Remove current children from virtual object before initializing conte…

…nt metadata

This prevents a situation where lots of manual clean-up is required to remove old children from a parent.

Fixes #409

app/services/reset_content_metadata_service.rb

@@ -1,15 +1,33 @@
 # frozen_string_literal: true
 
-# Clears the contentMetadata datastream to the default, wiping out any members.
-# item MUST allow modification, or save! will raise error
+# Clears the contentMetadata datastream to the default, wiping out any members,
+# and severing relationships bidirectionally.
+#
+# NOTE: item MUST allow modification, or `save!` will raise error
 class ResetContentMetadataService
-  def initialize(item:, type: 'image')
+  DEFAULT_ITEM_TYPE = 'image'
+
+  attr_reader :item, :type
+
+  def initialize(item:, type: DEFAULT_ITEM_TYPE)
     @item = item
     @type = type
   end
 
   def reset
-    @item.contentMetadata.content = "<contentMetadata objectId='#{@item.id}' type='#{@type}'/>"
-    @item.save!
+    disown_current_children!
+
+    item.contentMetadata.content = "<contentMetadata objectId='#{item.id}' type='#{type}'/>"
+    item.save!
+  end
+
+  private
+
+  def disown_current_children!
+    item.contentMetadata.ng_xml.xpath('//resource/relationship/@objectId').map(&:content).each do |child_id|
+      child = Dor::Item.find(child_id)
+      child.clear_relationship(:is_constituent_of)
+      child.save! if child.relationships_are_dirty?
+    end
   end
 end

spec/services/reset_content_metadata_service_spec.rb

@@ -0,0 +1,109 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe ResetContentMetadataService do
+  subject(:service) { described_class.new(args) }
+
+  let(:args) { { item: parent } }
+  let(:child1) do
+    instance_double(Dor::Item,
+                    id: 'druid:child1',
+                    relationships_are_dirty?: true,
+                    save!: true,
+                    clear_relationship: nil)
+  end
+  let(:child2) do
+    instance_double(Dor::Item,
+                    id: 'druid:child2',
+                    relationships_are_dirty?: true,
+                    save!: true,
+                    clear_relationship: nil)
+  end
+  let(:content_metadata) do
+    instance_double(Dor::ContentMetadataDS,
+                    ng_xml: xml,
+                    'content=': nil)
+  end
+  let(:default_content_xml) { "<contentMetadata objectId='druid:parent' type='image'/>" }
+  let(:parent) do
+    instance_double(Dor::Item,
+                    id: 'druid:parent',
+                    contentMetadata: content_metadata,
+                    save!: true)
+  end
+  let(:predicate) { :is_constituent_of }
+
+  describe '.new' do
+    let(:xml) { '<notUsed/>' }
+
+    context 'when only the `item:` argument is included' do
+      it 'uses the supplied `item` attribute' do
+        expect(service.item).to eq(parent)
+      end
+
+      it 'uses the default `type` attribute' do
+        expect(service.type).to eq(described_class::DEFAULT_ITEM_TYPE)
+      end
+    end
+
+    context 'when `item:` and `type:` arguments are included' do
+      let(:args) { { item: parent, type: custom_type } }
+      let(:custom_type) { 'book' }
+
+      it 'uses the supplied `type` attribute' do
+        expect(service.type).to eq(custom_type)
+      end
+    end
+  end
+
+  describe '#reset' do
+    context 'without child relationships recorded in content metadata' do
+      let(:xml) { Nokogiri::XML(default_content_xml) }
+
+      before do
+        allow(Dor::Item).to receive(:find)
+      end
+
+      it 'resets content metadata without touching children' do
+        service.reset
+        expect(content_metadata).to have_received(:content=).with(default_content_xml).once
+        expect(parent).to have_received(:save!).once
+        expect(Dor::Item).not_to have_received(:find)
+      end
+    end
+
+    context 'with child relationships recorded in content metadata' do
+      let(:xml) do
+        Nokogiri::XML(
+          <<~XML
+            <contentMetadata objectId="druid:parent1" type="image">
+              <resource sequence="1" id="druid:child1_1" type="image">
+                <relationship type="alsoAvailableAs" objectId="druid:child1"/>
+              </resource>
+              <resource sequence="2" id="druid:child2_2" type="image">
+                <relationship type="alsoAvailableAs" objectId="druid:child2"/>
+              </resource>
+            </contentMetadata>
+          XML
+        )
+      end
+
+      before do
+        allow(Dor::Item).to receive(:find).with(child1.id).and_return(child1)
+        allow(Dor::Item).to receive(:find).with(child2.id).and_return(child2)
+      end
+
+      it 'severs the child relationships and resets content metadata' do
+        service.reset
+        expect(content_metadata).to have_received(:content=).with(default_content_xml).once
+        expect(parent).to have_received(:save!).once
+        expect(Dor::Item).to have_received(:find).exactly(2).times
+        expect(child1).to have_received(:clear_relationship).with(predicate).once
+        expect(child2).to have_received(:clear_relationship).with(predicate).once
+        expect(child1).to have_received(:save!)
+        expect(child2).to have_received(:save!)
+      end
+    end
+  end
+end