gh-79579: Improve DML query detection in sqlite3 (#93623)

The fix involves using pysqlite_check_remaining_sql(), not only to check
for multiple statements, but now also to strip leading comments and
whitespace from SQL statements, so we can improve DML query detection.

pysqlite_check_remaining_sql() is renamed lstrip_sql(), to more
accurately reflect its function, and hardened to handle more SQL comment
corner cases.

Lib/test/test_sqlite3/test_dbapi.py

@@ -746,22 +746,44 @@ class CursorTests(unittest.TestCase):
         with self.assertRaises(sqlite.OperationalError):
             self.cu.execute("select asdf")
 
-    def test_execute_too_much_sql(self):
-        self.assertRaisesRegex(sqlite.ProgrammingError,
-                               "You can only execute one statement at a time",
-                               self.cu.execute, "select 5+4; select 4+5")
+    def test_execute_multiple_statements(self):
+        msg = "You can only execute one statement at a time"
+        dataset = (
+            "select 1; select 2",
+            "select 1; // c++ comments are not allowed",
+            "select 1; *not a comment",
+            "select 1; -*not a comment",
+            "select 1; /* */ a",
+            "select 1; /**/a",
+            "select 1; -",
+            "select 1; /",
+            "select 1; -\n- select 2",
+            """select 1;
+               -- comment
+               select 2
+            """,
+        )
+        for query in dataset:
+            with self.subTest(query=query):
+                with self.assertRaisesRegex(sqlite.ProgrammingError, msg):
+                    self.cu.execute(query)
 
-    def test_execute_too_much_sql2(self):
-        self.cu.execute("select 5+4; -- foo bar")
-
-    def test_execute_too_much_sql3(self):
-        self.cu.execute("""
+    def test_execute_with_appended_comments(self):
+        dataset = (
+            "select 1; -- foo bar",
+            "select 1; --",
+            "select 1; /*",  # Unclosed comments ending in \0 are skipped.
+            """
             select 5+4;
 
             /*
             foo
             */
-            """)
+            """,
+        )
+        for query in dataset:
+            with self.subTest(query=query):
+                self.cu.execute(query)
 
     def test_execute_wrong_sql_arg(self):
         with self.assertRaises(TypeError):
@@ -906,6 +928,30 @@ class CursorTests(unittest.TestCase):
         self.assertEqual(self.cu.fetchone()[0], 1)
         self.assertEqual(self.cu.rowcount, 1)
 
+    def test_rowcount_prefixed_with_comment(self):
+        # gh-79579: rowcount is updated even if query is prefixed with comments
+        self.cu.execute("""
+            -- foo
+            insert into test(name) values ('foo'), ('foo')
+        """)
+        self.assertEqual(self.cu.rowcount, 2)
+        self.cu.execute("""
+            /* -- messy *r /* /* ** *- *--
+            */
+            /* one more */ insert into test(name) values ('messy')
+        """)
+        self.assertEqual(self.cu.rowcount, 1)
+        self.cu.execute("/* bar */ update test set name='bar' where name='foo'")
+        self.assertEqual(self.cu.rowcount, 3)
+
+    def test_rowcount_vaccuum(self):
+        data = ((1,), (2,), (3,))
+        self.cu.executemany("insert into test(income) values(?)", data)
+        self.assertEqual(self.cu.rowcount, 3)
+        self.cx.commit()
+        self.cu.execute("vacuum")
+        self.assertEqual(self.cu.rowcount, -1)
+
     def test_total_changes(self):
         self.cu.execute("insert into test(name) values ('foo')")
         self.cu.execute("insert into test(name) values ('foo')")