[IMP] website, *: lazy load most frontend javascript

* web, survey

This commit takes advantage of the other commits of this PR to enable
lazy loading for most frontend javascript:

1) Extract the minimum part of the assets common:
- promises library and polyfill
- boot.js

2) Create "assets_common_lazy" which is "assets_common" - "minimum"

3) Include the "minimum" assets in frontend layouts using "defer"
   loading and "assets_common_lazy" using "lazy" loading

4) Create a script to do the actual lazy loading in a "minimum" frontend
   assets

5) Lazy load the current frontend / website editor assets

Part of https://github.com/odoo/odoo/pull/32181
task-1961045

9 files changed, 148 insertions, 38 deletions

diff --git a/addons/survey/views/survey_templates.xml b/addons/survey/views/survey_templates.xml
index 834d148a95f..20426c852ca 100644
--- a/addons/survey/views/survey_templates.xml
+++ b/addons/survey/views/survey_templates.xml
@@ -134,7 +134,7 @@
     <!-- new layout for survey -->
     <template id="survey.layout" name="Survey Layout" inherit_id="web.frontend_layout" primary="True">
         <xpath expr="//head/t[@t-call-assets][last()]" position="after">
-            <t t-call-assets="survey.survey_assets"/>
+            <t t-call-assets="survey.survey_assets" lazy_load="True"/>
         </xpath>
         <xpath expr="//header" position="before">
             <t t-set="no_header" t-value="no_header or survey.certificate"/>
diff --git a/addons/web/static/src/js/public/lazyloader.js b/addons/web/static/src/js/public/lazyloader.js
new file mode 100644
index 00000000000..7c873e1938d
--- /dev/null
+++ b/addons/web/static/src/js/public/lazyloader.js
@@ -0,0 +1,42 @@
+odoo.define('web.public.lazyloader', function (require) {
+'use strict';
+
+var doResolve = null;
+var _allScriptsLoaded = new Promise(function (resolve) {
+    if (doResolve) {
+        resolve();
+    } else {
+        doResolve = resolve;
+    }
+});
+
+window.addEventListener('load', function () {
+    setTimeout(_loadScripts, 0);
+});
+
+function _loadScripts(scripts, index) {
+    if (scripts === undefined) {
+        scripts = document.querySelectorAll('script[data-src]');
+    }
+    if (index === undefined) {
+        index = 0;
+    }
+    if (index >= scripts.length) {
+        if (typeof doResolve === 'function') {
+            doResolve();
+        } else {
+            doResolve = true;
+        }
+        return;
+    }
+    var script = scripts[index];
+    script.addEventListener('load', _loadScripts.bind(this, scripts, index + 1));
+    script.src = script.dataset.src;
+    script.removeAttribute('data-src');
+}
+
+return {
+    loadScripts: _loadScripts,
+    allScriptsLoaded: _allScriptsLoaded,
+};
+});
diff --git a/addons/web/views/webclient_templates.xml b/addons/web/views/webclient_templates.xml
index 1bcd6280dab..31a2e62ef53 100644
--- a/addons/web/views/webclient_templates.xml
+++ b/addons/web/views/webclient_templates.xml
@@ -40,6 +40,20 @@
         <link rel="stylesheet" type="text/scss" href="/web/static/src/scss/bootstrap_review.scss"/>
     </template>
 
+    <!-- The assets common minimal code should not require any library to work. -->
+    <!-- An exception is made for the promises polyfill and extensions that the -->
+    <!-- boot.js script needs to work -->
+    <template id="_assets_common_minimal_js">
+        <script type="text/javascript" src="/web/static/lib/es6-promise/es6-promise-polyfill.js"></script>
+        <script type="text/javascript" src="/web/static/lib/unhandled-rejection-polyfill/unhandled-rejection-polyfill.js"></script>
+        <script type="text/javascript" src="/web/static/src/js/promise_extension.js"></script>
+        <script type="text/javascript" src="/web/static/src/js/boot.js"></script>
+    </template>
+
+    <template id="assets_common_minimal_js">
+        <t t-call="web._assets_common_minimal_js"/>
+    </template>
+
     <template id="assets_common" name="Common Assets (used in backend interface and website)">
         <t t-call="web._assets_helpers"/>
 
@@ -65,8 +79,8 @@
 
         <link rel="stylesheet" type="text/less" href="/web/static/src/scss/fontawesome_overriden.scss"/>
 
-        <script type="text/javascript" src="/web/static/lib/es6-promise/es6-promise-polyfill.js"></script>
-        <script type="text/javascript" src="/web/static/lib/unhandled-rejection-polyfill/unhandled-rejection-polyfill.js"></script>
+        <t t-call="web._assets_common_minimal_js"/>
+
         <script type="text/javascript" src="/web/static/lib/underscore/underscore.js"></script>
         <script type="text/javascript" src="/web/static/lib/underscore.string/lib/underscore.string.js"></script>
         <script type="text/javascript" src="/web/static/lib/moment/moment.js"></script>
@@ -103,10 +117,6 @@
         <script type="text/javascript" src="/web/static/lib/jSignature/jSignatureCustom.js"></script>
 
         <script type="text/javascript" src="/web/static/lib/qweb/qweb2.js"></script>
-
-        <script type="text/javascript" src="/web/static/src/js/promise_extension.js"></script>
-        <script type="text/javascript" src="/web/static/src/js/boot.js"></script>
-
         <script type="text/javascript" src="/web/static/src/js/libs/autocomplete.js"></script>
         <script type="text/javascript" src="/web/static/src/js/libs/bootstrap.js"></script>
         <script type="text/javascript" src="/web/static/src/js/libs/jquery.js"></script>
@@ -149,6 +159,10 @@
         <script type="text/javascript" src="/web/static/src/js/widgets/rainbow_man.js"></script>
     </template>
 
+    <template id="assets_common_lazy" inherit_id="web.assets_common" primary="True">
+        <xpath expr="//t[@t-call='web._assets_common_minimal_js']" position="replace"/>
+    </template>
+
     <template id="assets_backend" name="Backend Assets (used in backend interface)">
         <t t-call="web._assets_helpers">
             <t t-call="web._assets_backend_helpers"/>
@@ -342,7 +356,15 @@
         <link rel="stylesheet" type="text/scss" href="/web/static/src/scss/report_backend.scss"/>
     </template>
 
-    <template id="web.assets_frontend" name="Website Assets">
+    <template id="_assets_frontend_minimal_js">
+        <script type="text/javascript" src="/web/static/src/js/public/lazyloader.js"/>
+    </template>
+
+    <template id="assets_frontend_minimal_js">
+        <t t-call="web._assets_frontend_minimal_js"/>
+    </template>
+
+    <template id="assets_frontend" name="Website Assets">
         <t t-call="web._assets_helpers">
             <t t-call="web._assets_frontend_helpers"/>
         </t>
@@ -351,6 +373,8 @@
         <link rel="stylesheet" type="text/scss" href="/web/static/src/scss/navbar_mobile.scss"/>
         <link rel="stylesheet" type="text/scss" href="/web/static/src/scss/notification.scss"/>
 
+        <t t-call="web._assets_frontend_minimal_js"/>
+
         <script type="text/javascript" src="/web/static/src/js/services/session.js"/>
         <script type="text/javascript" src="/web/static/src/js/public/public_notification.js"/>
         <script type="text/javascript" src="/web/static/src/js/public/public_root.js"/>
@@ -358,6 +382,10 @@
         <script type="text/javascript" src="/web/static/src/js/public/public_widget.js"/>
     </template>
 
+    <template id="assets_frontend_lazy" inherit_id="web.assets_frontend" primary="True">
+        <xpath expr="//t[@t-call='web._assets_frontend_minimal_js']" position="replace"/>
+    </template>
+
     <template id="web.layout" name="Web layout">&lt;!DOCTYPE html&gt;
         <html t-att="html_data or {}">
             <head>
@@ -391,8 +419,10 @@
             <script type="text/javascript">
                 odoo.session_info = <t t-raw="json.dumps(request.env['ir.http'].get_frontend_session_info())"/>;
             </script>
-            <t t-call-assets="web.assets_common" t-css="false"/>
-            <t t-call-assets="web.assets_frontend" t-css="false"/>
+            <t t-call-assets="web.assets_common_minimal_js" t-css="false" defer_load="True"/>
+            <t t-call-assets="web.assets_frontend_minimal_js" t-css="false" defer_load="True"/>
+            <t t-call-assets="web.assets_common_lazy" t-css="false" lazy_load="True"/>
+            <t t-call-assets="web.assets_frontend_lazy" t-css="false" lazy_load="True"/>
         </xpath>
         <xpath expr="//t[@t-raw='0']" position="replace">
             <div id="wrapwrap" t-attf-class="#{pageName or ''}">
diff --git a/addons/web_tour/static/src/js/public/tour_manager.js b/addons/web_tour/static/src/js/public/tour_manager.js
new file mode 100644
index 00000000000..a5b4c588833
--- /dev/null
+++ b/addons/web_tour/static/src/js/public/tour_manager.js
@@ -0,0 +1,21 @@
+odoo.define('web_tour.public.TourManager', function (require) {
+'use strict';
+
+var TourManager = require('web_tour.TourManager');
+var lazyloader = require('web.public.lazyloader');
+
+TourManager.include({
+    /**
+     * @override
+     */
+    _waitBeforeTourStart: function () {
+        return this._super.apply(this, arguments).then(function () {
+            return lazyloader.allScriptsLoaded;
+        }).then(function () {
+            return new Promise(function (resolve) {
+                setTimeout(resolve);
+            });
+        });
+    },
+});
+});
diff --git a/addons/web_tour/static/src/js/tour_manager.js b/addons/web_tour/static/src/js/tour_manager.js
index 18b2c47d6b3..fab05a7fb69 100644
--- a/addons/web_tour/static/src/js/tour_manager.js
+++ b/addons/web_tour/static/src/js/tour_manager.js
@@ -81,11 +81,32 @@ return core.Class.extend(mixins.EventDispatcherMixin, ServicesMixin, {
         }
         this.tours[name] = tour;
     },
+    /**
+     * Returns a promise which is resolved once the tour can be started. This
+     * is when the DOM is ready and at the end of the execution stack so that
+     * all tours have potentially been extended by all apps.
+     *
+     * @private
+     * @returns {Promise}
+     */
+    _waitBeforeTourStart: function () {
+        return new Promise(function (resolve) {
+            $(function () {
+                setTimeout(resolve);
+            });
+        });
+    },
     _register_all: function (do_update) {
-        if (this._all_registered) return;
-        this._all_registered = true;
-
-        _.each(this.tours, this._register.bind(this, do_update));
+        var self = this;
+        if (this._allRegistered) {
+            return Promise.resolve();
+        }
+        this._allRegistered = true;
+        return self._waitBeforeTourStart().then(function () {
+            return Promise.all(_.map(self.tours, function (tour, name) {
+                return self._register(do_update, tour, name);
+            }));
+        });
     },
     _register: function (do_update, tour, name) {
         if (tour.ready) return Promise.resolve();
@@ -193,7 +214,6 @@ return core.Class.extend(mixins.EventDispatcherMixin, ServicesMixin, {
      * @returns {boolean} true if a tip was found and activated/updated
      */
     _check_for_tooltip: function (tip, tour_name) {
-
         if ($('body').hasClass('o_ui_blocked')) {
             this._deactivate_tip(tip);
             this._log.push("blockUI is preventing the tip to be consumed");
diff --git a/addons/web_tour/static/src/js/tour_service.js b/addons/web_tour/static/src/js/tour_service.js
index 92e8148a901..87cf69b7d83 100644
--- a/addons/web_tour/static/src/js/tour_service.js
+++ b/addons/web_tour/static/src/js/tour_service.js
@@ -56,29 +56,19 @@ return session.is_bound.then(function () {
         }, 500);
         var observer = new MutationObserver(check_tooltip);
         var start_service = (function () {
-
             return function (observe) {
-
-                var promise = new Promise(function (resolve, reject) {
-                    $(function () {
-                        /**
-                         * Once the DOM is ready, we still have to wait all the modules are loaded before completing the tours
-                         * registration and starting listening for DOM mutations.
-                         */
-                        _.defer(function () {
-                            tour_manager._register_all(observe);
-                            if (observe) {
-                                observer.observe(document.body, {
-                                    attributes: true,
-                                    childList: true,
-                                    subtree: true,
-                                });
-                            }
-                            resolve();
-                        });
+                return new Promise(function (resolve, reject) {
+                    tour_manager._register_all(observe).then(function () {
+                        if (observe) {
+                            observer.observe(document.body, {
+                                attributes: true,
+                                childList: true,
+                                subtree: true,
+                            });
+                        }
+                        resolve();
                     });
                 });
-                return promise;
             };
         })();
 
diff --git a/addons/web_tour/views/tour_templates.xml b/addons/web_tour/views/tour_templates.xml
index 6830501ceeb..816405a39d5 100644
--- a/addons/web_tour/views/tour_templates.xml
+++ b/addons/web_tour/views/tour_templates.xml
@@ -18,5 +18,11 @@
                 <script type="text/javascript" src="/web_tour/static/src/js/debug_manager.js"></script>
             </xpath>
         </template>
+
+        <template id="assets_frontend" inherit_id="web.assets_frontend">
+            <xpath expr="//script[last()]" position="after">
+                <script type="text/javascript" src="/web_tour/static/src/js/public/tour_manager.js"/>
+            </xpath>
+        </template>
     </data>
 </odoo>
diff --git a/addons/website/static/src/js/menu/customize.js b/addons/website/static/src/js/menu/customize.js
index 00d2bef687b..4481d0f616c 100644
--- a/addons/website/static/src/js/menu/customize.js
+++ b/addons/website/static/src/js/menu/customize.js
@@ -199,8 +199,9 @@ var AceEditorMenu = websiteNavbarData.WebsiteNavbarActionWidget.extend({
                 self.globalEditor = new WebsiteAceEditor(self, $(document.documentElement).data('view-xmlid'), {
                     initialResID: initialResID,
                     defaultBundlesRestriction: [
-                        "web.assets_frontend",
-                        "website.assets_frontend",
+                        'web.assets_frontend',
+                        'web.assets_frontend_minimal',
+                        'web.assets_frontend_lazy',
                     ],
                 });
                 return self.globalEditor.appendTo(document.body);
diff --git a/addons/website/views/website_templates.xml b/addons/website/views/website_templates.xml
index 9917615d803..8de35096b51 100644
--- a/addons/website/views/website_templates.xml
+++ b/addons/website/views/website_templates.xml
@@ -230,7 +230,7 @@
         <t t-call-assets="website.assets_editor" t-js="false" groups="website.group_website_publisher"/>
     </xpath>
     <xpath expr="//head/t[@t-css='false'][last()]" position="after">
-        <t t-call-assets="website.assets_editor" t-css="false" groups="website.group_website_publisher"/>
+        <t t-call-assets="website.assets_editor" t-css="false" groups="website.group_website_publisher" lazy_load="True"/>
     </xpath>
 
     <xpath expr="//header//a[hasclass('navbar-brand')]" position="replace">