FIX: Do not error if autogenerated channel slug is blank (#19759)

In certain cases, like when `SiteSetting.slug_generation_method`
is set to `none` with certain locales, the autogenerated chat
channel slugs will end up blank. This was causing errors in
unrelated jobs calling `update!` on the channel. Instead, we
should just copy Category behaviour, which does not error
if the autogenerated slug ends up blank. We already allow
for this with chat channel URLs, using `-` in place of the
missing slug.

plugins/chat/app/models/category_channel.rb

@@ -28,16 +28,18 @@ class CategoryChannel < ChatChannel
   end
 
   def ensure_slug_ok
-    # if we don't unescape it first we strip the % from the encoded version
-    slug = SiteSetting.slug_generation_method == "encoded" ? CGI.unescape(self.slug) : self.slug
-    self.slug = Slug.for(slug, "", method: :encoded)
+    if self.slug.present?
+      # if we don't unescape it first we strip the % from the encoded version
+      slug = SiteSetting.slug_generation_method == "encoded" ? CGI.unescape(self.slug) : self.slug
+      self.slug = Slug.for(slug, "", method: :encoded)
 
-    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("chat.category_channel.errors.slug_contains_non_ascii_chars"))
-    elsif duplicate_slug?
-      errors.add(:slug, I18n.t("chat.category_channel.errors.is_already_in_use"))
+      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("chat.category_channel.errors.slug_contains_non_ascii_chars"))
+      elsif duplicate_slug?
+        errors.add(:slug, I18n.t("chat.category_channel.errors.is_already_in_use"))
+      end
     end
   end
 end

plugins/chat/spec/models/category_channel_spec.rb

@@ -124,6 +124,13 @@ RSpec.describe CategoryChannel do
           channel.validate
           expect(channel.errors.full_messages).to include("Slug is invalid")
         end
+
+        it "does not add a validation error when autogenerated slug ends up empty" do
+          SiteSetting.slug_generation_method = "none"
+          channel.update(name: "は無効です", slug: nil)
+          expect(channel).to be_valid
+          expect(channel.slug).to eq("")
+        end
       end
 
       context "when there is a duplicate slug" do