FIX: User directory for solutions should update when value changes from positive to zero

plugin.rb

@@ -291,23 +291,24 @@ after_initialize do
 
   query = <<~SQL
     WITH x AS (
-      SELECT p.user_id, COUNT(DISTINCT st.id) AS solutions
-      FROM discourse_solved_solved_topics AS st
-      JOIN posts AS p
-         ON p.id = st.answer_post_id
-        AND COALESCE(st.created_at, :since) > :since
-        AND p.deleted_at IS NULL
-      JOIN topics AS t
-         ON t.id = st.topic_id
-        AND t.archetype <> 'private_message'
-        AND t.deleted_at IS NULL
-      JOIN users AS u
-         ON u.id = p.user_id
-      WHERE u.id > 0
-        AND u.active
-        AND u.silenced_till IS NULL
-        AND u.suspended_till IS NULL
-      GROUP BY p.user_id
+      SELECT users.id AS user_id,
+             COUNT(DISTINCT CASE WHEN
+               st.topic_id IS NOT NULL AND
+               t.id IS NOT NULL AND
+               t.archetype <> 'private_message' AND
+               t.deleted_at IS NULL AND
+               p.deleted_at IS NULL
+             THEN st.topic_id ELSE NULL END) AS solutions
+      FROM users
+      LEFT JOIN posts p ON p.user_id = users.id
+      LEFT JOIN discourse_solved_solved_topics st
+             ON st.answer_post_id = p.id
+             AND st.created_at >= :since
+      LEFT JOIN topics t ON t.id = st.topic_id
+      WHERE users.active
+        AND users.silenced_till IS NULL
+        AND users.suspended_till IS NULL
+      GROUP BY users.id
     )
     UPDATE directory_items di
     SET solutions = x.solutions

spec/models/directory_item_spec.rb

@@ -101,5 +101,32 @@ describe DirectoryItem, type: :model do
         ).solutions,
       ).to eq(1)
     end
+
+    context "when refreshing across dates" do
+      it "updates the user's solution count from 1 to 0" do
+        freeze_time 40.days.ago
+        DiscourseSolved.accept_answer!(topic_post1, Discourse.system_user)
+
+        DirectoryItem.refresh!
+
+        expect(
+          DirectoryItem.find_by(
+            user_id: user.id,
+            period_type: DirectoryItem.period_types[:monthly],
+          ).solutions,
+        ).to eq(1)
+
+        unfreeze_time
+
+        DirectoryItem.refresh!
+
+        expect(
+          DirectoryItem.find_by(
+            user_id: user.id,
+            period_type: DirectoryItem.period_types[:monthly],
+          ).solutions,
+        ).to eq(0)
+      end
+    end
   end
 end