DEV: Support `created-by:<username>` filter on `/filter` route (#21067)

This commit adds support for the `created-by:<username>` query filter
which will return topics created by the specified user. Multiple
usernames can be specified by comma seperating the usernames like so:
`created-by:username1,username2`. This will filter for topics created by
either of the specified users. Multiple `created-by:<username>` can also
be composed together. `created-by:username1 created-by:username2` is
equivalent to `created-by:username1,username2`.

lib/topics_filter.rb

@@ -16,9 +16,11 @@ class TopicsFilter
     return @scope if query_string.blank?
 
     query_string.scan(
-      /(?<key_prefix>[-=])?(?<key>\w+):(?<value>[^\s]+)/,
+      /(?<key_prefix>[-=])?(?<key>[\w-]+):(?<value>[^\s]+)/,
     ) do |key_prefix, key, value|
       case key
+      when "created-by"
+        filter_created_by_user(usernames: value.split(","))
       when "in"
         @scope = filter_state(state: value)
       when "status"
@@ -90,6 +92,17 @@ class TopicsFilter
 
   private
 
+  def filter_created_by_user(usernames:)
+    register_scope(
+      key: :created_by_user,
+      params: {
+        usernames: usernames.map(&:downcase),
+      },
+    ) do |usernames_lower|
+      @scope.joins(:user).where("users.username_lower IN (?)", usernames_lower)
+    end
+  end
+
   def filter_state(state:)
     case state
     when "pinned"

spec/lib/topics_filter_spec.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 RSpec.describe TopicsFilter do
-  fab!(:user) { Fabricate(:user) }
+  fab!(:user) { Fabricate(:user, username: "username") }
   fab!(:admin) { Fabricate(:admin) }
   fab!(:group) { Fabricate(:group) }
 
@@ -737,5 +737,78 @@ RSpec.describe TopicsFilter do
         ).to contain_exactly(topic_without_tag.id, topic_with_group_only_tag.id)
       end
     end
+
+    describe "when filtering by topic author" do
+      fab!(:user2) { Fabricate(:user, username: "username2") }
+      fab!(:topic_by_user) { Fabricate(:topic, user: user) }
+      fab!(:topic2_by_user) { Fabricate(:topic, user: user) }
+      fab!(:topic_by_user2) { Fabricate(:topic, user: user2) }
+
+      describe "when query string is `created-by:username`" do
+        it "should return the topics created by the specified user" do
+          expect(
+            TopicsFilter
+              .new(guardian: Guardian.new)
+              .filter_from_query_string("created-by:#{user.username}")
+              .pluck(:id),
+          ).to contain_exactly(topic_by_user.id, topic2_by_user.id)
+        end
+      end
+
+      describe "when query string is `created-by:username2`" do
+        it "should return the topics created by the specified user" do
+          expect(
+            TopicsFilter
+              .new(guardian: Guardian.new)
+              .filter_from_query_string("created-by:#{user2.username}")
+              .pluck(:id),
+          ).to contain_exactly(topic_by_user2.id)
+        end
+      end
+
+      describe "when query string is `created-by:username created-by:username2`" do
+        it "should return the topics created by either of the specified users" do
+          expect(
+            TopicsFilter
+              .new(guardian: Guardian.new)
+              .filter_from_query_string("created-by:#{user.username} created-by:#{user2.username}")
+              .pluck(:id),
+          ).to contain_exactly(topic_by_user.id, topic2_by_user.id, topic_by_user2.id)
+        end
+      end
+
+      describe "when query string is `created-by:username,invalid`" do
+        it "should only return the topics created by the user with the valid username" do
+          expect(
+            TopicsFilter
+              .new(guardian: Guardian.new)
+              .filter_from_query_string("created-by:#{user.username},invalid")
+              .pluck(:id),
+          ).to contain_exactly(topic_by_user.id, topic2_by_user.id)
+        end
+      end
+
+      describe "when query string is `created-by:username,username2`" do
+        it "should return the topics created by either of the specified users" do
+          expect(
+            TopicsFilter
+              .new(guardian: Guardian.new)
+              .filter_from_query_string("created-by:#{user.username},#{user2.username}")
+              .pluck(:id),
+          ).to contain_exactly(topic_by_user.id, topic2_by_user.id, topic_by_user2.id)
+        end
+      end
+
+      describe "when query string is `created-by:invalid`" do
+        it "should not return any topics" do
+          expect(
+            TopicsFilter
+              .new(guardian: Guardian.new)
+              .filter_from_query_string("created-by:invalid")
+              .pluck(:id),
+          ).to eq([])
+        end
+      end
+    end
   end
 end

spec/requests/list_controller_spec.rb

@@ -1132,9 +1132,25 @@ RSpec.describe ListController do
   describe "#filter" do
     fab!(:category) { Fabricate(:category) }
     fab!(:tag) { Fabricate(:tag, name: "tag1") }
+    fab!(:group) { Fabricate(:group) }
+    fab!(:private_category) { Fabricate(:private_category, group: Fabricate(:group)) }
+    fab!(:private_message_topic) { Fabricate(:private_message_topic) }
+    fab!(:topic_in_private_category) { Fabricate(:topic, category: private_category) }
 
     before { SiteSetting.experimental_topics_filter = true }
 
+    it "should not return topics that the user is not allowed to view" do
+      sign_in(user)
+
+      get "/filter.json"
+
+      expect(response.status).to eq(200)
+
+      expect(
+        response.parsed_body["topic_list"]["topics"].map { |topic| topic["id"] },
+      ).to contain_exactly(topic.id)
+    end
+
     it "should respond with 403 response code for an anonymous user" do
       get "/filter.json"
 
@@ -1212,6 +1228,40 @@ RSpec.describe ListController do
       end
     end
 
+    describe "when filtering with the `created-by:<username>` filter" do
+      fab!(:topic2) { Fabricate(:topic, user: admin) }
+
+      before do
+        topic.update!(user: user)
+        user.update!(username: "username")
+        admin.update!(username: "username2")
+      end
+
+      it "returns only topics created by the user when `q` query param is `created-by:username`" do
+        sign_in(user)
+
+        get "/filter.json", params: { q: "created-by:username" }
+
+        expect(response.status).to eq(200)
+
+        expect(
+          response.parsed_body["topic_list"]["topics"].map { |topic| topic["id"] },
+        ).to contain_exactly(topic.id)
+      end
+
+      it "returns only topics created by either user when `q` query param is `created-by:username,username2`" do
+        sign_in(user)
+
+        get "/filter.json", params: { q: "created-by:username,username2" }
+
+        expect(response.status).to eq(200)
+
+        expect(
+          response.parsed_body["topic_list"]["topics"].map { |topic| topic["id"] },
+        ).to contain_exactly(topic.id, topic2.id)
+      end
+    end
+
     describe "when filtering with the `in:<topic_notification_level>` filter" do
       fab!(:user_muted_topic) do
         Fabricate(:topic).tap do |topic|