Merge branch 'ajk-212987-nil-wiki-page' into 'master'

Resolve "[Wiki] `@page` can be nil during `#edit`"

Closes #212987

See merge request gitlab-org/gitlab!29645

app/controllers/projects/wikis_controller.rb

@@ -10,8 +10,9 @@ class Projects::WikisController < Projects::ApplicationController
   before_action :authorize_admin_wiki!, only: :destroy
   before_action :load_project_wiki
   before_action :load_page, only: [:show, :edit, :update, :history, :destroy]
-  before_action :valid_encoding?,
-    if: -> { %w[show edit update].include?(action_name) && load_page }
+  before_action only: [:show, :edit, :update] do
+    @valid_encoding = valid_encoding?
+  end
   before_action only: [:edit, :update], unless: :valid_encoding? do
     redirect_to(project_wiki_path(@project, @page))
   end
@@ -167,7 +168,11 @@ class Projects::WikisController < Projects::ApplicationController
   end
 
   def load_page
-    @page ||= @project_wiki.find_page(*page_params)
+    @page ||= find_page
+  end
+
+  def find_page
+    @project_wiki.find_page(*page_params)
   end
 
   def page_params
@@ -178,9 +183,11 @@ class Projects::WikisController < Projects::ApplicationController
   end
 
   def valid_encoding?
-    strong_memoize(:valid_encoding) do
-      @page.content.encoding == Encoding::UTF_8
+    page_encoding == Encoding::UTF_8
   end
+
+  def page_encoding
+    strong_memoize(:page_encoding) { @page&.content&.encoding }
   end
 
   def set_encoding_error

changelogs/unreleased/ajk-212987-nil-wiki-page.yml

+---
+title: Eliminate errors in wiki controller during edit
+merge_request: 29645
+author:
+type: fixed

spec/controllers/projects/wikis_controller_spec.rb

@@ -200,7 +200,20 @@ describe Projects::WikisController do
 
         subject
 
-        expect(response).to redirect_to(project_wiki_path(project, project_wiki.list_pages.first))
+        expect(response).to redirect_to_wiki(project, project_wiki.list_pages.first)
+      end
+    end
+
+    context 'when the page has nil content' do
+      let(:page) { create(:wiki_page) }
+
+      it 'redirects to show' do
+        allow(page).to receive(:content).and_return(nil)
+        allow(controller).to receive(:find_page).and_return(page)
+
+        subject
+
+        expect(response).to redirect_to_wiki(project, page)
       end
     end
 
@@ -235,7 +248,7 @@ describe Projects::WikisController do
         allow(controller).to receive(:valid_encoding?).and_return(false)
 
         subject
-        expect(response).to redirect_to(project_wiki_path(project, project_wiki.list_pages.first))
+        expect(response).to redirect_to_wiki(project, project_wiki.list_pages.first)
       end
     end
 
@@ -265,4 +278,8 @@ describe Projects::WikisController do
     page = wiki.page(title: title, dir: dir)
     project_wiki.delete_page(page, "test commit")
   end
+
+  def redirect_to_wiki(project, page)
+    redirect_to(controller.project_wiki_path(project, page))
+  end
 end