Avoid marking read_only fields as required (#133)

* Avoid marking read_only fields as required

Read only properties cannot be marked as required by a schema.

CONTRIBUTING.rst

@@ -36,7 +36,7 @@ You want to contribute some code? Great! Here are a few steps to get you started
       $ virtualenv venv
       $ source venv/bin/activate
       (venv) $ pip install -e .[validation]
-      (venv) $ pip install -rrequirements/dev.txt "Django>=1.11.7"
+      (venv) $ pip install -r requirements/dev.txt
 
 #. **Make your changes and check them against the test project**
 

src/drf_yasg/inspectors/field.py

@@ -67,10 +67,12 @@ class InlineSerializerInspector(SerializerInspector):
                     }
                     prop_kwargs = filter_none(prop_kwargs)
 
-                    properties[property_name] = self.probe_field_inspectors(
+                    child_schema = self.probe_field_inspectors(
                         child, ChildSwaggerType, use_references, **prop_kwargs
                     )
-                    if child.required:
+                    properties[property_name] = child_schema
+
+                    if child.required and not getattr(child_schema, 'read_only', False):
                         required.append(property_name)
 
                 result = SwaggerType(

testproj/articles/serializers.py

@@ -11,7 +11,7 @@ class ArticleSerializer(serializers.ModelSerializer):
         read_only=True,
     )
     uuid = serializers.UUIDField(help_text="should articles have UUIDs?", read_only=True)
-    cover_name = serializers.FileField(use_url=False, source='cover', read_only=True)
+    cover_name = serializers.FileField(use_url=False, source='cover', required=True)
     group = serializers.SlugRelatedField(slug_field='uuid', queryset=ArticleGroup.objects.all())
     original_group = serializers.SlugRelatedField(slug_field='uuid', read_only=True)