Revert to Elixir-like behaviour (unit maps to nil), fix tests

rustler/src/serde/ser.rs

@@ -192,12 +192,7 @@ impl<'a> ser::Serializer for Serializer<'a> {
     /// Serializes unit (empty tuple) as `nil`.
     #[inline]
     fn serialize_unit(self) -> Result<Self::Ok, Self::Error> {
-        Ok(unsafe {
-            Term::new(
-                self.env,
-                rustler_sys::enif_make_tuple!(self.env.as_c_arg(), 0),
-            )
-        })
+        Ok(atoms::nil().to_term(self.env))
     }
 
     #[inline]

rustler_tests/mix.exs

@@ -17,6 +17,9 @@ defmodule RustlerTest.Mixfile do
   end
 
   defp deps do
-    [{:rustler, path: "../rustler_mix", runtime: false}]
+    [
+      {:rustler, path: "../rustler_mix", runtime: false},
+      {:map_diff, version: "~> 1.3"}
+    ]
   end
 end

rustler_tests/native/dynamic_load/src/lib.rs

@@ -7,7 +7,7 @@ fn initialize_dataset(mut asset_path: PathBuf) {
     asset_path.push("demo_dataset.txt");
 
     // https://github.com/elixir-lsp/elixir-ls/issues/604
-    eprintln!("Loading dataset from {:?}.", &asset_path);
+    // eprintln!("Loading dataset from {:?}.", &asset_path);
 
     let data = read_to_string(asset_path).unwrap().into_boxed_str();
     let data = Some(data);

rustler_tests/native/rustler_serde_test/src/lib.rs

@@ -11,6 +11,7 @@ mod types;
 
 use crate::types::Animal;
 use rustler::serde::{atoms, from_term, to_term, Deserializer, Error, Serializer};
+use rustler::SerdeTerm;
 use rustler::{types::tuple, Encoder, Env, NifResult, Term};
 
 init! {
@@ -34,9 +35,8 @@ init! {
 
 /// Implements the README example.
 #[nif]
-pub fn readme<'a>(env: Env<'a>, arg: Term<'a>) -> NifResult<Term<'a>> {
-    let animal: Animal = from_term(arg)?;
-    println!("\n deserialized animal from README example: {:?}", animal);
+pub fn readme<'a>(env: Env<'a>, SerdeTerm(animal): SerdeTerm<Animal>) -> NifResult<Term<'a>> {
+    // println!("\n deserialized animal from README example: {:?}", animal);
     to_term(env, animal).map_err(|err| err.into())
 }
 

rustler_tests/test/json_test.exs

@@ -139,8 +139,7 @@ defmodule SerdeRustlerTests.Json.JsonTest do
 
     assert expected == actual, ~s"""
       DECODING ERROR :: #{ctx[:filename]}
-      expected: #{inspect(expected)}
-      actual: #{inspect(actual)}
+      diff: #{diff(actual, expected)}
     """
   end
 
@@ -150,8 +149,18 @@ defmodule SerdeRustlerTests.Json.JsonTest do
 
     assert expected == actual, ~s"""
       ENCODING ERROR :: #{ctx[:filename]}
-      expected: #{inspect(expected)}
-      actual: #{inspect(actual)}
+      diff: #{diff(actual, expected)}
     """
   end
+
+  defp diff([actual | _], [expected | _]) do
+    diff(actual, expected)
+  end
+
+  defp diff(actual, expected) do
+    MapDiff.diff(expected, actual)
+    |> Map.delete(:value)
+    |> Enum.map(fn {k, v} -> "#{Atom.to_string(k)}: #{inspect(v)}" end)
+    |> Enum.join("\n")
+  end
 end

rustler_tests/test/serde_rustler_tests_test.exs

@@ -223,11 +223,11 @@ defmodule SerdeRustlerTests.NifTest do
 
   describe "Unit Types:" do
     test "unit", ctx do
-      run_tests("unit", {}, ctx)
+      run_tests("unit", nil, ctx)
     end
 
     test "unit struct", ctx do
-      run_tests("unit struct", {}, ctx)
+      run_tests("unit struct", nil, ctx)
     end
 
     test "unit variant", ctx do