Fix parsing language tags with a -u-tz short code than needs canonicalising

Author: kipcole9

CHANGELOG.md

@@ -2,9 +2,9 @@
 
 **Note that `ex_cldr` version 2.39.0 and later are supported on Elixir 1.12 and later only.**
 
-## Cldr v2.43.1
+## Cldr v2.43.2
 
-This is the changelog for Cldr v2.43.1 released on August 26th, 2025.  For older changelogs please consult the release tag on [GitHub](https://github.com/elixir-cldr/cldr/tags)
+This is the changelog for Cldr v2.43.2 released on ______, 2025.  For older changelogs please consult the release tag on [GitHub](https://github.com/elixir-cldr/cldr/tags)
 
 ### Upgrading
 
@@ -15,6 +15,14 @@ This is the changelog for Cldr v2.43.1 released on August 26th, 2025.  For older
 
 ### Bug Fixes
 
+* Fix Parsing a language tag when the U extension has a timezone short code that needs to be canonicalised. For example, "en-u-tz-est5edt" needs to become "en-u-tz-usnyc".
+
+## Cldr v2.43.1
+
+This is the changelog for Cldr v2.43.1 released on August 26th, 2025.  For older changelogs please consult the release tag on [GitHub](https://github.com/elixir-cldr/cldr/tags)
+
+### Bug Fixes
+
 * Fix `Cldr.Locale.timezone_from_locale/1` when the territory has one zone and the zone short code is not instantiated as part of the language tag.
 
 ## Cldr v2.43.0

lib/cldr/locale.ex

@@ -1369,11 +1369,11 @@ defmodule Cldr.Locale do
           zone_id
 
         %{prefer: short_zone} when not is_nil(short_zone)->
-          %{aliases: [zone_id]} =
+          %{aliases: zone_ids} =
             Cldr.Timezone.timezones()
             |> Map.fetch!(short_zone)
 
-          zone_id
+          hd(zone_ids)
 
         %{aliases: zones} ->
           ambiguous_timezone_error(territory, zones)

lib/cldr/validity/u.ex

@@ -173,7 +173,7 @@ defmodule Cldr.Validity.U do
   # valid function check that the value provided
   # is acceptable for the given key.
 
-  for {key, values} <- @validity_data, key in @process_keys do
+  for {key, values} <- @validity_data, key in @process_keys -- ["tz"] do
     defp valid(unquote(key), value) when value in unquote(Map.keys(values)) do
       unquote(Macro.escape(values))
       |> get_value(unquote(key), value)
@@ -182,6 +182,22 @@ defmodule Cldr.Validity.U do
     end
   end
 
+  # For timezones a nil value means its an acceptable
+  # time zone name but it needs to be resolved to its
+  # canonical version. For example, est5edt becomes usnyc
+  @tz_values @validity_data["tz"]
+  defp valid("tz", value) do
+    case Map.fetch(@tz_values, value) do
+      {:ok, nil} ->
+        {:ok, preferred} = preferred_timezone(value)
+        {:ok, %{aliases: aliases}} = Map.fetch(Cldr.Timezone.timezones(), preferred)
+        {:ok, hd(aliases)}
+
+      {:ok, values} when is_list(values) ->
+        {:ok, hd(values)}
+    end
+  end
+
   # Calendar names may be compound like
   # islamic-rgsa
   defp valid("ca", values) when is_list(values) do
@@ -266,6 +282,12 @@ defmodule Cldr.Validity.U do
     {:error, invalid_key_error(key)}
   end
 
+  defp preferred_timezone(timezone) do
+    Cldr.Timezone.timezones()
+    |> Map.fetch!(timezone)
+    |> Map.fetch(:preferred)
+  end
+
   defp get_value(map, "cu", value) do
     (Map.get(map, value) || value)
     |> String.upcase()

test/language_tag_test.exs

@@ -159,4 +159,12 @@ defmodule CldrLanguageTagTest do
              {:error,
               {Cldr.LanguageTag.ParseError, "The value \"bogus\" is not valid for the key \"mu\""}}
   end
+
+  test "with u extensions and time zone that requires canonicalisation" do
+    import Cldr.LanguageTag.Sigil
+
+    assert {:ok, tag} = Cldr.validate_locale("en-u-tz-est5edt")
+    assert "TestBackend.Cldr.Locale.new!(\"en-US-u-tz-usnyc\")" == inspect(tag)
+    assert "America/New_York" = tag.locale.timezone
+  end
 end