Allow custom lexer instances on FilterStack

sqlparse/engine/filter_stack.py

@@ -20,6 +20,7 @@ def __init__(self, strip_semicolon=False):
         self.stmtprocess = []
         self.postprocess = []
         self._grouping = False
+        self.lexer = lexer.Lexer.get_default_instance()
         if strip_semicolon:
             self.stmtprocess.append(StripTrailingSemicolonFilter())
 
@@ -28,7 +29,7 @@ def enable_grouping(self):
 
     def run(self, sql, encoding=None):
         try:
-            stream = lexer.tokenize(sql, encoding)
+            stream = self.lexer.get_tokens(sql, encoding)
             # Process token stream
             for filter_ in self.preprocess:
                 stream = filter_.process(stream)

tests/test_filter_stack.py

@@ -0,0 +1,17 @@
+from sqlparse import engine, tokens as T
+from sqlparse.lexer import Lexer
+
+
+class CustomLexer(Lexer):
+    def get_tokens(self, text, encoding=None):
+        yield T.Name, f'custom:{text}'
+
+
+def test_filter_stack_uses_custom_lexer():
+    stack = engine.FilterStack()
+    stack.lexer = CustomLexer()
+
+    statements = tuple(stack.run('input'))
+
+    assert len(statements) == 1
+    assert str(statements[0]) == 'custom:input'