Fix exception in admin when current language is deleted

This fixes a situation where the session contains a language id for a
language that no longer exists because it has been deleted.

This commit fixes this in two ways:

- when deleting the language, it is removed from the session if the
language is identical
- when trying to get the language from the session id, the lookup code
now falls back to the default language if it can't be found. This is
meant to fix the scenario where a different user deletes the language
instead of the user with the language id in the session

I believe both fixes are useful.

I've tried to come up with meaningful tests but I am somewhat unfamiliar
with the codebase so feel free to suggest extra things.

A backport to Alchemy 7 would be appreciated if possible, as it will
probably still take us a while to get to 8.

(cherry picked from commit 380d62c)

Author: halfbyte

app/controllers/alchemy/admin/languages_controller.rb

@@ -30,6 +30,9 @@ def create
 
       def destroy
         if @language.destroy
+          if session[:alchemy_language_id] == @language.id
+            session.delete(:alchemy_language_id)
+          end
           flash[:notice] = Alchemy.t("Language successfully removed")
         else
           flash[:warning] = @language.errors.full_messages.to_sentence

app/models/alchemy/language/code.rb

@@ -13,6 +13,7 @@ def code=(code)
 
   module ClassMethods
     def find_by_code(code)
+      return unless code.respond_to?(:split)
       codes = code.split("-")
       codes << "" if codes.length == 1
       on_current_site.find_by(

lib/alchemy/controller_actions.rb

@@ -80,7 +80,8 @@ def load_alchemy_language_from_params
 
     def load_alchemy_language_from_id_or_code(id_or_code)
       Language.find_by(id: id_or_code) ||
-        Language.find_by_code(id_or_code)
+        Language.find_by_code(id_or_code) ||
+        Language.default
     end
 
     # Stores language in +Current.language+

spec/controllers/alchemy/admin/languages_controller_spec.rb

@@ -118,6 +118,16 @@
         expect(response).to redirect_to admin_languages_path
         expect(flash[:notice]).to eq("Language successfully removed.")
       end
+
+      it "removes the language from session if present" do
+        session[:alchemy_language_id] = language.id
+
+        delete :destroy, params: {id: language.id}
+        expect(response).to redirect_to admin_languages_path
+        expect(flash[:notice]).to eq("Language successfully removed.")
+
+        expect(session[:alchemy_language_id]).to be_nil
+      end
     end
   end
 

spec/controllers/alchemy/admin/pages_controller_spec.rb

@@ -47,6 +47,19 @@
         end
       end
     end
+
+    context "with wrong or missing language in session" do
+      let!(:site_1) { create(:alchemy_site) }
+      let!(:site_1_default_language) { create :alchemy_language, site: site_1, default: true }
+
+      it "should fall back to existing language if session language does not exist" do
+        session[:alchemy_language_id] = 123456789
+
+        expect {
+          get :index
+        }.to_not raise_error
+      end
+    end
   end
 
   describe "#destroy" do