Allow custom lexer instances in 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 +1,15 @@
+from sqlparse import engine, tokens as T
+
+
+class CustomLexer:
+    def get_tokens(self, sql, encoding=None):
+        yield T.Keyword, "CUSTOM"
+
+
+def test_filter_stack_custom_lexer():
+    stack = engine.FilterStack()
+    stack.lexer = CustomLexer()
+
+    statement = next(stack.run("ignored input"))
+
+    assert str(statement) == "CUSTOM"