Fix #596: Fix empty-only-comments AST generation

src/vtlengine/AST/ASTConstructor.py

@@ -65,7 +65,10 @@ def visitStart(self, ctx: Parser.StartContext):
             for statement in statements:
                 statements_nodes.append(self.visitStatement(statement))
 
-        token_info = extract_token_info(ctx)
+        if ctx.stop is None:
+            token_info = {"column_start": 0, "column_stop": 0, "line_start": 1, "line_stop": 1}
+        else:
+            token_info = extract_token_info(ctx)
 
         start_node = Start(children=statements_nodes, **token_info)
 

tests/AST/test_AST.py

@@ -948,3 +948,26 @@ def test_rule_name_not_in_ruleset():
         """
     ast = create_ast(text=script)
     assert len(ast.children) == 1
+
+
+empty_script_params = [
+    "",
+    "//Comment",
+    "/*Comment*/",
+]
+
+
+@pytest.mark.parametrize("script", empty_script_params)
+def test_create_ast_empty_script(script):
+    ast = create_ast(text=script)
+    assert isinstance(ast, Start)
+    assert ast.children == []
+
+
+@pytest.mark.parametrize("script", empty_script_params)
+def test_create_ast_with_comments_empty_script(script):
+    from vtlengine.AST import Comment
+
+    ast = create_ast_with_comments(text=script)
+    assert isinstance(ast, Start)
+    assert all(isinstance(child, Comment) for child in ast.children)