From c9f862abbc1db0c8e236b3a021a4cae1996d1938 Mon Sep 17 00:00:00 2001
From: Peter Adams <18162810+Maxteabag@users.noreply.github.com>
Date: Tue, 14 Jul 2026 17:26:23 +0200
Subject: [PATCH] Prevent trailing comments from blocking single-query
 execution

The process worker counted raw SQL fragments before removing comment-only fragments, so a comment after a semicolon was rejected as a second statement. Reuse the existing comment classifier when enforcing the worker's single-statement boundary.

Constraint: Process workers must continue rejecting multiple executable statements
Rejected: Change SQL splitting semantics | broader behavior change than the worker validation bug requires
Confidence: high
Scope-risk: narrow
Directive: Keep worker statement validation aligned with other executable-statement paths
Tested: 48 focused process-worker and multi-statement tests; Ruff; mypy
Not-tested: Standalone trailing block comments
Related: #254
---
 .../process_worker/app/process_worker.py      |  9 ++-
 ...est_process_worker_statement_validation.py | 68 +++++++++++++++++++
 2 files changed, 76 insertions(+), 1 deletion(-)
 create mode 100644 tests/unit/test_process_worker_statement_validation.py

diff --git a/sqlit/domains/process_worker/app/process_worker.py b/sqlit/domains/process_worker/app/process_worker.py
index 31008e7c..ee3e4cd8 100644
--- a/sqlit/domains/process_worker/app/process_worker.py
+++ b/sqlit/domains/process_worker/app/process_worker.py
@@ -140,7 +140,14 @@ def _start_query(self, message: dict[str, Any]) -> None:
             )
             return
 
-        if len(split_statements(query)) > 1:
+        from sqlit.domains.query.editing.comments import is_comment_only_statement
+
+        executable_statements = [
+            statement
+            for statement in split_statements(query)
+            if not is_comment_only_statement(statement)
+        ]
+        if len(executable_statements) > 1:
             self.send(
                 {
                     "type": "error",
diff --git a/tests/unit/test_process_worker_statement_validation.py b/tests/unit/test_process_worker_statement_validation.py
new file mode 100644
index 00000000..ef8cba1b
--- /dev/null
+++ b/tests/unit/test_process_worker_statement_validation.py
@@ -0,0 +1,68 @@
+"""Regression tests for process-worker statement validation."""
+
+from __future__ import annotations
+
+from unittest.mock import MagicMock, patch
+
+from sqlit.domains.process_worker.app.process_worker import _WorkerState
+
+
+def test_single_statement_with_trailing_comment_reaches_provider_lookup() -> None:
+    """A trailing comment must not turn one query into two statements."""
+    connection = MagicMock()
+    state = _WorkerState(conn=connection)
+
+    with patch.object(state, "_get_provider", return_value=None) as get_provider:
+        state._start_query(
+            {
+                "id": 254,
+                "query": "SELECT 1;\n-- trailing comment",
+                "db_type": "sqlite",
+                "config": {
+                    "name": "issue-254",
+                    "db_type": "sqlite",
+                    "file_path": ":memory:",
+                },
+            }
+        )
+
+    rejection = next(
+        (
+            call.args[0]
+            for call in connection.send.call_args_list
+            if call.args[0].get("message")
+            == "Multi-statement queries are not supported in the process worker."
+        ),
+        None,
+    )
+    assert rejection is None, rejection["message"] if rejection else ""
+    get_provider.assert_called_once_with("sqlite")
+
+
+def test_multiple_executable_statements_are_rejected() -> None:
+    """The comment fix must not allow genuine multi-statement queries."""
+    connection = MagicMock()
+    state = _WorkerState(conn=connection)
+
+    with patch.object(state, "_get_provider") as get_provider:
+        state._start_query(
+            {
+                "id": 255,
+                "query": "SELECT 1; SELECT 2",
+                "db_type": "sqlite",
+                "config": {
+                    "name": "multi-statement",
+                    "db_type": "sqlite",
+                    "file_path": ":memory:",
+                },
+            }
+        )
+
+    get_provider.assert_not_called()
+    connection.send.assert_called_once_with(
+        {
+            "type": "error",
+            "id": 255,
+            "message": "Multi-statement queries are not supported in the process worker.",
+        }
+    )