Restrict detection of alias names (fixes #455).

This change adopts some parts of the pull request #509 by
john-bodley. Thanks!

4 files changed, 35 insertions, 20 deletions

diff --git a/CHANGELOG b/CHANGELOG
index b2df0af..713bad9 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -16,6 +16,8 @@ Bug Fixes
 * Remove support for parsing double slash comments introduced in
   0.3.0 (issue456) as it had some side-effects with other dialects and
   doesn't seem to be widely used (issue476).
+* Restrict detection of alias names to objects that acutally could
+  have an alias (issue455, adopted some parts of pr509 by john-bodley).
 
 
 Release 0.3.0 (Mar 11, 2019)
diff --git a/sqlparse/sql.py b/sqlparse/sql.py
index a752555..cff501c 100644
--- a/sqlparse/sql.py
+++ b/sqlparse/sql.py
@@ -16,6 +16,29 @@ from sqlparse.compat import string_types, text_type, unicode_compatible
 from sqlparse.utils import imt, remove_quotes
 
 
+class NameAliasMixin:
+    """Implements get_real_name and get_alias."""
+
+    def get_real_name(self):
+        """Returns the real name (object name) of this identifier."""
+        # a.b
+        dot_idx, _ = self.token_next_by(m=(T.Punctuation, '.'))
+        return self._get_first_name(dot_idx, real_name=True)
+
+    def get_alias(self):
+        """Returns the alias for this identifier or ``None``."""
+
+        # "name AS alias"
+        kw_idx, kw = self.token_next_by(m=(T.Keyword, 'AS'))
+        if kw is not None:
+            return self._get_first_name(kw_idx + 1, keywords=True)
+
+        # "name alias" or "complicated column expression alias"
+        _, ws = self.token_next_by(t=T.Whitespace)
+        if len(self.tokens) > 2 and ws is not None:
+            return self._get_first_name(reverse=True)
+
+
 @unicode_compatible
 class Token(object):
     """Base class for all other classes in this module.
@@ -341,16 +364,7 @@ class TokenList(Token):
 
     def get_alias(self):
         """Returns the alias for this identifier or ``None``."""
-
-        # "name AS alias"
-        kw_idx, kw = self.token_next_by(m=(T.Keyword, 'AS'))
-        if kw is not None:
-            return self._get_first_name(kw_idx + 1, keywords=True)
-
-        # "name alias" or "complicated column expression alias"
-        _, ws = self.token_next_by(t=T.Whitespace)
-        if len(self.tokens) > 2 and ws is not None:
-            return self._get_first_name(reverse=True)
+        return None
 
     def get_name(self):
         """Returns the name of this identifier.
@@ -363,9 +377,7 @@ class TokenList(Token):
 
     def get_real_name(self):
         """Returns the real name (object name) of this identifier."""
-        # a.b
-        dot_idx, _ = self.token_next_by(m=(T.Punctuation, '.'))
-        return self._get_first_name(dot_idx, real_name=True)
+        return None
 
     def get_parent_name(self):
         """Return name of the parent object if any.
@@ -433,7 +445,7 @@ class Statement(TokenList):
         return 'UNKNOWN'
 
 
-class Identifier(TokenList):
+class Identifier(NameAliasMixin, TokenList):
     """Represents an identifier.
 
     Identifiers may have aliases or typecasts.
@@ -599,7 +611,7 @@ class Case(TokenList):
         return ret
 
 
-class Function(TokenList):
+class Function(NameAliasMixin, TokenList):
     """A function or procedure call."""
 
     def get_parameters(self):
diff --git a/tests/test_grouping.py b/tests/test_grouping.py
index 63a01f2..c2d8860 100644
--- a/tests/test_grouping.py
+++ b/tests/test_grouping.py
@@ -294,9 +294,10 @@ def test_grouping_subquery_no_parens():
     assert isinstance(p.tokens[0], sql.Case)
 
 
-def test_grouping_alias_returns_none():
-    # see issue185
-    p = sqlparse.parse('foo.bar')[0]
+@pytest.mark.parametrize('s', ['foo.bar', 'x, y', 'x > y', 'x / y'])
+def test_grouping_alias_returns_none(s):
+    # see issue185 and issue445
+    p = sqlparse.parse(s)[0]
     assert len(p.tokens) == 1
     assert p.tokens[0].get_alias() is None
 
diff --git a/tests/test_parse.py b/tests/test_parse.py
index f2a2bda..c28cb06 100644
--- a/tests/test_parse.py
+++ b/tests/test_parse.py
@@ -431,8 +431,8 @@ def test_get_real_name():
     s = u"update a t set t.b=1"
     stmts = sqlparse.parse(s)
     assert len(stmts) == 1
-    assert 'a' == stmts[0].get_real_name()
-    assert 't' == stmts[0].get_alias()
+    assert 'a' == stmts[0].tokens[2].get_real_name()
+    assert 't' == stmts[0].tokens[2].get_alias()
 
 
 def test_from_subquery():