field2* converters should not handle files (#963)

Co-authored-by: Michael Howitz <mh@gocept.com>

CHANGES.rst

@@ -8,8 +8,8 @@ The change log for the previous version, Zope 4, is at
 https://github.com/zopefoundation/Zope/blob/4.x/CHANGES.rst
 
 
-5.1.3 (unreleased)
-------------------
+5.2 (unreleased)
+----------------
 
 - Updated/fixed the poll application tutorial in the Zope Developers Guide
   (`#958 <https://github.com/zopefoundation/Zope/issues/958>`_)
@@ -20,6 +20,13 @@ https://github.com/zopefoundation/Zope/blob/4.x/CHANGES.rst
   ``rfc850_date``, and ``rfc1123_date`` which used to be in ``App.Common``
   keeping backwards-compatibility imports in place.
 
+Backwards incompatible changes
+++++++++++++++++++++++++++++++
+
+- With the exception of ``field2bytes``, field converters do no longer try to
+  read file like objects
+  (`#558 <https://github.com/zopefoundation/Zope/issues/558>`_)
+
 
 5.1.2 (2021-03-02)
 ------------------

setup.py

@@ -29,7 +29,7 @@ def _read_file(filename):
 README = _read_file('README.rst')
 CHANGES = _read_file('CHANGES.rst')
 
-version = '5.1.3.dev0'
+version = '5.2.dev0'
 
 
 setup(

src/ZPublisher/Converters.py

@@ -23,20 +23,15 @@
 
 
 def field2string(v):
-    """Converts value to native strings.
-
-    So always to `str` no matter which Python version you are on.
-    """
-    if hasattr(v, 'read'):
-        return v.read()
-    elif isinstance(v, bytes):
+    """Converts value to string."""
+    if isinstance(v, bytes):
         return v.decode(default_encoding)
     else:
         return str(v)
 
 
 def field2bytes(v):
-    # Converts value to bytes.
+    """Converts value to bytes."""
     if hasattr(v, 'read'):
         return v.read()
     elif isinstance(v, str):
@@ -172,8 +167,6 @@ def __call__(self, v):
         #       <input name="description:utf8:ustring" .....
         # rather than
         #       <input name="description:ustring" .....
-        if hasattr(v, 'read'):
-            v = v.read()
         v = str(v)
         return self.convert_unicode(v)
 
@@ -209,8 +202,6 @@ def convert_unicode(self, v):
 
 class field2ulines:
     def __call__(self, v):
-        if hasattr(v, 'read'):
-            v = v.read()
         if isinstance(v, (list, tuple)):
             return [field2ustring(x) for x in v]
         v = str(v)

src/ZPublisher/tests/test_Converters.py

@@ -143,15 +143,6 @@ def test_field2string_with_string(self):
         to_convert = 'to_convert'
         self.assertEqual(field2string(to_convert), to_convert)
 
-    def test_field2string_with_filelike_object(self):
-        from ZPublisher.Converters import field2string
-        to_convert = 'to_convert'
-
-        class Filelike:
-            def read(self):
-                return to_convert
-        self.assertEqual(field2string(Filelike()), to_convert)
-
     def test_field2bytes_with_bytes(self):
         from ZPublisher.Converters import field2bytes
         to_convert = b'to_convert'
@@ -163,6 +154,15 @@ def test_field2bytes_with_text(self):
         expected = b'to_convert'
         self.assertEqual(field2bytes(to_convert), expected)
 
+    def test_field2bytes_with_filelike_object(self):
+        from ZPublisher.Converters import field2bytes
+        to_convert = b'to_convert'
+
+        class Filelike:
+            def read(self):
+                return to_convert
+        self.assertEqual(field2bytes(Filelike()), to_convert)
+
     def test_field2date_international_with_proper_date_string(self):
         from ZPublisher.Converters import field2date_international
         to_convert = "2.1.2019"