Check for reference leak detection only in mlua integratin tests.

This is not necessary an error and should not be enforced by default.
Fixes #268.

.github/workflows/main.yml

@@ -118,12 +118,14 @@ jobs:
         with:
           toolchain: ${{ matrix.rust }}
           target: ${{ matrix.target }}
-      - uses: Swatinem/rust-cache@v1
+      - uses: Swatinem/rust-cache@v2
       - name: Run ${{ matrix.lua }} tests
         run: |
           cargo test --features "${{ matrix.lua }},vendored"
           cargo test --features "${{ matrix.lua }},vendored,async,send,serialize,macros,parking_lot,unstable"
         shell: bash
+        env:
+          RUSTFLAGS: --cfg mlua_test
       - name: Run compile tests (macos lua54)
         if: ${{ matrix.os == 'macos-latest' && matrix.lua == 'lua54' }}
         run: |
@@ -149,12 +151,13 @@ jobs:
         with:
           toolchain: ${{ matrix.rust }}
           target: ${{ matrix.target }}
-      - uses: Swatinem/rust-cache@v1
+      - uses: Swatinem/rust-cache@v2
       - name: Run ${{ matrix.lua }} tests with address sanitizer
         run: |
-          RUSTFLAGS="-Z sanitizer=address" \
             cargo test --tests --features "${{ matrix.lua }},vendored,async,send,serialize,macros,parking_lot,unstable" --target x86_64-unknown-linux-gnu -- --skip test_too_many_recursions
         shell: bash
+        env:
+          RUSTFLAGS: --cfg mlua_test -Z sanitizer=address
 
   test_modules:
     name: Test modules
@@ -176,7 +179,7 @@ jobs:
         with:
           toolchain: ${{ matrix.rust }}
           target: ${{ matrix.target }}
-      - uses: Swatinem/rust-cache@v1
+      - uses: Swatinem/rust-cache@v2
       - name: Run ${{ matrix.lua }} module tests
         run: |
           (cd tests/module && cargo build --release --features "${{ matrix.lua }}")

src/lua.rs

@@ -247,6 +247,8 @@ impl Drop for LuaInner {
             {
                 (*ffi::lua_callbacks(self.state())).userdata = ptr::null_mut();
             }
+            // This is an internal assertion used in integration tests
+            #[cfg(mlua_test)]
             mlua_debug_assert!(
                 ffi::lua_gettop(extra.ref_thread) == extra.ref_stack_top
                     && extra.ref_stack_top as usize == extra.ref_free.len(),

tests/async.rs

@@ -9,7 +9,7 @@ use futures_util::stream::TryStreamExt;
 
 use mlua::{
     AnyUserDataExt, Error, Function, Lua, LuaOptions, Result, StdLib, Table, TableExt, UserData,
-    UserDataMethods,
+    UserDataMethods, Value,
 };
 
 #[tokio::test]
@@ -270,6 +270,28 @@ async fn test_async_thread() -> Result<()> {
     Ok(())
 }
 
+#[test]
+fn test_async_thread_leak() -> Result<()> {
+    let lua = Lua::new();
+
+    let f = lua.create_async_function(move |_lua, v: Value| async move {
+        tokio::task::yield_now().await;
+        drop(v);
+        Ok(())
+    })?;
+
+    let thread = lua.create_thread(f)?;
+    // After first resume, `v: Value` is captured in the coroutine
+    thread.resume::<_, ()>("abc").unwrap();
+    drop(thread);
+
+    // Without running garbage collection, the captured `v` would trigger "reference leak detected" error
+    // with `cfg(mlua_test)`
+    lua.gc_collect()?;
+
+    Ok(())
+}
+
 #[tokio::test]
 async fn test_async_table() -> Result<()> {
     let options = LuaOptions::new().thread_pool_size(4);