Fix InstanceSelectorBlocks in new wagtail versions

Author: jacobcolyvan

README.md

@@ -201,6 +201,9 @@ Much of this library was built atop of the work of others, specifically:
 
 ## Development notes
 
+### Upgrading Wagtail versions
+
+When upgrading this, ensure both `InstanceSelectorPanel` and `InstanceSelectorBlock` are tested manually via the example projects as they use different JavaScript integration approaches.
 
 ### Run tests
 

instance_selector/blocks.py

@@ -1,4 +1,3 @@
-from django import forms
 from django.utils.functional import cached_property, lazy
 from wagtail.blocks import ChooserBlock
 from wagtail.blocks.field_block import FieldBlockAdapter
@@ -10,8 +9,6 @@
 
 
 class InstanceSelectorBlock(ChooserBlock):
-    widget = forms.TextInput  # Dummy widget to satisfy Wagtail internals
-
     class Meta:
         icon = "placeholder"
 
@@ -29,9 +26,12 @@ def __init__(self, target_model, **kwargs):
     def target_model(self):
         return resolve_model_string(self._target_model)
 
+    @cached_property
+    def widget(self):
+        return InstanceSelectorWidget(self.target_model)
+
     def get_form_state(self, value):
-        widget = InstanceSelectorWidget(self.target_model)
-        return widget.get_value_data(value)
+        return self.widget.get_value_data(value)
 
     def get_instance_selector_icon(self):
         instance_selector = registry.get_instance_selector(self.target_model)

instance_selector/widgets.py

@@ -144,10 +144,16 @@ def get_js_config(self, id_, name):
 
     def build_attrs(self, *args, **kwargs):
         attrs = super().build_attrs(*args, **kwargs)
-        attrs["data-controller"] = "instance-selector"
-        attrs["data-instance-selector-config-value"] = json.dumps(
-            self.get_js_config(self.id_, self.name)
-        )
+
+        # Add Stimulus controller attributes for InstanceSelectorPanel usage.
+        # Skip during telepath serialisation for InstanceSelectorBlock
+        # (when id_ hasn't been set yet).
+        if hasattr(self, 'id_') and hasattr(self, 'name'):
+            attrs["data-controller"] = "instance-selector"
+            attrs["data-instance-selector-config-value"] = json.dumps(
+                self.get_js_config(self.id_, self.name)
+            )
+
         return attrs
 
     @property

tests/test_instance_selector.py

@@ -18,10 +18,9 @@
 
 class Tests(WebTest):
     """
-    Commented out tests are failing for the Wagtail 4.0 + releases.
-
-    Im not sure how relevant they are now that the widgets are being rendered
-    by javascript.
+    Tests for both InstanceSelectorPanel and InstanceSelectorBlock functionality:
+    - InstanceSelectorPanel is tested via ModelAdmin edit views.
+    - InstanceSelectorBlock is tested via StreamField edit views.
     """
 
     def setUp(self):