Add erlang.reference_from_dynamic.

CHANGELOG.md

@@ -1,8 +1,13 @@
 # Changelog
 
+## v0.26.1 - TBD
+
+- Add `reference_from_dynamic` to `gleam/erlang` for decoding references
+  [Erlang Reference](https://www.erlang.org/doc/system/data_types#reference)
+
 ## v0.26.0 - 2024-08-19
 
-- Add `port_from_dynamic` for decoding 
+- Add `port_from_dynamic` for decoding
   [Erlang Port](https://www.erlang.org/doc/system/ports).
 - Add `gleam/erlang/port` and the `Port` type.
 

src/gleam/erlang.gleam

@@ -1,4 +1,4 @@
-import gleam/dynamic.{type Dynamic}
+import gleam/dynamic.{type DecodeErrors, type Dynamic}
 import gleam/erlang/atom.{type Atom}
 import gleam/erlang/charlist.{type Charlist}
 import gleam/list
@@ -162,6 +162,29 @@ pub type Reference
 @external(erlang, "erlang", "make_ref")
 pub fn make_reference() -> Reference
 
+/// Checks to see whether a `Dynamic` value is a Reference, and return the Reference if
+/// it is.
+///
+/// ## Examples
+///
+/// ```gleam
+/// import gleam/dynamic
+///
+/// reference_from_dynamic(dynamic.from(make_reference()))
+/// // -> Ok(Reference)
+/// ```
+///
+/// ```gleam
+/// import gleam/dynamic
+///
+/// reference_from_dynamic(dynamic.from(123))
+/// // -> Error([DecodeError(expected: "Reference", found: "Int", path: [])])
+/// ```
+@external(erlang, "gleam_erlang_ffi", "reference_from_dynamic")
+pub fn reference_from_dynamic(
+  from from: Dynamic,
+) -> Result(Reference, DecodeErrors)
+
 /// Returns the path of a package's `priv` directory, where extra non-Gleam
 /// or Erlang files are typically kept.
 ///
@@ -173,6 +196,6 @@ pub fn make_reference() -> Reference
 /// 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/process.gleam

@@ -147,12 +147,12 @@ pub fn receive(
 /// let int_subject = new_subject()
 /// let float_subject = new_subject()
 /// send(int_subject, 1)
-/// 
+///
 /// let selector =
 ///   new_selector()
 ///   |> selecting(int_subject, int.to_string)
 ///   |> selecting(float_subject, float.to_string)
-/// 
+///
 /// select(selector, 10)
 /// // -> Ok("1")
 /// ```
@@ -731,7 +731,7 @@ pub fn trap_exits(a: Bool) -> Nil
 /// - The process for the pid no longer exists.
 /// - The name has already been registered.
 /// - The process already has a name.
-/// - The name is the atom `undefined`, which is reserved by Erlang. 
+/// - The name is the atom `undefined`, which is reserved by Erlang.
 ///
 @external(erlang, "gleam_erlang_ffi", "register_process")
 pub fn register(pid: Pid, name: Atom) -> Result(Nil, Nil)
@@ -756,13 +756,13 @@ pub fn named(name: Atom) -> Result(Pid, Nil)
 /// it is.
 ///
 /// ## Examples
-/// 
+///
 /// ```gleam
 /// import gleam/dynamic
 /// from_dynamic(dynamic.from(process.self()))
 /// // -> Ok(process.self())
 /// ```
-/// 
+///
 /// ```gleam
 /// from_dynamic(dynamic.from(123))
 /// // -> Error([DecodeError(expected: "Pid", found: "Int", path: [])])

src/gleam_erlang_ffi.erl

@@ -1,12 +1,13 @@
 -module(gleam_erlang_ffi).
 -export([
     atom_from_dynamic/1, rescue/1, atom_from_string/1, get_line/1,
-    ensure_all_started/1, sleep/1, os_family/0, sleep_forever/0, 
+    ensure_all_started/1, sleep/1, os_family/0, sleep_forever/0,
     get_all_env/0, get_env/1, set_env/2, unset_env/1, demonitor/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,
     priv_directory/1, connect_node/1, register_process/2, unregister_process/1,
-    process_named/1, identity/1, pid_from_dynamic/1, port_from_dynamic/1
+    process_named/1, identity/1, pid_from_dynamic/1, reference_from_dynamic/1,
+    port_from_dynamic/1
 ]).
 
 -spec atom_from_string(binary()) -> {ok, atom()} | {error, atom_not_loaded}.
@@ -25,6 +26,11 @@ pid_from_dynamic(Data) when is_pid(Data) ->
 pid_from_dynamic(Data) ->
     {error, [{decode_error, <<"Pid">>, gleam@dynamic:classify(Data), []}]}.
 
+reference_from_dynamic(Data) when is_reference(Data) ->
+    {ok, Data};
+reference_from_dynamic(Data) ->
+    {error, [{decode_error, <<"Reference">>, gleam@dynamic:classify(Data), []}]}.
+
 port_from_dynamic(Data) when is_port(Data) ->
     {ok, Data};
 port_from_dynamic(Data) ->
@@ -130,7 +136,7 @@ select({selector, Handlers}, Timeout) ->
         Msg when is_map_key({element(1, Msg), tuple_size(Msg)}, Handlers) ->
             Fn = maps:get({element(1, Msg), tuple_size(Msg)}, Handlers),
             {ok, Fn(Msg)};
-        
+
         Msg when AnythingHandler =/= undefined ->
             {ok, AnythingHandler(Msg)}
     after Timeout ->
@@ -141,7 +147,7 @@ demonitor({_, Reference}) ->
     erlang:demonitor(Reference, [flush]).
 
 link(Pid) ->
-    try 
+    try
         erlang:link(Pid)
     catch
         error:_ -> false
@@ -158,7 +164,7 @@ flush_messages() ->
 
 priv_directory(Name) ->
     try erlang:binary_to_existing_atom(Name) of
-        Atom -> 
+        Atom ->
             case code:priv_dir(Atom) of
                 {error, _} -> {error, nil};
                 Path -> {ok, unicode:characters_to_binary(Path)}
@@ -175,7 +181,7 @@ connect_node(Node) ->
     end.
 
 register_process(Pid, Name) ->
-    try 
+    try
         true = erlang:register(Name, Pid),
         {ok, nil}
     catch

test/gleam/erlang_test.gleam

@@ -1,4 +1,4 @@
-import gleam/dynamic
+import gleam/dynamic.{DecodeError}
 import gleam/erlang.{UnknownApplication}
 import gleam/erlang/atom
 import gleam/iterator
@@ -49,6 +49,27 @@ pub fn make_reference_test() {
   |> iterator.run
 }
 
+pub fn reference_from_dynamic_test() {
+  let reference = erlang.make_reference()
+  let assert Ok(reference_from_dynamic) =
+    reference
+    |> dynamic.from
+    |> erlang.reference_from_dynamic
+  let assert True = reference == reference_from_dynamic
+
+  let assert Error([DecodeError(expected: "Reference", found: "Int", path: [])]) =
+    123
+    |> dynamic.from
+    |> erlang.reference_from_dynamic
+
+  let assert Error([
+    DecodeError(expected: "Reference", found: "String", path: []),
+  ]) =
+    "abc"
+    |> dynamic.from
+    |> erlang.reference_from_dynamic
+}
+
 pub fn priv_directory_test() {
   let assert Error(Nil) = erlang.priv_directory("unknown_application")