v1.1.0

Author: lpil

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## v1.1.0 - 2025-06-25
+
+- The `gleam/erlang/atom` module gains the `to_dynamic` and `decoder` functions.
+
 ## v1.0.0 - 2025-06-12
 
 - The `gleam/erlang/node` module gains the `name` function.

gleam.toml

@@ -1,6 +1,6 @@
 name = "gleam_erlang"
 
-version = "1.0.0"
+version = "1.1.0"
 licences = ["Apache-2.0"]
 description = "Types and functions for programs running on Erlang!"
 

src/gleam/erlang/atom.gleam

@@ -1,3 +1,6 @@
+import gleam/dynamic
+import gleam/dynamic/decode
+
 /// Atom is a special string-like data-type that is most commonly used for
 /// interfacing with code written in other BEAM languages such as Erlang and
 /// Elixir. It is preferable to define your own custom types to use instead of
@@ -47,3 +50,32 @@ pub fn create(a: String) -> Atom
 ///
 @external(erlang, "erlang", "atom_to_binary")
 pub fn to_string(a: Atom) -> String
+
+/// Convert an atom to a dynamic value, throwing away the type information. 
+///
+/// This may be useful for testing decoders.
+///
+@external(erlang, "gleam_erlang_ffi", "identity")
+pub fn to_dynamic(a: Atom) -> dynamic.Dynamic
+
+@external(erlang, "gleam_erlang_ffi", "identity")
+pub fn cast_from_dynamic(a: dynamic.Dynamic) -> Atom
+
+/// A dynamic decoder for atoms.
+///
+/// You almost certainly should not use this to work with externally defined
+/// functions. They return known types, so you should define the external
+/// functions with the correct types, defining wrapper functions in Erlang if
+/// the external types cannot be mapped directly onto Gleam types.
+///
+pub fn decoder() -> decode.Decoder(Atom) {
+  decode.new_primitive_decoder("Atom", fn(data) {
+    case is_atom(data) {
+      True -> Ok(cast_from_dynamic(data))
+      False -> Error(create("nil"))
+    }
+  })
+}
+
+@external(erlang, "erlang", "is_atom")
+fn is_atom(data: dynamic.Dynamic) -> Bool

test/gleam/erlang/atom_test.gleam

@@ -1,3 +1,5 @@
+import gleam/dynamic
+import gleam/dynamic/decode
 import gleam/erlang/atom
 import gleam/int
 
@@ -22,3 +24,11 @@ pub fn to_string_test() {
   let assert "ok" = atom.to_string(atom.create("ok"))
   let assert "expect" = atom.to_string(atom.create("expect"))
 }
+
+pub fn dynamic_test() {
+  let wibble = atom.create("wibble")
+
+  assert decode.run(atom.to_dynamic(wibble), atom.decoder()) == Ok(wibble)
+  assert decode.run(dynamic.int(1), atom.decoder())
+    == Error([decode.DecodeError("Atom", "Int", [])])
+}