bpo-37523: Raise ValueError for I/O operations on a closed zipfile.ZipExtFile. (GH-14658)

Raises ValueError when calling the following on a closed zipfile.ZipExtFile: read, readable, seek, seekable, tell.

Lib/test/test_zipfile.py

@@ -571,6 +571,20 @@ class StoredTestsWithSourceFile(AbstractTestsWithSourceFile,
             with open(TESTFN, "rb") as f:
                 self.assertEqual(zipfp.read(TESTFN), f.read())
 
+    def test_io_on_closed_zipextfile(self):
+        fname = "somefile.txt"
+        with zipfile.ZipFile(TESTFN2, mode="w") as zipfp:
+            zipfp.writestr(fname, "bogus")
+
+        with zipfile.ZipFile(TESTFN2, mode="r") as zipfp:
+            with zipfp.open(fname) as fid:
+                fid.close()
+                self.assertRaises(ValueError, fid.read)
+                self.assertRaises(ValueError, fid.seek, 0)
+                self.assertRaises(ValueError, fid.tell)
+                self.assertRaises(ValueError, fid.readable)
+                self.assertRaises(ValueError, fid.seekable)
+
     def test_write_to_readonly(self):
         """Check that trying to call write() on a readonly ZipFile object
         raises a ValueError."""

Lib/zipfile.py

@@ -889,12 +889,16 @@ class ZipExtFile(io.BufferedIOBase):
         return self._readbuffer[self._offset: self._offset + 512]
 
     def readable(self):
+        if self.closed:
+            raise ValueError("I/O operation on closed file.")
         return True
 
     def read(self, n=-1):
         """Read and return up to n bytes.
         If the argument is omitted, None, or negative, data is read and returned until EOF is reached.
         """
+        if self.closed:
+            raise ValueError("read from closed file.")
         if n is None or n < 0:
             buf = self._readbuffer[self._offset:]
             self._readbuffer = b''
@@ -1031,9 +1035,13 @@ class ZipExtFile(io.BufferedIOBase):
             super().close()
 
     def seekable(self):
+        if self.closed:
+            raise ValueError("I/O operation on closed file.")
         return self._seekable
 
     def seek(self, offset, whence=0):
+        if self.closed:
+            raise ValueError("seek on closed file.")
         if not self._seekable:
             raise io.UnsupportedOperation("underlying stream is not seekable")
         curr_pos = self.tell()
@@ -1082,6 +1090,8 @@ class ZipExtFile(io.BufferedIOBase):
         return self.tell()
 
     def tell(self):
+        if self.closed:
+            raise ValueError("tell on closed file.")
         if not self._seekable:
             raise io.UnsupportedOperation("underlying stream is not seekable")
         filepos = self._orig_file_size - self._left - len(self._readbuffer) + self._offset

Misc/NEWS.d/next/Library/2019-10-02-02-55-37.bpo-37523.GguwJ6.rst

@@ -0,0 +1 @@
+Change :class:`zipfile.ZipExtFile` to raise ``ValueError`` when trying to access the underlying file object after it has been closed. This new behavior is consistent with how accessing closed files is handled in other parts of Python.