Hi everyone,
I’m happy to announce the first release of ocaml-cdp - typed OCaml libraries for the Chrome DevTools Protocol.
Why
CDP lets a program control a real Chrome: open pages, run JavaScript, take screenshots, render PDFs, watch network traffic.
OCaml had no CDP library. ocaml-cdp fills that gap: it turns the official protocol definitions into typed OCaml modules, so the compiler checks every command, event, and field.
What you get
Three packages:
| Package | Where | What it is |
|---|---|---|
cdp |
opam | Typed protocol domains: records, enums, commands, events, with JSON codecs. Transport-agnostic. |
cdp-gen |
opam | The generator CLI: protocol JSON in, OCaml out. Any revision, your own domain selection. |
cdp-lwt |
GitHub only for now (see below) | The client: launches or attaches to a Chrome and drives it over libcurl WebSockets. |
cdp ships 10 domains (Browser, DOM, Debugger, Emulation, IO, Network, Page, Runtime, Security, Target); the generator covers all 58.
Here is the full round trip: launch a headless Chrome, open a page, read its title back:
let%lwt chrome = Cdp_lwt.Chrome.launch () in
let%lwt transport = Cdp_lwt.Curl_transport.connect ~url:chrome.ws_url () in
let connection = Cdp_lwt.Connection.create transport in
let call ?session command = Cdp_lwt.Connection.call connection ?session command in
let%lwt created =
call (Cdp.Target.Create_target.command (Cdp.Target.Create_target.make_params ~url:"about:blank" ()))
in
let%lwt attached =
call (Cdp.Target.Attach_to_target.command
(Cdp.Target.Attach_to_target.make_params ~target_id:created.target_id ~flatten:true ()))
in
let session = attached.session_id in
let%lwt () = call ~session (Cdp.Page.Enable.command (Cdp.Page.Enable.make_params ())) in
let loaded = Cdp_lwt.Connection.next_event connection ~session Cdp.Page.Load_event_fired.event in
let%lwt _nav =
call ~session (Cdp.Page.Navigate.command
(Cdp.Page.Navigate.make_params ~url:"https://ocaml.org" ()))
in
let%lwt _fired = loaded in
let%lwt evaluated =
call ~session (Cdp.Runtime.Evaluate.command (Cdp.Runtime.Evaluate.make_params ~expression:"document.title" ()))
in
Why cdp-lwt is not on opam yet
cdp-lwt uses libcurl’s WebSocket API through the curl bindings. That API is on ocurl’s master branch, but not in any ocurl release yet. cdp-lwt builds fine from a clone (its opam file pins ocurl master). As soon as ocurl makes a release, cdp-lwt follows onto opam.
