Fix validation of fields in partial updates

For some reason validation of fields in partial updates wasn't
triggered. Investigating I found that in the case of partial updates
every field is marked as not-required when constructing the serializer:

rest_framework/fields.py:173
        if self.partial:
            self.required = False

but I couldn't a find where the place (if such a place exists) where the
fields that came in the PATCH request are marked as required again in
order to trigger their validation.

Basically this hotfix does that, mark as required every field present in
the PATCH request so their validation is performed.

taiga/base/serializers.py

@@ -118,3 +118,12 @@ class Serializer(serializers.Serializer):
                     self._errors['non_field_errors'] = err.messages
 
         return attrs
+
+
+class ModelSerializer(serializers.ModelSerializer):
+    def perform_validation(self, attrs):
+        for attr in attrs:
+            field = self.fields.get(attr, None)
+            if field:
+                field.required = True
+        return super().perform_validation(attrs)

taiga/projects/serializers.py

@@ -18,7 +18,7 @@ from os import path
 from rest_framework import serializers
 from django.utils.translation import ugettext_lazy as _
 
-from taiga.base.serializers import JsonField, PgArrayField
+from taiga.base.serializers import JsonField, PgArrayField, ModelSerializer
 from taiga.users.models import Role, User
 from taiga.users.services import get_photo_or_gravatar_url
 from taiga.users.serializers import UserSerializer
@@ -32,12 +32,12 @@ from . validators import ProjectExistsValidator
 
 # User Stories common serializers
 
-class PointsSerializer(serializers.ModelSerializer):
+class PointsSerializer(ModelSerializer):
     class Meta:
         model = models.Points
 
 
-class UserStoryStatusSerializer(serializers.ModelSerializer):
+class UserStoryStatusSerializer(ModelSerializer):
     class Meta:
         model = models.UserStoryStatus
 
@@ -61,36 +61,36 @@ class UserStoryStatusSerializer(serializers.ModelSerializer):
 
 # Task common serializers
 
-class TaskStatusSerializer(serializers.ModelSerializer):
+class TaskStatusSerializer(ModelSerializer):
     class Meta:
         model = models.TaskStatus
 
 
 # Issues common serializers
 
-class SeveritySerializer(serializers.ModelSerializer):
+class SeveritySerializer(ModelSerializer):
     class Meta:
         model = models.Severity
 
 
-class PrioritySerializer(serializers.ModelSerializer):
+class PrioritySerializer(ModelSerializer):
     class Meta:
         model = models.Priority
 
 
-class IssueStatusSerializer(serializers.ModelSerializer):
+class IssueStatusSerializer(ModelSerializer):
     class Meta:
         model = models.IssueStatus
 
 
-class IssueTypeSerializer(serializers.ModelSerializer):
+class IssueTypeSerializer(ModelSerializer):
     class Meta:
         model = models.IssueType
 
 
 # Projects
 
-class MembershipSerializer(serializers.ModelSerializer):
+class MembershipSerializer(ModelSerializer):
     role_name = serializers.CharField(source='role.name', required=False, read_only=True)
     full_name = serializers.CharField(source='user.get_full_name', required=False, read_only=True)
     color = serializers.CharField(source='user.color', required=False, read_only=True)
@@ -121,7 +121,7 @@ class MembershipSerializer(serializers.ModelSerializer):
             return UserSerializer(queryset).data
 
 
-class ProjectMembershipSerializer(serializers.ModelSerializer):
+class ProjectMembershipSerializer(ModelSerializer):
     role_name = serializers.CharField(source='role.name', required=False)
     full_name = serializers.CharField(source='user.get_full_name', required=False)
     color = serializers.CharField(source='user.color', required=False)
@@ -134,7 +134,7 @@ class ProjectMembershipSerializer(serializers.ModelSerializer):
         return get_photo_or_gravatar_url(project.user)
 
 
-class ProjectSerializer(serializers.ModelSerializer):
+class ProjectSerializer(ModelSerializer):
     tags = PgArrayField(required=False)
     anon_permissions = PgArrayField(required=False)
     public_permissions = PgArrayField(required=False)
@@ -182,13 +182,13 @@ class ProjectDetailSerializer(ProjectSerializer):
         return serializer.data
 
 
-class ProjectRoleSerializer(serializers.ModelSerializer):
+class ProjectRoleSerializer(ModelSerializer):
     class Meta:
         model = Role
         fields = ('id', 'name', 'slug', 'order', 'computable')
 
 
-class RoleSerializer(serializers.ModelSerializer):
+class RoleSerializer(ModelSerializer):
     members_count = serializers.SerializerMethodField("get_members_count")
     permissions = PgArrayField(required=False)
 
@@ -200,7 +200,7 @@ class RoleSerializer(serializers.ModelSerializer):
         return obj.memberships.count()
 
 
-class ProjectTemplateSerializer(serializers.ModelSerializer):
+class ProjectTemplateSerializer(ModelSerializer):
     default_options = JsonField(required=False, label=_("Default options"))
     us_statuses = JsonField(required=False, label=_("User story's statuses"))
     points = JsonField(required=False, label=_("Points"))
@@ -215,7 +215,7 @@ class ProjectTemplateSerializer(serializers.ModelSerializer):
         model = models.ProjectTemplate
 
 
-class StarredSerializer(serializers.ModelSerializer):
+class StarredSerializer(ModelSerializer):
     class Meta:
         model = models.Project
         fields = ['id', 'name', 'slug']