Remove Option wrapper for Config.theme

Does so by assuming empty string implyies default theme in Theme::new.
Paves the way to make Config::default() to be derivable.

helix-term/src/application.rs

@@ -355,9 +355,8 @@ impl Application {
                 document.detect_language(self.editor.lang_configs_loader.clone());
             }
 
-            if let Some(theme_name) = &self.config.load().theme {
-                self.editor.set_theme(Theme::new(theme_name)?);
-            }
+            self.editor
+                .set_theme(Theme::new(&self.config.load().theme)?);
 
             Ok(())
         };

helix-term/src/config.rs

@@ -7,7 +7,8 @@ use std::collections::HashMap;
 #[derive(Debug, Clone, PartialEq, Deserialize)]
 #[serde(deny_unknown_fields)]
 pub struct Config {
-    pub theme: Option<String>,
+    #[serde(default)]
+    pub theme: String,
     #[serde(default = "default::default")]
     pub keys: HashMap<Mode, KeyTrie>,
     #[serde(default)]
@@ -43,7 +44,7 @@ impl Config {
 impl Default for Config {
     fn default() -> Config {
         Config {
-            theme: None,
+            theme: String::default(),
             keys: default::default(),
             editor: helix_view::editor::EditorConfig::default(),
         }

helix-term/src/main.rs

@@ -64,10 +64,7 @@ async fn main_impl() -> Result<i32> {
                 .map(|v| matches!(v.as_str(), "truecolor" | "24bit"))
                 .unwrap_or(false),
     );
-    let theme: Theme = match config.theme.as_deref() {
-        Some(theme_name) => check_config_load(Theme::new(theme_name), None, "theme"),
-        None => Theme::default(),
-    };
+    let theme = check_config_load(Theme::new(&config.theme), None, "theme");
 
     // TODO: use the thread local executor to spawn the application task separately from the work pool
     let mut app = Application::new(args, config, theme, language_configurations)

helix-view/src/theme.rs

@@ -61,11 +61,15 @@ impl Theme {
     }
 
     pub fn new(theme_name: &str) -> Result<Theme> {
-        let theme = Self::load(theme_name)?;
-        if !Self::get_true_color_support() && !theme.is_16_color() {
-            anyhow::bail!("Unsupported theme: theme requires true color support")
+        if theme_name.is_empty() {
+            Ok(Self::default())
+        } else {
+            let theme = Self::load(theme_name)?;
+            if !Self::get_true_color_support() && !theme.is_16_color() {
+                anyhow::bail!("Unsupported theme: true color support is required")
+            }
+            Ok(theme)
         }
-        Ok(theme)
     }
 
     pub fn default() -> Theme {