Fix instantiation of attribute-less AST nodes

Fixes #138.

CHANGES.rst

@@ -11,6 +11,11 @@ Version 5
 5.6 (unreleased)
 ~~~~~~~~~~~~~~~~
 
+- Fix issue `#138`__, a defect that hindered the creation of AST nodes that act as *markers*,
+  (currently ``A_Star`` and ``CheckPointStmt``), that do not carry any other information
+
+  __ https://github.com/lelit/pglast/issues/138
+
 - Use `Cython 3.0.6`__
 
   __ https://github.com/cython/cython/blob/master/CHANGES.rst#306-2023-11-26

pglast/ast.py

@@ -74,9 +74,13 @@ def __init__(self, data):
             v = data.get(a)
             if v is not None:
                 if isinstance(v, dict) and '@' in v:
-                    v = G[v['@']](v)
+                    if len(v) > 1:
+                        v = G[v['@']](v)
+                    else:
+                        v = G[v['@']]()
                 elif isinstance(v, (tuple, list)):
-                    v = tuple(G[i['@']](i) if isinstance(i, dict) and '@' in i else i
+                    v = tuple((G[i['@']](i) if len(i) > 1 else G[i['@']]())
+                              if isinstance(i, dict) and '@' in i else i
                               for i in v)
             setattr(self, a, v)
 

tests/test_ast.py

@@ -99,3 +99,8 @@ def test_issue_97():
             }
         ),
     })
+
+
+def test_issue_138():
+    raw = parse_sql('select * from foo')[0]
+    ast.RawStmt(raw())

tools/extract_ast.py

@@ -94,9 +94,13 @@ def __init__(self, data):
             v = data.get(a)
             if v is not None:
                 if isinstance(v, dict) and '@' in v:
-                    v = G[v['@']](v)
+                    if len(v) > 1:
+                        v = G[v['@']](v)
+                    else:
+                        v = G[v['@']]()
                 elif isinstance(v, (tuple, list)):
-                    v = tuple(G[i['@']](i) if isinstance(i, dict) and '@' in i else i
+                    v = tuple((G[i['@']](i) if len(i) > 1 else G[i['@']]())
+                              if isinstance(i, dict) and '@' in i else i
                               for i in v)
             setattr(self, a, v)