preserve Rust docs in JS bindings (#13)

codegen.ts

@@ -74,11 +74,7 @@ const _lib = await Plug.prepare(opts, {
     ).join(", ")
   } });
 ${
-    Object.keys(decl).map((def) =>
-      `export type ${def} = {
-${typescript[def]}
-}`
-    ).join("\n")
+    Object.keys(decl).map((def) => typescript[def]).join("\n")
   }
 ${
     Object.keys(signature).map((sig) =>

example/bindings/bindings.ts

@@ -3,49 +3,47 @@ import { Plug } from "https://deno.land/x/[email protected]/mod.ts";
 const encode = (s: string) => new TextEncoder().encode(s);
 const opts = {
   name: "add",
-  url: "target/debug",
+  url: "target/debug"
 };
 const _lib = await Plug.prepare(opts, {
-  test_serde: { parameters: ["buffer", "usize"], result: "u8" },
-  test_mixed: { parameters: ["isize", "buffer", "usize"], result: "i32" },
-  add: { parameters: ["i32", "i32"], result: "i32" },
-  add2: { parameters: ["buffer", "usize"], result: "i32" },
-  test_mixed_order: {
-    parameters: ["i32", "buffer", "usize", "i32"],
-    result: "i32",
-  },
-});
-export type MyStruct = {
-  arr: Array<string>;
-};
+  add: { parameters: [ "i32", "i32" ], result: "i32" }, test_mixed: { parameters: [ "isize", "buffer", "usize" ], result: "i32" }, test_serde: { parameters: [ "buffer", "usize" ], result: "u8" }, add2: { parameters: [ "buffer", "usize" ], result: "i32" }, test_mixed_order: { parameters: [ "i32", "buffer", "usize", "i32" ], result: "i32" } });
 export type OptionStruct = {
-  maybe: string | undefined | null;
+    maybe: string | undefined | null;
 };
+/**
+  * Doc comment for `Input` struct.
+  * ...testing multiline
+  **/
 export type Input = {
+  /**
+  * Doc comments get 
+  * transformed to JS doc
+  * comments.
+  **/
   a: number;
   b: number;
 };
-export function test_serde(a0: MyStruct) {
-  const a0_buf = encode(JSON.stringify(a0));
-  return _lib.symbols.test_serde(a0_buf, a0_buf.byteLength) as number;
+export type MyStruct = {
+    arr: Array<string>;
+};
+export function add(a0: number,a1: number) {
+
+  return _lib.symbols.add(a0, a1) as number
 }
-export function test_mixed(a0: number, a1: Input) {
+export function test_mixed(a0: number,a1: Input) {
   const a1_buf = encode(JSON.stringify(a1));
-  return _lib.symbols.test_mixed(a0, a1_buf, a1_buf.byteLength) as number;
+  return _lib.symbols.test_mixed(a0, a1_buf, a1_buf.byteLength) as number
 }
-export function add(a0: number, a1: number) {
-  return _lib.symbols.add(a0, a1) as number;
+export function test_serde(a0: MyStruct) {
+  const a0_buf = encode(JSON.stringify(a0));
+  return _lib.symbols.test_serde(a0_buf, a0_buf.byteLength) as number
 }
 export function add2(a0: Input) {
   const a0_buf = encode(JSON.stringify(a0));
-  return _lib.symbols.add2(a0_buf, a0_buf.byteLength) as number;
+  return _lib.symbols.add2(a0_buf, a0_buf.byteLength) as number
 }
-export function test_mixed_order(a0: number, a1: Input, a2: number) {
+export function test_mixed_order(a0: number,a1: Input,a2: number) {
   const a1_buf = encode(JSON.stringify(a1));
-  return _lib.symbols.test_mixed_order(
-    a0,
-    a1_buf,
-    a1_buf.byteLength,
-    a2,
-  ) as number;
+  return _lib.symbols.test_mixed_order(a0, a1_buf, a1_buf.byteLength, a2) as number
 }
+

example/src/lib.rs

@@ -10,7 +10,12 @@ fn add(a: i32, b: i32) -> i32 {
 // Test Structs
 
 #[deno_bindgen]
+/// Doc comment for `Input` struct.
+/// ...testing multiline
 pub struct Input {
+  /// Doc comments get
+  /// transformed to JS doc
+  /// comments.
   a: i32,
   b: i32,
 }

src/lib.rs

@@ -296,6 +296,7 @@ fn process_struct(
       .as_ref()
       .expect("Field without ident")
       .to_string();
+
     match field.ty {
       syn::Type::Path(ref ty) => {
         let segment = &ty.path.segments.first().unwrap();
@@ -305,16 +306,50 @@ fn process_struct(
       _ => unimplemented!(),
     };
 
-    typescript.push(format!("  {}: {};", ident, types_to_ts(&field.ty)));
+    let doc_str = get_docs(&field.attrs);
+    typescript.push(format!(
+      "{}  {}: {};",
+      doc_str,
+      ident,
+      types_to_ts(&field.ty)
+    ));
   }
 
   metadata.type_defs.insert(name.to_string(), fmap.clone());
-  metadata
-    .ts_types
-    .insert(name.to_string(), typescript.join("\n").to_string());
+
+  let doc_str = get_docs(&input.attrs);
+  let typescript = format!(
+    "{}export type {} = {{\n  {}\n}};",
+    doc_str,
+    name,
+    typescript.join("\n")
+  );
+  metadata.ts_types.insert(name.to_string(), typescript);
   Ok(fmap)
 }
 
+fn get_docs(attrs: &Vec<syn::Attribute>) -> String {
+  let mut doc: Vec<String> = vec![];
+  for attr in attrs {
+    if let Ok(syn::Meta::NameValue(meta)) = attr.parse_meta() {
+      if !meta.path.is_ident("doc") {
+        continue;
+      }
+      if let syn::Lit::Str(lit) = meta.lit {
+        doc.push(lit.value());
+      }
+    }
+  }
+
+  let doc_str = if doc.len() > 0 {
+    format!("/**\n  *{}\n  **/\n", doc.join("\n  *"))
+  } else {
+    String::new()
+  };
+
+  doc_str
+}
+
 fn types_to_ts(ty: &syn::Type) -> String {
   match ty {
     syn::Type::Array(_) => String::from("any"),