Thermite

Thermite is a Rake-based helper for building and distributing Rust-based Ruby extensions.

Features

• Provides wrappers for cargo commands.
• Handles non-standard cargo installations via the CARGO environment variable.
• Opt-in to allow users to install pre-compiled Rust extensions hosted on GitHub releases.
• Opt-in to allow users to install pre-compiled Rust extensions hosted on a third party server.
• Provides a wrapper for initializing a Rust extension via Fiddle.

Usage

1. Add the following to your gemspec file:

spec.extensions << 'ext/Rakefile'
spec.add_runtime_dependency 'thermite', '~> 0'

2. Create ext/Rakefile with the following code, assuming that the Cargo project root is the same
   as the Ruby project root:

require 'thermite/tasks'

project_dir = File.dirname(File.dirname(__FILE__))
Thermite::Tasks.new(cargo_project_path: project_dir, ruby_project_path: project_dir)
task default: %w(thermite:build)

3. In Rakefile, integrate Thermite into your build-test workflow:

require 'thermite/tasks'

Thermite::Tasks.new

desc 'Run Rust & Ruby testsuites'
task test: ['thermite:build', 'thermite:test'] do
  # …
end

Run rake -T thermite to view all of the available tasks in the thermite namespace.

Configuration

Task configuration for your project can be set in two ways:

• passing arguments to Thermite::Tasks.new
• adding a package.metadata.thermite section to Cargo.toml. These settings override the
  arguments passed to the Tasks class. Due to the conflict, it is infeasible for
  cargo_project_path or cargo_workspace_member to be set in this way. Example section:

[package.metadata.thermite]

github_releases = true

Possible options:

• binary_uri_format - if set, the interpolation-formatted string used to construct the download
  URI for the pre-built native extension. If the environment variable THERMITE_BINARY_URI_FORMAT
  is set, it takes precedence over this option. Either method of setting this option overrides the
  github_releases option.
  Example: https://example.com/download/%{version}/%{filename}. Replacement variables:
  • filename - The value of Config.tarball_filename
  • version - the crate version from Cargo.toml
• cargo_project_path - the path to the top-level Cargo project. Defaults to the current working
  directory.
• cargo_workspace_member - if set, the relative path to the Cargo workspace member. Usually used
  when it is part of a repository containing multiple crates.
• github_releases - whether to look for Rust binaries via GitHub releases when installing
  the gem, and cargo is not found. Defaults to false.
• github_release_type - when github_releases is true, the mode to use to download the Rust
  binary from GitHub releases. 'cargo' (the default) uses the version in Cargo.toml, along with
  the git_tag_format option (described below) to determine the download URI. 'latest' takes the
  latest release matching the git_tag_regex option (described below) to determine the download
  URI.
• git_tag_format - when github_release_type is 'cargo' (the default), the
  format string used to determine the tag used
  in the GitHub download URI. Defaults to v%s, where %s is the version in Cargo.toml.
• git_tag_regex - when github_releases is enabled and github_release_type is 'latest', a
  regular expression (expressed as a String) that determines which tagged releases to look for
  precompiled Rust tarballs. One group must be specified that indicates the version number to be
  used in the tarball filename. Defaults to the semantic versioning 2.0.0
  format. In this case, the group is around the entire
  expression.
• optional_rust_extension - prints a warning to STDERR instead of raising an exception, if Cargo
  is unavailable and github_releases is either disabled or unavailable. Useful for projects where
  either fallback code exists, or a native extension is desirable but not required. Defaults
  to false.
• ruby_project_path - the top-level directory of the Ruby gem's project. Defaults to the
  current working directory.
• ruby_extension_dir - the directory relative to ruby_project_path where the extension is
  located. Defaults to lib.

Example

Using the cliché Rust+Ruby example, the rusty_blank repository contains an example of using Thermite with ruru to provide a String.blank? speedup extension. While the example uses ruru, this gem should be usable with any method of integrating Rust and Ruby that you choose.

Debug / release build

By default Thermite will do a release build of your Rust code. To do a debug build instead, set the CARGO_PROFILE environment variable to debug.

For example, you can run CARGO_PROFILE=debug rake thermite:build.

Troubleshooting

Debug statements can be written to a file specified by the THERMITE_DEBUG_FILENAME environment variable.

FAQ

Why is it named Thermite?

According to Wikipedia:

• The chemical formula for ruby includes Al2O3, or aluminum oxide.
• Rust is iron oxide, or Fe2O3.
• A common thermite reaction uses iron oxide and aluminum to produce iron and aluminum oxide:
  Fe2O3 + 2Al → 2Fe + Al2O3

Release Notes

Contributing

Legal

This gem is licensed under the MIT license.