feat(macros): add render_route macro and renderify attribute for render

pipeline error routing

1 files changed, 48 insertions, 0 deletions

diff --git a/mingling_macros/src/extensions/renderify.rs b/mingling_macros/src/extensions/renderify.rs
new file mode 100644
index 0000000..9be8acc
--- /dev/null
+++ b/mingling_macros/src/extensions/renderify.rs
@@ -0,0 +1,48 @@
+//! The `#[renderify]` extension — transforms `expr?` into `render_route!(expr)`.
+//!
+//! Designed as an extension for the Mingling attribute macro system, intended
+//! to be used with `#[renderer(renderify)]`, `#[help(renderify)]`,
+//! or standalone as `#[renderify]`.
+//!
+//! # How it works
+//!
+//! The macro parses the function AST and replaces every `Expr::Try` node with an
+//! equivalent `render_route!(expr)` invocation, which routes errors to the
+//! rendering pipeline via `crate::ThisProgram::render(AnyOutput::new(e))`.
+
+use proc_macro::TokenStream;
+use quote::ToTokens;
+use syn::spanned::Spanned;
+use syn::visit_mut::VisitMut;
+use syn::{Expr, ItemFn, parse_macro_input};
+
+struct RenderifyTransform;
+
+impl VisitMut for RenderifyTransform {
+    fn visit_expr_mut(&mut self, expr: &mut Expr) {
+        syn::visit_mut::visit_expr_mut(self, expr);
+
+        if let Expr::Try(try_expr) = expr {
+            let inner = &*try_expr.expr;
+            let inner_tokens = inner.to_token_stream();
+
+            // Set the span of the generated `render_route` ident to the `?` token's span,
+            // so that rust-analyzer resolves the `?` position to the `render_route!` macro
+            // instead of the standard Try trait, showing the render_route macro's docs on hover.
+            let q_span = try_expr.question_token.span();
+            let route_ident = proc_macro2::Ident::new("render_route", q_span);
+
+            if let Ok(macro_expr) = syn::parse2::<Expr>(quote::quote! {
+                ::mingling::macros::#route_ident!(#inner_tokens)
+            }) {
+                *expr = macro_expr;
+            }
+        }
+    }
+}
+
+pub(crate) fn renderify_impl(_attr: TokenStream, item: TokenStream) -> TokenStream {
+    let mut input_fn = parse_macro_input!(item as ItemFn);
+    RenderifyTransform.visit_item_fn_mut(&mut input_fn);
+    input_fn.to_token_stream().into()
+}