refactor: use derive macro

Cargo.lock

@@ -301,6 +301,15 @@ dependencies = [
  "powerfmt",
 ]
 
+[[package]]
+name = "derive_macro"
+version = "0.1.0"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "derive_more"
 version = "2.0.1"
@@ -1951,6 +1960,7 @@ version = "0.1.0"
 dependencies = [
  "color-eyre",
  "crossterm 0.29.0",
+ "derive_macro",
  "dirs",
  "ratatui",
  "serde",

Cargo.toml

@@ -19,3 +19,4 @@ toml = "0.8"
 dirs = "6.0"
 transmission-rpc = "0.5"
 url = "2.5"
+derive_macro = { path = "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()
+}
+

src/app/command.rs

@@ -20,8 +20,9 @@ impl Torrents {
                 self.client
                     .torrent_action(action, vec![id])
                     .await
-                    .map_err(|e| color_eyre::eyre::eyre!("Transmission RPC error: {}", e.to_string()))?;
+                    .map_err(|e| {
-
+                        color_eyre::eyre::eyre!("Transmission RPC error: {}", e.to_string())
+                    })?;
             }
         }
         Ok(())
@@ -48,7 +49,9 @@ impl Torrents {
             self.client
                 .torrent_action(action, vec![id])
                 .await
-                .map_err(|e| color_eyre::eyre::eyre!("Transmission RPC error: {}", e.to_string()))?;
+                .map_err(|e| {
+                    color_eyre::eyre::eyre!("Transmission RPC error: {}", e.to_string())
+                })?;
         }
         Ok(())
     }
@@ -71,12 +74,18 @@ impl Torrents {
             self.client
                 .torrent_set_location(vec![id], location.to_string_lossy().into(), move_from)
                 .await
-                .map_err(|e| color_eyre::eyre::eyre!("Transmission RPC error: {}", e.to_string()))?;
+                .map_err(|e| {
+                    color_eyre::eyre::eyre!("Transmission RPC error: {}", e.to_string())
+                })?;
         }
         Ok(())
     }
 
-    pub async fn delete(&mut self, ids: Selected, delete_local_data: bool) -> color_eyre::eyre::Result<()> {
+    pub async fn delete(
+        &mut self,
+        ids: Selected,
+        delete_local_data: bool,
+    ) -> color_eyre::eyre::Result<()> {
         self.client
             .torrent_remove(ids.into(), delete_local_data)
             .await
@@ -89,7 +98,9 @@ impl Torrents {
             self.client
                 .torrent_rename_path(vec![id], old_name, name.to_string_lossy().into())
                 .await
-                .map_err(|e| color_eyre::eyre::eyre!("Transmission RPC error: {}", e.to_string()))?;
+                .map_err(|e| {
+                    color_eyre::eyre::eyre!("Transmission RPC error: {}", e.to_string())
+                })?;
         }
         Ok(())
     }

src/config/colors.rs

@@ -1,8 +1,9 @@
-use crate::merge_fields;
+use crate::merge::Merge;
+use derive_macro::Merge;
 use ratatui::prelude::*;
 use serde::{Deserialize, Serialize};
 
-#[derive(Debug, Deserialize, Serialize)]
+#[derive(Debug, Deserialize, Serialize, Merge)]
 pub struct ColorsConfig {
     pub highlight_background: Option<String>,
     pub highlight_foreground: Option<String>,
@@ -32,18 +33,6 @@ impl ColorsConfig {
             None => Color::Reset,
         }
     }
-
-    pub fn merge(&mut self, other: Self) {
-        merge_fields!(
-            self,
-            other,
-            highlight_background,
-            highlight_foreground,
-            warning_foreground,
-            info_foreground,
-            error_foreground
-        );
-    }
 }
 
 impl Default for ColorsConfig {

src/config/keybinds.rs

@@ -1,7 +1,8 @@
+use crate::merge::Merge;
+use derive_macro::Merge;
 use serde::{Deserialize, Serialize};
-use crate::merge_fields;
 
-#[derive(Debug, Deserialize, Serialize)]
+#[derive(Debug, Deserialize, Serialize, Merge)]
 pub struct KeybindsConfig {
     pub quit: Option<String>,
     pub next_tab: Option<String>,
@@ -19,29 +20,6 @@ pub struct KeybindsConfig {
     pub toggle_help: Option<String>,
 }
 
-impl KeybindsConfig {
-    pub fn merge(&mut self, other: Self) {
-        merge_fields!(
-            self,
-            other,
-            quit,
-            next_tab,
-            prev_tab,
-            next_torrent,
-            prev_torrent,
-            switch_tab_1,
-            switch_tab_2,
-            switch_tab_3,
-            toggle_torrent,
-            toggle_all,
-            delete,
-            delete_force,
-            select,
-            toggle_help
-        );
-    }
-}
-
 impl Default for KeybindsConfig {
     fn default() -> Self {
         Self {

src/config/mod.rs

@@ -1,24 +1,15 @@
 mod colors;
 mod keybinds;
 
+use crate::merge::Merge;
 use color_eyre::Result;
 use colors::ColorsConfig;
+use derive_macro::Merge;
 use keybinds::KeybindsConfig;
 use serde::{Deserialize, Serialize};
 use std::path::PathBuf;
 
-#[macro_export]
+#[derive(Debug, Default, Deserialize, Serialize, Merge)]
-macro_rules! merge_fields {
-    ($self:ident, $other:ident, $($field:ident),*) => {
-        $(
-            if let Some($field) = $other.$field {
-                $self.$field = Some($field);
-            }
-        )*
-    };
-}
-
-#[derive(Debug, Default, Deserialize, Serialize)]
 pub struct Config {
     pub keybinds: KeybindsConfig,
     pub colors: ColorsConfig,
@@ -64,9 +55,4 @@ impl Config {
             });
         Ok(config_dir.join("traxor").join("config.toml"))
     }
-
-    pub fn merge(&mut self, other: Self) {
-        self.keybinds.merge(other.keybinds);
-        self.colors.merge(other.colors);
-    }
 }

src/handler.rs

@@ -72,8 +72,12 @@ pub fn get_action(key_event: KeyEvent, app: &App) -> Option<Action> {
         _ if matches_keybind(&key_event, &config_keybinds.quit) => Some(Action::Quit),
         _ if matches_keybind(&key_event, &config_keybinds.next_tab) => Some(Action::NextTab),
         _ if matches_keybind(&key_event, &config_keybinds.prev_tab) => Some(Action::PrevTab),
-        _ if matches_keybind(&key_event, &config_keybinds.next_torrent) => Some(Action::NextTorrent),
+        _ if matches_keybind(&key_event, &config_keybinds.next_torrent) => {
-        _ if matches_keybind(&key_event, &config_keybinds.prev_torrent) => Some(Action::PrevTorrent),
+            Some(Action::NextTorrent)
+        }
+        _ if matches_keybind(&key_event, &config_keybinds.prev_torrent) => {
+            Some(Action::PrevTorrent)
+        }
         _ if matches_keybind(&key_event, &config_keybinds.switch_tab_1) => {
             Some(Action::SwitchTab(0))
         }

src/lib.rs

@@ -1,7 +1,8 @@
-pub mod config;
 pub mod app;
+pub mod config;
 pub mod event;
 pub mod handler;
 pub mod log;
+pub mod merge;
 pub mod tui;
 pub mod ui;

src/main.rs

@@ -53,4 +53,3 @@ async fn main() -> Result<()> {
     tui.exit()?;
     Ok(())
 }
-

src/merge.rs

@@ -0,0 +1,21 @@
+pub trait Merge {
+    fn merge(&mut self, other: Self);
+}
+
+impl Merge for String {
+    fn merge(&mut self, other: Self) {
+        *self = other;
+    }
+}
+
+impl Merge for u32 {
+    fn merge(&mut self, other: Self) {
+        *self = other;
+    }
+}
+
+impl Merge for bool {
+    fn merge(&mut self, other: Self) {
+        *self = other;
+    }
+}

src/ui/help.rs

@@ -1,5 +1,5 @@
-use ratatui::{prelude::*, widgets::*};
 use crate::app::App;
+use ratatui::{prelude::*, widgets::*};
 
 pub fn render_help(frame: &mut Frame, app: &App) {
     let block = Block::default()
@@ -11,23 +11,62 @@ pub fn render_help(frame: &mut Frame, app: &App) {
     let keybinds = &app.config.keybinds;
 
     let rows = vec![
-        Row::new(vec![Cell::from(keybinds.toggle_help.as_deref().unwrap_or("?")), Cell::from("Show help")]),
+        Row::new(vec![
-        Row::new(vec![Cell::from(keybinds.quit.as_deref().unwrap_or("q")), Cell::from("Quit")]),
+            Cell::from(keybinds.toggle_help.as_deref().unwrap_or("?")),
-        Row::new(vec![Cell::from(keybinds.prev_tab.as_deref().unwrap_or("h")), Cell::from("Left")]),
+            Cell::from("Show help"),
-        Row::new(vec![Cell::from(keybinds.next_tab.as_deref().unwrap_or("l")), Cell::from("Right")]),
+        ]),
-        Row::new(vec![Cell::from(keybinds.next_torrent.as_deref().unwrap_or("j")), Cell::from("Down")]),
+        Row::new(vec![
-        Row::new(vec![Cell::from(keybinds.prev_torrent.as_deref().unwrap_or("k")), Cell::from("Up")]),
+            Cell::from(keybinds.quit.as_deref().unwrap_or("q")),
-        Row::new(vec![Cell::from(keybinds.switch_tab_1.as_deref().unwrap_or("1")), Cell::from("Switch to All tab")]),
+            Cell::from("Quit"),
-        Row::new(vec![Cell::from(keybinds.switch_tab_2.as_deref().unwrap_or("2")), Cell::from("Switch to Active tab")]),
+        ]),
+        Row::new(vec![
+            Cell::from(keybinds.prev_tab.as_deref().unwrap_or("h")),
+            Cell::from("Left"),
+        ]),
+        Row::new(vec![
+            Cell::from(keybinds.next_tab.as_deref().unwrap_or("l")),
+            Cell::from("Right"),
+        ]),
+        Row::new(vec![
+            Cell::from(keybinds.next_torrent.as_deref().unwrap_or("j")),
+            Cell::from("Down"),
+        ]),
+        Row::new(vec![
+            Cell::from(keybinds.prev_torrent.as_deref().unwrap_or("k")),
+            Cell::from("Up"),
+        ]),
+        Row::new(vec![
+            Cell::from(keybinds.switch_tab_1.as_deref().unwrap_or("1")),
+            Cell::from("Switch to All tab"),
+        ]),
+        Row::new(vec![
+            Cell::from(keybinds.switch_tab_2.as_deref().unwrap_or("2")),
+            Cell::from("Switch to Active tab"),
+        ]),
         Row::new(vec![
             Cell::from(keybinds.switch_tab_3.as_deref().unwrap_or("3")),
             Cell::from("Switch to Downloading tab"),
         ]),
-        Row::new(vec![Cell::from(keybinds.toggle_torrent.as_deref().unwrap_or("t")), Cell::from("Toggle torrent")]),
+        Row::new(vec![
-        Row::new(vec![Cell::from(keybinds.toggle_all.as_deref().unwrap_or("a")), Cell::from("Toggle all torrents")]),
+            Cell::from(keybinds.toggle_torrent.as_deref().unwrap_or("t")),
-        Row::new(vec![Cell::from(keybinds.delete.as_deref().unwrap_or("d")), Cell::from("Delete torrent")]),
+            Cell::from("Toggle torrent"),
-        Row::new(vec![Cell::from(keybinds.delete_force.as_deref().unwrap_or("D")), Cell::from("Delete torrent and data")]),
+        ]),
-        Row::new(vec![Cell::from(keybinds.select.as_deref().unwrap_or(" ")), Cell::from("Select torrent")]),
+        Row::new(vec![
+            Cell::from(keybinds.toggle_all.as_deref().unwrap_or("a")),
+            Cell::from("Toggle all torrents"),
+        ]),
+        Row::new(vec![
+            Cell::from(keybinds.delete.as_deref().unwrap_or("d")),
+            Cell::from("Delete torrent"),
+        ]),
+        Row::new(vec![
+            Cell::from(keybinds.delete_force.as_deref().unwrap_or("D")),
+            Cell::from("Delete torrent and data"),
+        ]),
+        Row::new(vec![
+            Cell::from(keybinds.select.as_deref().unwrap_or(" ")),
+            Cell::from("Select torrent"),
+        ]),
     ];
 
     let table = Table::new(
@@ -35,7 +74,12 @@ pub fn render_help(frame: &mut Frame, app: &App) {
         &[Constraint::Percentage(20), Constraint::Percentage(80)],
     )
     .block(block)
-    .style(Style::default().fg(app.config.colors.get_color(&app.config.colors.info_foreground)));
+    .style(
+        Style::default().fg(app
+            .config
+            .colors
+            .get_color(&app.config.colors.info_foreground)),
+    );
 
     let area = frame.area();
     let height = 15; // Desired height for the help menu
@@ -51,4 +95,3 @@ pub fn render_help(frame: &mut Frame, app: &App) {
     frame.render_widget(Clear, popup_area);
     frame.render_widget(table, popup_area);
 }
-

src/ui/mod.rs

@@ -32,8 +32,18 @@ pub fn render(app: &mut App, frame: &mut Frame) {
                 .border_type(BorderType::Rounded),
         )
         .select(app.index())
-        .style(Style::default().fg(app.config.colors.get_color(&app.config.colors.info_foreground)))
+        .style(
-        .highlight_style(Style::default().fg(app.config.colors.get_color(&app.config.colors.warning_foreground)))
+            Style::default().fg(app
+                .config
+                .colors
+                .get_color(&app.config.colors.info_foreground)),
+        )
+        .highlight_style(
+            Style::default().fg(app
+                .config
+                .colors
+                .get_color(&app.config.colors.warning_foreground)),
+        )
         .divider("|");
 
     frame.render_widget(tabs, chunks[0]); // renders tab

src/ui/table.rs

@@ -10,8 +10,14 @@ pub fn render_table<'a>(app: &mut App, tab: Tab) -> Table<'a> {
     let selected = &app.torrents.selected.clone();
     let torrents = &app.torrents.set_fields(None).torrents;
 
-    let highlight_bg = app.config.colors.get_color(&app.config.colors.highlight_background);
+    let highlight_bg = app
-    let highlight_fg = app.config.colors.get_color(&app.config.colors.highlight_foreground);
+        .config
+        .colors
+        .get_color(&app.config.colors.highlight_background);
+    let highlight_fg = app
+        .config
+        .colors
+        .get_color(&app.config.colors.highlight_foreground);
     let highlight_style = Style::default().bg(highlight_bg).fg(highlight_fg);
 
     let rows: Vec<Row<'_>> = torrents
@@ -38,7 +44,10 @@ pub fn render_table<'a>(app: &mut App, tab: Tab) -> Table<'a> {
         .map(|&field| Constraint::Length(field.width()))
         .collect::<Vec<_>>();
 
-    let header_fg = app.config.colors.get_color(&app.config.colors.warning_foreground);
+    let header_fg = app
+        .config
+        .colors
+        .get_color(&app.config.colors.warning_foreground);
     let header = Row::new(
         fields
             .iter()
@@ -47,8 +56,14 @@ pub fn render_table<'a>(app: &mut App, tab: Tab) -> Table<'a> {
     )
     .style(Style::default().fg(header_fg));
 
-    let row_highlight_bg = app.config.colors.get_color(&app.config.colors.info_foreground);
+    let row_highlight_bg = app
-    let row_highlight_fg = app.config.colors.get_color(&app.config.colors.highlight_foreground);
+        .config
+        .colors
+        .get_color(&app.config.colors.info_foreground);
+    let row_highlight_fg = app
+        .config
+        .colors
+        .get_color(&app.config.colors.highlight_foreground);
     let row_highlight_style = Style::default().bg(row_highlight_bg).fg(row_highlight_fg);
 
     Table::new(rows, widths)

tests/handler.rs

@@ -1,5 +1,5 @@
 use crossterm::event::{KeyCode, KeyEvent};
-use traxor::{app::action::Action, handler::get_action, app::App, config::Config};
+use traxor::{app::action::Action, app::App, config::Config, handler::get_action};
 
 #[test]
 fn test_get_action_quit() {

tests/merge.rs

@@ -0,0 +1,286 @@
+use derive_macro::Merge;
+use traxor::merge::Merge;
+
+#[derive(Debug, PartialEq, Merge)]
+struct NestedStruct {
+    value: u32,
+    name: Option<String>,
+}
+
+#[derive(Debug, PartialEq, Merge)]
+struct TestStruct {
+    a: u32,
+    b: Option<String>,
+    c: Option<bool>,
+    nested: NestedStruct,
+    optional_nested: Option<NestedStruct>,
+}
+
+#[test]
+fn test_merge_basic_fields() {
+    let mut s1 = TestStruct {
+        a: 1,
+        b: Some("hello".to_string()),
+        c: None,
+        nested: NestedStruct {
+            value: 10,
+            name: Some("original".to_string()),
+        },
+        optional_nested: None,
+    };
+    let s2 = TestStruct {
+        a: 2,
+        b: Some("world".to_string()),
+        c: Some(true),
+        nested: NestedStruct {
+            value: 20,
+            name: Some("new".to_string()),
+        },
+        optional_nested: Some(NestedStruct {
+            value: 30,
+            name: Some("optional".to_string()),
+        }),
+    };
+
+    s1.merge(s2);
+
+    assert_eq!(s1.a, 2);
+    assert_eq!(s1.b, Some("world".to_string()));
+    assert_eq!(s1.c, Some(true));
+    assert_eq!(s1.nested.value, 20);
+    assert_eq!(s1.nested.name, Some("new".to_string()));
+    assert_eq!(
+        s1.optional_nested,
+        Some(NestedStruct {
+            value: 30,
+            name: Some("optional".to_string())
+        })
+    );
+}
+
+#[test]
+fn test_merge_option_none_other() {
+    let mut s1 = TestStruct {
+        a: 1,
+        b: Some("hello".to_string()),
+        c: Some(false),
+        nested: NestedStruct {
+            value: 10,
+            name: Some("original".to_string()),
+        },
+        optional_nested: Some(NestedStruct {
+            value: 100,
+            name: Some("existing".to_string()),
+        }),
+    };
+    let s2 = TestStruct {
+        a: 2,
+        b: None,
+        c: None,
+        nested: NestedStruct {
+            value: 20,
+            name: None,
+        },
+        optional_nested: None,
+    };
+
+    s1.merge(s2);
+
+    assert_eq!(s1.a, 2);
+    assert_eq!(s1.b, Some("hello".to_string())); // Should remain Some("hello")
+    assert_eq!(s1.c, Some(false)); // Should remain Some(false)
+    assert_eq!(s1.nested.value, 20);
+    assert_eq!(s1.nested.name, Some("original".to_string())); // Should remain original
+    assert_eq!(
+        s1.optional_nested,
+        Some(NestedStruct {
+            value: 100,
+            name: Some("existing".to_string())
+        })
+    ); // Should remain existing
+}
+
+#[test]
+fn test_merge_option_some_other() {
+    let mut s1 = TestStruct {
+        a: 1,
+        b: None,
+        c: None,
+        nested: NestedStruct {
+            value: 10,
+            name: None,
+        },
+        optional_nested: None,
+    };
+    let s2 = TestStruct {
+        a: 2,
+        b: Some("world".to_string()),
+        c: Some(true),
+        nested: NestedStruct {
+            value: 20,
+            name: Some("new".to_string()),
+        },
+        optional_nested: Some(NestedStruct {
+            value: 30,
+            name: Some("optional".to_string()),
+        }),
+    };
+
+    s1.merge(s2);
+
+    assert_eq!(s1.a, 2);
+    assert_eq!(s1.b, Some("world".to_string()));
+    assert_eq!(s1.c, Some(true));
+    assert_eq!(s1.nested.value, 20);
+    assert_eq!(s1.nested.name, Some("new".to_string()));
+    assert_eq!(
+        s1.optional_nested,
+        Some(NestedStruct {
+            value: 30,
+            name: Some("optional".to_string())
+        })
+    );
+}
+
+#[test]
+fn test_merge_nested_struct_with_none_name() {
+    let mut s1 = TestStruct {
+        a: 1,
+        b: None,
+        c: None,
+        nested: NestedStruct {
+            value: 10,
+            name: Some("original".to_string()),
+        },
+        optional_nested: None,
+    };
+    let s2 = TestStruct {
+        a: 2,
+        b: None,
+        c: None,
+        nested: NestedStruct {
+            value: 20,
+            name: None,
+        },
+        optional_nested: None,
+    };
+
+    s1.merge(s2);
+
+    assert_eq!(s1.nested.value, 20);
+    assert_eq!(s1.nested.name, Some("original".to_string())); // Should remain original
+}
+
+#[test]
+fn test_merge_optional_nested_struct_some_to_some() {
+    let mut s1 = TestStruct {
+        a: 1,
+        b: None,
+        c: None,
+        nested: NestedStruct {
+            value: 10,
+            name: None,
+        },
+        optional_nested: Some(NestedStruct {
+            value: 100,
+            name: Some("existing".to_string()),
+        }),
+    };
+    let s2 = TestStruct {
+        a: 2,
+        b: None,
+        c: None,
+        nested: NestedStruct {
+            value: 20,
+            name: None,
+        },
+        optional_nested: Some(NestedStruct {
+            value: 200,
+            name: Some("new_optional".to_string()),
+        }),
+    };
+
+    s1.merge(s2);
+
+    assert_eq!(
+        s1.optional_nested,
+        Some(NestedStruct {
+            value: 200,
+            name: Some("new_optional".to_string())
+        })
+    );
+}
+
+#[test]
+fn test_merge_optional_nested_struct_none_to_some() {
+    let mut s1 = TestStruct {
+        a: 1,
+        b: None,
+        c: None,
+        nested: NestedStruct {
+            value: 10,
+            name: None,
+        },
+        optional_nested: None,
+    };
+    let s2 = TestStruct {
+        a: 2,
+        b: None,
+        c: None,
+        nested: NestedStruct {
+            value: 20,
+            name: None,
+        },
+        optional_nested: Some(NestedStruct {
+            value: 200,
+            name: Some("new_optional".to_string()),
+        }),
+    };
+
+    s1.merge(s2);
+
+    assert_eq!(
+        s1.optional_nested,
+        Some(NestedStruct {
+            value: 200,
+            name: Some("new_optional".to_string())
+        })
+    );
+}
+
+#[test]
+fn test_merge_optional_nested_struct_some_to_none() {
+    let mut s1 = TestStruct {
+        a: 1,
+        b: None,
+        c: None,
+        nested: NestedStruct {
+            value: 10,
+            name: None,
+        },
+        optional_nested: Some(NestedStruct {
+            value: 100,
+            name: Some("existing".to_string()),
+        }),
+    };
+    let s2 = TestStruct {
+        a: 2,
+        b: None,
+        c: None,
+        nested: NestedStruct {
+            value: 20,
+            name: None,
+        },
+        optional_nested: None,
+    };
+
+    s1.merge(s2);
+
+    assert_eq!(
+        s1.optional_nested,
+        Some(NestedStruct {
+            value: 100,
+            name: Some("existing".to_string())
+        })
+    ); // Should remain existing
+}