refactor: use derive macro

derive_macro/Cargo.lock

@@ -0,0 +1,47 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "derive_macro"
+version = "0.1.0"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "proc-macro2"
+version = "1.0.95"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "02b3e5e68a3a1a02aad3ec490a98007cbc13c37cbe84a3cd7b8e406d76e7f778"
+dependencies = [
+ "unicode-ident",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.40"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1885c039570dc00dcb4ff087a89e185fd56bae234ddc7f056a945bf36467248d"
+dependencies = [
+ "proc-macro2",
+]
+
+[[package]]
+name = "syn"
+version = "2.0.104"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "17b6f705963418cdb9927482fa304bc562ece2fdd4f616084c50b7023b435a40"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-ident",
+]
+
+[[package]]
+name = "unicode-ident"
+version = "1.0.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5a5f39404a5da50712a4c1eecf25e90dd62b613502b7e925fd4e4d19b5c96512"

derive_macro/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "derive_macro"
+version = "0.1.0"
+edition = "2024"
+
+[lib]
+crate-type = ["proc-macro"]
+
+[dependencies]
+proc-macro2 = "1.0"
+quote = "1.0"
+syn = { version = "2.0", features = ["full", "extra-traits"] }

derive_macro/src/lib.rs

@@ -0,0 +1,11 @@
+mod merge;
+
+use proc_macro::TokenStream;
+use syn::{DeriveInput, parse_macro_input};
+
+#[proc_macro_derive(Merge)]
+pub fn merge_derive(input: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(input as DeriveInput);
+    merge::impl_merge_derive(input)
+}
+

derive_macro/src/merge.rs

@@ -0,0 +1,58 @@
+use proc_macro::TokenStream;
+use quote::quote;
+use syn::{Data, DeriveInput, Fields, Type};
+
+pub fn impl_merge_derive(input: DeriveInput) -> TokenStream {
+    let name = &input.ident;
+    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
+
+    let fields = match input.data {
+        Data::Struct(data) => match data.fields {
+            Fields::Named(fields) => fields.named,
+            _ => unimplemented!("Only named fields are supported for Merge derive macro"),
+        },
+        _ => unimplemented!("Only structs are supported for Merge derive macro"),
+    };
+
+    let merge_logic = fields.iter().map(|field| {
+        let field_name = &field.ident;
+        let field_type = &field.ty;
+
+        // Check if the field is an Option<T>
+        if let Type::Path(type_path) = field_type {
+            if let Some(segment) = type_path.path.segments.last() {
+                if segment.ident == "Option" {
+                    // This is an Option<T> field
+                    return quote! {
+                        if let Some(o_val) = other.#field_name {
+                            if let Some(s_val) = self.#field_name.as_mut() {
+                                // If both are Some, attempt to merge recursively
+                                s_val.merge(o_val);
+                            } else {
+                                // If self is None, take the other's Some value
+                                self.#field_name = Some(o_val);
+                            }
+                        }
+                        // If other is None, self remains unchanged
+                    };
+                }
+            }
+        }
+
+        // For non-Option fields, attempt to merge recursively
+        quote! {
+            self.#field_name.merge(other.#field_name);
+        }
+    });
+
+    let expanded = quote! {
+        impl #impl_generics Merge for #name #ty_generics #where_clause {
+            fn merge(&mut self, other: Self) {
+                #(#merge_logic)*
+            }
+        }
+    };
+
+    expanded.into()
+}
+