Add feature to transfer docblocks from Rust public functions to gener…

…ated Dart functions

example/src/application/simple.rs

@@ -10,6 +10,10 @@ pub fn contacts() -> impl Stream<Item = Result<data::Contact, data::Error>> {
   futures::stream::iter(vec![Ok(data::Contact::default())])
 }
 
+///
+/// This is a docblock that was written in Rust and
+/// will be added to the generated Dart code.
+///
 #[async_dart(namespace = "accounts")]
 pub async fn contact(user_id: String) -> Result<data::Contact, data::Error> {
   println!("async {:?}", thread::current().id());

membrane/src/generators/functions.rs

@@ -254,6 +254,7 @@ trait Callable {
 impl Callable for Ffi {
   fn begin(&mut self) -> &mut Self {
     self.output += &self.fun.begin();
+    self.output += self.fun.docblock;
     self
   }
 
@@ -434,6 +435,7 @@ impl Callable for Ffi {
 impl Callable for Web {
   fn begin(&mut self) -> &mut Self {
     self.output += &self.fun.begin();
+    self.output += self.fun.docblock;
     self
   }
 

membrane/src/lib.rs

@@ -206,6 +206,7 @@ pub struct Function {
   pub dart_transforms: &'static str,
   pub dart_inner_args: &'static str,
   pub location: SourceCodeLocation,
+  pub docblock: &'static str,
 }
 
 #[doc(hidden)]

membrane/tests/integration_tests.rs

@@ -58,11 +58,25 @@ mod test {
 
     let api = read_to_string(path.join("lib/src").join("accounts_ffi.dart")).unwrap();
     assert!(api.contains("@immutable\nclass AccountsApi {"));
-    assert!(api.contains("Future<Contact> contact({required String userId}) async {"));
+    assert_contains_part(
+      &api,
+      "///
+/// This is a docblock that was written in Rust and
+/// will be added to the generated Dart code.
+///
+Future<Contact> contact({required String userId}) async {",
+    );
 
     let web_api = read_to_string(path.join("lib/src").join("accounts_web.dart")).unwrap();
     assert!(web_api.contains("@immutable\nclass AccountsApi {"));
-    assert!(web_api.contains("Future<Contact> contact({required String userId}) async {"));
+    assert_contains_part(
+      &web_api,
+      "///
+/// This is a docblock that was written in Rust and
+/// will be added to the generated Dart code.
+///
+Future<Contact> contact({required String userId}) async {",
+    );
 
     let dart_type = read_to_string(
       path

membrane_macro/src/lib.rs

@@ -3,6 +3,7 @@ use membrane_types::c::CHeaderTypes;
 use membrane_types::dart::{DartArgs, DartParams, DartTransforms};
 use membrane_types::heck::ToLowerCamelCase;
 use membrane_types::rust::{flatten_types, RustArgs, RustExternParams, RustTransforms};
+use membrane_types::syn::Attribute;
 use membrane_types::{proc_macro2, quote, syn, Input, OutputStyle};
 use options::{extract_options, Options};
 use proc_macro::TokenStream;
@@ -23,12 +24,28 @@ struct ReprDart {
   output_style: OutputStyle,
   output: syn::Type,
   error: syn::Type,
+  docblock: String,
 }
 
 impl Parse for ReprDart {
   fn parse(input: ParseStream) -> Result<Self> {
     let arg_buffer;
 
+    let docblock = input
+      .call(Attribute::parse_outer)?
+      .iter()
+      .map(|x| Ok(x.meta.require_name_value()?))
+      .map(|x: Result<&MetaNameValue>| Ok(x?.value.clone()))
+      .filter_map(|x: Result<syn::Expr>| match x {
+        Ok(syn::Expr::Lit(syn::ExprLit {
+          lit: syn::Lit::Str(comment),
+          ..
+        })) => Some(Ok(format!("/// {}\n", &comment.value()))),
+        _ => None,
+      })
+      .collect::<Result<Vec<String>>>()?
+      .join("");
+
     input.parse::<Token![pub]>()?;
     if input.peek(Token![async]) {
       input.parse::<Token![async]>()?;
@@ -50,6 +67,7 @@ impl Parse for ReprDart {
       output_style,
       output: ret_type,
       error: err_type,
+      docblock,
     })
   }
 }
@@ -144,6 +162,7 @@ fn to_token_stream(
     output,
     error,
     inputs,
+    docblock,
     ..
   } = repr_dart;
 
@@ -367,6 +386,7 @@ fn to_token_stream(
                 dart_inner_args: #dart_inner_args,
                 output: "",
                 location: #debug_location,
+                docblock: #docblock,
               },
               namespace: #namespace,
               trace: |