test(db): cover delete/empty-changes/empty-history; clarify map_row naming

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

crates/db/src/audit.rs

@@ -41,6 +41,7 @@ pub async fn history_for<'e, E>(
 where
     E: sqlx::PgExecutor<'e>,
 {
+    // TODO: add LIMIT/keyset pagination before exposing history_for via the API.
     let rows = sqlx::query(
         "SELECT seq, at, actor_kind, actor_id, action, entity_type, entity_id, changes \
          FROM audit_log \
@@ -60,7 +61,7 @@ fn map_row(row: sqlx::postgres::PgRow) -> Result<AuditEntry, sqlx::Error> {
     let at: time::OffsetDateTime = row.try_get("at")?;
     let actor_kind: String = row.try_get("actor_kind")?;
     let actor_id: Option<Uuid> = row.try_get("actor_id")?;
-    let action: String = row.try_get("action")?;
+    let action_str: String = row.try_get("action")?;
     let entity_type: String = row.try_get("entity_type")?;
     let entity_id: Uuid = row.try_get("entity_id")?;
     let changes: sqlx::types::Json<Vec<FieldChange>> = row.try_get("changes")?;
@@ -77,8 +78,8 @@ fn map_row(row: sqlx::postgres::PgRow) -> Result<AuditEntry, sqlx::Error> {
         }
     };
 
-    let action = domain::AuditAction::from_db(&action)
+    let action = domain::AuditAction::from_db(&action_str)
-        .ok_or_else(|| sqlx::Error::Decode(format!("unknown action: {action}").into()))?;
+        .ok_or_else(|| sqlx::Error::Decode(format!("unknown action: {action_str}").into()))?;
 
     Ok(AuditEntry {
         seq,

crates/db/tests/audit.rs

@@ -68,3 +68,38 @@ async fn history_is_scoped_to_one_entity(pool: PgPool) {
     assert_eq!(only_a.len(), 1);
     assert_eq!(only_a[0].entity_id, a);
 }
+
+#[sqlx::test]
+async fn deleted_action_with_empty_changes_round_trips(pool: PgPool) {
+    let db = Db::from_pool(pool);
+    let id = Uuid::new_v4();
+
+    audit::record(
+        db.pool(),
+        &NewAuditEvent {
+            actor: AuditActor::System,
+            action: AuditAction::Deleted,
+            entity_type: "object".into(),
+            entity_id: id,
+            changes: vec![],
+        },
+    )
+    .await
+    .unwrap();
+
+    let history = audit::history_for(db.pool(), "object", id).await.unwrap();
+    assert_eq!(history.len(), 1);
+    assert_eq!(history[0].action, AuditAction::Deleted);
+    assert!(history[0].changes.is_empty());
+}
+
+#[sqlx::test]
+async fn history_is_empty_for_unknown_entity(pool: PgPool) {
+    let db = Db::from_pool(pool);
+
+    let history = audit::history_for(db.pool(), "object", Uuid::new_v4())
+        .await
+        .unwrap();
+
+    assert!(history.is_empty());
+}