move asyncify.rs to its own crate

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

Cargo.toml

@@ -42,6 +42,8 @@ wit-bindgen-csharp = { path = 'crates/csharp', version = '0.16.0' }
 wit-bindgen-markdown = { path = 'crates/markdown', version = '0.16.0' }
 wit-bindgen = { path = 'crates/guest-rust', version = '0.16.0', default-features = false }
 
+isyswasfa-transform = { path = "../transform" }
+
 [[bin]]
 name = "wit-bindgen"
 
@@ -57,6 +59,7 @@ wit-bindgen-go = { workspace = true, features = ['clap'], optional = true }
 wit-bindgen-csharp = { workspace = true, features = ['clap'], optional = true }
 wit-component = { workspace = true }
 wasm-encoder = { workspace = true }
+isyswasfa-transform = { workspace = true }
 
 [features]
 default = [

crates/core/src/lib.rs

@@ -9,8 +9,6 @@ mod ns;
 pub use ns::Ns;
 pub mod source;
 pub use source::{Files, Source};
-pub mod asyncify;
-pub use asyncify::asyncify;
 
 #[derive(Default, Copy, Clone, PartialEq, Eq, Debug)]
 pub enum Direction {

crates/rust-macro/Cargo.toml

@@ -23,3 +23,4 @@ wit-bindgen-core = { workspace = true }
 wit-bindgen-rust = { workspace = true }
 wit-component = { workspace = true }
 anyhow = { workspace = true }
+isyswasfa-transform = { workspace = true }

crates/rust-macro/src/lib.rs

@@ -94,14 +94,14 @@ impl Parse for Config {
                             .collect()
                     }
                     Opt::With(with) => opts.with.extend(with),
-                    Opt::Asyncify(suffix) => {
-                        if opts.asyncify.is_some() {
+                    Opt::Isyswasfa(suffix) => {
+                        if opts.isyswasfa.is_some() {
                             return Err(Error::new(
                                 suffix.span(),
-                                "cannot specify second asyncify suffix",
+                                "cannot specify second isyswasfa suffix",
                             ));
                         }
-                        opts.asyncify = Some(suffix.value())
+                        opts.isyswasfa = Some(suffix.value())
                     }
                 }
             }
@@ -116,8 +116,8 @@ impl Parse for Config {
         let world = resolve
             .select_world(pkg, world.as_deref())
             .map_err(|e| Error::new(call_site, format!("{e:?}")))?;
-        let (resolve, world) = if let Some(suffix) = opts.asyncify.as_deref() {
-            wit_bindgen_core::asyncify(&resolve, world, suffix)
+        let (resolve, world) = if let Some(suffix) = opts.isyswasfa.as_deref() {
+            isyswasfa_transform::transform(&resolve, world, Some(suffix))
         } else {
             (resolve, world)
         };
@@ -200,7 +200,7 @@ mod kw {
     syn::custom_keyword!(export_prefix);
     syn::custom_keyword!(additional_derives);
     syn::custom_keyword!(with);
-    syn::custom_keyword!(asyncify);
+    syn::custom_keyword!(isyswasfa);
 }
 
 #[derive(Clone)]
@@ -261,7 +261,7 @@ enum Opt {
     // Parse as paths so we can take the concrete types/macro names rather than raw strings
     AdditionalDerives(Vec<syn::Path>),
     With(HashMap<String, String>),
-    Asyncify(syn::LitStr),
+    Isyswasfa(syn::LitStr),
 }
 
 impl Parse for Opt {
@@ -352,10 +352,10 @@ impl Parse for Opt {
             input.parse::<kw::export_prefix>()?;
             input.parse::<Token![:]>()?;
             Ok(Opt::ExportPrefix(input.parse()?))
-        } else if l.peek(kw::asyncify) {
-            input.parse::<kw::asyncify>()?;
+        } else if l.peek(kw::isyswasfa) {
+            input.parse::<kw::isyswasfa>()?;
             input.parse::<Token![:]>()?;
-            Ok(Opt::Asyncify(input.parse()?))
+            Ok(Opt::Isyswasfa(input.parse()?))
         } else if l.peek(kw::additional_derives) {
             input.parse::<kw::additional_derives>()?;
             input.parse::<Token![:]>()?;

crates/rust/src/interface.rs

@@ -127,7 +127,7 @@ impl InterfaceGenerator<'_> {
                 sig.self_is_first_param = true;
             }
             self.print_signature(func, TypeMode::Owned, &sig);
-            if let Some(suffix) = self.gen.opts.asyncify.clone() {
+            if let Some(suffix) = self.gen.opts.isyswasfa.clone() {
                 if func.name == format!("isyswasfa-poll{suffix}") {
                     self.src.push_str("{ isyswasfa_guest::poll(input) }\n");
                 } else if let Some(prefix) = func.name.strip_suffix("-isyswasfa") {
@@ -191,14 +191,22 @@ impl InterfaceGenerator<'_> {
         // there's only one implementation of this trait and it must be
         // pre-configured.
         for (export_key, (trait_name, local_impl_name, methods)) in traits {
-            let impl_name = self.gen.lookup_export(&export_key)?;
-            let path_to_root = self.path_to_root();
-            uwriteln!(
-                self.src,
-                "use {path_to_root}{impl_name} as {local_impl_name};"
-            );
+            if self.gen.opts.isyswasfa.is_some()
+                && matches!(export_key, ExportKey::World)
+                && methods.len() == 1
+            {
+                uwriteln!(self.src, "struct {local_impl_name};");
+                uwriteln!(self.src, "impl {trait_name} for {local_impl_name} {{}}");
+            } else {
+                let impl_name = self.gen.lookup_export(&export_key)?;
+                let path_to_root = self.path_to_root();
+                uwriteln!(
+                    self.src,
+                    "use {path_to_root}{impl_name} as {local_impl_name};"
+                );
+            }
 
-            if self.gen.opts.asyncify.is_some() {
+            if self.gen.opts.isyswasfa.is_some() {
                 self.src.push_str("#[async_trait(?Self)]\n");
             }
             uwriteln!(self.src, "pub trait {trait_name} {{");
@@ -363,7 +371,7 @@ impl InterfaceGenerator<'_> {
         self.src.push_str("}\n");
         self.src.push_str("}\n");
 
-        if self.gen.opts.asyncify.is_some() {
+        if self.gen.opts.isyswasfa.is_some() {
             if let Some(prefix) = func.name.strip_suffix("-isyswasfa") {
                 sig.async_ = true;
                 self.src.push_str("#[allow(unused_unsafe, clippy::all)]\n");