Deprecate writing directly to attributes hash.

lib/valkyrie/resource.rb

@@ -97,9 +97,35 @@ def optimistic_locking_enabled?
       self.class.optimistic_locking_enabled?
     end
 
+    class DeprecatedHashWrite < Hash
+      def []=(_k, _v)
+        warn "[DEPRECATION] Writing directly to attributes has been deprecated." \
+          " Please use #set_value(k, v) instead." \
+          " In the next major version, this hash will be frozen. \n" \
+          "Called from #{Gem.location_of_caller.join(':')}"
+        super
+      end
+
+      def delete(*_args)
+        warn "[DEPRECATION] Writing directly to attributes has been deprecated." \
+          " Please use #set_value(k, v) instead." \
+          " In the next major version, this hash will be frozen. \n" \
+          "Called from #{Gem.location_of_caller.join(':')}"
+        super
+      end
+
+      def delete_if(*_args)
+        warn "[DEPRECATION] Writing directly to attributes has been deprecated." \
+          " Please use #set_value(k, v) instead." \
+          " In the next major version, this hash will be frozen. \n" \
+          "Called from #{Gem.location_of_caller.join(':')}"
+        super
+      end
+    end
+
     # @return [Hash] Hash of attributes
     def attributes
-      to_h.freeze
+      DeprecatedHashWrite.new.merge(to_h)
     end
 
     # @param name [Symbol] Attribute name

lib/valkyrie/specs/shared_specs/resource.rb

@@ -137,7 +137,9 @@ class MyCustomResource < Valkyrie::Resource
 
       expect(resource.attributes).to have_key(:bla)
       expect(resource.attributes[:internal_resource]).to eq resource_klass.to_s
-      expect { resource.attributes[:internal_resource] = "bla" }.to raise_error "can't modify frozen Hash"
+      expect { resource.attributes[:internal_resource] = "bla" }.to output(/\[DEPRECATION\]/).to_stderr
+      expect { resource.attributes.delete_if { true } }.to output(/\[DEPRECATION\]/).to_stderr
+      expect { resource.attributes.delete(:internal_resource) }.to output(/\[DEPRECATION\]/).to_stderr
 
       resource_klass.schema.delete(:bla)
     end