macros: Fix field ids when deriving Introspectable for structs

macros/CHANGELOG.md

@@ -5,6 +5,12 @@ 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
+
+### Fixed
+
+- Fix custom ids (`[aldrin(id = ...)]`) for struct fields.
+
 ## [0.10.0] - 2024-11-26
 
 - Bump for Aldrin 0.10.0 release.

macros/src/derive/introspectable.rs

@@ -157,7 +157,7 @@ fn gen_field(
         }
     };
 
-    Ok((layout, references, default_id))
+    Ok((layout, references, id))
 }
 
 fn gen_enum(

macros/src/test.rs

@@ -1,3 +1,6 @@
+use aldrin::core::introspection::Introspection;
+use aldrin::Introspectable;
+
 mod raw_identifiers {
     #![allow(non_camel_case_types)]
 
@@ -40,3 +43,33 @@ mod raw_identifiers {
     #[aldrin(schema = "raw_identifiers")]
     enum r#false {}
 }
+
+#[test]
+fn introspection_non_default_field_ids() {
+    #[allow(dead_code)]
+    #[derive(Introspectable)]
+    #[aldrin(schema = "test")]
+    struct NonDefaultFieldIds {
+        field0: (),
+
+        #[aldrin(id = 2)]
+        field2: (),
+
+        field3: (),
+    }
+
+    let introspection = Introspection::new::<NonDefaultFieldIds>();
+    let layout = introspection.as_struct_layout().unwrap();
+
+    let field0 = layout.fields().get(&0).unwrap();
+    assert_eq!(field0.id(), 0);
+    assert_eq!(field0.name(), "field0");
+
+    let field2 = layout.fields().get(&2).unwrap();
+    assert_eq!(field2.id(), 2);
+    assert_eq!(field2.name(), "field2");
+
+    let field3 = layout.fields().get(&3).unwrap();
+    assert_eq!(field3.id(), 3);
+    assert_eq!(field3.name(), "field3");
+}