[WHIT-3631] Fall back to draft content store for unpublished document collection links

app/models/document_collection_non_whitehall_link/govuk_url.rb

@@ -41,7 +41,7 @@ def content_id
   def content_item_from_content_store
     path = parsed_url.path
 
-    item = Services.content_store.content_item(path).to_h
+    item = content_item_for(path)
 
     if item["base_path"] != path && item["document_type"] != "guide"
       raise GdsApi::HTTPNotFound, 404
@@ -51,4 +51,11 @@ def content_item_from_content_store
   rescue GdsApi::ContentStore::ItemNotFound
     raise GdsApi::HTTPNotFound, 404
   end
+
+  def content_item_for(path)
+    Services.content_store.content_item(path).to_h
+  rescue GdsApi::ContentStore::ItemNotFound
+    # Fall back to the draft content store for unpublished content
+    Services.draft_content_store.content_item(path).to_h
+  end
 end

lib/services.rb

@@ -16,6 +16,13 @@ def self.content_store
     @content_store ||= GdsApi::ContentStore.new(Plek.find("content-store"))
   end
 
+  def self.draft_content_store
+    @draft_content_store ||= GdsApi::ContentStore.new(
+      Plek.find("draft-content-store"),
+      bearer_token: ENV.fetch("DRAFT_CONTENT_STORE_BEARER_TOKEN", "example"),
+    )
+  end
+
   def self.asset_manager
     @asset_manager ||= GdsApi::AssetManager.new(
       Plek.find("asset-manager"),

test/unit/app/models/document_collection_non_whitehall_link/govuk_url_test.rb

@@ -98,8 +98,27 @@ class DocumentCollectionNonWhitehallLink::GovukUrlTest < ActiveSupport::TestCase
     assert url.valid?
   end
 
-  test "should be invalid when content store returns a 404" do
+  test "should be valid for an unpublished URL found only in the draft content store" do
+    draft_content_id = SecureRandom.uuid
+    Services.content_store.stubs(:content_item).with("/unpublished").raises(GdsApi::ContentStore::ItemNotFound.new(404))
+    Services.draft_content_store.stubs(:content_item).with("/unpublished").returns(
+      "content_id" => draft_content_id,
+      "title" => "Unpublished",
+      "base_path" => "/unpublished",
+      "publishing_app" => "whitehall",
+    )
+
+    url = DocumentCollectionNonWhitehallLink::GovukUrl.new(
+      url: "https://www.gov.uk/unpublished",
+      document_collection_group: build(:document_collection_group),
+    )
+
+    assert url.valid?
+  end
+
+  test "should be invalid when neither content store has the path" do
     Services.content_store.stubs(:content_item).raises(GdsApi::ContentStore::ItemNotFound.new(404))
+    Services.draft_content_store.stubs(:content_item).raises(GdsApi::ContentStore::ItemNotFound.new(404))
 
     url = DocumentCollectionNonWhitehallLink::GovukUrl.new(
       url: "https://www.gov.uk/test",