bpo-40355: Improve error messages in ast.literal_eval with malformed Dict nodes (GH-19868)

miss-islington · curtisbucher · web-flow · commit 2a3b876b0286 · 2020-05-05T13:00:57.000-07:00
Co-authored-by: Pablo Galindo <Pablogsal@gmail.com> (cherry picked from commit c21c512) Co-authored-by: Curtis Bucher <cpbucher5@gmail.com>
diff --git a/Lib/ast.py b/Lib/ast.py
@@ -59,11 +59,12 @@ def literal_eval(node_or_string):
         node_or_string = parse(node_or_string, mode='eval')
     if isinstance(node_or_string, Expression):
         node_or_string = node_or_string.body
+    def _raise_malformed_node(node):
+        raise ValueError(f'malformed node or string: {node!r}')
     def _convert_num(node):
-        if isinstance(node, Constant):
-            if type(node.value) in (int, float, complex):
-                return node.value
-        raise ValueError('malformed node or string: ' + repr(node))
+        if not isinstance(node, Constant) or type(node.value) not in (int, float, complex):
+            _raise_malformed_node(node)
+        return node.value
     def _convert_signed_num(node):
         if isinstance(node, UnaryOp) and isinstance(node.op, (UAdd, USub)):
             operand = _convert_num(node.operand)
@@ -82,6 +83,8 @@ def _convert(node):
         elif isinstance(node, Set):
             return set(map(_convert, node.elts))
         elif isinstance(node, Dict):
+            if len(node.keys) != len(node.values):
+                _raise_malformed_node(node)
             return dict(zip(map(_convert, node.keys),
                             map(_convert, node.values)))
         elif isinstance(node, BinOp) and isinstance(node.op, (Add, Sub)):
diff --git a/Lib/test/test_ast.py b/Lib/test/test_ast.py
@@ -869,6 +869,12 @@ def test_literal_eval_complex(self):
         self.assertRaises(ValueError, ast.literal_eval, '3+(0+6j)')
         self.assertRaises(ValueError, ast.literal_eval, '-(3+6j)')
 
+    def test_literal_eval_malformed_dict_nodes(self):
+        malformed = ast.Dict(keys=[ast.Constant(1), ast.Constant(2)], values=[ast.Constant(3)])
+        self.assertRaises(ValueError, ast.literal_eval, malformed)
+        malformed = ast.Dict(keys=[ast.Constant(1)], values=[ast.Constant(2), ast.Constant(3)])
+        self.assertRaises(ValueError, ast.literal_eval, malformed)
+
     def test_bad_integer(self):
         # issue13436: Bad error message with invalid numeric values
         body = [ast.ImportFrom(module='time',
diff --git a/Misc/NEWS.d/next/Library/2020-05-02-14-24-48.bpo-40355.xTujaB.rst b/Misc/NEWS.d/next/Library/2020-05-02-14-24-48.bpo-40355.xTujaB.rst
@@ -0,0 +1,2 @@
+Improve error reporting in :func:`ast.literal_eval` in the presence of malformed :class:`ast.Dict`
+nodes instead of silently ignoring any non-conforming elements. Patch by Curtis Bucher.

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	+Improve error reporting in :func:`ast.literal_eval` in the presence of malformed :class:`ast.Dict`
	`2`	`+nodes instead of silently ignoring any non-conforming elements. Patch by Curtis Bucher.`