fix up the PATCH scenario with the char_prompts in WFJT node

awx/api/serializers.py

@@ -2270,14 +2270,27 @@ class WorkflowJobTemplateNodeSerializer(WorkflowNodeBaseSerializer):
 
     def to_internal_value(self, data):
         internal_value = super(WorkflowNodeBaseSerializer, self).to_internal_value(data)
-        char_prompts = self.extract_char_prompts(data)
+        view = self.context.get('view', None)
+        request_method = None
+        if view and view.request:
+            request_method = view.request.method
+        if request_method in ['PATCH']:
+            obj = view.get_object()
+            char_prompts = copy.copy(obj.char_prompts)
+            char_prompts.update(self.extract_char_prompts(data))
+        else:
+            char_prompts = self.extract_char_prompts(data)
+        for fd in copy.copy(char_prompts):
+            if char_prompts[fd] is None:
+                char_prompts.pop(fd)
         internal_value['char_prompts'] = char_prompts
         return internal_value
 
     def extract_char_prompts(self, data):
         char_prompts = {}
         for fd in ['job_type', 'job_tags', 'skip_tags', 'limit']:
-            if data.get(fd, None):
+            # Accept null values, if given
+            if fd in data:
                 char_prompts[fd] = data[fd]
         return char_prompts
 

awx/main/migrations/0037_v310_workflow_rbac_prompts.py

@@ -10,7 +10,7 @@ import awx.main.fields
 class Migration(migrations.Migration):
 
     dependencies = [
-        ('main', '0035_v310_jobevent_uuid'),
+        ('main', '0036_v310_remove_tower_settings'),
     ]
 
     operations = [

awx/main/tests/unit/api/serializers/test_workflow_serializers.py

@@ -104,6 +104,42 @@ class TestWorkflowJobTemplateNodeSerializerGetRelated():
         assert 'workflow_job_template' not in related
 
 
+class FakeView:
+    def __init__(self, obj):
+        self.obj = obj
+
+    def get_object(self):
+        return self.obj
+
+class FakeRequest:
+    pass
+
+class TestWorkflowJobTemplateNodeSerializerCharPrompts():
+
+    @pytest.fixture
+    def WFJT_serializer(self):
+        serializer = WorkflowJobTemplateNodeSerializer()
+        node = WorkflowJobTemplateNode(pk=1)
+        node.char_prompts = {'limit': 'webservers'}
+        view = FakeView(node)
+        view.request = FakeRequest()
+        view.request.method = "PATCH"
+        serializer.context = {'view': view}
+        return serializer
+
+    def test_change_single_field(self, WFJT_serializer):
+        "Test that a single prompt field can be changed without affecting other fields"
+        internal_value = WFJT_serializer.to_internal_value({'job_type': 'check'})
+        assert internal_value['char_prompts']['job_type'] == 'check'
+        assert internal_value['char_prompts']['limit'] == 'webservers'
+
+    def test_null_single_field(self, WFJT_serializer):
+        "Test that a single prompt field can be removed without affecting other fields"
+        internal_value = WFJT_serializer.to_internal_value({'job_type': None})
+        assert 'job_type' not in internal_value['char_prompts']
+        assert internal_value['char_prompts']['limit'] == 'webservers'
+
+
 @mock.patch('awx.api.serializers.WorkflowNodeBaseSerializer.get_related', lambda x,y: {})
 class TestWorkflowJobNodeSerializerGetRelated():
     @pytest.fixture