Fix JMAP: Email/query total miscount when collapseThreads is enabled

CHANGELOG.md

@@ -19,6 +19,7 @@ If you are upgrading from v0.16.x, replace the binary (or run `docker pull`). If
   - Default calendars and address books are not subscribed by default.
   - Unchanged immutable `id` property is rejected on `/set`.
   - `filter: null` rejected as `notRequest` on `/query` and `/queryChanges`.
+  - `Email/query` total miscount when `collapseThreads` is enabled.
 - OIDC: Add default domain name to groups that are not email addresses.
 - RocksDB: Enable blob garbage collection to reclaim disk space from deleted blobs.
 

crates/jmap/src/email/query.rs

@@ -349,15 +349,30 @@ impl EmailQuery for Server {
             )
             .await?;
 
+        let collapse_threads = request.arguments.collapse_threads.unwrap_or(false);
+        let total_results = if collapse_threads {
+            let mut seen_thread_ids = AHashSet::new();
+            results
+                .iter()
+                .filter_map(|document_id| {
+                    cached_messages
+                        .email_by_id(document_id)
+                        .map(|email| email.thread_id)
+                })
+                .filter(|thread_id| seen_thread_ids.insert(*thread_id))
+                .count()
+        } else {
+            results.len()
+        };
+
         let mut response = QueryResponseBuilder::new(
-            results.len(),
+            total_results,
             self.core.jmap.query_max_results,
             cached_messages.get_state(false),
             &request,
         );
 
         if !results.is_empty() {
-            let collapse_threads = request.arguments.collapse_threads.unwrap_or(false);
             let mut seen_thread_ids = AHashSet::new();
 
             for document_id in results {