Forward allow and cfg attrs to builder

If a struct is conditionally present, its builder should only be present in the same conditions.

If a struct disables lints, its builder should disable the same lints.

Fixes #222

derive_builder/CHANGELOG.md

@@ -2,6 +2,9 @@
 All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org/).
 
+## [Unreleased]
+- Forward `allow` and `cfg` attributes from the deriving struct to the builder and its impl block #222
+
 ## [0.11.0] - 2022-03-15
 - Support shorthand and long-form collection setters; `#[builder(setter(each = "..."))]` and `#[builder(setter(each(name = "...")))]` #234
 - Allow collection setters to be generic over `Into` using `#[builder(setter(each(name = "...", into)))] #234 and #214

derive_builder/tests/forward_allow_attr.rs

@@ -0,0 +1,24 @@
+#![deny(non_snake_case)]
+
+#[macro_use]
+extern crate derive_builder;
+
+#[derive(Builder)]
+// If this attribute is not forwarded to both the struct and the impl block, there would
+// be a compile error on either the field or the setter method name. Therefore, forwarding
+// is working as-expected if this test compiles.
+#[allow(non_snake_case)]
+pub struct Example {
+    aPascalName: &'static str,
+}
+
+fn main() {
+    assert_eq!(
+        ExampleBuilder::default()
+            .aPascalName("hello")
+            .build()
+            .unwrap()
+            .aPascalName,
+        "hello"
+    );
+}

derive_builder_core/src/builder.rs

@@ -92,6 +92,8 @@ pub struct Builder<'a> {
     pub pattern: BuilderPattern,
     /// Traits to automatically derive on the builder type.
     pub derives: &'a [Path],
+    /// Attributes to include on the builder `struct` declaration and its inherent `impl`.
+    pub attrs: &'a [syn::Attribute],
     /// When true, generate `impl Default for #ident` which calls the `create_empty` inherent method.
     ///
     /// Note that the name of `create_empty` can be overridden; see the `create_empty` field for more.
@@ -168,13 +170,16 @@ impl<'a> ToTokens for Builder<'a> {
                 }
             };
 
+            let attrs = self.attrs;
+
             let builder_doc_comment = &self.doc_comment;
             let deprecation_notes = &self.deprecation_notes.as_item();
 
             #[cfg(not(feature = "clippy"))]
             tokens.append_all(quote!(#[allow(clippy::all)]));
 
             tokens.append_all(quote!(
+                #(#attrs)*
                 #derive_attr
                 #builder_doc_comment
                 #builder_vis struct #builder_ident #struct_generics #where_clause {
@@ -186,6 +191,7 @@ impl<'a> ToTokens for Builder<'a> {
             tokens.append_all(quote!(#[allow(clippy::all)]));
 
             tokens.append_all(quote!(
+                #(#attrs)*
                 #[allow(dead_code)]
                 impl #impl_generics #builder_ident #ty_generics #where_clause {
                     #(#functions)*
@@ -324,6 +330,7 @@ macro_rules! default_builder {
             ident: syn::Ident::new("FooBuilder", ::proc_macro2::Span::call_site()),
             pattern: Default::default(),
             derives: &vec![],
+            attrs: &vec![],
             impl_default: true,
             create_empty: syn::Ident::new("create_empty", ::proc_macro2::Span::call_site()),
             generics: None,

derive_builder_core/src/macro_options/darling_opts.rs

@@ -345,18 +345,12 @@ fn default_create_empty() -> Ident {
 }
 
 #[derive(Debug, Clone, FromDeriveInput)]
-#[darling(
-    attributes(builder),
-    forward_attrs(doc, cfg, allow),
-    supports(struct_named)
-)]
+#[darling(attributes(builder), forward_attrs(cfg, allow), supports(struct_named))]
 pub struct Options {
     ident: Ident,
 
-    // These are currently unused, but that means the generated builder cannot have
-    // inherited the cfg or allow attributes from the base struct.
-    // see https://github.com/colin-kiegel/rust-derive-builder/issues/222
-    // attrs: Vec<Attribute>,
+    attrs: Vec<Attribute>,
+
     vis: Visibility,
 
     generics: Generics,
@@ -493,6 +487,7 @@ impl Options {
             ident: self.builder_ident(),
             pattern: self.pattern,
             derives: &self.derive,
+            attrs: &self.attrs,
             impl_default: {
                 let custom_constructor: bool = self.custom_constructor.into();
                 !custom_constructor