Do not ignore Union argument ordering in tests (#248)

* Revert "Ignore union ordering"

This reverts commit b61cd50.

* test: mark expected failure, add separate test of its non-failing bits

* ci(tests): report skipped/xfailed tests

* docs(test): add link for context

Co-authored-by: Ophir LOJKINE <contact@ophir.dev>

---------

Co-authored-by: Ophir LOJKINE <contact@ophir.dev>

Author: dairiki

.github/workflows/python-package.yml

@@ -47,4 +47,4 @@ jobs:
       if: ${{ matrix.python_version != 'pypy3' && matrix.python_version != '3.6' }}
       run: pre-commit run --all-files
     - name: Test with pytest
-      run: pytest
+      run: pytest -ra

tests/test_field_for_schema.py

@@ -1,3 +1,4 @@
+import copy
 import inspect
 import sys
 import typing
@@ -26,18 +27,11 @@ class TestFieldForSchema(unittest.TestCase):
     def assertFieldsEqual(self, a: fields.Field, b: fields.Field):
         self.assertEqual(a.__class__, b.__class__, "field class")
 
-        def canonical(k, v):
-            if k == "union_fields":
-                # See https://github.com/lovasoa/marshmallow_dataclass/pull/246#issuecomment-1722291806
-                return k, sorted(map(repr, v))
-            elif inspect.isclass(v):
-                return k, f"{v!r} ({v.__mro__!r})"
-            else:
-                return k, repr(v)
-
         def attrs(x):
             return sorted(
-                canonical(k, v) for k, v in vars(x).items() if not k.startswith("_")
+                (k, f"{v!r} ({v.__mro__!r})" if inspect.isclass(v) else repr(v))
+                for k, v in x.__dict__.items()
+                if not k.startswith("_")
             )
 
         self.assertEqual(attrs(a), attrs(b))
@@ -189,7 +183,11 @@ def test_union_multiple_types_with_none(self):
             ),
         )
 
+    @unittest.expectedFailure
     def test_optional_multiple_types(self):
+        # excercise bug (see #247)
+        Optional[Union[str, int]]
+
         self.assertFieldsEqual(
             field_for_schema(Optional[Union[int, str]]),
             union_field.Union(
@@ -203,6 +201,26 @@ def test_optional_multiple_types(self):
             ),
         )
 
+    def test_optional_multiple_types_ignoring_union_field_order(self):
+        # see https://github.com/lovasoa/marshmallow_dataclass/pull/246#issuecomment-1722204048
+        result = field_for_schema(Optional[Union[int, str]])
+        expected = union_field.Union(
+            [
+                (int, fields.Integer(required=True)),
+                (str, fields.String(required=True)),
+            ],
+            required=False,
+            dump_default=None,
+            load_default=None,
+        )
+
+        def sort_union_fields(field):
+            rv = copy.copy(field)
+            rv.union_fields = sorted(field.union_fields, key=repr)
+            return rv
+
+        self.assertFieldsEqual(sort_union_fields(result), sort_union_fields(expected))
+
     def test_newtype(self):
         self.assertFieldsEqual(
             field_for_schema(typing.NewType("UserId", int), default=0),