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CLAUDE.md

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CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Build & Test Commands

# Build
cargo build --all-features

# Test all features
cargo test --all-features

# Test only sync
cargo test --features sync

# Test only async
cargo test --features async

# Run a single test
cargo test --all-features test_name

# Run tests in a specific file
cargo test --all-features --test sync
cargo test --all-features --test async

# Lint
cargo clippy --all-features

# Format
cargo fmt

# Run examples
cargo run --example simple --features sync
cargo run --example async_simple --features async

Architecture

This is cron_tab, a Rust cron job scheduler library published on crates.io. It provides both synchronous (thread-based) and asynchronous (tokio-based) schedulers, gated behind feature flags.

Feature Flags

  • sync (default) — enables Cron<Z> and Entry<Z>
  • async — enables AsyncCron<Z> and AsyncEntry<Z>, pulls in tokio/futures
  • all — both

Module Layout

The sync and async implementations are parallel in structure:

Sync (feature = "sync") Async (feature = "async") Role
cron.rs → Cron<Z> async_cron.rs → AsyncCron<Z> Scheduler: manages entries, runs the select loop
entry.rs → Entry<Z> async_entry.rs → AsyncEntry<Z> Job entry: holds schedule, next fire time, callback

error.rs and lib.rs are always compiled regardless of features.

Key Design Patterns

  • Timezone-generic: Both schedulers are generic over Z: TimeZone, accepting Utc, FixedOffset, Local, etc.
  • Two job types: Recurring jobs have schedule: Some(cron::Schedule), one-time jobs have schedule: None. The is_once() method on entries derives this from the schedule field.
  • Scheduler loop: Uses crossbeam_channel::select! (sync) or tokio::select! (async) with three/four branches: timer expiry, add channel, remove channel (async only), stop channel.
  • Job dispatch: Sync spawns std::thread, async spawns tokio::task. Jobs are Arc-wrapped for safe sharing.
  • Channel-based communication: Both add_fn/add_fn_once and remove send through channels when the scheduler is running. The async version also supports direct push to entries when not running.

Cron Expression Format

7-field format with second precision: sec min hour day month weekday year. The cron crate (v0.15) handles parsing. Both 6-field and 7-field formats are accepted.