add dynamic load test

Author: kaaboaye

Cargo.toml

@@ -8,6 +8,7 @@ members = [
   "rustler_tests/native/rustler_test",
   "rustler_tests/native/rustler_bigint_test",
   "rustler_tests/native/deprecated_macros",
+  "rustler_tests/native/dynamic_load",
   "rustler_tests/native/rustler_compile_tests",
   "rustler_benchmarks/native/benchmark",
 ]

rustler_tests/lib/dynamic_data.ex

@@ -0,0 +1,14 @@
+defmodule DynamicData.Config do
+  def nif_data do
+    %{priv_path: :code.priv_dir(:rustler_test) |> IO.iodata_to_binary()}
+  end
+end
+
+defmodule DynamicData do
+  use Rustler,
+    otp_app: :rustler_test,
+    crate: :dynamic_load,
+    load_data_fun: {DynamicData.Config, :nif_data}
+
+  def get_dataset, do: :erlang.nif_error(:nif_not_loaded)
+end

rustler_tests/native/dynamic_load/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "dynamic_load"
+version = "0.1.0"
+edition = "2021"
+
+[lib]
+name = "dynamic_load"
+path = "src/lib.rs"
+crate-type = ["cdylib"]
+
+[dependencies]
+rustler_bigint = { path = "../../../rustler_bigint" }
+rustler = { path = "../../../rustler" }

rustler_tests/native/dynamic_load/src/lib.rs

@@ -0,0 +1,40 @@
+use rustler::Atom;
+use std::{ffi::OsStr, fs::read_to_string, os::unix::prelude::OsStrExt, path::PathBuf};
+
+static mut DATASET: Option<Box<str>> = None;
+
+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);
+
+    let data = read_to_string(asset_path).unwrap().into_boxed_str();
+    let data = Some(data);
+
+    // Safety: assumes that this function is being called once when
+    // dynamically loading this library.
+    // `load()` is being called exactly once and OTP will not allow any other function call
+    // before this function returns
+    unsafe { DATASET = data };
+}
+
+#[rustler::nif]
+fn get_dataset() -> &'static str {
+    // Safety: see `initialize_dataset()`
+    unsafe { DATASET.as_ref() }.expect("Dataset is not initialized")
+}
+
+fn load<'a>(env: rustler::Env<'a>, args: rustler::Term<'a>) -> bool {
+    let key = Atom::from_str(env, "priv_path").unwrap().to_term(env);
+    let priv_path = args.map_get(key).unwrap();
+    let priv_path = priv_path.into_binary().unwrap().as_slice();
+    let priv_path = OsStr::from_bytes(priv_path);
+    let asset_path = PathBuf::from(priv_path);
+
+    initialize_dataset(asset_path);
+
+    true
+}
+
+rustler::init!("Elixir.DynamicData", [get_dataset], load = load);

rustler_tests/priv/.gitkeep

@@ -0,0 +1 @@
+some random dataset

rustler_tests/priv/demo_dataset.txt

@@ -0,0 +1,10 @@
+defmodule RustlerTest.DynamicDataTest do
+  use ExUnit.Case, async: true
+
+  test "rust has access to demo_dataset.txt via dynamic priv path" do
+    %{priv_path: path} = DynamicData.Config.nif_data()
+    path = Path.join(path, "demo_dataset.txt")
+
+    assert File.read!(path) == DynamicData.get_dataset()
+  end
+end