Merge lp:~cjwatson/lazr.restful/etag-json into lp:lazr.restful

[Colin Watson]

Encode non-text/bytes field values for ETags using JSON.

Otherwise e.g. lists of strings were encoded as `[u'foo', u'bar']` on Python 2 but `['foo', 'bar']` on Python 3, causing ETag mismatches.

[Cristian Gonzalez (cristiangsp)]

Looks good!

review: Approve

=== modified file 'NEWS.rst'
--- NEWS.rst	2021-05-18 17:01:08 +0000
+++ NEWS.rst	2021-05-18 17:01:08 +0000
@@ -12,6 +12,9 @@
 
 Use a stable ordering for fields in entry representations.
 
+Stabilize ETags of entries containing collections of strings between Python
+2 and 3 (bug 1928474).
+
 1.0.2 (2021-05-14)
 ==================
 

=== modified file 'src/lazr/restful/_resource.py'
--- src/lazr/restful/_resource.py	2021-05-18 17:01:08 +0000
+++ src/lazr/restful/_resource.py	2021-05-18 17:01:08 +0000
@@ -160,20 +160,7 @@
     elif isinstance(value, bytes):
         return value.decode("utf-8")
     else:
-        return six.text_type(value)
-
-
-def encode_value(value):
-    """Return a UTF-8 string corresponding to `value`.
-
-    Non-unicode strings are assumed to be UTF-8 already.
-    """
-    if isinstance(value, six.text_type):
-        return value.encode("utf-8")
-    elif isinstance(value, bytes):
-        return value
-    else:
-        return bytes(value)
+        return simplejson.dumps(value)
 
 
 def _default_html_renderer(value):

=== modified file 'src/lazr/restful/tests/test_etag.py'
--- src/lazr/restful/tests/test_etag.py	2021-01-20 23:45:18 +0000
+++ src/lazr/restful/tests/test_etag.py	2021-05-18 17:01:08 +0000
@@ -5,6 +5,7 @@
 
 __metaclass__ = type
 
+from collections import OrderedDict
 import unittest
 
 from zope.component import provideUtility
@@ -80,6 +81,21 @@
             [b'first-not-writable\x00second-not-writable',
              b'first-writable\x00second-writable'])
 
+    def test_collection_fields(self):
+        # Field values that are something other than text or bytes are
+        # encoded using JSON.
+        field_details = [
+            ('list_field',
+             {'writable': False,
+              'value': ['first', 'second']}),
+            ('dict_field',
+             {'writable': False,
+              'value': OrderedDict((('first', 'one'), ('second', 'two')))}),
+            ]
+        self.assertEqual(
+            make_entry_etag_cores(field_details),
+            [b'["first", "second"]\0{"first": "one", "second": "two"}', b''])
+
 
 class TestHTTPResourceETags(unittest.TestCase):