Update SourceProvider and bundle() to be async (parcel-bundler#174

)

The two `SourceProvider` methods are now `async` which will give a hook for JavaScript to implement them and be called from the main thread. Everything is `async` now where possible and `bundle()` executes the `Future` synchronously to maintain its contract. Since it won't support custom JavaScript resolvers, there should never be a case where `bundle()` can't execute synchronously.

Rayon doesn't seem to support `async` iterators, but also shouldn't be as necessary here. Removed it in order to call `async` APIs.

Cargo.toml

@@ -25,6 +25,9 @@ path = "src/lib.rs"
 crate-type = ["rlib"]
 
 [dependencies]
+async-recursion = "1.0.0"
+async-trait = "0.1.53"
+futures = "0.3.21"
 serde = { version = "1.0.123", features = ["derive"] }
 cssparser = "0.29.1"
 parcel_selectors = { version = "0.24.4", path = "./selectors" }
@@ -35,12 +38,12 @@ parcel_sourcemap = "2.0.2"
 data-encoding = "2.3.2"
 lazy_static = "1.4.0"
 const-str = "0.3.1"
+tokio = { version = "1.19.1", features = ["macros", "rt", "rt-multi-thread"] }
 # CLI deps
 clap = { version = "3.0.6", features = ["derive"], optional = true }
 serde_json = { version = "1.0.78", optional = true }
 pathdiff = { version = "0.2.1", optional = true }
 browserslist-rs = { version = "0.7.0", optional = true }
-rayon = "1.5.1"
 dashmap = "5.0.0"
 
 [target.'cfg(target_os = "macos")'.dependencies]

node/Cargo.toml

@@ -22,6 +22,7 @@ jemallocator = { version = "0.3.2", features = ["disable_initial_exec_tls"] }
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
 napi = {version = "2.2.0", default-features = false, features = ["napi4", "compat-mode", "serde-json"]}
 napi-derive = "2"
+tokio = {version = "1.19.0", features = ["rt", "rt-multi-thread"]}
 
 [target.'cfg(target_arch = "wasm32")'.dependencies]
 js-sys = "0.3"