Fix serializing StyleType::Custom.

`StyleType` should serialize as a TOML table to account for
`StyleType::Custom` taking a value.

I added two attributes to `StyleType` to hint that the `toml` crate
should serialize it as a table instead of a simple key = value.

src/configs/types/config_settings.rs

@@ -10,7 +10,8 @@ use crate::{Language, StyleType};
 
 #[derive(Serialize, Deserialize, Default)]
 pub struct ConfigSettings {
-    pub style: Arc<StyleType>,
     pub language: Language,
     pub notifications: Notifications,
+    // This field should be last so that the TOML for StyleType can serialize properly
+    pub style: Arc<StyleType>,
 }

src/gui/styles/types/custom_style.rs

@@ -136,7 +136,7 @@ mod tests {
         deserialize_from_path, serialize_to_path, CustomPalette, CustomStyle, Palette,
         PaletteExtension,
     };
-    use crate::translations::types::language::Language;
+    use crate::{translations::types::language::Language, StyleType};
     use iced::color;
     use serde::{Deserialize, Serialize};
     use serde_test::{assert_tokens, Token};
@@ -200,11 +200,55 @@ mod tests {
         })
     }
 
+    // Test that split deserialization works for `CustomStyle`.
+    // This is different than testing that `StyleType` properly deserializes.
     #[test]
-    fn test_styletype_split_de() {
+    fn test_customstyle_split_de() {
         let style_test = catppuccin_style();
         // This is only used for the test which requires an &'static str.
         let path: &'static str = Box::leak(style_path().into_boxed_str());
         assert_tokens(&style_test, &[Token::String(path)]);
     }
+
+    // Ensure that StyleType itself still deserializes properly
+    #[test]
+    fn test_styletype_unit_split_de() {
+        // Unit variant without a struct
+        assert_tokens(
+            &StyleType::DeepSea,
+            &[
+                Token::Struct {
+                    name: "StyleType",
+                    len: 1,
+                },
+                Token::Str("style"),
+                Token::Str("DeepSea"),
+                Token::StructEnd,
+            ],
+        );
+    }
+
+    // Test that StyleType::Custom successfully deserializes.
+    // Originally, StyleType::Custom did not ser/de correctly because of how TOML
+    // handles enums.
+    #[test]
+    fn test_styletype_custom_split_de() {
+        // CustomStyle
+        // This is only used for the test so leaking it is fine.
+        let path = &*Box::leak(style_path().into_boxed_str());
+        assert_tokens(
+            &StyleType::Custom(catppuccin_style().0),
+            &[
+                Token::Struct {
+                    name: "StyleType",
+                    len: 2,
+                },
+                Token::Str("style"),
+                Token::Str("Custom"),
+                Token::Str("path"),
+                Token::Str(path),
+                Token::StructEnd,
+            ],
+        );
+    }
 }

src/gui/styles/types/style_type.rs

@@ -4,6 +4,7 @@ use super::custom_style::{deserialize_from_path, serialize_to_path, CustomStyle}
 
 /// Used to specify the kind of style of the application
 #[derive(Clone, Serialize, Deserialize, Debug, Hash, PartialEq)]
+#[serde(tag = "style", content = "path")]
 pub enum StyleType {
     Night,
     Day,