bpo-36434: Properly handle writing errors in ZIP files. (GH-12559)

Errors during writing no longer prevent to properly close
the ZIP file.

Lib/test/test_zipfile.py

@@ -402,6 +402,43 @@ class AbstractTestsWithSourceFile:
             self.assertEqual(one_info._compresslevel, 1)
             self.assertEqual(nine_info._compresslevel, 9)
 
+    def test_writing_errors(self):
+        class BrokenFile(io.BytesIO):
+            def write(self, data):
+                nonlocal count
+                if count is not None:
+                    if count == stop:
+                        raise OSError
+                    count += 1
+                super().write(data)
+
+        stop = 0
+        while True:
+            testfile = BrokenFile()
+            count = None
+            with zipfile.ZipFile(testfile, 'w', self.compression) as zipfp:
+                with zipfp.open('file1', 'w') as f:
+                    f.write(b'data1')
+                count = 0
+                try:
+                    with zipfp.open('file2', 'w') as f:
+                        f.write(b'data2')
+                except OSError:
+                    stop += 1
+                else:
+                    break
+                finally:
+                    count = None
+            with zipfile.ZipFile(io.BytesIO(testfile.getvalue())) as zipfp:
+                self.assertEqual(zipfp.namelist(), ['file1'])
+                self.assertEqual(zipfp.read('file1'), b'data1')
+
+        with zipfile.ZipFile(io.BytesIO(testfile.getvalue())) as zipfp:
+            self.assertEqual(zipfp.namelist(), ['file1', 'file2'])
+            self.assertEqual(zipfp.read('file1'), b'data1')
+            self.assertEqual(zipfp.read('file2'), b'data2')
+
+
     def tearDown(self):
         unlink(TESTFN)
         unlink(TESTFN2)

Lib/zipfile.py

@@ -1105,6 +1105,7 @@ class _ZipWriteFile(io.BufferedIOBase):
     def close(self):
         if self.closed:
             return
+        try:
             super().close()
             # Flush any data from the compressor, and update header info
             if self._compressor:
@@ -1127,11 +1128,11 @@ class _ZipWriteFile(io.BufferedIOBase):
             else:
                 if not self._zip64:
                     if self._file_size > ZIP64_LIMIT:
-                    raise RuntimeError('File size unexpectedly exceeded ZIP64 '
-                                       'limit')
+                        raise RuntimeError(
+                            'File size unexpectedly exceeded ZIP64 limit')
                     if self._compress_size > ZIP64_LIMIT:
-                    raise RuntimeError('Compressed size unexpectedly exceeded '
-                                       'ZIP64 limit')
+                        raise RuntimeError(
+                            'Compressed size unexpectedly exceeded ZIP64 limit')
                 # Seek backwards and write file header (which will now include
                 # correct CRC and file sizes)
 
@@ -1141,11 +1142,13 @@ class _ZipWriteFile(io.BufferedIOBase):
                 self._fileobj.write(self._zinfo.FileHeader(self._zip64))
                 self._fileobj.seek(self._zipfile.start_dir)
 
-        self._zipfile._writing = False
-
             # Successfully written: Add file to our caches
             self._zipfile.filelist.append(self._zinfo)
             self._zipfile.NameToInfo[self._zinfo.filename] = self._zinfo
+        finally:
+            self._zipfile._writing = False
+
+
 
 class ZipFile:
     """ Class with methods to open, read, write, close, list zip files.

Misc/NEWS.d/next/Library/2019-03-26-14-20-59.bpo-36434.PTdidw.rst

@@ -0,0 +1 @@
+Errors during writing to a ZIP file no longer prevent to properly close it.