Eliminate xref warning from last commit

mix.exs

@@ -87,6 +87,7 @@ defmodule Ejabberd.MixProject do
              if_version_below('23', [{:d, :USE_OLD_PG2}]) ++
              if_version_below('24', [{:d, :COMPILER_REPORTS_ONLY_LINES}]) ++
              if_version_below('24', [{:d, :SYSTOOLS_APP_DEF_WITHOUT_OPTIONAL}]) ++
+             if_function_exported(:uri_string, :normalize, 1, [{:d, :HAVE_URI_STRING}])
              if_function_exported(:erl_error, :format_exception, 6, [{:d, :HAVE_ERL_ERROR}])
     defines = for {:d, value} <- result, do: {:d, value}
     result ++ [{:d, :ALL_DEFS, defines}]

rebar.config

@@ -110,6 +110,7 @@
             {if_var_true, sip, {d, 'SIP'}},
             {if_var_true, stun, {d, 'STUN'}},
             {if_have_fun, {erl_error, format_exception, 6}, {d, 'HAVE_ERL_ERROR'}},
+            {if_have_fun, {uri_string, normalize, 1}, {d, 'HAVE_URI_STRING'}},
             {src_dirs, [src,
                         {if_rebar3, sql},
                         {if_var_true, tools, tools},

src/rest.erl

@@ -191,6 +191,18 @@ base_url(Server, Path) ->
         _ -> Url
     end.
 
+-ifdef(HAVE_URI_STRING).
+uri_hack(Str) ->
+    case uri_string:normalize("%25") of
+        "%" -> % This hack around bug in httpc >21 <23.2
+            binary:replace(Str, <<"%25">>, <<"%2525">>, [global]);
+        _ -> Str
+    end.
+-else.
+uri_hack(Str) ->
+    Str.
+-endif.
+
 url(Url, []) ->
     Url;
 url(Url, Params) ->
@@ -198,17 +210,7 @@ url(Url, Params) ->
           (misc:url_encode(Value))/binary>>
             || {Key, Value} <- Params],
     <<$&, Encoded0/binary>> = iolist_to_binary(L),
-    Encoded =
-    case erlang:function_exported(uri_string, normalize, 1) of
-        true ->
-            case uri_string:normalize("%25") of
-                "%" -> % This hack around bug in httpc >21 <23.2
-                    binary:replace(Encoded0, <<"%25">>, <<"%2525">>, [global]);
-                _ -> Encoded0
-            end;
-        _ ->
-            Encoded0
-    end,
+    Encoded = uri_hack(Encoded0),
     <<Url/binary, $?, Encoded/binary>>.
 url(Server, Path, Params) ->
     case binary:split(base_url(Server, Path), <<"?">>) of