From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Sat, 24 Jul 2021 00:55:25 +0000 (+0100)
Subject: macros wip
X-Git-Tag: hippotat/1.0.0~500
X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ian/git?a=commitdiff_plain;h=69f2efec8cc5d334d2aa7a027b5b4559596c5774;p=hippotat.git

macros wip

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
---

diff --git a/Cargo.lock b/Cargo.lock
index 7f9a853..247b02f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -215,6 +215,7 @@ dependencies = [
 name = "hippotat-macros"
 version = "0.0.0"
 dependencies = [
+ "itertools",
  "proc-macro2",
  "quote",
  "syn",
diff --git a/macros/Cargo.toml b/macros/Cargo.toml
index 391ac2a..e71c494 100644
--- a/macros/Cargo.toml
+++ b/macros/Cargo.toml
@@ -9,6 +9,7 @@ edition = "2018"
 description="Asinine HTTP-over-IP, proc-macros"
 
 [dependencies]
+itertools = "0.10"
 syn = "1"
 proc-macro2 = "1"
 quote = "1"
diff --git a/macros/macros.rs b/macros/macros.rs
index 89c165b..6576c27 100644
--- a/macros/macros.rs
+++ b/macros/macros.rs
@@ -2,3 +2,30 @@
 // SPDX-License-Identifier: AGPL-3.0-or-later
 // There is NO WARRANTY.
 
+use syn::{parse_macro_input, Data, DataStruct, DeriveInput};
+use quote::{quote, quote_spanned};
+
+use itertools::Itertools;
+
+#[proc_macro_derive(ResolveConfig)]
+pub fn resolve(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+  let input = parse_macro_input!(input as DeriveInput);
+
+  let fields = match input.data {
+    Data::Struct(DataStruct { fields: syn::Fields::Named(ref f),.. }) => f,
+    _ => panic!(),
+  };
+
+  let target = &input.ident;
+  let names = fields.named.iter().map(
+    |f| f.ident.as_ref().unwrap()
+  )
+    .collect_vec();
+
+  let output = quote! {
+    impl #target {
+      const FIELDS: &[&str] = &[ #( #names ),* ];
+    }
+  };
+  output.into()
+}