allow to derive protocols with Any

fixes rune-rs#583

Author: ModProg

crates/rune-macros/src/any.rs

@@ -79,7 +79,9 @@ impl Derive {
         let generics = &self.input.generics;
         let mut installers = Vec::new();
 
-        let Ok(()) = expand_install_with(&cx, &self.input, &tokens, &attr, generics, &mut installers) else {
+        let Ok(()) =
+            expand_install_with(&cx, &self.input, &tokens, &attr, generics, &mut installers)
+        else {
             return Err(cx.errors.into_inner());
         };
 
@@ -152,6 +154,8 @@ pub(crate) fn expand_install_with(
         }
     }
 
+    installers.extend(attr.protocols.iter().map(|protocol| protocol.expand()));
+
     if let Some(install_with) = &attr.install_with {
         installers.push(quote_spanned! { input.span() =>
             #install_with(module)?;

crates/rune-macros/src/context.rs

@@ -3,8 +3,8 @@ use std::cell::RefCell;
 use crate::internals::*;
 use proc_macro2::Span;
 use proc_macro2::TokenStream;
-use quote::quote_spanned;
-use quote::{quote, ToTokens};
+use quote::{quote, quote_spanned, ToTokens};
+use syn::parse::Parse;
 use syn::parse::ParseStream;
 use syn::punctuated::Punctuated;
 use syn::spanned::Spanned as _;
@@ -74,6 +74,8 @@ pub(crate) struct TypeAttr {
     pub(crate) item: Option<syn::Path>,
     /// `#[rune(constructor)]`.
     pub(crate) constructor: bool,
+    /// Protocols to "derive"
+    pub(crate) protocols: Vec<TypeProtocol>,
     /// Parsed documentation.
     pub(crate) docs: Vec<syn::Expr>,
 }
@@ -113,6 +115,60 @@ pub(crate) struct FieldProtocol {
     custom: Option<syn::Path>,
 }
 
+pub(crate) struct TypeProtocol {
+    protocol: syn::Ident,
+    handler: Option<syn::Path>,
+}
+
+impl TypeProtocol {
+    pub fn expand(&self) -> TokenStream {
+        if let Some(handler) = &self.handler {
+            let protocol = &self.protocol;
+            return quote_spanned! {protocol.span()=>
+                module.associated_function(rune::runtime::Protocol::#protocol, #handler)?;
+            };
+        }
+        match self.protocol.to_string().as_str() {
+            "ADD" => quote_spanned! {self.protocol.span()=>
+                module.associated_function(rune::runtime::Protocol::ADD, |this: Self, other: Self| this + other)?;
+            },
+            "STRING_DISPLAY" => quote_spanned! {self.protocol.span()=>
+                module.associated_function(rune::runtime::Protocol::STRING_DISPLAY, |this: &Self, buf: &mut String| {
+                    use ::std::fmt::Write as _;
+                    ::std::write!(buf, "{this}")
+                })?;
+            },
+            "STRING_DEBUG" => quote_spanned! {self.protocol.span()=>
+                module.associated_function(rune::runtime::Protocol::STRING_DEBUG, |this: &Self, buf: &mut String| {
+                    use ::std::fmt::Write as _;
+                    ::std::write!(buf, "{this:?}")
+                })?;
+            },
+            _ => syn::Error::new_spanned(
+                &self.protocol,
+                format!(
+                    "`{}` is not a protocol supported for automatic generation on a type",
+                    self.protocol
+                ),
+            )
+            .to_compile_error(),
+        }
+    }
+}
+
+impl Parse for TypeProtocol {
+    fn parse(input: ParseStream) -> syn::Result<Self> {
+        Ok(Self {
+            protocol: input.parse()?,
+            handler: if input.parse::<Token![=]>().is_ok() {
+                Some(input.parse()?)
+            } else {
+                None
+            },
+        })
+    }
+}
+
 #[derive(Default)]
 pub(crate) struct Context {
     pub(crate) errors: RefCell<Vec<syn::Error>>,
@@ -445,6 +501,12 @@ impl Context {
                         attr.install_with = Some(parse_path_compat(meta.input)?);
                     } else if meta.path == CONSTRUCTOR {
                         attr.constructor = true;
+                    } else if meta.path == PROTOCOLS {
+                        // Parse `#[rune(protocols(<protocol>,*))]`
+                        let protocols;
+                        syn::parenthesized!(protocols in meta.input);
+                        attr.protocols
+                            .extend(protocols.parse_terminated(TypeProtocol::parse, Token![,])?);
                     } else {
                         return Err(syn::Error::new_spanned(
                             &meta.path,

crates/rune-macros/src/internals.rs

@@ -19,6 +19,7 @@ pub const NAME: Symbol = Symbol("name");
 pub const ITEM: Symbol = Symbol("item");
 pub const MODULE: Symbol = Symbol("module");
 pub const INSTALL_WITH: Symbol = Symbol("install_with");
+pub const PROTOCOLS: Symbol = Symbol("protocols");
 
 pub const CONSTRUCTOR: Symbol = Symbol("constructor");
 pub const GET: Symbol = Symbol("get");