bpo-41887: omit leading spaces/tabs on ast.literal_eval (#22469)

Also document that eval() does this (the same way).

2 files changed, 7 insertions, 1 deletions

diff --git a/Lib/ast.py b/Lib/ast.py
index d860917..d8bd337 100644
--- a/Lib/ast.py
+++ b/Lib/ast.py
@@ -59,7 +59,7 @@ def literal_eval(node_or_string):
     sets, booleans, and None.
     """
     if isinstance(node_or_string, str):
-        node_or_string = parse(node_or_string, mode='eval')
+        node_or_string = parse(node_or_string.lstrip(" \t"), mode='eval')
     if isinstance(node_or_string, Expression):
         node_or_string = node_or_string.body
     def _raise_malformed_node(node):
diff --git a/Lib/test/test_ast.py b/Lib/test/test_ast.py
index 5f57ce8..be4b0f7 100644
--- a/Lib/test/test_ast.py
+++ b/Lib/test/test_ast.py
@@ -1005,6 +1005,12 @@ Module(
         malformed = ast.Dict(keys=[ast.Constant(1)], values=[ast.Constant(2), ast.Constant(3)])
         self.assertRaises(ValueError, ast.literal_eval, malformed)
 
+    def test_literal_eval_trailing_ws(self):
+        self.assertEqual(ast.literal_eval("    -1"), -1)
+        self.assertEqual(ast.literal_eval("\t\t-1"), -1)
+        self.assertEqual(ast.literal_eval(" \t -1"), -1)
+        self.assertRaises(IndentationError, ast.literal_eval, "\n -1")
+
     def test_bad_integer(self):
         # issue13436: Bad error message with invalid numeric values
         body = [ast.ImportFrom(module='time',