Issue #20111: pathlib.Path.with_suffix() now sanity checks the given suffix.

1 files changed, 6 insertions, 0 deletions

diff --git a/Lib/pathlib.py b/Lib/pathlib.py
index b999ab24fb..8d08e8b413 100644
--- a/Lib/pathlib.py
+++ b/Lib/pathlib.py
@@ -755,6 +755,12 @@ class PurePath(object):
     def with_suffix(self, suffix):
         """Return a new path with the file suffix changed (or added, if none)."""
         # XXX if suffix is None, should the current suffix be removed?
+        drv, root, parts = self._flavour.parse_parts((suffix,))
+        if drv or root or len(parts) != 1:
+            raise ValueError("Invalid suffix %r" % (suffix))
+        suffix = parts[0]
+        if not suffix.startswith('.'):
+            raise ValueError("Invalid suffix %r" % (suffix))
         name = self.name
         if not name:
             raise ValueError("%r has an empty name" % (self,))