Add async constructor & callback support for Dart bindings

Cargo.toml

@@ -73,6 +73,7 @@ members = [
     "fixtures/simple-fns",
     "fixtures/trait-methods",
     "fixtures/trait-interfaces",
+    "fixtures/dart_async",
     #"fixtures/*",
 ]
 

fixtures/dart_async/Cargo.toml

@@ -11,16 +11,18 @@ name = "dart_async"
 crate-type = ["lib", "cdylib"]
 
 [dependencies]
-uniffi = { workspace = true, features = ["tokio"]}
-tokio = { version = "1.24.1", features = ["time"] }
-thiserror = "1.0"
+uniffi = { workspace = true, features = ["tokio", "cli", "scaffolding-ffi-buffer-fns"] }
+async-trait = "0.1"
+futures = "0.3"
+tokio = { version = "1.38.2", features = ["time", "sync"] }
+once_cell = "1.18.0"
+thiserror = "2"
 
 [build-dependencies]
+uniffi = { workspace = true, features = ["build", "scaffolding-ffi-buffer-fns"] }
 uniffi-dart = { path = "../../", features = ["build"] }
 
 [dev-dependencies]
+uniffi = { workspace = true, features = ["bindgen-tests"] }
 uniffi-dart = { path = "../../", features = ["bindgen-tests"] }
-uniffi = { workspace = true, features = [
-  "bindgen-tests",
-] }
 anyhow = "1"

fixtures/dart_async/src/api.udl

@@ -1,7 +1,7 @@
-namespace dart_async { 
+namespace dart_async {
     // UDL-defined async functions (testing UDL vs proc-macro async support)
     [Async]
-    boolean udl_always_ready();
+    boolean always_ready();
 };
 
 // UDL-defined async trait interface