How to bind a js lib without mutating the global object.

[hhugo]

gen_js_api seems to advertise mutating the global object in order to make js values accessible on the OCaml side using [@@js.get ], [@@js.global], ...

For example,
cat node-test/bindings/imports.mli

[@@@js.scope "__LIB__NODE__IMPORTS"]

val path: Ojs.t [@@js.global]
val fs: Ojs.t [@@js.global]

cat node-test/bindings/imports.js

globalThis.__LIB__NODE__IMPORTS = {
  path: require('path'),
  fs: require('fs'),
};

This causes problems when loading multiple js files generated by jsoo because one could override a global value with an incompatible one , see ocsigen/js_of_ocaml#1622 and ocamllabs/vscode-ocaml-platform#1617.

I'm opening this to understand if this issue has already been solved, if it has already been identified and discuss possible solutions.

Note that jsoo is able to bind to js libs relying on external primitives without mutating the global object.

[smorimoto]

Gentle ping @mlasson

[mlasson]

Hello!

Thank you for the ping, @smorimoto, and apologies for the delay in responding to this issue.

You’re absolutely right—we need a solution that avoids mutating the global object.

Here’s a proposal that relies on stubs like imports.js:

// Provides: node_path
var node_path = require('node:path');

// Provides: node_fs
var node_fs = require('node:fs');

And the corresponding OCaml interface in imports.mli:

[@@@js.scope Ojs.runtime]

val path: Ojs.t [@@js.global "node_path"]
val fs: Ojs.t [@@js.global "node_fs"]

Here, Ojs.runtime would serve as an alias for (pure_js_expr "globalThis.jsoo_runtime").
More generally, I’m not aware of any established "good practice" for writing a js_of_ocaml library that loads modules using require in its stubs. Do you know of any examples that follow such an approach?

[mlasson]

If we go this route, perhaps it would be a good idea to ask for "globalThis.jsoo_runtime" to be exposed as part of the Jsoo_runtime module ?