Merge pull request #66 from stevejalim/pluggable-serializers

Support custom/pluggable serializers

docs/settings.md

@@ -139,3 +139,36 @@ def register_my_custom_adapter():
     return {models.Field: MyCustomAdapter}
 
 ```
+
+
+### `register_custom_serializers`
+
+In exceptional cases, such as limiting the fields you export to only a subset of the content, you may need to use a custom serializer instead of the default `PageSerializer`.
+You can register a custom serializer by using the `register_custom_serializers` hook.
+A function registered with this hook should return a dictionary which maps model classes to serializer classes (note that with inheritance, the serializer registered with the closest ancestor class will be used).
+For example, to register a custom serializer against `myapp.MyModel`:
+
+```python
+# <my_app>/wagtail_hooks.py
+
+
+from wagtail.core import hooks
+from wagtail_transfer.serializers import PageSerializer
+
+from myapp.models import MyModel
+
+class MyModelCustomSerializer(PageSerializer):
+
+    ignored_fields = PageSerializer.ignored_fields + [
+        'secret_field_1',
+        'environment_specific_data_field_123',
+        ...
+    ]
+    pass
+
+
+@hooks.register('register_custom_serializers')
+def register_my_custom_serializer():
+    return {MyModel: MyModelCustomSerializer}
+
+```

wagtail_transfer/field_adapters.py

@@ -230,7 +230,7 @@ def get_object_deletions(self, instance, value, context):
 
             return {child for child in self._get_related_objects(instance) if child.pk not in matched_destination_ids}
         return set()
-    
+
     def get_objects_to_serialize(self, instance):
         if self.is_parental:
             return getattr(instance, self.name).all()
@@ -372,14 +372,15 @@ class AdapterRegistry:
     def __init__(self):
         self._scanned_for_adapters = False
         self.adapters_by_field_class = {}
-    
+
     def _scan_for_adapters(self):
         adapters = dict(self.BASE_ADAPTERS_BY_FIELD_CLASS)
 
         for fn in hooks.get_hooks('register_field_adapters'):
             adapters.update(fn())
-    
+
         self.adapters_by_field_class = adapters
+        self._scanned_for_adapters = True
 
     @lru_cache(maxsize=None)
     def get_field_adapter(self, field):

wagtail_transfer/serializers.py

@@ -3,8 +3,8 @@
 from django.core.exceptions import ObjectDoesNotExist
 from django.db import models
 from django.db.models.constants import LOOKUP_SEP
-from modelcluster.fields import ParentalKey
 from treebeard.mp_tree import MP_Node
+from wagtail.core import hooks
 from wagtail.core.models import Page
 
 from .field_adapters import adapter_registry
@@ -85,7 +85,7 @@ def __init__(self, model):
 
             # ignore primary keys (including MTI parent pointers)
             if getattr(field, 'primary_key', False):
-                    continue
+                continue
 
             adapter = adapter_registry.get_field_adapter(field)
 
@@ -95,7 +95,6 @@ def __init__(self, model):
 
         self.field_adapters = [adapter for adapter in field_adapters if adapter.name not in adapter_managed_fields]
 
-
     def get_objects_by_ids(self, ids):
         """
         Given a list of IDs, return a list of model instances that we can
@@ -169,17 +168,37 @@ def get_objects_by_ids(self, ids):
         return self.model.objects.filter(pk__in=ids).specific()
 
 
-SERIALIZERS_BY_MODEL_CLASS = {
-    models.Model: ModelSerializer,
-    MP_Node: TreeModelSerializer,
-    Page: PageSerializer,
-}
+class SerializerRegistry:
+    BASE_SERIALIZERS_BY_MODEL_CLASS = {
+        models.Model: ModelSerializer,
+        MP_Node: TreeModelSerializer,
+        Page: PageSerializer,
+    }
+
+    def __init__(self):
+        self._scanned_for_serializers = False
+        self.serializers_by_model_class = {}
+
+    def _scan_for_serializers(self):
+        serializers = dict(self.BASE_SERIALIZERS_BY_MODEL_CLASS)
+
+        for fn in hooks.get_hooks('register_custom_serializers'):
+            serializers.update(fn())
+
+        self.serializers_by_model_class = serializers
+        self._scanned_for_serializers = True
+
+    @lru_cache(maxsize=None)
+    def get_model_serializer(self, model):
+        # find the serializer class for the most specific class in the model's inheritance tree
+
+        if not self._scanned_for_serializers:
+            self._scan_for_serializers()
+
+        for cls in model.__mro__:
+            if cls in self.serializers_by_model_class:
+                serializer_class = self.serializers_by_model_class[cls]
+                return serializer_class(model)
 
 
-@lru_cache(maxsize=None)
-def get_model_serializer(model):
-    # find the serializer class for the most specific class in the model's inheritance tree
-    for cls in model.__mro__:
-        if cls in SERIALIZERS_BY_MODEL_CLASS:
-            serializer_class = SERIALIZERS_BY_MODEL_CLASS[cls]
-            return serializer_class(model)
+serializer_registry = SerializerRegistry()

wagtail_transfer/views.py

@@ -16,7 +16,7 @@
 from .locators import get_locator_for_model
 from .models import get_model_for_path
 from .operations import ImportPlanner
-from .serializers import get_model_serializer
+from .serializers import serializer_registry
 from .vendor.wagtail_admin_api.serializers import AdminPageSerializer
 from .vendor.wagtail_admin_api.views import PagesAdminAPIViewSet
 
@@ -43,7 +43,7 @@ def pages_for_export(request, root_page_id):
 
     while models_to_serialize:
         model = models_to_serialize.pop()
-        serializer = get_model_serializer(type(model))
+        serializer = serializer_registry.get_model_serializer(type(model))
         objects.append(serializer.serialize(model))
         object_references.update(serializer.get_object_references(model))
         models_to_serialize.update(serializer.get_objects_to_serialize(model).difference(serialized_models))
@@ -92,7 +92,7 @@ def models_for_export(request, model_path, object_id=None):
 
     while models_to_serialize:
         model = models_to_serialize.pop()
-        serializer = get_model_serializer(type(model))
+        serializer = serializer_registry.get_model_serializer(type(model))
         objects.append(serializer.serialize(model))
         object_references.update(serializer.get_object_references(model))
         models_to_serialize.update(serializer.get_objects_to_serialize(model).difference(serialized_models))
@@ -134,12 +134,12 @@ def objects_for_export(request):
 
     for model_path, ids in request_data.items():
         model = get_model_for_path(model_path)
-        serializer = get_model_serializer(model)
+        serializer = serializer_registry.get_model_serializer(model)
 
         models_to_serialize.update(serializer.get_objects_by_ids(ids))
         while models_to_serialize:
             instance = models_to_serialize.pop()
-            serializer = get_model_serializer(type(instance))
+            serializer = serializer_registry.get_model_serializer(type(instance))
             objects.append(serializer.serialize(instance))
             object_references.update(serializer.get_object_references(instance))
             models_to_serialize.update(serializer.get_objects_to_serialize(instance).difference(serialized_models))