python-3.6.zip added from Github

README.cosmo contains the necessary links.

third_party/python/Lib/lib2to3/tests/pytree_idempotency.py

@@ -0,0 +1,94 @@
+#!/usr/bin/env python3
+# Copyright 2006 Google, Inc. All Rights Reserved.
+# Licensed to PSF under a Contributor Agreement.
+
+"""Main program for testing the infrastructure."""
+
+from __future__ import print_function
+
+__author__ = "Guido van Rossum <guido@python.org>"
+
+# Support imports (need to be imported first)
+from . import support
+
+# Python imports
+import os
+import sys
+import logging
+
+# Local imports
+from .. import pytree
+from .. import pgen2
+from ..pgen2 import driver
+
+logging.basicConfig()
+
+def main():
+    gr = driver.load_grammar("Grammar.txt")
+    dr = driver.Driver(gr, convert=pytree.convert)
+
+    fn = "example.py"
+    tree = dr.parse_file(fn, debug=True)
+    if not diff(fn, tree):
+        print("No diffs.")
+    if not sys.argv[1:]:
+        return # Pass a dummy argument to run the complete test suite below
+
+    problems = []
+
+    # Process every imported module
+    for name in sys.modules:
+        mod = sys.modules[name]
+        if mod is None or not hasattr(mod, "__file__"):
+            continue
+        fn = mod.__file__
+        if fn.endswith(".pyc"):
+            fn = fn[:-1]
+        if not fn.endswith(".py"):
+            continue
+        print("Parsing", fn, file=sys.stderr)
+        tree = dr.parse_file(fn, debug=True)
+        if diff(fn, tree):
+            problems.append(fn)
+
+    # Process every single module on sys.path (but not in packages)
+    for dir in sys.path:
+        try:
+            names = os.listdir(dir)
+        except OSError:
+            continue
+        print("Scanning", dir, "...", file=sys.stderr)
+        for name in names:
+            if not name.endswith(".py"):
+                continue
+            print("Parsing", name, file=sys.stderr)
+            fn = os.path.join(dir, name)
+            try:
+                tree = dr.parse_file(fn, debug=True)
+            except pgen2.parse.ParseError as err:
+                print("ParseError:", err)
+            else:
+                if diff(fn, tree):
+                    problems.append(fn)
+
+    # Show summary of problem files
+    if not problems:
+        print("No problems.  Congratulations!")
+    else:
+        print("Problems in following files:")
+        for fn in problems:
+            print("***", fn)
+
+def diff(fn, tree):
+    f = open("@", "w")
+    try:
+        f.write(str(tree))
+    finally:
+        f.close()
+    try:
+        return os.system("diff -u %s @" % fn)
+    finally:
+        os.remove("@")
+
+if __name__ == "__main__":
+    main()