2 files changed, 64 insertions, 0 deletions
diff --git a/cli/napi_sym/Cargo.toml b/cli/napi_sym/Cargo.toml
new file mode 100644
index 000000000..797ddf0bf
--- /dev/null
+++ b/cli/napi_sym/Cargo.toml
@@ -0,0 +1,18 @@
+[package]
+name = "napi_sym"
+version = "0.1.0"
+edition = "2021"
+license = "MIT"
+readme = "../README.md"
+description = "proc macro for writing N-API symbols"
+
+[lib]
+path = "./lib.rs"
+proc-macro = true
+
+[dependencies]
+proc-macro2 = "1"
+quote = "1"
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"
+syn = { version = "1", features = ["full", "extra-traits"] }
diff --git a/cli/napi_sym/lib.rs b/cli/napi_sym/lib.rs
new file mode 100644
index 000000000..caef3da65
--- /dev/null
+++ b/cli/napi_sym/lib.rs
@@ -0,0 +1,46 @@
+// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
+
+use proc_macro::TokenStream;
+use quote::quote;
+use serde::Deserialize;
+
+static NAPI_EXPORTS: &str =
+  include_str!("../../tools/napi/symbol_exports.json");
+
+#[derive(Deserialize)]
+struct SymbolExports {
+  pub symbols: Vec<String>,
+}
+
+#[proc_macro_attribute]
+pub fn napi_sym(_attr: TokenStream, item: TokenStream) -> TokenStream {
+  let func = syn::parse::<syn::ItemFn>(item).expect("expected a function");
+
+  let exports: SymbolExports =
+    serde_json::from_str(NAPI_EXPORTS).expect("failed to parse exports");
+  let name = &func.sig.ident;
+  assert!(
+    exports.symbols.contains(&name.to_string()),
+    "tools/napi/symbol_exports.json is out of sync!"
+  );
+
+  let block = &func.block;
+  let inputs = &func.sig.inputs;
+  let output = &func.sig.output;
+  let ret_ty = match output {
+    syn::ReturnType::Default => panic!("expected a return type"),
+    syn::ReturnType::Type(_, ty) => quote! { #ty },
+  };
+  TokenStream::from(quote! {
+      // SAFETY: it's an NAPI function.
+      #[no_mangle]
+      pub unsafe extern "C" fn #name(#inputs) -> napi_status {
+        let mut inner = || -> #ret_ty {
+          #block
+        };
+        inner()
+          .map(|_| napi_ok)
+          .unwrap_or_else(|e| e.into())
+      }
+  })
+}