hash-crate

hash-crate is a fast, deterministic hashing tool for Rust crates and their transitive dependencies.

It is designed for CI environments and large workspaces where you want to:

• Cache prebuilt binaries for local crates

• Detect when a crate actually needs to be rebuilt

• Avoid over-invalidating caches due to unrelated changes in a workspace

• Scale to hundreds or thousands of dependencies

• The output hash is intended to be stable across machines and independent of filesystem layout.

Why?

Cargo does not provide a built-in way to compute a content-based hash for a single crate in a workspace, considering only the dependencies it actually uses.

hash-crate solves this by:

• Resolving the per-crate transitive dependency graph

• Hashing the contents of all path dependencies

• Including version/source information for non-path dependencies

• Producing a single deterministic hash suitable for cache keys

This makes it ideal for:

• Large monorepos

• xtask-style tooling (without needing cargo xtask)

Features

• Very fast (uses Rayon + BLAKE3)

• Deterministic (order-independent, thread-safe)

• Per-crate granularity

Handles:

• Path dependencies

• Workspace members

• [patch] overrides

• Deduplicated dependencies

Installation

cargo binstall hash-crate

Usage

hash-crate <package-name>

Example:

hash-crate xtask-build

Output:

9e8b7a4b1d9c4b6b3f8c6c1a1a4e0d9e7c9a5f0c2c0c3a7e8c6b9e1f4d2

This hash represents:

• The target crate

• All of its transitive dependencies

• The contents of any path dependencies

What affects the hash?

The hash will change if any of the following change:

• Files inside a path dependency

• Dependency versions

• Git revisions

• Dependency graph structure

• Cargo patch overrides

The hash should not depend on:

• Absolute filesystem paths

• Dependency resolution order

• Thread scheduling

• Host machine

Intended use in CI

Typical pattern:

1. Compute the hash:

   HASH=$(hash-crate xtask-build)
   

2. Use it as an artifact key:

   # for some local crate called `xtask-build`
   xtask-build-${HASH}-${RUNNER_TYPE}.tar.gz
   

3. If the artifact exists:

   • Download and run it

4. Otherwise:

   • Build the crate

   • Upload the artifact

Invalidation is automatic.

Performance

hash-crate is optimized for large workspaces:

• Parallel directory hashing using Rayon and BLAKE3

• Streaming dependency resolution

• Deterministic folding of results

On large applications (1000+ dependencies), runtime is typically dominated by cargo metadata generation.

Non-goals

• Replacing Cargo’s dependency resolver

• Being human-readable

• Supporting partial or heuristic hashing

• This tool is intentionally strict and conservative.

License

MIT OR Apache-2.0

Note

This README was originally written using AI. The crate was not.