[FIX] web: reimplement custom widgets in basic views

With the new views, we lost a (almost unused and undocumented) feature:
the ability to instantiate custom widgets in a form view, not linked to
a particular field.  For example:

<widget type="weekly_timesheet" attrs="{'readonly': [['state', 'not in', ['new', 'draft']]]}"/>

We reintroduce this feature in this commit, with a nice twist: it also
works for the list view and the kanban view.

1 files changed, 27 insertions, 0 deletions

diff --git a/addons/web/static/src/js/views/basic/widget_registry.js b/addons/web/static/src/js/views/basic/widget_registry.js
new file mode 100644
index 00000000000..470127bd12e
--- /dev/null
+++ b/addons/web/static/src/js/views/basic/widget_registry.js
@@ -0,0 +1,27 @@
+odoo.define('web.widget_registry', function (require) {
+    "use strict";
+
+    // This registry is supposed to contain all custom widgets that will be
+    // available in the basic views, with the tag <widget/>.  There are
+    // currently no such widget in the web client, but the functionality is
+    // certainly useful to be able to cleanly add custom behaviour in basic
+    // views (and most notably, the form view)
+    //
+    // The way custom widgets work is that they register themselves to this
+    // registry:
+    //
+    // widgetRegistry.add('some_name', MyWidget);
+    //
+    // Then, they are available with the <widget/> tag (in the arch):
+    //
+    // <widget name="some_name"/>
+    //
+    // Widgets will be then properly instantiated, rendered and destroyed at the
+    // appropriate time, with the current state in second argument.
+    //
+    // For more examples, look at the tests (grep '<widget' in the test folder)
+
+    var Registry = require('web.Registry');
+
+    return new Registry();
+});