws.path().join("steps").join(agent_id).join("001");
    std::fs::create_dir_all(&step_dir).unwrap();

    let empty_data_root = TempDir::new().unwrap();
    let lernie = crate::test_support::lernie_binary();
    let clock = SystemClock;
    let exec =
        SpawnTool::new(empty_data_root.path(), &clock, &lernie).with_path_lookup(Box::new(NoPath));
    let outcome = exec
        .execute(
            ToolCall {
                id: "toolu_write",
                name: "bash",
                input: &json!({ "command": "echo hello > out.txt" }),
            },
            &step_dir,
            &AtomicBool::new(false),
        )
        .expect("bash executes");
    assert!(!outcome.is_error, "write should succeed: {outcome:?}");

    // Half one: the write landed on the agent's branch, not wherever the
    // test binary was launched from.
    assert_eq!(
        std::fs::read_to_string(worktree.join("out.txt")).unwrap(),
        "hello\n"
    );

    // Half two: the tool commit captures it alongside the result entry.
    let tool_result = Content::ToolResult {
        tool_use_id: "toolu_write".into(),
        content: vec![Content::Text(String::new())],
        is_error: false,
    };
    commit_tool(&worktree, agent_id, &tool_result, &git).unwrap();

    let committed = git
        .run_capture(&worktree, &["show", "--name-only", "--pretty=", "HEAD"])
        .unwrap();
    let names: Vec<&str> = committed.lines().collect();
    assert!(
        names.contains(&"out.txt"),
        "the tool's worktree side effect rides the tool commit: {names:?}"
    );
    assert!(
        names.contains(&"messages/002-tool.json"),
        "the result entry is in the same commit: {names:?}"
    );
    assert!(
        git.run_capture(&worktree, &["status", "--porcelain"])
            .unwrap()
            .is_empty(),
        "nothing is left dirty between sibling tool calls (§3.3)"
    );
}

/// A recording executor: run_tool_calls hands it only `tool_use` blocks,
/// so the names it sees are the loop's block filter, observable.
struct Recorder(std::cell::RefCell<Vec<String>>);

impl ToolExecutor for Recorder {
    fn execute(
        &self,
        call: ToolCall<'_>,
        _step_dir: &std::path::Path,
        _stop: &AtomicBool,
    ) -> Result<crate::prompt::tool::ToolOutcome, crate::prompt::tool::ExecError> {
        self.0.borrow_mut().push(call.name.to_string());
        Ok(crate::prompt::tool::ToolOutcome {
            content: b"ok".to_vec(),
            is_error: false,
        })
    }
}

#[test]
fn run_tool_calls_executes_only_the_tool_use_blocks() {
    // A model turn interleaves prose with its tool calls (§3.3); only
    // the `tool_use` blocks reach the executor, and the loop reports
    // "continue" (no stop observed).
    struct NoAdapter;
    impl crate::prompt::adapter::AdapterRunner for NoAdapter {
        fn run(
            &self,
            _b: &std::ffi::OsString,
            _a: &[&str],
            _s: &[u8],
            _o: &mut dyn FnMut(&[u8]) -> std::io::Result<()>,
        ) -> std::io::Result<Vec<u8>> {
            unreachable!("adapter is never reached")
        }
    }
    struct NoSleeper;
    impl crate::prompt::dispatch::Sleeper for NoSleeper {
        fn sleep(&self, _d: std::time::Duration) {
            unreachable!("sleeper is never reached")
        }
    }
    struct NoLauncher;
    impl crate::prompt::inbox::Launcher for NoLauncher {
        fn launch(&self, _ws: &std::path::Path, _agent: &str) -> std::io::Result<()> {
            unreachable!("launcher is never reached")
        }
    }

    let agent_id = "agent-6f1b";
    let ws = TempDir::new().unwrap();
    let worktree = crate::workspace::agent_worktree(ws.path(), agent_id);
    std::fs::create_dir_all(&worktree).unwrap();
    let git = RealGit::new();
    let branch = crate::workspace::agent_ref(agent_id);
    git.run(&worktree, &["init", "-b", &branch]).unwrap();
    git.run(&worktree, &["config", "user.email", "t@t"])
        .unwrap();
    git.run(&worktree, &["config", "user.name", "t"]).unwrap();
    git.run(&worktree, &["config", "core.hooksPath", "/dev/null"])
        .unwrap();
    std::fs::create_dir_all(worktree.join("messages")).unwrap();
    std::fs::write(worktree.join("messages/001-model.json"), b"[]").unwrap();
    git.run(&worktree, &["add", "-A"]).unwrap();
    git.run(&worktree, &["commit", "-m", "dispatch"]).unwrap();
    let step_dir_rel = format!("steps/{agent_id}/001");
    std::fs::create_dir_all(ws.path().join(&step_dir_rel)).unwrap();

    let recorder = Recorder(std::cell::RefCell::new(Vec::new()));
    let stop = AtomicBool::new(false);
    let clock = SystemClock;
    let id_gen = crate::prompt::NanoIdGen;
    let cfg = TempDir::new().unwrap();
    let deps = crate::prompt::Deps {
        adapter: &NoAdapter,
        sleeper: &NoSleeper,
        git: &git,
        clock: &clock,
        id_gen: &id_gen,
        tool_executor: &recorder,
        config_root: cfg.path(),
        adapter_target: None,
        stop: &stop,
        launcher: &NoLauncher,
    };
    let content = vec![
        Content::Text("running the check".into()),
        Content::ToolUse {
            id: "t1".into(),
            name: "bash".into(),
            input: json!({"command": "true"}),
            signature: None,
        },
    ];
    let stopped = super::run_tool_calls(
        ws.path(),
        &worktree,
        agent_id,
        crate::prompt::WORKER_ROLE,
        &step_dir_rel,
        &content,
        &deps,
    )
    .unwrap();
    assert!(!stopped, "no stop was requested");
    assert_eq!(*recorder.0.borrow(), vec!["bash".to_string()]);
    // The single tool result was committed as the next transcript entry.
    assert!(worktree.join("messages/002-tool.json").exists());
}