DEV: Add topic custom field for nesting

app/controllers/discourse_nested_replies/nested_topics_controller.rb

@@ -5,13 +5,27 @@ class NestedTopicsController < ::ApplicationController
     requires_plugin PLUGIN_NAME
 
     before_action :ensure_nested_replies_enabled
-    before_action :find_topic, except: [:respond]
+    before_action :find_topic, except: %i[respond check]
 
     # Serves the Ember app shell for hard refreshes on /nested/:slug/:topic_id
     def respond
       render
     end
 
+    # GET /nested/check/:topic_id
+    # Lightweight endpoint for the frontend redirect logic.
+    # Returns only the nested view flag without loading posts or full TopicView.
+    def check
+      topic = Topic.find_by(id: params[:topic_id].to_i)
+      raise Discourse::NotFound unless topic
+      guardian.ensure_can_see!(topic)
+
+      render json: {
+               is_nested_view:
+                 !!topic.custom_fields[DiscourseNestedReplies::TOPIC_NESTED_VIEW_FIELD],
+             }
+    end
+
     # GET /nested/:slug/:topic_id/roots
     # On page 0 (initial load), includes topic metadata, OP post, sort, and message_bus_last_id.
     # On subsequent pages, returns only roots for pagination.
@@ -252,6 +266,19 @@ def pin
       render json: { pinned_post_number: post_number }
     end
 
+    # PUT /nested/:slug/:topic_id/toggle
+    # Staff-only: enable or disable nested replies for the topic.
+    def toggle
+      guardian.ensure_can_edit!(@topic)
+      raise Discourse::InvalidAccess unless guardian.is_staff?
+
+      enabled = params[:enabled].to_s == "true"
+      @topic.custom_fields[DiscourseNestedReplies::TOPIC_NESTED_VIEW_FIELD] = enabled
+      @topic.save_custom_fields
+
+      render json: { is_nested_view: enabled }
+    end
+
     private
 
     def ensure_nested_replies_enabled

assets/javascripts/discourse/api-initializers/nested-replies-topic-admin-button.js

@@ -0,0 +1,48 @@
+import { ajax } from "discourse/lib/ajax";
+import { popupAjaxError } from "discourse/lib/ajax-error";
+import { apiInitializer } from "discourse/lib/api";
+import DiscourseURL from "discourse/lib/url";
+
+export default apiInitializer((api) => {
+  const siteSettings = api.container.lookup("service:site-settings");
+
+  api.addTopicAdminMenuButton((topic) => {
+    if (!siteSettings.nested_replies_enabled) {
+      return;
+    }
+
+    if (!api.getCurrentUser()?.staff) {
+      return;
+    }
+
+    const isNested = topic.get("is_nested_view");
+
+    return {
+      icon: "nested-thread",
+      className: "topic-admin-nested-replies",
+      label: isNested
+        ? "discourse_nested_replies.topic_admin_menu.disable_nested_replies"
+        : "discourse_nested_replies.topic_admin_menu.enable_nested_replies",
+      action: () => {
+        const newValue = !isNested;
+        const topicId = topic.get("id");
+        const slug = topic.get("slug");
+
+        ajax(`/nested/${slug}/${topicId}/toggle`, {
+          type: "PUT",
+          data: { enabled: newValue },
+        })
+          .then(() => {
+            topic.set("is_nested_view", newValue || null);
+
+            if (newValue) {
+              DiscourseURL.routeTo(`/nested/${slug}/${topicId}`);
+            } else {
+              DiscourseURL.routeTo(`/t/${slug}/${topicId}`);
+            }
+          })
+          .catch(popupAjaxError);
+      },
+    };
+  });
+});

assets/javascripts/discourse/api-initializers/nested-view-redirect.js

@@ -1,6 +1,5 @@
 import { ajax } from "discourse/lib/ajax";
 import { apiInitializer } from "discourse/lib/api";
-import Category from "discourse/models/category";
 import nestedPostUrl from "../lib/nested-post-url";
 
 const TOPIC_URL_RE = /^\/t\/([^/]+)\/(\d+)(?:\/(\d+))?(?:\?(.*))?$/;
@@ -13,30 +12,36 @@ function buildNestedPath(slug, topicId, postNumber) {
   return path;
 }
 
-function isNestedDefault(siteSettings, categoryId) {
-  if (siteSettings.nested_replies_default) {
-    return true;
-  }
-
-  if (categoryId) {
-    const category = Category.findById(categoryId);
-    if (category?.nested_replies_default) {
-      return true;
-    }
-  }
-
-  return false;
-}
-
 export default apiInitializer((api) => {
   const siteSettings = api.container.lookup("service:site-settings");
   const router = api.container.lookup("service:router");
   const appEvents = api.container.lookup("service:app-events");
-  const topicTrackingState = api.container.lookup(
-    "service:topic-tracking-state"
-  );
   let composerSaveInfo = null;
 
+  // Tracks which topic IDs have is_nested_view, populated as topics
+  // flow through topic lists and topic view responses.
+  const nestedTopicIds = new Set();
+
+  api.registerValueTransformer(
+    "topic-list-item-class",
+    ({ value, context }) => {
+      if (context.topic?.is_nested_view) {
+        nestedTopicIds.add(context.topic.id);
+      }
+      return value;
+    }
+  );
+
+  api.registerValueTransformer(
+    "latest-topic-list-item-class",
+    ({ value, context }) => {
+      if (context.topic?.is_nested_view) {
+        nestedTopicIds.add(context.topic.id);
+      }
+      return value;
+    }
+  );
+
   appEvents.on("composer:saved", () => {
     if (!siteSettings.nested_replies_enabled) {
       return;
@@ -86,7 +91,7 @@ export default apiInitializer((api) => {
       }
 
       const { topic } = context;
-      if (isNestedDefault(siteSettings, topic.category_id)) {
+      if (topic.is_nested_view) {
         const slug = topic.slug || "topic";
         return `/nested/${slug}/${topic.id}`;
       }
@@ -143,26 +148,17 @@ export default apiInitializer((api) => {
 
     const id = parseInt(topicId, 10);
 
-    // Look up category from topic tracking state (most reliable source)
-    // or fall back to session topic list for discovery-loaded topics.
-    let categoryId;
-    const trackedState = topicTrackingState.findState(id);
-    if (trackedState) {
-      categoryId = trackedState.category_id;
-    }
-
-    if (isNestedDefault(siteSettings, categoryId)) {
+    if (nestedTopicIds.has(id)) {
       return buildNestedPath(slug, topicId, postNumber);
     }
 
     return path;
   });
 
   // Fallback: if a topic URL wasn't intercepted by the route-to-url
-  // transformer (e.g. direct URL entry where the topic isn't in tracking
-  // state yet), intercept before the topic route's model hook runs.
-  // When the topic isn't in tracking state, abort and fetch topic info
-  // to determine the category before deciding which view to load.
+  // transformer (e.g. direct URL entry where the topic isn't known to
+  // be nested yet), intercept before the topic route's model hook runs
+  // and fetch topic info to check the is_nested_view field.
   const checkedTopicIds = new Map();
   const CHECKED_TOPIC_TTL_MS = 60_000;
 
@@ -199,24 +195,7 @@ export default apiInitializer((api) => {
       return;
     }
 
-    const tracked = topicTrackingState.findState(topicId);
-    if (tracked) {
-      if (!isNestedDefault(siteSettings, tracked.category_id)) {
-        return;
-      }
-
-      transition.abort();
-      const nearPost = transition.to?.params?.nearPost;
-      const queryParams = {};
-      if (nearPost) {
-        queryParams.post_number = nearPost;
-      }
-      router.transitionTo("nested", slug, topicId, { queryParams });
-      return;
-    }
-
-    // Topic not in tracking state (e.g. direct URL entry). Abort, look
-    // up the category via a lightweight request, then redirect or resume.
+    // Already checked this topic recently and it wasn't nested — let it through
     const checkedAt = checkedTopicIds.get(topicId);
     if (checkedAt && Date.now() - checkedAt < CHECKED_TOPIC_TTL_MS) {
       return;
@@ -236,14 +215,15 @@ export default apiInitializer((api) => {
     const fromRoute = router.currentRouteName;
     transition.abort();
 
-    ajax(`/t/${topicId}.json`, { data: { track_visit: false } })
+    ajax(`/nested/check/${topicId}.json`)
       .then((data) => {
         // Bail if user navigated away during the async lookup
         if (router.currentRouteName !== fromRoute) {
           return;
         }
 
-        if (isNestedDefault(siteSettings, data.category_id)) {
+        if (data.is_nested_view) {
+          nestedTopicIds.add(topicId);
           const queryParams = {};
           const nearPost = transition.to?.params?.nearPost;
           if (nearPost) {

assets/javascripts/discourse/connectors/topic-navigation/nested-view-link.gjs

@@ -1,6 +1,5 @@
 import Component from "@glimmer/component";
 import getURL from "discourse/lib/get-url";
-import Category from "discourse/models/category";
 import { i18n } from "discourse-i18n";
 
 export default class NestedViewLink extends Component {
@@ -13,18 +12,10 @@ export default class NestedViewLink extends Component {
       return true;
     }
 
-    if (context.siteSettings.nested_replies_default) {
+    if (args.topic?.is_nested_view) {
       return true;
     }
 
-    const categoryId = args.topic?.category_id;
-    if (categoryId) {
-      const category = Category.findById(categoryId);
-      if (category?.nested_replies_default) {
-        return true;
-      }
-    }
-
     return false;
   }
 

config/locales/client.en.yml

@@ -36,6 +36,9 @@ en:
       pinned_reply: "Pinned"
       pin_reply: "Pin to top"
       unpin_reply: "Unpin"
+      topic_admin_menu:
+        enable_nested_replies: "Enable nested replies"
+        disable_nested_replies: "Disable nested replies"
       context:
         banner: "You are viewing a single thread from this topic."
         view_full_topic: "View full topic"

config/routes.rb

@@ -1,12 +1,15 @@
 # frozen_string_literal: true
 
 DiscourseNestedReplies::Engine.routes.draw do
+  get "/nested/check/:topic_id" => "nested_topics#check", :constraints => { topic_id: /\d+/ }
+
   scope "/nested/:slug/:topic_id", constraints: { topic_id: /\d+/ } do
     get "/" => "nested_topics#respond"
     get "/roots" => "nested_topics#roots"
     get "/children/:post_number" => "nested_topics#children"
     get "/context/:post_number" => "nested_topics#context"
     put "/pin" => "nested_topics#pin"
+    put "/toggle" => "nested_topics#toggle"
   end
 end
 

plugin.rb

@@ -17,6 +17,7 @@ module ::DiscourseNestedReplies
   PLUGIN_NAME = "discourse-nested-replies"
   CATEGORY_DEFAULT_FIELD = "nested_replies_default_for_category"
   PINNED_POST_NUMBER_FIELD = "nested_replies_pinned_post_number"
+  TOPIC_NESTED_VIEW_FIELD = "nested"
 end
 
 require_relative "lib/discourse_nested_replies/engine"
@@ -94,6 +95,35 @@ module ::DiscourseNestedReplies
     staff_only: true,
   )
 
+  # --- Topic-level nested view field ---
+  # Each topic carries its own "nested" flag so the frontend can decide
+  # which view to render without looking up category settings every time.
+  register_topic_custom_field_type(DiscourseNestedReplies::TOPIC_NESTED_VIEW_FIELD, :boolean)
+  add_preloaded_topic_list_custom_field(DiscourseNestedReplies::TOPIC_NESTED_VIEW_FIELD)
+
+  add_to_serializer(:topic_list_item, :is_nested_view) do
+    object.custom_fields[DiscourseNestedReplies::TOPIC_NESTED_VIEW_FIELD]
+  end
+
+  add_to_serializer(:topic_view, :is_nested_view) do
+    object.topic.custom_fields[DiscourseNestedReplies::TOPIC_NESTED_VIEW_FIELD]
+  end
+
+  # Auto-set the nested field on new topics when the category or global
+  # setting calls for nested view.
+  on(:topic_created) do |topic, _opts, _user|
+    next unless SiteSetting.nested_replies_enabled
+
+    is_nested =
+      SiteSetting.nested_replies_default ||
+        topic.category&.custom_fields&.dig(DiscourseNestedReplies::CATEGORY_DEFAULT_FIELD)
+
+    if is_nested
+      topic.custom_fields[DiscourseNestedReplies::TOPIC_NESTED_VIEW_FIELD] = true
+      topic.save_custom_fields
+    end
+  end
+
   # --- Preserve ?post_number through URL canonicalization redirects ---
   register_modifier(:redirect_to_correct_topic_additional_query_parameters) do |params|
     params + %w[post_number]