Use conventional meta-item syntax for attributes

Using the conventional form for attributes, which is compatible with
rustfmt and syn's meta-item parsing. This change is breaking and
substantial, but the necessary edits are largely mechanical.

With meta-items, it becomes possible to offload attribute parsing and
validation to `darling`. This offload fixes rustwasm#2874, as `darling` will
automatically generate errors for unexpected meta-item names. This also
makes it easier for people who are new to the codebase to understand
how to add new options.

benchmarks/src/lib.rs

@@ -7,20 +7,20 @@ use web_sys::Node;
 
 #[wasm_bindgen(raw_module = "../globals.js")]
 extern "C" {
-    #[wasm_bindgen(js_name = jsthunk)]
+    #[wasm_bindgen(js_name = "jsthunk")]
     fn js_thunk();
-    #[wasm_bindgen(js_name = add)]
+    #[wasm_bindgen(js_name = "add")]
     fn js_add(a: i32, b: i32) -> i32;
 
     pub type Foo;
-    #[wasm_bindgen(method, final, js_name = bar)]
+    #[wasm_bindgen(method, final, js_name = "bar")]
     fn bar_final(this: &Foo);
-    #[wasm_bindgen(method, structural, js_name = bar)]
+    #[wasm_bindgen(method, structural, js_name = "bar")]
     fn bar_structural(this: &Foo);
 
-    #[wasm_bindgen(js_name = jsthunk)]
+    #[wasm_bindgen(js_name = "jsthunk")]
     fn doesnt_throw();
-    #[wasm_bindgen(catch, js_name = jsthunk)]
+    #[wasm_bindgen(catch, js_name = "jsthunk")]
     fn doesnt_throw_catch() -> Result<(), JsValue>;
 }
 
@@ -102,9 +102,9 @@ pub fn call_doesnt_throw_with_catch_n_times(n: usize) {
 extern "C" {
     pub type Element;
 
-    #[wasm_bindgen(method, js_name = firstChild, final, getter)]
+    #[wasm_bindgen(method, js_name = "firstChild", final, getter)]
     fn first_child_final(this: &Element) -> Element;
-    #[wasm_bindgen(method, js_name = firstChild, structural, getter)]
+    #[wasm_bindgen(method, js_name = "firstChild", structural, getter)]
     fn first_child_structural(this: &Element) -> Element;
 }
 

crates/backend/Cargo.toml

@@ -17,6 +17,7 @@ extra-traits = ["syn/extra-traits"]
 
 [dependencies]
 bumpalo = "3.0.0"
+darling = "0.14"
 lazy_static = "1.0.2"
 log = "0.4"
 proc-macro2 = "1.0"

crates/backend/src/error.rs

@@ -30,6 +30,7 @@ enum Repr {
         text: String,
         span: Option<(Span, Span)>,
     },
+    Darling(TokenStream),
     SynError(Error),
     Multi {
         diagnostics: Vec<Diagnostic>,
@@ -86,6 +87,7 @@ impl Diagnostic {
             Repr::Single { text, .. } => panic!("{}", text),
             Repr::SynError(error) => panic!("{}", error),
             Repr::Multi { diagnostics } => diagnostics[0].panic(),
+            Repr::Darling(_error) => panic!("Darling error"),
         }
     }
 }
@@ -98,6 +100,14 @@ impl From<Error> for Diagnostic {
     }
 }
 
+impl From<darling::Error> for Diagnostic {
+    fn from(err: darling::Error) -> Self {
+        Self {
+            inner: Repr::Darling(err.write_errors()),
+        }
+    }
+}
+
 fn extract_spans(node: &dyn ToTokens) -> Option<(Span, Span)> {
     let mut t = TokenStream::new();
     node.to_tokens(&mut t);
@@ -129,6 +139,9 @@ impl ToTokens for Diagnostic {
             Repr::SynError(err) => {
                 err.to_compile_error().to_tokens(dst);
             }
+            Repr::Darling(err) => {
+                err.to_tokens(dst);
+            }
         }
     }
 }

crates/cli/tests/wasm-bindgen/main.rs

@@ -144,12 +144,12 @@ fn namespace_global_and_noglobal_works() {
                 use wasm_bindgen::prelude::*;
                 #[wasm_bindgen(module = "fs")]
                 extern "C" {
-                    #[wasm_bindgen(js_namespace = window)]
+                    #[wasm_bindgen(js_namespace = "window")]
                     fn t1();
                 }
                 #[wasm_bindgen]
                 extern "C" {
-                    #[wasm_bindgen(js_namespace = window)]
+                    #[wasm_bindgen(js_namespace = "window")]
                     fn t2();
                 }
                 #[wasm_bindgen]
@@ -189,7 +189,7 @@ fn bin_crate_works() {
                 use wasm_bindgen::prelude::*;
                 #[wasm_bindgen]
                 extern "C" {
-                    #[wasm_bindgen(js_namespace = console)]
+                    #[wasm_bindgen(js_namespace = "console")]
                     fn log(data: &str);
                 }
 

crates/futures/src/task/multithread.rs

@@ -187,13 +187,13 @@ fn wait_async(ptr: &AtomicI32, current_value: i32) -> Option<js_sys::Promise> {
         type Atomics;
         type WaitAsyncResult;
 
-        #[wasm_bindgen(static_method_of = Atomics, js_name = waitAsync)]
+        #[wasm_bindgen(static_method_of = "Atomics", js_name = "waitAsync")]
         fn wait_async(buf: &js_sys::Int32Array, index: i32, value: i32) -> WaitAsyncResult;
 
-        #[wasm_bindgen(static_method_of = Atomics, js_name = waitAsync, getter)]
+        #[wasm_bindgen(static_method_of = "Atomics", js_name = "waitAsync", getter)]
         fn get_wait_async() -> JsValue;
 
-        #[wasm_bindgen(method, getter, structural, js_name = async)]
+        #[wasm_bindgen(method, getter, structural, js_name = "async")]
         fn async_(this: &WaitAsyncResult) -> bool;
 
         #[wasm_bindgen(method, getter, structural)]