Conditionally include backported safe_relative_path/1

Author: jhlywa

src/elli_static.erl

@@ -111,26 +111,27 @@ maybe_file(Req, Prefix, Dir) ->
             nothing
     end.
 
+
+%% OTP_RELEASE macro was introduced in 21, `filename:safe_relative_path/1' in
+%% 19.3.
+-ifdef(OTP_RELEASE).
+  -ifdef(?OTP_RELEASE >= 21).
+safe_relative_path(Path) ->
+    filename:safe_relative_path(Path).
+  -endif.
+-else.
+
 %% @doc Backport of `filename:safe_relative_path/1' from 19.3. This code was
 %% lifted from:
 %% https://github.com/erlang/otp/blob/master/lib/stdlib/src/filename.erl#L811
 -spec safe_relative_path(file:name_all()) -> unsafe | file:name_all().
 safe_relative_path(Path) ->
-    %% prefer the OTP version of `safe_relative_path/1' if it exists
-    case lists:member({safe_relative_path, 1},
-                      filename:module_info(exports)) of
-        true ->
-            %% to suppress xref warnings on 19.2 and lower
-            Mod = filename,
-            Mod:safe_relative_path(Path);
-        false ->
-            case filename:pathtype(Path) of
-                relative ->
-                    Cs0 = filename:split(Path),
-                    safe_relative_path_1(Cs0, []);
-                _ ->
-                    unsafe
-            end
+    case filename:pathtype(Path) of
+        relative ->
+            Cs0 = filename:split(Path),
+            safe_relative_path_1(Cs0, []);
+        _ ->
+            unsafe
     end.
 
 safe_relative_path_1(["."|T], Acc) ->
@@ -152,35 +153,4 @@ climb(_, []) ->
     unsafe;
 climb(T, [_|Acc]) ->
     safe_relative_path_1(T, Acc).
-
-
--ifdef(TEST).
--include_lib("eunit/include/eunit.hrl").
-
-safe_relative_path_test() ->
-    %% binary args
-    ?assertMatch([], safe_relative_path(<<>>)),
-    ?assertMatch(unsafe, safe_relative_path(<<"/">>)),
-    ?assertMatch(unsafe, safe_relative_path(<<"/root">>)),
-    ?assertMatch(unsafe, safe_relative_path(<<"..">>)),
-    ?assertMatch(unsafe, safe_relative_path(<<"dir/../../dir">>)),
-    ?assertMatch(<<"dir">>, safe_relative_path(<<"dir">>)),
-    ?assertMatch(<<"dir">>, safe_relative_path(<<"dir/../dir">>)),
-    ?assertMatch(<<"dir/sub">>, safe_relative_path(<<"dir/sub/../sub">>)),
-    ?assertMatch(<<"dir/sub">>, safe_relative_path(<<"dir/./sub">>)),
-    ?assertMatch(<<"dir/sub">>, safe_relative_path(<<"dir/././../dir/././sub">>)),
-
-    %% string args
-    %% (these are here for completeness since `filename:safe_relative_path'
-    %% supports string arguments
-    ?assertMatch([], safe_relative_path("")),
-    ?assertMatch(unsafe, safe_relative_path("/")),
-    ?assertMatch(unsafe, safe_relative_path("/root")),
-    ?assertMatch(unsafe, safe_relative_path("..")),
-    ?assertMatch(unsafe, safe_relative_path("dir/../../dir")),
-    ?assertMatch("dir", safe_relative_path("dir")),
-    ?assertMatch("dir", safe_relative_path("dir/../dir")),
-    ?assertMatch("dir/sub", safe_relative_path("dir/sub/../sub")),
-    ?assertMatch("dir/sub", safe_relative_path("dir/./sub")),
-    ?assertMatch("dir/sub", safe_relative_path("dir/././../dir/././sub")).
 -endif.