[component_macro] Add host_bindgen!()

This adds a proc-macro crate that exposes the bindings code generation
from hyperlight_component_util as a macro suitable for using WIT to
define a hyperlight host<->guest interface.

Signed-off-by: Lucy Menon <[email protected]>

Author: syntactically

Cargo.toml

@@ -9,6 +9,7 @@ members = [
     "src/hyperlight_guest_capi",
     "fuzz",
     "src/hyperlight_component_util",
+    "src/hyperlight_component_macro",
 ]
 # Guests have custom linker flags, so we need to exclude them from the workspace
 exclude = [
@@ -32,6 +33,7 @@ hyperlight-host = { path = "src/hyperlight_host", version = "0.2.0", default-fea
 hyperlight-guest = { path = "src/hyperlight_guest", version = "0.2.0", default-features = false }
 hyperlight-testing = { path = "src/hyperlight_testing", default-features = false }
 hyperlight-component-util = { path = "src/hyperlight_component_util" }
+hyperlight-component-macro = { path = "src/hyperlight_component_macro" }
 
 [workspace.lints.rust]
 unsafe_op_in_unsafe_fn = "deny"

src/hyperlight_component_macro/Cargo.toml

@@ -0,0 +1,25 @@
+[package]
+name = "hyperlight-component-macro"
+version.workspace = true
+edition.workspace = true
+rust-version.workspace = true
+license.workspace = true
+homepage.workspace = true
+repository.workspace = true
+readme.workspace = true
+description = """
+Procedural macros to generate Hyperlight host and guest bindings from component types
+"""
+
+[lib]
+name = "hyperlight_component_macro"
+proc-macro = true
+
+[dependencies]
+wasmparser = { version = "0.224.0" }
+quote = { version = "1.0.38" }
+proc-macro2 = { version = "1.0.93" }
+syn = { version = "2.0.96" }
+itertools = { version = "0.14.0" }
+prettyplease = { version = "0.2.31" }
+hyperlight-component-util = { workspace = true }

src/hyperlight_component_macro/src/lib.rs

@@ -0,0 +1,18 @@
+extern crate proc_macro;
+
+use hyperlight_component_util::*;
+
+#[proc_macro]
+pub fn host_bindgen(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    let path: Option<syn::LitStr> = syn::parse_macro_input!(input as Option<syn::LitStr>);
+    let path = path
+        .map(|x| x.value().into())
+        .unwrap_or_else(|| std::env::var_os("HYPERLIGHT_WASM_WORLD").unwrap());
+    util::read_wit_type_from_file(path, |kebab_name, ct| {
+        let decls = emit::run_state(false, |s| {
+            rtypes::emit_toplevel(s, &kebab_name, ct);
+            host::emit_toplevel(s, &kebab_name, ct);
+        });
+        util::emit_decls(decls).into()
+    })
+}