Allow renaming struct fields (paritytech#209)

* Allow renaming struct fields

* Handle `#[scale_info(rename = ...)]` with struct field

* Clean up by replacing if-else block with match expression

* Rebase on master to align with syn@2

* Add more checks to rename_field test

* Update CHANGELOG.md

Author: conr2d

CHANGELOG.md

@@ -5,6 +5,10 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+- Add `rename` attribute for renaming struct fields [(#209)](https://github.com/paritytech/scale-info/pull/209)
+
 ## [2.11.6] - 2024-11-20
 
 - add `#[allow(deprecated)]` attribute to the generated code.

derive/src/lib.rs

@@ -184,10 +184,12 @@ impl TypeInfoImpl {
                 } else {
                     quote!(ty)
                 };
-                let name = if let Some(ident) = ident {
-                    quote!(.name(::core::stringify!(#ident)))
-                } else {
-                    quote!()
+                let name = match utils::maybe_renamed(f) {
+                    Some(ident) => quote!(.name(#ident)),
+                    None => ident
+                        .as_ref()
+                        .map(|ident| quote!(.name(::core::stringify!(#ident))))
+                        .unwrap_or(quote!()),
                 };
                 quote!(
                     .field(|f| f

derive/src/utils.rs

@@ -96,6 +96,29 @@ pub fn should_skip(attrs: &[Attribute]) -> bool {
     .is_some()
 }
 
+/// Look for a `#[scale_info(rename = $str)]` outer attribute on the given `Field`.
+pub fn maybe_renamed(field: &syn::Field) -> Option<String> {
+    let outer_attrs = field
+        .attrs
+        .iter()
+        .filter(|attr| attr.style == AttrStyle::Outer);
+    scale_info_meta_item(outer_attrs, |meta| {
+        if let Meta::NameValue(ref nv) = meta {
+            if nv.path.is_ident("rename") {
+                if let Expr::Lit(ExprLit {
+                    lit: Lit::Str(ref v),
+                    ..
+                }) = nv.value
+                {
+                    return Some(v.value());
+                }
+            }
+        }
+
+        None
+    })
+}
+
 fn codec_meta_item<'a, F, R, I, M>(itr: I, pred: F) -> Option<R>
 where
     F: FnMut(M) -> Option<R> + Clone,
@@ -105,6 +128,15 @@ where
     find_meta_item("codec", itr, pred)
 }
 
+fn scale_info_meta_item<'a, F, R, I, M>(itr: I, pred: F) -> Option<R>
+where
+    F: FnMut(M) -> Option<R> + Clone,
+    I: Iterator<Item = &'a Attribute>,
+    M: Parse,
+{
+    find_meta_item("scale_info", itr, pred)
+}
+
 fn find_meta_item<'a, F, R, I, M>(kind: &str, mut itr: I, mut pred: F) -> Option<R>
 where
     F: FnMut(M) -> Option<R> + Clone,

test_suite/derive_tests_no_std/src/main.rs

@@ -1,5 +1,4 @@
-// Copyright 2019-2020
-//     Parity Technologies (UK) Ltd. Technologies (UK) Ltd.
+// Copyright 2019-2020 Parity Technologies (UK) Ltd.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.

test_suite/tests/derive.rs

@@ -907,3 +907,25 @@ fn replace_segments_works() {
 
     assert_type!(R, ty);
 }
+
+#[test]
+fn rename_field() {
+    #[allow(unused)]
+    #[derive(TypeInfo)]
+    pub struct S {
+        #[scale_info(rename = "type")]
+        r#type: bool,
+        #[scale_info(rename = "bar")]
+        foo: u8,
+        baz: u16,
+    }
+
+    let ty = Type::builder().path(Path::new("S", "derive")).composite(
+        Fields::named()
+            .field(|f| f.ty::<bool>().name("type").type_name("bool"))
+            .field(|f| f.ty::<u8>().name("bar").type_name("u8"))
+            .field(|f| f.ty::<u16>().name("baz").type_name("u16")),
+    );
+
+    assert_type!(S, ty);
+}