FIX: Do not render user-avatar-flair element when user has no flair (#13369)

Rendering an empty flair element with the css `background-image: url();` causes the browser to attempt an image request against the current document URL. Making duplicate requests for the document URL can cause some unusual race conditions, especially related to cookies. If this user-avatar-flair element was present on the site homepage (e.g. if categories+latest is the homepage), then it can prevent the signup flow from working correctly.

This commit updates the user-avatar-flair component to be a transparent wrapper around the avatar-flair component. If the user has no flair, no avatar-flair element will be rendered. This avoids the `background-image: url();` situation, and fixes the auth flow.

This commit also removes the duplicate avatar flair rendering from the `latest-topic-list-item` component. This wasn't particularly obvious, since the duplicate flairs were being rendered directly on top of each other.

app/assets/javascripts/discourse/app/components/user-avatar-flair.js

@@ -1,41 +1,38 @@
-import MountWidget from "discourse/components/mount-widget";
-import { observes } from "discourse-common/utils/decorators";
+import Component from "@ember/component";
 import autoGroupFlairForUser from "discourse/lib/avatar-flair";
+import discourseComputed from "discourse-common/utils/decorators";
 
-export default MountWidget.extend({
-  widget: "avatar-flair",
+export default Component.extend({
+  tagName: "",
 
-  @observes("user")
-  _rerender() {
-    this.queueRerender();
-  },
-
-  buildArgs() {
-    if (!this.user) {
+  @discourseComputed("user")
+  flair(user) {
+    if (!user) {
       return;
     }
+    return this.primaryGroupFlair(user) || this.automaticGroupFlair(user);
+  },
 
-    if (
-      this.user.primary_group_flair_url ||
-      this.user.primary_group_flair_bg_color
-    ) {
+  primaryGroupFlair(user) {
+    if (user.primary_group_flair_url || user.primary_group_flair_bg_color) {
       return {
-        primary_group_flair_url: this.user.primary_group_flair_url,
-        primary_group_flair_bg_color: this.user.primary_group_flair_bg_color,
-        primary_group_flair_color: this.user.primary_group_flair_color,
-        primary_group_name: this.user.primary_group_name,
+        flairURL: user.primary_group_flair_url,
+        flairBgColor: user.primary_group_flair_bg_color,
+        flairColor: user.primary_group_flair_color,
+        groupName: user.primary_group_name,
+      };
+    }
+  },
+
+  automaticGroupFlair(user) {
+    const autoFlairAttrs = autoGroupFlairForUser(this.site, user);
+    if (autoFlairAttrs) {
+      return {
+        flairURL: autoFlairAttrs.primary_group_flair_url,
+        flairBgColor: autoFlairAttrs.primary_group_flair_bg_color,
+        flairColor: autoFlairAttrs.primary_group_flair_color,
+        groupName: autoFlairAttrs.primary_group_name,
       };
-    } else {
-      const autoFlairAttrs = autoGroupFlairForUser(this.site, this.user);
-      if (autoFlairAttrs) {
-        return {
-          primary_group_flair_url: autoFlairAttrs.primary_group_flair_url,
-          primary_group_flair_bg_color:
-            autoFlairAttrs.primary_group_flair_bg_color,
-          primary_group_flair_color: autoFlairAttrs.primary_group_flair_color,
-          primary_group_name: autoFlairAttrs.primary_group_name,
-        };
-      }
     }
   },
 });

app/assets/javascripts/discourse/app/templates/components/latest-topic-list-item.hbs

@@ -3,13 +3,6 @@
     {{avatar topic.lastPosterUser imageSize="large"}}
   {{/user-link}}
   {{user-avatar-flair user=topic.lastPosterUser}}
-  {{#if topic.lastPosterGroup}}
-    {{avatar-flair
-      flairURL=topic.lastPosterGroup.flair_url
-      flairBgColor=topic.lastPosterGroup.flair_bg_color
-      flairColor=topic.lastPosterGroup.flair_color
-      groupName=topic.lastPosterGroup.name}}
-  {{/if}}
 </div>
 <div class="main-link">
   <div class="top-row">

app/assets/javascripts/discourse/app/templates/components/user-avatar-flair.hbs

@@ -0,0 +1,7 @@
+{{#if flair}}
+  {{avatar-flair
+    flairURL=flair.flairURL
+    flairBgColor=flair.flairBgColor
+    flairColor=flair.flairColor
+    groupName=flair.groupName}}
+{{/if}}

app/assets/javascripts/discourse/tests/integration/components/user-avatar-flair-test.js

@@ -175,5 +175,23 @@ discourseModule(
         );
       },
     });
+
+    componentTest("user-avatar-flair for user with no flairs", {
+      template: hbs`{{user-avatar-flair user=args}}`,
+      beforeEach() {
+        resetFlair();
+        this.set("args", {
+          admin: false,
+          moderator: false,
+          trust_level: 1,
+        });
+      },
+      afterEach() {
+        resetFlair();
+      },
+      test(assert) {
+        assert.ok(!exists(".avatar-flair"), "it does not render a flair");
+      },
+    });
   }
 );