bpo-36917: Add default implementation of ast.NodeVisitor.visit_Constant(). (GH-15490)

It emits a deprecation warning and calls corresponding method
visit_Num(), visit_Str(), etc.

1 files changed, 51 insertions, 0 deletions

diff --git a/Lib/test/test_ast.py b/Lib/test/test_ast.py
index f35d9e6..3d12397 100644
--- a/Lib/test/test_ast.py
+++ b/Lib/test/test_ast.py
@@ -3,6 +3,7 @@ import dis
 import os
 import sys
 import unittest
+import warnings
 import weakref
 from textwrap import dedent
 
@@ -1662,6 +1663,56 @@ class EndPositionTests(unittest.TestCase):
         self.assertEqual(ast.get_source_segment(s, cdef.body[0], padded=True), s_method)
 
 
+class NodeVisitorTests(unittest.TestCase):
+    def test_old_constant_nodes(self):
+        class Visitor(ast.NodeVisitor):
+            def visit_Num(self, node):
+                log.append((node.lineno, 'Num', node.n))
+            def visit_Str(self, node):
+                log.append((node.lineno, 'Str', node.s))
+            def visit_Bytes(self, node):
+                log.append((node.lineno, 'Bytes', node.s))
+            def visit_NameConstant(self, node):
+                log.append((node.lineno, 'NameConstant', node.value))
+            def visit_Ellipsis(self, node):
+                log.append((node.lineno, 'Ellipsis', ...))
+        mod = ast.parse(dedent('''\
+            i = 42
+            f = 4.25
+            c = 4.25j
+            s = 'string'
+            b = b'bytes'
+            t = True
+            n = None
+            e = ...
+            '''))
+        visitor = Visitor()
+        log = []
+        with warnings.catch_warnings(record=True) as wlog:
+            warnings.filterwarnings('always', '', DeprecationWarning)
+            visitor.visit(mod)
+        self.assertEqual(log, [
+            (1, 'Num', 42),
+            (2, 'Num', 4.25),
+            (3, 'Num', 4.25j),
+            (4, 'Str', 'string'),
+            (5, 'Bytes', b'bytes'),
+            (6, 'NameConstant', True),
+            (7, 'NameConstant', None),
+            (8, 'Ellipsis', ...),
+        ])
+        self.assertEqual([str(w.message) for w in wlog], [
+            'visit_Num is deprecated; add visit_Constant',
+            'visit_Num is deprecated; add visit_Constant',
+            'visit_Num is deprecated; add visit_Constant',
+            'visit_Str is deprecated; add visit_Constant',
+            'visit_Bytes is deprecated; add visit_Constant',
+            'visit_NameConstant is deprecated; add visit_Constant',
+            'visit_NameConstant is deprecated; add visit_Constant',
+            'visit_Ellipsis is deprecated; add visit_Constant',
+        ])
+
+
 def main():
     if __name__ != '__main__':
         return