[IMP] web: add es6 class patcher

This commit implements a new way to monkey-patch ES6
classes (for instance, Owl Components).

Usage
-----

odoo.module('module.BaseClass', function (require) {
    const patchMixin = require('web.patchMixin');

    // Define your class as usual
    class BaseClass {
        constructor() {
            this.foo = 'foo';
        }
        bar() {
            console.log(this.foo);
        }
    }

    // but export it like this to have a "patchable" version
    return patchMixin(BaseClass);
});

odoo.module('module.Patch', function (require) {
    // imports the "patchable" version
    const BaseClass = require('module.BaseClass');

    BaseClass.patch('key', T =>
        class extends T {
            constructor() {
                super();
                this.foo = 'patched foo';
            }
            bar() {
                super.bar();
                console.log('patched bar()');
            }
        }
    );
});

odoo.module('module.instance', function (require) {
    // imports the "patchable" version
    const BaseClass = require('module.BaseClass');

    const obj = new BaseClass();
    obj.bar();
    // if module.patch is loaded before this module the patch
    // will be apply and calling obj.bar() will log:
    // patched foo
    // patched bar()

    // You can unpatch a patchable class
    BaseClass.unpatch('key');
});

1 files changed, 6 insertions, 1 deletions

diff --git a/addons/web/static/src/js/core/utils.js b/addons/web/static/src/js/core/utils.js
index f1d4b00c6a9..e8924747616 100644
--- a/addons/web/static/src/js/core/utils.js
+++ b/addons/web/static/src/js/core/utils.js
@@ -527,7 +527,12 @@ var utils = {
     /**
      * Patch a class and return a function that remove the patch
      * when called.
-     *
+     * 
+     * This function is the last resort solution for monkey-patching an
+     * ES6 Class, for people that do not control the code defining the Class
+     * to patch (e.g. partners), and when that Class isn't patchable already
+     * (i.e. when it doesn't have a 'patch' function, defined by the 'web.PatchMixin').
+     * 
      * @param {Class} C Class to patch
      * @param {string} patchName
      * @param {Object} patch