unify JavaScript handling of form submissions

- drop the `js-submit` class and merge the two separate `submit` event handlers into one
  - it's now easy to run custom functions both before and after a form submission
    - however, the after functions may not be called if the server responds to the form submission with an error
  - the unified function's source code is commented
  - the unified function sends debugging messages to the console
  - form inputs are no longer disabled during submission, because it was complicating the JavaScript code
    - CSS is used instead to gray out the entire form and disable mouse events, but keyboard events aren't be disabled
  - the submission feedback overlay is back, for forms making slow requests before submitting
- replace most uses of `jQuery.ajax()` with `fetch()`, simplifying the `Liberapay.error()` function and removing the need for the `Liberapay.getCookie()` function
  - all forms are now required to include an anti-CSRF token, whereas previously the forms that required JavaScript didn't need to contain the token as it would be taken from the cookies anyway
  - since we no longer need the `csrf_token` cookie to be accessible from JavaScript, mark it as `httponly`

error.spt

@@ -88,11 +88,13 @@ user_agent = request.headers.get(b'User-Agent')
     % endif
 % endblock
 [----------------------------------------] application/json via json_dump
-{ "error_code": code
-, "error_message_short": msg
-, "error_message_long": err
-, "error_id": sentry_ident
-, "error_location": error_location
- }
+{
+    "error_code": code,
+    "error_id": sentry_ident,
+    "error_location": error_location,
+    "error_message_long": err,
+    "error_message_short": msg,
+    "html_template": getattr(response, 'html_template', None),
+}
 [----------------------------------------] text/plain
 {{err or msg}}

js/10-base.js

@@ -1,23 +1,4 @@
-Liberapay.getCookie = function(key) {
-    var o = new RegExp("(?:^|; ?)" + escape(key) + "=([^;]+)").exec(document.cookie);
-    if (!o) return null;
-    var value = o[1];
-    if (value.charAt(0) === '"') value = value.slice(1, -1);
-    return unescape(value);
-}
-
 Liberapay.init = function() {
-    // https://docs.djangoproject.com/en/dev/ref/contrib/csrf/#ajax
-    jQuery.ajaxSetup({
-        beforeSend: function(xhr, settings) {
-            var safeMethod = (/^(GET|HEAD|OPTIONS|TRACE)$/.test(settings.type));
-            if (!safeMethod && !settings.crossDomain) {
-                // We have to avoid httponly on the csrf_token cookie because of this.
-                xhr.setRequestHeader("X-CSRF-TOKEN", Liberapay.getCookie('csrf_token'));
-            }
-        }
-    });
-
     Liberapay.forms.jsSubmit();
 
     var success_re = /([?&])success=[^&]*/;
@@ -129,31 +110,27 @@ Liberapay.init = function() {
 
 $(function(){ Liberapay.init(); });
 
-Liberapay.error = function(jqXHR, textStatus, errorThrown) {
-    var msg = null;
-    if (jqXHR.responseText > "") {
-        try {
-            msg = JSON.parse(jqXHR.responseText).error_message_long;
-        } catch(exc) {}
-    }
-    if (typeof msg != "string" || msg.length == 0) {
-        msg = "An error occurred (" + (errorThrown || textStatus || jqXHR.status) + ").\n" +
+Liberapay.error = function(exc) {
+    console.error(exc);
+    var msg = "An error occurred (" + exc + ").\n" +
               "Please contact support@liberapay.com if the problem persists.";
-    }
     Liberapay.notification(msg, 'error', -1);
 }
 
 Liberapay.wrap = function(f) {
-    return function() {
+    return async function() {
         try {
-            return f.apply(this, arguments);
-        } catch (e) {
-            console.log(e);
-            Liberapay.notification(e, 'error', -1);
+            return await f.apply(this, arguments);
+        } catch (exc) {
+            Liberapay.error(exc);
         }
     }
 };
 
+Liberapay.get_object_by_name = function(name) {
+    return name.split('.').reduce(function(o, k) {return o[k]}, window);
+}
+
 Liberapay.jsonml = function(jsonml) {
     var node  = document.createElement(jsonml[0]);
 

js/charts.js

@@ -16,19 +16,21 @@ Liberapay.charts.init = function() {
 }
 
 Liberapay.charts.load = function(url, $container) {
-    jQuery.get(url, function(series) {
-        $(function() {
-            Liberapay.charts.make(series, $container);
-        });
-    }).fail(Liberapay.error);
+    fetch(url).then(function(response) {
+        response.json().then(function(series) {
+            $(function() {
+                Liberapay.charts.make(series, $container);
+            });
+        }).catch(Liberapay.error);
+    }).catch(Liberapay.error);
 }
 
 Liberapay.charts.make = function(series, $container) {
     if (series.length) {
         $('.chart-wrapper').show();
     } else {
-        if (!!$container.data('msg-empty')) {
-            $container.append($('<span>').text(' '+$container.data('msg-empty')));
+        if ($container.attr('data-msg-empty')) {
+            $container.append($('<span>').text(' '+$container.attr('data-msg-empty')));
         }
         return;
     }