cel-rs-rb

Ruby bindings for the Rust cel crate, implemented with Magnus.

• Ruby-first API over the Rust CEL engine
• Close semantic compatibility with Rust cel::Program + cel::Context
• Ruby variable and function interop
• Thread-safe concurrent execution
• GVL released while CEL evaluation runs

gem "cel-rs-rb"

require "cel"

context = CEL::Context.build(user: {"name" => "Ada"}, scores: [10, 20, 30]) do |ctx|
  ctx.define_function("sum") { |*args| args.sum }
end

program = CEL.compile("sum(scores[0], scores[1], scores[2])")
program.execute(context)
# => 60

• CEL.compile(source) -> CEL::Program
• CEL::Program.compile(source) -> CEL::Program
• CEL::Program#execute(context = nil) -> Ruby value
• CEL::Program#references -> { "variables" => [...], "functions" => [...] }
• CEL::Context.new(empty = false) -> context with builtins (false) or empty (true)
• CEL::Context#add_variable(name, value)
• CEL::Context#define_function(name) { |*args| ... }
• CEL::Duration.new(seconds) -> duration value for context variables and duration results

• nil -> null
• true/false -> bool
• Integer -> int
• Float -> double
• String / Symbol -> string
• binary String (ASCII-8BIT, e.g. "abc".b) -> bytes
• Time -> timestamp
• CEL::Duration -> duration
• Array -> list
• Hash with keys String|Symbol|Integer|Boolean -> map

• null -> nil
• scalar primitives map naturally
• bytes -> binary Ruby String
• timestamp -> Time
• duration -> CEL::Duration
• list -> Array
• map -> Hash

• CEL::Error
• CEL::ParseError
• CEL::ExecutionError
• CEL::TypeError

• Compiled CEL::Program instances can be shared and executed concurrently from multiple Ruby threads with separate execution contexts.
• Each thread may pass its own CEL::Context; context data is mutex-protected and copied into an immutable execution snapshot for each run.
• CEL evaluation runs with the Ruby GVL released, so other Ruby threads can keep progressing while a program executes.
• Ruby callbacks from CEL functions temporarily re-acquire the GVL before invoking Ruby code.

Uses mise for versions:

[tools]
ruby = "4.0"
rust = "1.96.0"

bundle exec rake

This runs:

• standard (format/lint)
• native extension compile
• rspec

CI also runs the test suite on Ruby 3.3, Ruby 3.4, and Ruby 4.0 through Buildkite.

• Some CEL value variants (e.g. opaque custom Rust types) cannot be fully marshaled to Ruby and raise CEL::TypeError.
• This project targets broad CEL compatibility, but parity for every Rust-only extension point is still evolving.