[ty] Allow overriding rules for specific files (#18648)

crates/ruff_macros/src/rust_doc.rs

@@ -0,0 +1,62 @@
+use proc_macro2::TokenStream;
+use quote::quote;
+use syn::{Attribute, DeriveInput, Error, Lit, LitStr, Meta};
+
+pub(crate) fn derive_impl(input: DeriveInput) -> syn::Result<TokenStream> {
+    let docs = get_docs(&input.attrs)?;
+
+    let name = input.ident;
+
+    let (impl_generics, ty_generics, where_clause) = &input.generics.split_for_impl();
+
+    Ok(quote! {
+        #[automatically_derived]
+        impl #impl_generics ruff_db::RustDoc for #name #ty_generics #where_clause {
+            fn rust_doc() -> &'static str {
+                #docs
+            }
+        }
+    })
+}
+/// Collect all doc comment attributes into a string
+fn get_docs(attrs: &[Attribute]) -> syn::Result<String> {
+    let mut explanation = String::new();
+    for attr in attrs {
+        if attr.path().is_ident("doc") {
+            if let Some(lit) = parse_attr(["doc"], attr) {
+                let value = lit.value();
+                // `/// ` adds
+                let line = value.strip_prefix(' ').unwrap_or(&value);
+                explanation.push_str(line);
+                explanation.push('\n');
+            } else {
+                return Err(Error::new_spanned(attr, "unimplemented doc comment style"));
+            }
+        }
+    }
+    Ok(explanation)
+}
+
+fn parse_attr<'a, const LEN: usize>(
+    path: [&'static str; LEN],
+    attr: &'a Attribute,
+) -> Option<&'a LitStr> {
+    if let Meta::NameValue(name_value) = &attr.meta {
+        let path_idents = name_value
+            .path
+            .segments
+            .iter()
+            .map(|segment| &segment.ident);
+
+        if path_idents.eq(path) {
+            if let syn::Expr::Lit(syn::ExprLit {
+                lit: Lit::Str(lit), ..
+            }) = &name_value.value
+            {
+                return Some(lit);
+            }
+        }
+    }
+
+    None
+}