FIX: Don't accept accents in slug if generation_method == 'ascii' (#15702)

* FIX: Don't accept accents in slug if generation_method == 'ascii'

Fixes bug reported in:
- https://meta.discourse.org/t/404-when-trying-to-edit-category-with-accent-in-slug/214762
- https://meta.discourse.org/t/formatting-and-accents-in-urls/215734/5

Assuming `SiteSetting.slug_generation_method == 'ascii'.

If the user provides a slug containing non-ascii characters while
creating the category, the user will receive a 404 error just
after saving the category since the slug will be escaped anyway but
Category.find_by_slug_path won't escape the category slug
causing the Edit Page of the category to be inaccessible.

This commit checks the provided slug and raises an error if the
provided slugcontains non-ascii characters ensuring that the
provided value is consistent with the site settings.

It also changes Category.find_by_slug_path to always escape the slug,
since if present, it is escaped anyway in Category.ensure_slug to
prevent the 404 in the Edit Category Page in case the user already
have some category with a non-ascii slug.

* Removed trailing whitespace

app/models/category.rb

@@ -353,6 +353,8 @@ class Category < ActiveRecord::Base
 
       if self.slug.blank?
         errors.add(:slug, :invalid)
+      elsif SiteSetting.slug_generation_method == 'ascii' && !CGI.unescape(self.slug).ascii_only?
+        errors.add(:slug, I18n.t("category.errors.slug_contains_non_ascii_chars"))
       elsif duplicate_slug?
         errors.add(:slug, 'is already in use')
       end
@@ -803,11 +805,7 @@ class Category < ActiveRecord::Base
     return nil if slug_path.size > SiteSetting.max_category_nesting
 
     slug_path.map! do |slug|
-      if SiteSetting.slug_generation_method == "encoded"
       CGI.escape(slug.downcase)
-      else
-        slug.downcase
-      end
     end
 
     query =

config/locales/server.en.yml

@@ -704,6 +704,7 @@ en:
       permission_conflict: "Any group that is allowed to access a subcategory must also be allowed to access the parent category. The following groups have access to one of the subcategories, but no access to parent category: %{group_names}."
       disallowed_topic_tags: "This topic has tags not allowed by this category: '%{tags}'"
       disallowed_tags_generic: "This topic has disallowed tags."
+      slug_contains_non_ascii_chars: "contains non-ascii characters"
     cannot_delete:
       uncategorized: "This category is special. It is intended as a holding area for topics that have no category; it cannot be deleted."
       has_subcategories: "Can't delete this category because it has sub-categories."

spec/models/category_spec.rb

@@ -362,6 +362,19 @@ describe Category do
       expect(@cat).to be_valid
       expect(@cat.errors[:slug]).not_to be_present
     end
+
+    context 'if SiteSettings.slug_generation_method = ascii' do
+      before do
+        SiteSetting.slug_generation_method = 'ascii'
+      end
+
+      it 'fails if slug contains non-ascii characters' do
+        c = Fabricate.build(:category, name: "Sem acentuação", slug: "sem-acentuação")
+        expect(c).not_to be_valid
+
+        expect(c.errors[:slug]).to be_present
+      end
+    end
   end
 
   describe 'description_text' do