#15546: Also fix GzipFile.peek().

Lib/gzip.py

@@ -413,6 +413,8 @@ class GzipFile(io.BufferedIOBase):
             if self.fileobj is None:
                 return b''
             try:
+                # Ensure that we don't return b"" if we haven't reached EOF.
+                while self.extrasize == 0:
                     # 1024 is the same buffering heuristic used in read()
                     self._read(max(n, 1024))
             except EOFError:

Misc/NEWS

@@ -81,8 +81,8 @@ Library
   constructor, objects in the ipaddress module no longer implement __index__
   (they still implement __int__ as appropriate)
 
-- Issue #15546: Fix handling of pathological input data in the read1() method of
-  the BZ2File, GzipFile and LZMAFile classes.
+- Issue #15546: Fix handling of pathological input data in the peek() and
+  read1() methods of the BZ2File, GzipFile and LZMAFile classes.
 
 - Issue #13052: Fix IDLE crashing when replace string in Search/Replace dialog
   ended with '\'. Patch by Roger Serwy.