identifier_case: keep the case of backtick-, acute- and bracket-quoted identifiers

CHANGELOG

@@ -1,7 +1,12 @@
 Development Version
 -------------------
 
-Nothing yet.
+Bug Fixes
+
+* `identifier_case` no longer changes the case of identifiers quoted with
+  backticks, acute accents or square brackets. Only double-quoted identifiers
+  were exempt before, although the lexer recognizes all four quoting styles
+  (issue433).
 
 
 Release 0.6.0 (Aug 13, 2026)

sqlparse/filters/tokens.py

@@ -29,9 +29,15 @@ class KeywordCaseFilter(_CaseFilter):
 class IdentifierCaseFilter(_CaseFilter):
     ttype = T.Name, T.String.Symbol
 
+    # Opening delimiters of a quoted identifier. SQL_REGEX recognizes four
+    # quoting styles, and only the double-quoted one reaches this filter as
+    # T.String.Symbol; the backtick, acute-accent and [bracket] forms arrive
+    # as plain T.Name, indistinguishable from a bare identifier here.
+    QUOTES = '"`´['
+
     def process(self, stream):
         for ttype, value in stream:
-            if ttype in self.ttype and value.strip()[0] != '"':
+            if ttype in self.ttype and value.strip()[0] not in self.QUOTES:
                 value = self.convert(value)
             yield ttype, value
 

tests/test_format.py

@@ -38,6 +38,18 @@ def test_identifiercase_quotes(self):
         res = sqlparse.format(sql, identifier_case="upper")
         assert res == 'select * from "foo"."bar"'
 
+    @pytest.mark.parametrize('sql', [
+        'select * from `myS`.`Tbl`',      # MySQL
+        'select * from ´myS´.´Tbl´',
+        'select * from [myS].[Tbl]',      # T-SQL / SQLite
+    ])
+    @pytest.mark.parametrize('case', ['upper', 'lower', 'capitalize'])
+    def test_identifiercase_non_ansi_quotes(self, sql, case):
+        # issue433: a delimited identifier keeps its case whichever of the
+        # four quoting styles SQL_REGEX recognizes was used. The mixed-case
+        # names make every one of the three conversions observable.
+        assert sqlparse.format(sql, identifier_case=case) == sql
+
     def test_strip_comments_single(self):
         sql = 'select *-- statement starts here\nfrom foo'
         res = sqlparse.format(sql, strip_comments=True)