From 4fccff5e27e054e949cf363f83f2a09882001859 Mon Sep 17 00:00:00 2001
From: greg <greg.shuflin@protonmail.com>
Date: Thu, 27 Sep 2018 04:07:42 -0700
Subject: [PATCH] Working on improved proc_macro handling

---
 schala-codegen/Cargo.toml |  1 +
 schala-codegen/src/lib.rs | 36 ++++++++++++++++++++++++++++++++++--
 schala-lang/src/lib.rs    |  3 ++-
 3 files changed, 37 insertions(+), 3 deletions(-)

diff --git a/schala-codegen/Cargo.toml b/schala-codegen/Cargo.toml
index 5a63e5e..3317294 100644
--- a/schala-codegen/Cargo.toml
+++ b/schala-codegen/Cargo.toml
@@ -6,6 +6,7 @@ authors = ["greg <greg.shuflin@protonmail.com>"]
 [dependencies]
 syn = { version = "0.15.6", features = ["full", "extra-traits"] }
 quote = "0.6.8"
+proc-macro2 = "0.4.19"
 schala-repl = { path = "../schala-repl" }
 
 [lib]
diff --git a/schala-codegen/src/lib.rs b/schala-codegen/src/lib.rs
index 3dd7714..e026d2f 100644
--- a/schala-codegen/src/lib.rs
+++ b/schala-codegen/src/lib.rs
@@ -1,5 +1,6 @@
 #![feature(trace_macros)]
 extern crate proc_macro;
+extern crate proc_macro2;
 #[macro_use]
 extern crate quote;
 extern crate syn;
@@ -51,8 +52,17 @@ fn extract_attribute_list(name: &str, attrs: &Vec<Attribute>) -> Option<Vec<(Ide
   })
 }
 
+fn find_attr_by_name<'a>(name: &str, attrs: &'a Vec<Attribute>) -> Option<&'a Attribute> {
+  attrs.iter().find(|attr| {
+    let first = attr.path.segments.first();
+    let seg: Option<&&syn::PathSegment> = first.as_ref().map(|x| x.value());
+    seg.map(|seg| seg.ident.to_string() == name).unwrap_or(false)
+  })
+}
+
 #[proc_macro_derive(ProgrammingLanguageInterface, attributes(LanguageName, SourceFileExtension, PipelineSteps, DocMethod))]
 pub fn derive_programming_language_interface(input: TokenStream) -> TokenStream {
+
   let ast: DeriveInput = syn::parse(input).unwrap();
   let name = &ast.ident;
   let attrs = &ast.attrs;
@@ -61,7 +71,29 @@ pub fn derive_programming_language_interface(input: TokenStream) -> TokenStream
   let file_ext = extract_attribute_arg_by_name("SourceFileExtension", attrs).expect("SourceFileExtension is required");
   let passes = extract_attribute_list("PipelineSteps", attrs).expect("PipelineSteps are required");
   let pass_idents = passes.iter().map(|x| x.0.clone());
-  let doc_method: Option<String> = extract_attribute_arg_by_name("DocMethod", attrs);
+
+  let doc_method: Option<String>= find_attr_by_name("DocMethod", attrs).and_then(|attr| {
+    let tts = attr.tts.clone().into_iter().collect::<Vec<_>>();
+
+    if tts.len() == 2 {
+      let ref after_equals: proc_macro2::TokenTree = tts[1];
+      match after_equals {
+        proc_macro2::TokenTree::Ident(ident)  => Some(ident.to_string()),
+        _ => None
+      }
+    } else {
+      None
+    }
+  });
+
+  let doc_method_body = match doc_method {
+    None => quote! { },
+    Some(s) => quote!{
+      fn get_doc(&self, commands: &Vec<&str>) -> Option<String> {
+        #s(commands)
+      }
+    }
+  };
 
   //let pass_names: Vec<String> = passes.iter().map(|pass| pass.0.to_string()).collect();
   let pass_descriptors = passes.iter().map(|pass| {
@@ -97,7 +129,7 @@ pub fn derive_programming_language_interface(input: TokenStream) -> TokenStream
         //vec![ #(PassDescriptor { name: #pass_names.to_string(), debug_options: vec![] }),* ]
       }
     }
-    //TODO if  doc_method is defined, add code here
+      #doc_method_body
   };
 
   let output: TokenStream = tokens.into();
diff --git a/schala-lang/src/lib.rs b/schala-lang/src/lib.rs
index 231db05..390ef98 100644
--- a/schala-lang/src/lib.rs
+++ b/schala-lang/src/lib.rs
@@ -1,4 +1,5 @@
 #![feature(trace_macros)]
+#![feature(unrestricted_attribute_tokens)]
 #![feature(slice_patterns, box_patterns, box_syntax)]
 extern crate itertools;
 #[macro_use]
@@ -35,7 +36,7 @@ mod eval;
 #[LanguageName = "Schala"]
 #[SourceFileExtension = "schala"]
 #[PipelineSteps(tokenizing, parsing(compact,expanded,trace), symbol_table, typechecking, ast_reducing, eval)]
-#[DocMethod = "get_doc"]
+#[DocMethod = get_doc]
 pub struct Schala {
   state: eval::State<'static>,
   symbol_table: Rc<RefCell<symbol_table::SymbolTable>>,