Fix end unconditionally decrementing the split level, but case not incrementing it in a plain select

sqlparse/engine/statement_splitter.py

@@ -80,10 +80,12 @@ def _change_splitlevel(self, ttype, value):
                 self._in_case = False
             return -1
 
-        if (unified in ('IF', 'FOR', 'WHILE', 'CASE')
+        if unified == 'CASE':
+            self._in_case = True
+            return 1
+
+        if (unified in ('IF', 'FOR', 'WHILE')
                 and self._is_create and self._begin_depth > 0):
-            if unified == 'CASE':
-                self._in_case = True
             return 1
 
         if unified in ('END IF', 'END FOR', 'END WHILE'):

tests/test_split.py

@@ -284,3 +284,34 @@ def test_split_begin_transaction_formatted():  # issue826
     assert stmts[1].startswith('DELETE')
     assert stmts[2].startswith('INSERT')
     assert stmts[3] == 'END\nTRANSACTION;'
+
+
+def test_splitlevel_case_end():
+    # CASE in a plain SELECT did not increment the level, but its matching END
+    # decremented it unconditionally. This led to levels being wrong after the
+    # CASE WHEN ... END block.
+    s = sqlparse.engine.statement_splitter.StatementSplitter()
+    level = s.level
+
+    token_stream = [
+        (sqlparse.tokens.Keyword.DML, 'SELECT'),
+        (sqlparse.tokens.Keyword,     'CASE'),
+        (sqlparse.tokens.Keyword,     'WHEN'),
+        (sqlparse.tokens.Name,        'foo'),
+        (sqlparse.tokens.Keyword,     'THEN'),
+        (sqlparse.tokens.Number,      '1'),
+        (sqlparse.tokens.Keyword,     'END'),
+        (sqlparse.tokens.Keyword,     'FROM'),
+        (sqlparse.tokens.Name,        't'),
+    ]
+
+    for ttype, value in token_stream:
+        level += s._change_splitlevel(ttype, value)
+
+    assert level == 0
+
+    # This issue could lead to incorrectly treating a semicolon inside a text
+    # literal as a statement terminator and incorrectly splitting the query.
+    assert len(sqlparse.parse(
+        "SELECT CASE WHEN 1 THEN 2 END, test IN ('foo \\', 'foo;') FROM t"
+    )) == 1