Rewrite wagtail.core.telepath to recursively pack constructor args

js_args and get_media methods no longer receive the context object, since they are not responsible for packing their own arguments.

wagtail/admin/rich_text/editors/draftail/__init__.py

@@ -86,7 +86,7 @@ class DraftailRichTextArea(widgets.HiddenInput):
 class DraftailRichTextAreaAdapter(WidgetAdapter):
     js_constructor = 'wagtail.widgets.DraftailRichTextArea'
 
-    def js_args(self, widget, context):
+    def js_args(self, widget):
         return [
             widget.options,
         ]

wagtail/admin/widgets/chooser.py

@@ -173,7 +173,7 @@ class AdminPageChooser(AdminChooser):
 class PageChooserAdapter(WidgetAdapter):
     js_constructor = 'wagtail.widgets.PageChooser'
 
-    def js_args(self, widget, context):
+    def js_args(self, widget):
         return [
             widget.render_html('__NAME__', None, attrs={'id': '__ID__'}),
             widget.id_for_label('__ID__'),

wagtail/core/blocks/field_block.py

@@ -74,7 +74,7 @@ class FieldBlock(Block):
 class FieldBlockAdapter(Adapter):
     js_constructor = 'wagtail.blocks.FieldBlock'
 
-    def js_args(self, block, context):
+    def js_args(self, block):
         classname = [
             'field',
             camelcase_to_underscore(block.field.__class__.__name__),
@@ -85,7 +85,7 @@ class FieldBlockAdapter(Adapter):
 
         return [
             block.name,
-            context.pack(block.field.widget),
+            block.field.widget,
             {
                 'label': block.label,
                 'required': block.required,

wagtail/core/blocks/list_block.py

@@ -143,10 +143,10 @@ class ListBlock(Block):
 class ListBlockAdapter(Adapter):
     js_constructor = 'wagtail.blocks.ListBlock'
 
-    def js_args(self, block, context):
+    def js_args(self, block):
         return [
             block.name,
-            context.pack(block.child_block),
+            block.child_block,
             {
                 'label': block.label, 'icon': block.meta.icon, 'classname': block.meta.form_classname,
                 'helpText': getattr(block.meta, 'help_text', None),

wagtail/core/blocks/stream_block.py

@@ -611,10 +611,10 @@ class StreamValue(MutableSequence):
 class StreamBlockAdapter(Adapter):
     js_constructor = 'wagtail.blocks.StreamBlock'
 
-    def js_args(self, block, context):
+    def js_args(self, block):
         return [
             block.name,
-            [context.pack(child) for child in block.child_blocks.values()],
+            block.child_blocks.values(),
             {
                 'label': block.label, 'required': block.required, 'icon': block.meta.icon,
                 'classname': block.meta.form_classname, 'helpText': getattr(block.meta, 'help_text', None),

wagtail/core/blocks/struct_block.py

@@ -214,10 +214,10 @@ class StructBlock(BaseStructBlock, metaclass=DeclarativeSubBlocksMetaclass):
 class StructBlockAdapter(Adapter):
     js_constructor = 'wagtail.blocks.StructBlock'
 
-    def js_args(self, block, context):
+    def js_args(self, block):
         return [
             block.name,
-            [context.pack(child) for child in block.child_blocks.values()],
+            block.child_blocks.values(),
             {
                 'label': block.label, 'required': block.required, 'icon': block.meta.icon,
                 'classname': block.meta.form_classname, 'helpText': getattr(block.meta, 'help_text', None),

wagtail/core/telepath.py

@@ -4,7 +4,73 @@ from django.forms import MediaDefiningClass
 from wagtail.admin.staticfiles import versioned_static
 
 
-adapters = {}
+DICT_RESERVED_KEYS = ['_type', '_args', '_dict']
+
+
+class BaseAdapter:
+    """Handles serialisation of a specific object type"""
+    def pack(self, obj, context):
+        """
+        Translates obj into serialisable form. Any media declarations that will be required for
+        deserialisation of the object should be passed to context.add_media().
+
+        This base implementation handles simple JSON-serialisable values such as strings, and
+        returns them unchanged.
+        """
+        return obj
+
+
+class DictAdapter(BaseAdapter):
+    """Handles serialisation of dicts"""
+    def pack(self, obj, context):
+        packed_obj = {
+            str(key): context.pack(val)
+            for key, val in obj.items()
+        }
+        if any(reserved_key in packed_obj for reserved_key in DICT_RESERVED_KEYS):
+            # this dict contains keys such as _type that would collide with our object notation,
+            # so wrap it in an explicit _dict to disambiguate
+            return {'_dict': packed_obj}
+        else:
+            return packed_obj
+
+
+class Adapter(BaseAdapter, metaclass=MediaDefiningClass):
+    """
+    Handles serialisation of custom types.
+    Subclasses should define:
+    - js_constructor: namespaced identifier for the JS constructor function that will unpack this
+        object
+    - js_args(obj): returns a list of (telepath-packable) arguments to be passed to the constructor
+    - get_media(obj) or class Media: media definitions necessary for unpacking
+
+    The adapter should then be registered with register(adapter, cls).
+    """
+
+    def get_media(self, obj):
+        return self.media
+
+    def pack(self, obj, context):
+        context.add_media(self.get_media(obj))
+        return {
+            '_type': self.js_constructor,
+            '_args': [context.pack(arg) for arg in self.js_args(obj)]
+        }
+
+
+adapters = {
+    # Primitive value types that are unchanged on serialisation
+    type(None): BaseAdapter(),
+    bool: BaseAdapter(),
+    int: BaseAdapter(),
+    float: BaseAdapter(),
+    str: BaseAdapter(),
+
+    # Container types to be serialised recursively
+    dict: DictAdapter(),
+    # Iterable types (list, tuple, odict_values...) do not have a reliably recognisable
+    # superclass, so will be handled as a special case
+}
 
 
 def register(adapter, cls):
@@ -16,21 +82,27 @@ class JSContext:
         self.media = forms.Media(js=[
             versioned_static('wagtailadmin/js/telepath/telepath.js')
         ])
-        self.objects = {}
+
+        # Keep track of media declarations that have already added to self.media - ones that
+        # exactly match a previous one can be ignored, as they will not affect the result
+        self.media_fragments = set([str(self.media)])
+
+    def add_media(self, media):
+        media_str = str(media)
+        if media_str not in self.media_fragments:
+            self.media += media
+            self.media_fragments.add(media_str)
 
     def pack(self, obj):
         for cls in type(obj).__mro__:
             adapter = adapters.get(cls)
             if adapter:
-                break
+                return adapter.pack(obj, self)
 
-        if adapter is None:
-            raise Exception("don't know how to add object to JS context: %r" % obj)
+        # as fallback, try handling as an iterable
+        try:
+            return [self.pack(item) for item in obj]
+        except TypeError:
+            pass
 
-        self.media += adapter.get_media(obj, self)
-        return [adapter.js_constructor, *adapter.js_args(obj, self)]
-
-
-class Adapter(metaclass=MediaDefiningClass):
-    def get_media(self, obj, context):
-        return self.media
+        raise Exception("don't know how to pack object: %r" % obj)

wagtail/core/widget_adapters.py

@@ -13,14 +13,14 @@ from wagtail.core.telepath import Adapter, register
 class WidgetAdapter(Adapter):
     js_constructor = 'wagtail.widgets.Widget'
 
-    def js_args(self, widget, context):
+    def js_args(self, widget):
         return [
             widget.render('__NAME__', None, attrs={'id': '__ID__'}),
             widget.id_for_label('__ID__'),
         ]
 
-    def get_media(self, widget, context):
-        media = super().get_media(widget, context)
+    def get_media(self, widget):
+        media = super().get_media(widget)
         return media + widget.media
 
     class Media:

wagtail/documents/widgets.py

@@ -62,7 +62,7 @@ class AdminDocumentChooser(AdminChooser):
 class DocumentChooserAdapter(WidgetAdapter):
     js_constructor = 'wagtail.documents.widgets.DocumentChooser'
 
-    def js_args(self, widget, context):
+    def js_args(self, widget):
         return [
             widget.render_html('__NAME__', None, attrs={'id': '__ID__'}),
             widget.id_for_label('__ID__'),

wagtail/images/widgets.py

@@ -71,7 +71,7 @@ class AdminImageChooser(AdminChooser):
 class ImageChooserAdapter(WidgetAdapter):
     js_constructor = 'wagtail.images.widgets.ImageChooser'
 
-    def js_args(self, widget, context):
+    def js_args(self, widget):
         return [
             widget.render_html('__NAME__', None, attrs={'id': '__ID__'}),
             widget.id_for_label('__ID__'),

wagtail/snippets/widgets.py

@@ -79,7 +79,7 @@ class AdminSnippetChooser(AdminChooser):
 class SnippetChooserAdapter(WidgetAdapter):
     js_constructor = 'wagtail.snippets.widgets.SnippetChooser'
 
-    def js_args(self, widget, context):
+    def js_args(self, widget):
         return [
             widget.render_html('__NAME__', None, attrs={'id': '__ID__'}),
             widget.id_for_label('__ID__'), widget.model_string