Merge pull request #10912 from alphagov/avoid-accidentally-overwriting-base-path

Check if existing base path is associated with same content ID [WHIT-1842]

Author: GDSNewt

features/support/publishing_api.rb

@@ -19,6 +19,8 @@
     .to_return(body: { links: {} }.to_json)
   stub_request(:get, %r{\A#{Plek.find('publishing-api')}/v2/expanded-links})
     .to_return(body: { expanded_links: {} }.to_json)
+  # Prevent publishing API base path checks from interfering with tests
+  Whitehall::PublishingApi.stubs(:ensure_base_path_is_associated_with_this_content_id!).returns(nil)
 end
 
 World(GdsApi::TestHelpers::PublishingApi)

lib/whitehall/publishing_api.rb

@@ -69,6 +69,8 @@ def self.save_draft_translation(
 
         content.merge!(bulk_publishing: true) if bulk_publishing
 
+        ensure_base_path_is_associated_with_this_content_id!(content[:base_path], model_instance.content_id)
+
         Services.publishing_api.put_content(presenter.content_id, content)
       end
     rescue GdsApi::HTTPUnprocessableEntity => e
@@ -178,5 +180,12 @@ def self.assert_public_edition!(instance)
         raise UnpublishableInstanceError, "#{instance.class} with ID #{instance.id} is not publishable"
       end
     end
+
+    def self.ensure_base_path_is_associated_with_this_content_id!(base_path, content_id)
+      existing_content_id = Services.publishing_api.lookup_content_id(base_path:)
+      return if existing_content_id.nil? || existing_content_id == content_id
+
+      raise UnpublishableInstanceError, "Cannot save draft (content_id #{content_id}). There is existing content at the '#{base_path}' route, under a different content_id (#{existing_content_id}). Try changing your title to resolve the conflict."
+    end
   end
 end

test/test_helper.rb

@@ -76,6 +76,8 @@ class ActiveSupport::TestCase
     Services.publishing_api.stubs(:get_events_for_content_id).returns([])
     Services.stubs(:asset_manager).returns(stub_everything("asset-manager"))
     TaxonValidator.any_instance.stubs(:validate)
+    # Prevent publishing API base path checks from interfering with tests
+    Whitehall::PublishingApi.stubs(:ensure_base_path_is_associated_with_this_content_id!).returns(nil)
   end
 
   teardown do

test/unit/lib/whitehall/publishing_api_test.rb

@@ -274,16 +274,46 @@ class Whitehall::PublishingApiTest < ActiveSupport::TestCase
     assert_equal english_path, PublishingApiUnscheduleWorker.jobs[1]["args"].first
   end
 
-  test ".save_draft publishes a draft edition" do
+  test ".save_draft publishes a draft edition if no content exists at the route yet" do
     draft_edition = create(:draft_case_study)
     payload = PublishingApiPresenters.presenter_for(draft_edition)
     request = stub_publishing_api_put_content(payload.content_id, payload.content)
+    Whitehall::PublishingApi.unstub(:ensure_base_path_is_associated_with_this_content_id!)
+    Services.publishing_api.expects(:lookup_content_id).with(base_path: draft_edition.public_path).returns(nil)
 
     Whitehall::PublishingApi.save_draft(draft_edition)
 
     assert_requested request
   end
 
+  test ".save_draft publishes a draft edition if there is a live content item with the same base path and same content ID" do
+    draft_edition = create(:draft_case_study)
+    payload = PublishingApiPresenters.presenter_for(draft_edition)
+    request = stub_publishing_api_put_content(payload.content_id, payload.content)
+    Whitehall::PublishingApi.unstub(:ensure_base_path_is_associated_with_this_content_id!)
+    Services.publishing_api.expects(:lookup_content_id).with(base_path: draft_edition.public_path).returns(payload.content_id)
+
+    Whitehall::PublishingApi.save_draft(draft_edition)
+
+    assert_requested request
+  end
+
+  test ".save_draft raises exception if there is a live content item with the same base path but different content ID" do
+    ConfigurableDocumentType.setup_test_types(build_configurable_document_type("test_type"))
+    edition = create(:draft_standard_edition)
+    Whitehall::PublishingApi.unstub(:ensure_base_path_is_associated_with_this_content_id!)
+    Services.publishing_api.expects(:lookup_content_id).with(base_path: edition.public_path).returns("different-content-id")
+
+    error = assert_raises Whitehall::UnpublishableInstanceError do
+      Whitehall::PublishingApi.save_draft(edition)
+    end
+
+    assert_equal(
+      "Cannot save draft (content_id #{edition.content_id}). There is existing content at the '#{edition.public_path}' route, under a different content_id (different-content-id). Try changing your title to resolve the conflict.",
+      error.message,
+    )
+  end
+
   test ".publish_redirect_async publishes a redirect to the Publishing API" do
     document = create(:document)
     destination = "/government/people/milli-vanilli"