Reference only handling

lib/iknow_view_models/version.rb

@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module IknowViewModels
-  VERSION = '3.11.0'
+  VERSION = '3.12.0'
 end

lib/view_model/active_record/update_data.rb

@@ -522,6 +522,10 @@ def has_key?(name)
 
     delegate :new?, :child_update?, :auto_child_update?, to: :metadata
 
+    def reference_only?
+      attributes.empty? && associations.empty? && referenced_associations.empty?
+    end
+
     def self.parse_hashes(root_subtree_hashes, referenced_subtree_hashes = {})
       valid_reference_keys = referenced_subtree_hashes.keys.to_set
 

lib/view_model/active_record/update_operation.rb

@@ -44,6 +44,10 @@ def built?
       @built
     end
 
+    def reference_only?
+      update_data.reference_only? && reparent_to.nil? && reposition_to.nil?
+    end
+
     # Evaluate a built update tree, applying and saving changes to the models.
     def run!(deserialize_context:)
       raise ViewModel::DeserializationError::Internal.new('Internal error: UpdateOperation run before build') unless built?
@@ -123,9 +127,14 @@ def run!(deserialize_context:)
             end
           end
 
-          # validate
-          deserialize_context.run_callback(ViewModel::Callbacks::Hook::BeforeValidate, viewmodel)
-          viewmodel.validate!
+          # If a request makes no assertions about the model, we don't demand
+          # that the current state of the model is valid. This permits making
+          # edits to other models that refer to this model when this model is
+          # invalid.
+          unless reference_only? && !viewmodel.new_model?
+            deserialize_context.run_callback(ViewModel::Callbacks::Hook::BeforeValidate, viewmodel)
+            viewmodel.validate!
+          end
 
           # Save if the model has been altered. Covers not only models with
           # view changes but also lock version assertions.

lib/view_model/migration.rb

@@ -5,8 +5,18 @@ class ViewModel::Migration
   require 'view_model/migration/one_way_error'
   require 'view_model/migration/unspecified_version_error'
 
+  REFERENCE_ONLY_KEYS = [
+    ViewModel::TYPE_ATTRIBUTE,
+    ViewModel::ID_ATTRIBUTE,
+    ViewModel::VERSION_ATTRIBUTE,
+  ].freeze
+
   def up(view, _references)
-    raise ViewModel::Migration::OneWayError.new(view[ViewModel::TYPE_ATTRIBUTE], :up)
+    # Only a reference-only view may be (trivially) migrated up without an
+    # explicit migration.
+    if (view.keys - REFERENCE_ONLY_KEYS).present?
+      raise ViewModel::Migration::OneWayError.new(view[ViewModel::TYPE_ATTRIBUTE], :up)
+    end
   end
 
   def down(view, _references)