BREAKING (rarely) - [#56] FIX strange JVM handling for locales #{:he …

…:yi :id} (@juhani-hietikko)

The JVM's Locale constructor has some unexpected odd behaviour for
these locales:

> Locale's constructor has always converted three language codes to their
> earlier, obsoleted forms: he maps to iw, yi maps to ji, and id maps to in.
> This continues to be the case, in order to not break backwards
> compatibility.
- From http://docs.oracle.com/javase/8/docs/api/java/util/Locale.html

Before this fix:
  (kw-locale :he) => :iw,
  (kw-locale :iw) => :iw

  (kw-locale :yi) => :ji
  (kw-locale :ji) => :ji

  (kw-locale :id) => :in
  (kw-locale :in) => :in

After this fix:
  (kw-locale :he) => :he
  (kw-locale :iw) => :he

  (kw-locale :yi) => :yi
  (kw-locale :ji) => :yi

  (kw-locale :id) => :id
  (kw-locale :in) => :id

This will clearly be BREAKING for anyone with dictionaries using any of
the obsolete #{:iw :ji :in} locale keys.

MIGRATION INSTRUCTIONS
----------------------
Update any locale keys in your dictionaries by substituting
{:iw :he, :ji :yi, :in :id}

src/taoensso/tower.cljx

@@ -81,16 +81,24 @@
       (let [loc-name
             #+cljs (name (or ?loc :nil))
             #+clj  (if-let [jvm-loc (try-jvm-locale ?loc lang-only?)]
-                     (str jvm-loc)
+                     ;; (str jvm-loc) ; No! See [1] in comments below
+                     (.toLanguageTag ^Locale jvm-loc)
                      (name (or ?loc :nil)))
             loc-name (str/replace loc-name "_" "-")
             loc-name (if-not lang-only? loc-name
                        (first (str/split loc-name #"-")))]
         (keyword loc-name)))))
 
 (comment
+  ;; [1] Ref. https://github.com/ptaoussanis/tower/issues/56 re: weird JVM
+  ;; locale handling for certain locales:
+  [(str (Locale. "id")) (Locale. "id") (.toLanguageTag (Locale. "id"))
+   (kw-locale :id)]
+
   (map #(kw-locale %) [nil :whatever-foo :en (jvm-locale :en) "en-GB" :jvm-default])
-  (map #(kw-locale % :lang-only) [nil :whatever-foo :en (jvm-locale :en) "en-GB" :jvm-default]))
+  (map #(kw-locale % :lang-only) [nil :whatever-foo :en (jvm-locale :en) "en-GB" :jvm-default])
+
+  )
 
 ;;;; Localization
 ;; The Java date API is a mess, but we (thankfully!) don't need much of it for