Issue #20289: cgi.FieldStorage() now supports the context management protocol.

Author: berkerpeksag

Doc/library/cgi.rst

@@ -157,6 +157,9 @@ return bytes)::
            if not line: break
            linecount = linecount + 1
 
+:class:`FieldStorage` objects also support being used in a :keyword:`with`
+statement, which will automatically close them when done.
+
 If an error is encountered when obtaining the contents of an uploaded file
 (for example, when the user interrupts the form submission by clicking on
 a Back or Cancel button) the :attr:`~FieldStorage.done` attribute of the
@@ -182,6 +185,10 @@ A form submitted via POST that also has a query string will contain both
    The :attr:`~FieldStorage.file` attribute is automatically closed upon the
    garbage collection of the creating :class:`FieldStorage` instance.
 
+.. versionchanged:: 3.5
+   Added support for the context management protocol to the
+   :class:`FieldStorage` class.
+
 
 Higher Level Interface
 ----------------------

Doc/whatsnew/3.5.rst

@@ -136,6 +136,12 @@ New Modules
 Improved Modules
 ================
 
+cgi
+---
+
+* :class:`FieldStorage` now supports the context management protocol.
+  (Contributed by Berker Peksag in :issue:`20289`.)
+
 code
 ----
 

Lib/cgi.py

@@ -566,6 +566,12 @@ def __del__(self):
         except AttributeError:
             pass
 
+    def __enter__(self):
+        return self
+
+    def __exit__(self, *args):
+        self.file.close()
+
     def __repr__(self):
         """Return a printable representation."""
         return "FieldStorage(%r, %r, %r)" % (

Lib/test/test_cgi.py

@@ -1,4 +1,4 @@
-from test.support import run_unittest, check_warnings
+from test.support import check_warnings
 import cgi
 import os
 import sys
@@ -307,6 +307,17 @@ def test_fieldstorage_multipart_w3c(self):
                 got = getattr(files[x], k)
                 self.assertEqual(got, exp)
 
+    def test_fieldstorage_as_context_manager(self):
+        fp = BytesIO(b'x' * 10)
+        env = {'REQUEST_METHOD': 'PUT'}
+        with cgi.FieldStorage(fp=fp, environ=env) as fs:
+            content = fs.file.read()
+            self.assertFalse(fs.file.closed)
+        self.assertTrue(fs.file.closed)
+        self.assertEqual(content, 'x' * 10)
+        with self.assertRaisesRegex(ValueError, 'I/O operation on closed file'):
+            fs.file.read()
+
     _qs_result = {
         'key1': 'value1',
         'key2': ['value2x', 'value2y'],
@@ -481,9 +492,5 @@ def test_parse_header(self):
 --AaB03x--
 """
 
-
-def test_main():
-    run_unittest(CgiTests)
-
 if __name__ == '__main__':
-    test_main()
+    unittest.main()

Misc/NEWS

@@ -235,6 +235,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #20289: cgi.FieldStorage() now supports the context management
+  protocol.
+
 - Issue #13128: Print response headers for CONNECT requests when debuglevel
   > 0. Patch by Demian Brecht.