New macro setup

1 files changed, 82 insertions, 0 deletions

diff --git a/macros/src/func.rs b/macros/src/func.rs
new file mode 100644
index 00000000..af558f96
--- /dev/null
+++ b/macros/src/func.rs
@@ -0,0 +1,82 @@
+use super::*;
+
+/// Expand the `#[func]` macro.
+pub fn func(item: syn::Item) -> Result<TokenStream> {
+    let doc = documentation(&item)?;
+
+    if let syn::Item::Fn(item) = &item {
+        let vis = &item.vis;
+        let ident = &item.sig.ident;
+        let s = ident.to_string();
+        let mut chars = s.trim_end_matches("_").chars();
+        let ty = quote::format_ident!(
+            "{}{}Func",
+            chars.next().unwrap().to_ascii_uppercase(),
+            chars.as_str()
+        );
+
+        let full = if item.sig.inputs.len() == 1 {
+            quote! { |_, args| #ident(args) }
+        } else {
+            quote! { #ident }
+        };
+
+        Ok(quote! {
+            #item
+
+            #[doc(hidden)]
+            #vis enum #ty {}
+
+            impl::typst::model::FuncType for #ty {
+                fn create_func(name: &'static str) -> ::typst::model::Func {
+                    ::typst::model::Func::from_fn(name, #full, #doc)
+                }
+            }
+        })
+    } else {
+        let (ident, generics) = match &item {
+            syn::Item::Struct(s) => (&s.ident, &s.generics),
+            syn::Item::Enum(s) => (&s.ident, &s.generics),
+            _ => bail!(item, "only structs, enums, and functions are supported"),
+        };
+
+        let (params, args, clause) = generics.split_for_impl();
+
+        Ok(quote! {
+            #item
+
+            impl #params ::typst::model::FuncType for #ident #args #clause {
+                fn create_func(name: &'static str) -> ::typst::model::Func {
+                    ::typst::model::Func::from_node::<Self>(name, #doc)
+                }
+            }
+        })
+    }
+}
+
+/// Extract the item's documentation.
+fn documentation(item: &syn::Item) -> Result<String> {
+    let mut doc = String::new();
+
+    // Extract attributes.
+    let attrs = match item {
+        syn::Item::Struct(item) => &item.attrs,
+        syn::Item::Enum(item) => &item.attrs,
+        syn::Item::Fn(item) => &item.attrs,
+        _ => return Ok(doc),
+    };
+
+    // Parse doc comments.
+    for attr in attrs {
+        if let syn::Meta::NameValue(meta) = attr.parse_meta()? {
+            if meta.path.is_ident("doc") {
+                if let syn::Lit::Str(string) = &meta.lit {
+                    doc.push_str(&string.value());
+                    doc.push('\n');
+                }
+            }
+        }
+    }
+
+    Ok(doc.trim().into())
+}