Delete a discussion when its last post is deleted. fixes #823

framework/core/js/forum/dist/app.js

@@ -33836,7 +33836,7 @@ System.register('flarum/utils/PostControls', ['flarum/components/EditPostCompose
                 onclick: this.restoreAction.bind(post)
               }));
             }
-            if (post.canDelete() && post.number() !== 1) {
+            if (post.canDelete()) {
               items.add('delete', Button.component({
                 icon: 'times',
                 children: app.translator.trans('core.forum.post_controls.delete_forever_button'),
@@ -33893,7 +33893,22 @@ System.register('flarum/utils/PostControls', ['flarum/components/EditPostCompose
           if (context) context.loading = true;
 
           return this['delete']().then(function () {
-            _this2.discussion().removePost(_this2.id());
+            var discussion = _this2.discussion();
+
+            discussion.removePost(_this2.id());
+
+            // If this was the last post in the discussion, then we will assume that
+            // the whole discussion was deleted too.
+            if (!discussion.posts.length) {
+              // If there is a discussion list in the cache, remove this discussion.
+              if (app.cache.discussionList) {
+                app.cache.discussionList.removeDiscussion(discussion);
+              }
+
+              if (app.viewingDiscussion(discussion)) {
+                app.history.back();
+              }
+            }
           })['catch'](function () {}).then(function () {
             if (context) context.loading = false;
             m.redraw();

framework/core/js/forum/src/utils/PostControls.js

@@ -97,7 +97,7 @@ export default {
           onclick: this.restoreAction.bind(post)
         }));
       }
-      if (post.canDelete() && post.number() !== 1) {
+      if (post.canDelete()) {
         items.add('delete', Button.component({
           icon: 'times',
           children: app.translator.trans('core.forum.post_controls.delete_forever_button'),
@@ -149,7 +149,22 @@ export default {
 
     return this.delete()
       .then(() => {
-        this.discussion().removePost(this.id());
+        const discussion = this.discussion();
+
+        discussion.removePost(this.id());
+
+        // If this was the last post in the discussion, then we will assume that
+        // the whole discussion was deleted too.
+        if (!discussion.posts.length) {
+          // If there is a discussion list in the cache, remove this discussion.
+          if (app.cache.discussionList) {
+            app.cache.discussionList.removeDiscussion(discussion);
+          }
+
+          if (app.viewingDiscussion(discussion)) {
+            app.history.back();
+          }
+        }
       })
       .catch(() => {})
       .then(() => {

framework/core/src/Core/Listener/DiscussionMetadataUpdater.php

@@ -51,6 +51,12 @@ class DiscussionMetadataUpdater
     public function whenPostWasDeleted(PostWasDeleted $event)
     {
         $this->removePost($event->post);
+
+        $discussion = $event->post->discussion;
+
+        if ($discussion->comments_count === 0) {
+            $discussion->delete();
+        }
     }
 
     /**

framework/core/src/Core/Post.php

@@ -88,14 +88,6 @@ class Post extends AbstractModel
             $post->discussion->save();
         });
 
-        // Don't allow the first post in a discussion to be deleted, because
-        // it doesn't make sense. The discussion must be deleted instead.
-        static::deleting(function (Post $post) {
-            if ($post->number == 1) {
-                throw new DomainException('Cannot delete the first post of a discussion');
-            }
-        });
-
         static::deleted(function (Post $post) {
             $post->raise(new PostWasDeleted($post));
         });