Fallback to a variant if the language in general is not supported

For an example, here, zh is not supported, but zh_Hans and zh_Hant
are. If the user asks for zh, we should choose a variant for them
instead of fallbacking to default.

Some browsers (e.g. Firefox) does not allow users to customize
their language codes. For example, there is no zh-Hans, but only
zh, zh-CN, zh-TW, zh-HK, etc. This provides a workaround for
those users suffering from bad design decisions.

2 files changed, 20 insertions, 0 deletions

diff --git a/lib/pleroma/web/gettext.ex b/lib/pleroma/web/gettext.ex
index 828b98b15..cfd92f991 100644
--- a/lib/pleroma/web/gettext.ex
+++ b/lib/pleroma/web/gettext.ex
@@ -49,6 +49,20 @@ defmodule Pleroma.Web.Gettext do
     |> Enum.member?(locale)
   end
 
+  def variant?(locale), do: String.contains?(locale, "_")
+
+  def supported_variants_of_locale(locale) do
+    cond do
+      variant?(locale) ->
+        [locale]
+      supports_locale?(locale) ->
+        [locale]
+      true ->
+        Gettext.known_locales(Pleroma.Web.Gettext)
+        |> Enum.filter(fn l -> String.starts_with?(l, locale <> "_") end)
+    end
+  end
+
   def locale_or_default(locale) do
     if supports_locale?(locale) do
       locale
diff --git a/lib/pleroma/web/plugs/set_locale_plug.ex b/lib/pleroma/web/plugs/set_locale_plug.ex
index 4c6e44fb5..78ae566c7 100644
--- a/lib/pleroma/web/plugs/set_locale_plug.ex
+++ b/lib/pleroma/web/plugs/set_locale_plug.ex
@@ -20,6 +20,12 @@ defmodule Pleroma.Web.Plugs.SetLocalePlug do
     conn
     |> extract_preferred_language()
     |> normalize_language_codes()
+    |> first_supported()
+  end
+
+  defp first_supported(locales) do
+    locales
+    |> Enum.flat_map(&Pleroma.Web.Gettext.supported_variants_of_locale/1)
     |> Enum.find(&supported_locale?/1)
   end