Support loading custom syntax themes from a file (#2565)

Author: acuteenvy

CHANGELOG.md

@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## Unreleased
 
 ### Added
+* support loading custom syntax highlighting themes from a file [[@acuteenvy](https://github.com/acuteenvy)] ([#2565](https://github.com/gitui-org/gitui/pull/2565))
 * Select syntax highlighting theme out of the defaults from syntect [[@vasilismanol](https://github.com/vasilismanol)] ([#1931](https://github.com/extrawurst/gitui/issues/1931))
 * new command-line option to override the default log file path (`--logfile`) [[@acuteenvy](https://github.com/acuteenvy)] ([#2539](https://github.com/gitui-org/gitui/pull/2539))
 

Cargo.lock

@@ -56,6 +56,7 @@ syntect = { version = "5.2", default-features = false, features = [
     "parsing",
     "default-syntaxes",
     "default-themes",
+    "plist-load",
     "html",
 ] }
 tui-textarea = "0.7"

Cargo.toml

@@ -49,7 +49,9 @@ pub fn process_cmdline() -> Result<CliArgs> {
 		.get_one::<String>("theme")
 		.map_or_else(|| PathBuf::from("theme.ron"), PathBuf::from);
 
-	let theme = get_app_config_path()?.join(arg_theme);
+	let confpath = get_app_config_path()?;
+	fs::create_dir_all(&confpath)?;
+	let theme = confpath.join(arg_theme);
 
 	let notify_watcher: bool =
 		*arg_matches.get_one("watcher").unwrap_or(&false);
@@ -166,7 +168,6 @@ pub fn get_app_config_path() -> Result<PathBuf> {
 	.ok_or_else(|| anyhow!("failed to find os config dir."))?;
 
 	path.push("gitui");
-	fs::create_dir_all(&path)?;
 	Ok(path)
 }
 

src/args.rs

@@ -136,6 +136,7 @@ mod tests {
 	#[test]
 	fn test_symbolic_links() {
 		let app_home = get_app_config_path().unwrap();
+		fs::create_dir_all(&app_home).unwrap();
 		// save current config
 		let original_key_list_path = app_home.join(KEY_LIST_FILENAME);
 		let renamed_key_list = if original_key_list_path.exists() {

src/keys/key_config.rs

@@ -2,7 +2,7 @@ use asyncgit::{
 	asyncjob::{AsyncJob, RunParams},
 	ProgressPercent,
 };
-use once_cell::sync::Lazy;
+use once_cell::sync::{Lazy, OnceCell};
 use ratatui::text::{Line, Span};
 use scopetime::scope_time;
 use std::{
@@ -14,7 +14,7 @@ use std::{
 use syntect::{
 	highlighting::{
 		FontStyle, HighlightState, Highlighter,
-		RangedHighlightIterator, Style, ThemeSet,
+		RangedHighlightIterator, Style, Theme, ThemeSet,
 	},
 	parsing::{ParseState, ScopeStack, SyntaxSet},
 };
@@ -35,7 +35,7 @@ pub struct SyntaxText {
 
 static SYNTAX_SET: Lazy<SyntaxSet> =
 	Lazy::new(two_face::syntax::extra_no_newlines);
-static THEME_SET: Lazy<ThemeSet> = Lazy::new(ThemeSet::load_defaults);
+static THEME: OnceCell<Theme> = OnceCell::new();
 
 pub struct AsyncProgressBuffer {
 	current: usize,
@@ -89,13 +89,25 @@ impl SyntaxText {
 			ParseState::new(syntax)
 		};
 
-		let theme =
-			THEME_SET.themes.get(syntax).unwrap_or_else(|| {
-				log::error!("The syntax theme:\"{}\" cannot be found. Using default theme:\"{}\" instead.", syntax, DEFAULT_SYNTAX_THEME);
-				&THEME_SET.themes[DEFAULT_SYNTAX_THEME]
-			});
-		let highlighter = Highlighter::new(theme);
+		let theme = THEME.get_or_try_init(|| -> Result<Theme, asyncgit::Error> {
+			let theme_path = crate::args::get_app_config_path()
+				.map_err(|e| asyncgit::Error::Generic(e.to_string()))?.join(format!("{syntax}.tmTheme"));
+
+			match ThemeSet::get_theme(&theme_path) {
+				Ok(t) => return Ok(t),
+			    Err(e) => log::info!("could not load '{}': {e}, trying from the set of default themes", theme_path.display()),
+			}
 
+			let mut theme_set = ThemeSet::load_defaults();
+			if let Some(t) = theme_set.themes.remove(syntax) {
+			    return Ok(t);
+			}
+
+			log::error!("the syntax theme '{syntax}' cannot be found. Using default theme ('{DEFAULT_SYNTAX_THEME}') instead");
+			Ok(theme_set.themes.remove(DEFAULT_SYNTAX_THEME).expect("the default theme should be there"))
+		})?;
+
+		let highlighter = Highlighter::new(theme);
 		let mut syntax_lines: Vec<SyntaxLine> = Vec::new();
 
 		let mut highlight_state =