FIX: correct tracking when mute all categories (#11441)

Currently, we have a solution for muted topics. Basically, when a post is created first we send a `muted` message to users who muted that specific topic:

https://github.com/discourse/discourse/blob/master/app/models/topic_tracking_state.rb#L91

Later, topic tracking state filters if the topic is muted or not before update state:

https://github.com/discourse/discourse/blob/master/app/assets/javascripts/discourse/app/models/topic-tracking-state.js#L58:L67

That solution works quite well.

I wanted to extend it to handle `mute all categories by default` setting as well.

In that case, we should only inform the user about new topic/post when they explicitly want to.

If that setting is enabled, we would send "unmuted" message to a user who watches specific category, topic or tag. In all other cases, don't inform user about new topic as all categories are muted by default.

Meta: https://meta.discourse.org/t/threads-muted-by-mute-all-by-default-are-showing-up-as-new-but-not-visible/168324

app/assets/javascripts/discourse/app/models/topic-tracking-state.js

@@ -55,17 +55,24 @@ const TopicTrackingState = EmberObject.extend({
     const tracker = this;
 
     const process = (data) => {
-      if (data.message_type === "muted") {
-        tracker.trackMutedTopic(data.topic_id);
+      if (["muted", "unmuted"].includes(data.message_type)) {
+        tracker.trackMutedOrUnmutedTopic(data);
         return;
       }
 
-      tracker.pruneOldMutedTopics();
+      tracker.pruneOldMutedAndUnmutedTopics();
 
       if (tracker.isMutedTopic(data.topic_id)) {
         return;
       }
 
+      if (
+        this.siteSettings.mute_all_categories_by_default &&
+        !tracker.isUnmutedTopic(data.topic_id)
+      ) {
+        return;
+      }
+
       if (data.message_type === "delete") {
         tracker.removeTopic(data.topic_id);
         tracker.incrementMessageCount();
@@ -166,26 +173,47 @@ const TopicTrackingState = EmberObject.extend({
     return (this.currentUser && this.currentUser.muted_topics) || [];
   },
 
-  trackMutedTopic(topicId) {
-    let mutedTopics = this.mutedTopics().concat({
-      topicId: topicId,
-      createdAt: Date.now(),
-    });
-    this.currentUser && this.currentUser.set("muted_topics", mutedTopics);
+  unmutedTopics() {
+    return (this.currentUser && this.currentUser.unmuted_topics) || [];
   },
 
-  pruneOldMutedTopics() {
+  trackMutedOrUnmutedTopic(data) {
+    let topics, key;
+    if (data.message_type === "muted") {
+      key = "muted_topics";
+      topics = this.mutedTopics();
+    } else {
+      key = "unmuted_topics";
+      topics = this.unmutedTopics();
+    }
+    topics = topics.concat({
+      topicId: data.topic_id,
+      createdAt: Date.now(),
+    });
+    this.currentUser && this.currentUser.set(key, topics);
+  },
+
+  pruneOldMutedAndUnmutedTopics() {
     const now = Date.now();
     let mutedTopics = this.mutedTopics().filter(
       (mutedTopic) => now - mutedTopic.createdAt < 60000
     );
-    this.currentUser && this.currentUser.set("muted_topics", mutedTopics);
+    let unmutedTopics = this.unmutedTopics().filter(
+      (unmutedTopic) => now - unmutedTopic.createdAt < 60000
+    );
+    this.currentUser &&
+      this.currentUser.set("muted_topics", mutedTopics) &&
+      this.currentUser.set("unmuted_topics", unmutedTopics);
   },
 
   isMutedTopic(topicId) {
     return !!this.mutedTopics().findBy("topicId", topicId);
   },
 
+  isUnmutedTopic(topicId) {
+    return !!this.unmutedTopics().findBy("topicId", topicId);
+  },
+
   updateSeen(topicId, highestSeen) {
     if (!topicId || !highestSeen) {
       return;

app/assets/javascripts/discourse/tests/unit/models/topic-tracking-state-test.js

@@ -327,7 +327,7 @@ module("Unit | Model | topic-tracking-state", function (hooks) {
     assert.equal(state.countNew(4), 0);
   });
 
-  test("mute topic", function (assert) {
+  test("mute and unmute topic", function (assert) {
     let currentUser = User.create({
       username: "chuck",
       muted_category_ids: [],
@@ -335,14 +335,19 @@ module("Unit | Model | topic-tracking-state", function (hooks) {
 
     const state = TopicTrackingState.create({ currentUser });
 
-    state.trackMutedTopic(1);
+    state.trackMutedOrUnmutedTopic({ topic_id: 1, message_type: "muted" });
     assert.equal(currentUser.muted_topics[0].topicId, 1);
 
-    state.pruneOldMutedTopics();
+    state.trackMutedOrUnmutedTopic({ topic_id: 2, message_type: "unmuted" });
+    assert.equal(currentUser.unmuted_topics[0].topicId, 2);
+
+    state.pruneOldMutedAndUnmutedTopics();
     assert.equal(state.isMutedTopic(1), true);
+    assert.equal(state.isUnmutedTopic(2), true);
 
     this.clock.tick(60000);
-    state.pruneOldMutedTopics();
+    state.pruneOldMutedAndUnmutedTopics();
     assert.equal(state.isMutedTopic(1), false);
+    assert.equal(state.isUnmutedTopic(2), false);
   });
 });