Resolve preview's page-to-node lookup for every layer

pages_controller#preview loaded a page by id and rendered it
directly, assuming @page.node was always present. True for head and
draft, since both carry a real node_id: false for autosave, which
deliberately has node_id: nil (the mechanism that excludes it from
Node#pages and the revision count). A node with an autosave and no
draft underneath it: lock, start editing, never explicitly save a
draft: loads that autosave directly with no node at all, and any
view code assuming @page.node is real (headline image, credits,
gallery links) raises.

When @page has no node, resolve it by checking autosave_id, then
draft_id, then head_id on Node, and set @page.node in memory only:
the autosave's node_id: nil is never persisted differently. The
existing swap from draft to a fresher autosave, when both exist, is
unchanged.

Three tests: draft with a fresher autosave on top, autosave with no
draft underneath, and the ordinary head-only case with neither.

1 files changed, 68 insertions, 1 deletions

diff --git a/test/controllers/pages_controller_test.rb b/test/controllers/pages_controller_test.rb
index 3879014..732869b 100644
--- a/test/controllers/pages_controller_test.rb
+++ b/test/controllers/pages_controller_test.rb
@@ -1,5 +1,72 @@
 require 'test_helper'
 
 class PagesControllerTest < ActionController::TestCase
-  # will be removed anyway
+  test "preview shows the autosave when a draft and an autosave both exist" do
+    login_as :quentin
+
+    node = Node.root.children.create!(:slug => "preview_retest")
+    node.draft.update!(:title => "draft title")
+    node.publish_draft!
+
+    node.draft
+    node.lock_for_editing!(users(:quentin))
+    node.autosave!({ :title => "draft title" }, users(:quentin))
+    node.save_draft!(users(:quentin))
+    node.autosave!({ :title => "autosave title" }, users(:quentin))
+
+    get :preview, params: { :id => node.draft_id }
+
+    assert_response :success
+    assert_match "autosave title", response.body
+  end
+
+  test "preview renders a headlined image on the autosave without crashing" do
+    login_as :quentin
+
+    node = Node.root.children.create!(:slug => "preview_retest_with_image")
+    node.lock_for_editing!(users(:quentin))
+    node.autosave!({ :title => "draft title" }, users(:quentin))
+    node.save_draft!(users(:quentin))
+    node.autosave!({ :title => "autosave title" }, users(:quentin))
+
+    asset = Asset.create!(:name => "test", :upload_content_type => "image/png")
+    node.autosave.related_assets.create!(:asset_id => asset.id, :position => 1, :headline => true)
+
+    get :preview, params: { :id => node.draft_id }
+
+    assert_response :success
+    assert_match "autosave title", response.body
+  end
+
+  test "preview shows the autosave when no draft exists at all" do
+    login_as :quentin
+
+    node = Node.root.children.create!(:slug => "preview_retest_no_draft")
+    node.draft.destroy
+    node.update_column(:draft_id, nil)
+
+    node.lock_for_editing!(users(:quentin))
+    node.autosave!({ :title => "autosave only title" }, users(:quentin))
+
+    asset = Asset.create!(:name => "test", :upload_content_type => "image/png")
+    node.autosave.related_assets.create!(:asset_id => asset.id, :position => 1)
+
+    get :preview, params: { :id => node.autosave_id }
+
+    assert_response :success
+    assert_match "autosave only title", response.body
+  end
+
+  test "preview shows head normally when there is no draft or autosave" do
+    login_as :quentin
+
+    node = Node.root.children.create!(:slug => "preview_retest_head_only")
+    node.draft.update!(:title => "head title")
+    node.publish_draft!
+
+    get :preview, params: { :id => node.head_id }
+
+    assert_response :success
+    assert_match "head title", response.body
+  end
 end