This README is the one indexed from the repository at its latest ref, not from the tag for this version.

Crystal CORS handler

CORS is a HTTP::Handler handler (middleware) implementing Cross Origin Resource Sharing W3 specification in Crystal.

Installation

In shards.yml:

dependencies:
  cors:
    github: prutya/cors
    branch: master # OR: version: x.x.x (Check the releases tab)

Then:

require "cors"

Getting Started

Add this handler to your HTTP::Server initializer call

server = HTTP::Server.new([
  SomeHandler.new,
  Cors::Handler.new(
    respond_ok: ->(ctx : HTTP::Server::Context) {
      # Whatever you do when you want to respond with 200 OK
      #
      # e.g.
      ctx.response.status = HTTP::Status::OK
      ctx.response.content_type = "application/json"
      ctx.response.print("{}")
    },
    allowed_origins: ["https://example.com"]
  ),
  SomeOtherHandler.new,
])

Configuration

respond_ok (required) Proc with HTTP::Server::Context argument. Called when the preflight processing is finished.

max_age (optional) Int32, defaults to 0. If greater than 0, goes to Access-Control-Max-Age header in the preflight response, otherwise does nothing.

allow_credentials (optional) Bool, defaults to false If set to true, adds the Access-Control-Allow-Credentials header to the response, otherwise does nothing.

allowed_origins (optional) Array(String). Defaults to an empty array. The list of allowed origins. If the array contains "*", allows all origins. Access-Control-Allow-Origin.

allowed_methods (optional) Array(String). Defaults to ["GET", "POST", "PUT"]. The list of allowed HTTP methods. If empty, results in all requests being disallowed. Access-Control-Allow-Methods.

allowed_headers (optional) Array(String). Defaults to ["Origin", "Accept", "Content-Type", "X-Requested-With"]. If empty, results in only Origin header being allowed, otherwise results in Origin header and headers provided being allowed. Access-Control-Allow-Headers.

exposed_headers (optional) Array(String). Defaults to and empty array. Access-Control-Expose-Headers.

Benchmarks (TBD)