From bbbfcce337ae1045ff403fae088f1d70651cb9f9 Mon Sep 17 00:00:00 2001
From: Liang Jingyi <124090346@link.cuhk.edu.cn>
Date: Fri, 23 Oct 2026 02:34:39 +0800
Subject: [PATCH] Fix explicit AS aliases for current date and time scalars

---
 CHANGELOG                   |  3 ++-
 sqlparse/engine/grouping.py |  4 +++-
 tests/test_format.py        | 33 +++++++++++++++++++++++++++++++++
 tests/test_grouping.py      | 22 ++++++++++++++++++++++
 4 files changed, 60 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG b/CHANGELOG
index 44d5938e..06d13b51 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,7 +1,8 @@
 Development Version
 -------------------
 
-Nothing yet.
+* Fix SELECT-list alignment for CURRENT_DATE, CURRENT_TIME, and
+  CURRENT_TIMESTAMP with explicit AS aliases (issue550).
 
 
 Release 0.6.0 (Aug 13, 2026)
diff --git a/sqlparse/engine/grouping.py b/sqlparse/engine/grouping.py
index d8cfa9e1..29294d09 100644
--- a/sqlparse/engine/grouping.py
+++ b/sqlparse/engine/grouping.py
@@ -196,7 +196,9 @@ def match(token):
         return token.is_keyword and token.normalized == 'AS'
 
     def valid_prev(token):
-        return token.normalized == 'NULL' or not token.is_keyword
+        return (token.normalized in ('NULL', 'CURRENT_DATE', 'CURRENT_TIME',
+                                     'CURRENT_TIMESTAMP')
+                or not token.is_keyword)
 
     def valid_next(token):
         ttypes = T.DML, T.DDL, T.CTE
diff --git a/tests/test_format.py b/tests/test_format.py
index 93495067..f048f807 100644
--- a/tests/test_format.py
+++ b/tests/test_format.py
@@ -491,6 +491,39 @@ def test_identifier_list(self):
             'from a,',
             '     b'])
 
+    @pytest.mark.parametrize('date', [
+        'CURRENT_DATE', 'CURRENT_TIME', 'CURRENT_TIMESTAMP',
+    ])
+    @pytest.mark.parametrize('case', [str.upper, str.lower, str.title])
+    def test_date_scalar_as_alias(self, date, case):
+        # issue550
+        aliased = f'{case(date)} {case("AS")} CREATED_AT'
+        s = (f"SELECT 'value 1' AS VALUE_1, {aliased}, "
+             "'testing' AS VALUE_2, 'testing2' AS VALUE_3 FROM TABLE_1")
+        expected = '\n'.join([
+            "SELECT 'value 1' AS VALUE_1,",
+            f'       {aliased},',
+            "       'testing' AS VALUE_2,",
+            "       'testing2' AS VALUE_3",
+            'FROM TABLE_1',
+        ])
+        assert sqlparse.format(s, reindent=True) == expected
+        assert sqlparse.format(expected, reindent=True) == expected
+
+    def test_date_scalar_as_alias_trailing_comma(self):
+        # Preserve the trailing comma in issue550's reported output separately
+        # from the valid SELECT-list regression above.
+        s = ("SELECT 'value 1' AS VALUE_1, CURRENT_DATE AS CREATED_AT, "
+             "'testing' AS VALUE_2, 'testing2' AS VALUE_3, FROM TABLE_1")
+        assert str(sqlparse.parse(s)[0]) == s
+        assert sqlparse.format(s, reindent=True) == '\n'.join([
+            "SELECT 'value 1' AS VALUE_1,",
+            '       CURRENT_DATE AS CREATED_AT,',
+            "       'testing' AS VALUE_2,",
+            "       'testing2' AS VALUE_3,",
+            'FROM TABLE_1',
+        ])
+
     def test_identifier_list_with_wrap_after(self):
         f = lambda sql: sqlparse.format(sql, reindent=True, wrap_after=14)
         s = 'select foo, bar, baz from table1, table2 where 1 = 2'
diff --git a/tests/test_grouping.py b/tests/test_grouping.py
index 20fab9b7..b9cb29f5 100644
--- a/tests/test_grouping.py
+++ b/tests/test_grouping.py
@@ -332,6 +332,28 @@ def test_grouping_alias():
     assert p.tokens[4].get_alias() == 'view'
 
 
+@pytest.mark.parametrize('expression', [
+    'CURRENT_DATE', 'CURRENT_TIME', 'CURRENT_TIMESTAMP', 'NULL', 'created_on',
+])
+@pytest.mark.parametrize('case', [str.upper, str.lower, str.title])
+def test_grouping_date_scalar_as_alias(expression, case):
+    # issue550: the scalar and its explicit alias must stay in one projection.
+    aliased = f'{case(expression)}\t{case("AS")}\n  CREATED_AT'
+    s = (f"SELECT 'value 1' AS VALUE_1, {aliased}, "
+         "'testing' AS VALUE_2, 'testing2' AS VALUE_3 FROM TABLE_1")
+    p = sqlparse.parse(s)[0]
+    assert str(p) == s
+    assert isinstance(p.tokens[2], sql.IdentifierList)
+    identifiers = list(p.tokens[2].get_identifiers())
+    assert [str(item) for item in identifiers] == [
+        "'value 1' AS VALUE_1", aliased,
+        "'testing' AS VALUE_2", "'testing2' AS VALUE_3",
+    ]
+    assert [item.get_alias() for item in identifiers] == [
+        'VALUE_1', 'CREATED_AT', 'VALUE_2', 'VALUE_3',
+    ]
+
+
 def test_grouping_alias_case():
     # see issue46
     p = sqlparse.parse('CASE WHEN 1 THEN 2 ELSE 3 END foo')[0]