Fix zero return imports, and support for result types

.gitignore

@@ -36,3 +36,6 @@ wapm.lock
 # ignore local builds
 checksum-Elixir.Wasmex.Native.exs
 *.so
+
+package.json
+package-lock.json

.tool-versions

@@ -1,3 +1,3 @@
-erlang 27.1.2
-elixir 1.17.3-otp-27
+erlang 27.2.4
+elixir 1.18.2-otp-27
 rust 1.82.0

native/wasmex/src/component_instance.rs

@@ -131,7 +131,9 @@ fn call_elixir_import(
         return Err(anyhow::anyhow!("Callback failed"));
     }
 
-    result_values[0] = returned_values[0].clone();
+    if !returned_values.is_empty() {
+        result_values[0] = returned_values[0].clone();
+    }
     Ok(())
 }
 
@@ -341,6 +343,10 @@ fn populate_return_values(
 
     let wit_type = match results {
         wit_parser::Results::Anon(wit_type) => wit_type,
+        wit_parser::Results::Named(vec) if vec.is_empty() => {
+            *return_values = Some((true, vals));
+            return Ok(());
+        }
         wit_parser::Results::Named(_vec) => {
             return Err(anyhow!("Named return values not supported"))
         }

test/component_fixtures/importer/importer.js

@@ -1,12 +1,26 @@
-import getSecretWord from 'get-secret-word';
-import getNumber from 'get-number';
-import getList from 'get-list';
-import getPoint from 'get-point';
-import getTuple from 'get-tuple';
+import getSecretWord from "get-secret-word";
+import getNumber from "get-number";
+import getList from "get-list";
+import getPoint from "get-point";
+import getTuple from "get-tuple";
+import print from "print";
 
+export function printOrError(msg) {
+  print(msg);
+  if (msg === "error") {
+    throw "error";
+  }
+
+  return msg;
+}
+
+export function printSecretWord() {
+  const secret = getSecretWord(7, "foo");
+  print(secret);
+}
 export function revealSecretWord() {
   const secretWord = getSecretWord(7, "foo");
-  const {x, y} = getPoint();
+  const { x, y } = getPoint();
   return `${secretWord} ${getNumber()} ${getList().join()} x: ${x} y: ${y}`;
 }
 

test/component_fixtures/importer/importer.wit

@@ -10,6 +10,10 @@ world importer {
   import get-list: func() -> list<string>;
   import get-point: func() -> point;
   import get-tuple: func() -> tuple<u32, string>;
+  import print: func(word: string);
+
+  export print-or-error: func(msg: string) -> result<string, string>;
+  export print-secret-word: func();
   export reveal-secret-word: func() -> string;
   export show-tuple: func() -> string;
 }

test/components/import_test.exs

@@ -10,7 +10,8 @@ defmodule Wasmex.Components.ImportTest do
       "get-number" => {:fn, fn -> 42 end},
       "get-list" => {:fn, fn -> ["hi", "there"] end},
       "get-point" => {:fn, fn -> %{x: 1, y: 2} end},
-      "get-tuple" => {:fn, fn -> {1, "foo"} end}
+      "get-tuple" => {:fn, fn -> {1, "foo"} end},
+      "print" => {:fn, fn x -> IO.puts(x) end}
     }
 
     component_pid =
@@ -26,5 +27,13 @@ defmodule Wasmex.Components.ImportTest do
 
     assert {:ok, "1 foo"} =
              Wasmex.Components.call_function(component_pid, "show-tuple", [])
+
+    assert {:ok, _} = Wasmex.Components.call_function(component_pid, "print-secret-word", [])
+
+    assert {:ok, {:ok, "bananas"}} =
+             Wasmex.Components.call_function(component_pid, "print-or-error", ["bananas"])
+
+    assert {:ok, {:error, "error"}} =
+             Wasmex.Components.call_function(component_pid, "print-or-error", ["error"])
   end
 end