Fix commit message loading fallback

apps/native/src-tauri/src/commands/summarize.rs

@@ -79,7 +79,7 @@ pub async fn finalize_restore(
 
 /// Generates a commit message from the current semantic change map via the pipeline.
 #[tauri::command]
-pub async fn generate_commit_message(app: AppHandle) -> Result<String, String> {
+pub async fn generate_commit_message(app: AppHandle) -> Result<Option<String>, String> {
     crate::summarize::pipelines::commit_message::generate(&app)
         .await
         .map_err(|e| capture_err("generate_commit_message", e))

apps/native/src-tauri/src/summarize/pipelines/commit_message.rs

@@ -1,12 +1,17 @@
 //! Commit message pipeline — returns the stored whole-diff summary when available.
 
+use crate::summarize::find_existing::FoundSetForCurrent;
 use anyhow::Result;
 use tauri::{AppHandle, Runtime};
 
-pub async fn generate<R: Runtime>(app: &AppHandle<R>) -> Result<String> {
+pub async fn generate<R: Runtime>(app: &AppHandle<R>) -> Result<Option<String>> {
     let base_ref = crate::summarize::active_summary_base_ref(app);
     let change_sets = crate::summarize::found_change_sets_since(app, &base_ref)?;
 
+    Ok(stored_generated_commit_message(&change_sets))
+}
+
+fn stored_generated_commit_message(change_sets: &[FoundSetForCurrent]) -> Option<String> {
     change_sets
         .iter()
         .find_map(|entry| {
@@ -17,5 +22,46 @@ pub async fn generate<R: Runtime>(app: &AppHandle<R>) -> Result<String> {
                 .filter(|message| !message.trim().is_empty())
         })
         .map(str::to_string)
-        .ok_or_else(|| anyhow::anyhow!("no generated commit message found"))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::sqlite_types::ChangeSet;
+
+    fn found_with_message(generated_commit_message: Option<&str>) -> FoundSetForCurrent {
+        FoundSetForCurrent {
+            change_set: Some(ChangeSet {
+                id: 1,
+                commit_id: None,
+                base_commit_id: 1,
+                commit_message: None,
+                generated_commit_message: generated_commit_message.map(str::to_string),
+                created_at: 0,
+                evolution_id: None,
+            }),
+            changes: vec![],
+            missed_hashes: vec![],
+        }
+    }
+
+    #[test]
+    fn missing_generated_commit_message_is_expected_absence() {
+        let change_sets = vec![found_with_message(None), found_with_message(Some("   "))];
+
+        assert_eq!(stored_generated_commit_message(&change_sets), None);
+    }
+
+    #[test]
+    fn returns_first_non_empty_generated_commit_message() {
+        let change_sets = vec![
+            found_with_message(None),
+            found_with_message(Some("feat(nix): update shell packages")),
+        ];
+
+        assert_eq!(
+            stored_generated_commit_message(&change_sets).as_deref(),
+            Some("feat(nix): update shell packages"),
+        );
+    }
 }