api: return input string in function string_iconv_from_internal when current locale is wrong

This fixes a bug when writing configuration files with a wrong locale: now
UTF-8 is kept and written in files instead of string converted using a wrong
charset.

CHANGELOG.md

@@ -1,5 +1,11 @@
 # WeeChat ChangeLog
 
+## Version 4.5.3 (under dev)
+
+### Fixed
+
+- core: save configuration files as UTF-8 when the locale is wrong
+
 ## Version 4.5.2 (2025-02-20)
 
 ### Fixed

src/core/core-string.c

@@ -3253,7 +3253,8 @@ string_iconv_to_internal (const char *charset, const char *string)
 }
 
 /*
- * Converts internal string to terminal charset, for display.
+ * Converts internal string to terminal charset, for display or write of
+ * configuration files.
  *
  * Note: result must be freed after use.
  */
@@ -3270,6 +3271,10 @@ string_iconv_from_internal (const char *charset, const char *string)
     if (!input)
         return NULL;
 
+    /* if the locale is wrong, we keep UTF-8 */
+    if (!weechat_locale_ok)
+        return input;
+
     /*
      * optimized for UTF-8: if charset is NULL => we use term charset => if
      * this charset is already UTF-8, then no iconv is needed

src/core/weechat.h

@@ -118,6 +118,7 @@ extern char *weechat_data_dir;
 extern char *weechat_state_dir;
 extern char *weechat_cache_dir;
 extern char *weechat_runtime_dir;
+extern int weechat_locale_ok;
 extern char *weechat_local_charset;
 extern int weechat_plugin_no_dlclose;
 extern int weechat_no_gnutls;