commands: Make no arg ':theme' show name

Most commands that accept an argument show their current value if no
argument is specified. The `:theme` command previously displayed an
error message in the status bar if not provided with an argument:

```
Theme name not provided
```

It now shows the current theme name in the status bar if no argument is
specified.

Signed-off-by: James O. D. Hunt <jamesodhunt@gmail.com>

book/src/generated/typable-cmd.md

@@ -28,7 +28,7 @@
 | `:quit-all!`, `:qa!` | Force close all views ignoring unsaved changes. |
 | `:cquit`, `:cq` | Quit with exit code (default 1). Accepts an optional integer exit code (:cq 2). |
 | `:cquit!`, `:cq!` | Force quit with exit code (default 1) ignoring unsaved changes. Accepts an optional integer exit code (:cq! 2). |
-| `:theme` | Change the editor theme. |
+| `:theme` | Change the editor theme (show current theme if no name specified). |
 | `:clipboard-yank` | Yank main selection into system clipboard. |
 | `:clipboard-yank-join` | Yank joined selections into system clipboard. A separator can be provided as first argument. Default value is newline. |
 | `:primary-clipboard-yank` | Yank main selection into system primary clipboard. |

helix-term/src/commands/typed.rs

@@ -725,16 +725,21 @@ fn theme(
             };
         }
         PromptEvent::Validate => {
-            let theme_name = args.first().with_context(|| "Theme name not provided")?;
-            let theme = cx
-                .editor
-                .theme_loader
-                .load(theme_name)
-                .with_context(|| "Theme does not exist")?;
-            if !(true_color || theme.is_16_color()) {
-                bail!("Unsupported theme: theme requires true color support");
+            if let Some(theme_name) = args.first() {
+                let theme = cx
+                    .editor
+                    .theme_loader
+                    .load(theme_name)
+                    .with_context(|| "Theme does not exist")?;
+                if !(true_color || theme.is_16_color()) {
+                    bail!("Unsupported theme: theme requires true color support");
+                }
+                cx.editor.set_theme(theme);
+            } else {
+                let name = cx.editor.theme.name().to_string();
+
+                cx.editor.set_status(name);
             }
-            cx.editor.set_theme(theme);
         }
     };
 
@@ -1720,7 +1725,7 @@ pub const TYPABLE_COMMAND_LIST: &[TypableCommand] = &[
         TypableCommand {
             name: "theme",
             aliases: &[],
-            doc: "Change the editor theme.",
+            doc: "Change the editor theme (show current theme if no name specified).",
             fun: theme,
             completer: Some(completers::theme),
         },

helix-view/src/theme.rs

@@ -12,11 +12,14 @@ use toml::Value;
 
 pub use crate::graphics::{Color, Modifier, Style};
 
-pub static DEFAULT_THEME: Lazy<Theme> = Lazy::new(|| {
-    toml::from_slice(include_bytes!("../../theme.toml")).expect("Failed to parse default theme")
+pub static DEFAULT_THEME: Lazy<Theme> = Lazy::new(|| Theme {
+    name: "default".into(),
+    ..toml::from_slice(include_bytes!("../../theme.toml")).expect("Failed to parse default theme")
 });
-pub static BASE16_DEFAULT_THEME: Lazy<Theme> = Lazy::new(|| {
-    toml::from_slice(include_bytes!("../../base16_theme.toml"))
+
+pub static BASE16_DEFAULT_THEME: Lazy<Theme> = Lazy::new(|| Theme {
+    name: "base16_theme".into(),
+    ..toml::from_slice(include_bytes!("../../base16_theme.toml"))
         .expect("Failed to parse base 16 default theme")
 });
 
@@ -52,7 +55,13 @@ impl Loader {
         };
 
         let data = std::fs::read(&path)?;
-        toml::from_slice(data.as_slice()).context("Failed to deserialize theme")
+
+        let theme = Theme {
+            name: name.into(),
+            ..toml::from_slice(data.as_slice()).context("Failed to deserialize theme")?
+        };
+
+        Ok(theme)
     }
 
     pub fn read_names(path: &Path) -> Vec<String> {
@@ -96,8 +105,10 @@ impl Loader {
     }
 }
 
-#[derive(Clone, Debug)]
+#[derive(Clone, Debug, Default)]
 pub struct Theme {
+    name: String,
+
     // UI styles are stored in a HashMap
     styles: HashMap<String, Style>,
     // tree-sitter highlight styles are stored in a Vec to optimize lookups
@@ -147,6 +158,7 @@ impl<'de> Deserialize<'de> for Theme {
             scopes,
             styles,
             highlights,
+            ..Default::default()
         })
     }
 }
@@ -157,6 +169,10 @@ impl Theme {
         self.highlights[index]
     }
 
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
     pub fn get(&self, scope: &str) -> Style {
         self.try_get(scope).unwrap_or_default()
     }