Priv directory

Author: lpil

src/gleam/erlang.gleam

@@ -141,3 +141,16 @@ pub type Reference
 ///
 @external(erlang, "erlang", "make_ref")
 pub fn make_reference() -> Reference
+
+/// Returns the path of an application's `priv` directory, where extra non-Gleam
+/// or Erlang files are typically kept.
+///
+/// # Example
+///
+/// ```gleam
+/// > erlang.priv_directory("my_app")
+/// // -> Ok("/some/location/my_app/priv")
+/// ```
+/// 
+@external(erlang, "gleam_erlang_ffi", "priv_directory")
+pub fn priv_directory(name: String) -> Result(String, Nil)

src/gleam_erlang_ffi.erl

@@ -6,7 +6,8 @@
     set_env/2, unset_env/1, delete_directory/1, recursive_delete/1,
     list_directory/1, demonitor/1, make_directory/1, new_selector/0, link/1,
     insert_selector_handler/3, select/1, select/2, trap_exits/1, map_selector/2,
-    merge_selector/2, flush_messages/0, file_info/1, link_info/1
+    merge_selector/2, flush_messages/0, file_info/1, link_info/1,
+    priv_directory/1
 ]).
 
 -define(is_posix_error(Error),
@@ -216,3 +217,14 @@ flush_messages() ->
     receive _Message -> flush_messages()
     after 0 -> nil
     end.
+
+priv_directory(Name) ->
+    try erlang:binary_to_existing_atom(Name) of
+        Atom -> 
+            case code:priv_dir(Atom) of
+                {error, _} -> {error, nil};
+                Path -> {ok, unicode:characters_to_binary(Path)}
+            end
+    catch
+        error:badarg -> {error, nil}
+    end.

test/gleam/erlang_test.gleam

@@ -1,3 +1,4 @@
+import gleam/string
 import gleam/dynamic
 import gleam/iterator
 import gleam/erlang.{UnknownApplication}
@@ -47,3 +48,13 @@ pub fn make_reference_test() {
   })
   |> iterator.run
 }
+
+pub fn priv_directory_test() {
+  let assert Error(Nil) = erlang.priv_directory("unknown_application")
+
+  let assert Ok(dir) = erlang.priv_directory("gleam_erlang")
+  let assert True = string.ends_with(dir, "/gleam_erlang/priv")
+
+  let assert Ok(dir) = erlang.priv_directory("gleam_stdlib")
+  let assert True = string.ends_with(dir, "/gleam_stdlib/priv")
+}