Expose new theme selection in CLI

src/bin/bat/app.rs

@@ -9,6 +9,9 @@ use crate::{
     config::{get_args_from_config_file, get_args_from_env_opts_var, get_args_from_env_vars},
 };
 use bat::style::StyleComponentList;
+use bat::theme::{
+    theme, ColorScheme, ColorSchemeDetector, DetectColorScheme, ThemeOptions, ThemeRequest,
+};
 use bat::StripAnsiMode;
 use clap::ArgMatches;
 
@@ -16,7 +19,6 @@ use console::Term;
 
 use crate::input::{new_file_input, new_stdin_input};
 use bat::{
-    assets::HighlightingAssets,
     bat_warning,
     config::{Config, VisibleLines},
     error::*,
@@ -254,18 +256,7 @@ impl App {
                 Some("auto") => StripAnsiMode::Auto,
                 _ => unreachable!("other values for --strip-ansi are not allowed"),
             },
-            theme: self
-                .matches
-                .get_one::<String>("theme")
-                .map(String::from)
-                .map(|s| {
-                    if s == "default" {
-                        String::from(HighlightingAssets::default_theme())
-                    } else {
-                        s
-                    }
-                })
-                .unwrap_or_else(|| String::from(HighlightingAssets::default_theme())),
+            theme: theme(self.theme_options(), &TerminalColorSchemeDetector),
             visible_lines: match self.matches.try_contains_id("diff").unwrap_or_default()
                 && self.matches.get_flag("diff")
             {
@@ -424,4 +415,72 @@ impl App {
 
         Ok(styled_components)
     }
+
+    fn theme_options(&self) -> ThemeOptions {
+        let theme = self
+            .matches
+            .get_one::<String>("theme")
+            .map(|t| ThemeRequest::from_str(t).unwrap());
+        let theme_dark = self
+            .matches
+            .get_one::<String>("theme-dark")
+            .map(|t| ThemeRequest::from_str(t).unwrap());
+        let theme_light = self
+            .matches
+            .get_one::<String>("theme-light")
+            .map(|t| ThemeRequest::from_str(t).unwrap());
+        let detect_color_scheme = match self
+            .matches
+            .get_one::<String>("detect-color-scheme")
+            .map(|s| s.as_str())
+        {
+            Some("auto") => DetectColorScheme::Auto,
+            Some("never") => DetectColorScheme::Never,
+            Some("always") => DetectColorScheme::Always,
+            _ => unreachable!("other values for --detect-color-scheme are not allowed"),
+        };
+        ThemeOptions {
+            theme,
+            theme_dark,
+            theme_light,
+            detect_color_scheme,
+        }
+    }
+}
+
+struct TerminalColorSchemeDetector;
+
+#[cfg(feature = "detect-color-scheme")]
+impl ColorSchemeDetector for TerminalColorSchemeDetector {
+    fn should_detect(&self) -> bool {
+        // Querying the terminal for its colors via OSC 10 / OSC 11 requires "exclusive" access
+        // since we read/write from the terminal and enable/disable raw mode.
+        // This causes race conditions with pagers such as less when they are attached to the
+        // same terminal as us.
+        //
+        // This is usually only an issue when the output is manually piped to a pager.
+        // For example: `bat Cargo.toml | less`.
+        // Otherwise, if we start the pager ourselves, then there's no race condition
+        // since the pager is started *after* the color is detected.
+        std::io::stdout().is_terminal()
+    }
+
+    fn detect(&self) -> Option<ColorScheme> {
+        use terminal_colorsaurus::{color_scheme, ColorScheme as ColorsaurusScheme, QueryOptions};
+        match color_scheme(QueryOptions::default()).ok()? {
+            ColorsaurusScheme::Dark => Some(ColorScheme::Dark),
+            ColorsaurusScheme::Light => Some(ColorScheme::Light),
+        }
+    }
+}
+
+#[cfg(not(feature = "detect-color-scheme"))]
+impl ColorSchemeDetector for TerminalColorSchemeDetector {
+    fn should_detect(&self) -> bool {
+        false
+    }
+
+    fn detect(&self) -> Option<ColorScheme> {
+        None
+    }
 }

src/bin/bat/clap_app.rs

@@ -375,13 +375,64 @@ pub fn build_app(interactive_output: bool) -> Command {
                 .overrides_with("theme")
                 .help("Set the color theme for syntax highlighting.")
                 .long_help(
-                    "Set the theme for syntax highlighting. Use '--list-themes' to \
+                    "Set the theme for syntax highlighting. Note that this option overrides \
+                    '--theme-dark' and '--theme-light'. Use '--list-themes' to \
                      see all available themes. To set a default theme, add the \
                      '--theme=\"...\"' option to the configuration file or export the \
                      BAT_THEME environment variable (e.g.: export \
                      BAT_THEME=\"...\").",
                 ),
         )
+        .arg(
+            Arg::new("detect-color-scheme")
+                .long("detect-color-scheme")
+                .overrides_with("detect-color-scheme")
+                .value_name("when")
+                .value_parser(["auto", "never", "always"])
+                .default_value("auto")
+                .hide_default_value(true)
+                .help("Specify when to query the terminal for its colors.")
+                .long_help(
+                    "Specify when to query the terminal for its colors \
+                     in order to pick an appropriate syntax highlighting theme. \
+                     Use '--theme-light' and '--theme-dark' (or the environment variables \
+                     BAT_THEME_LIGHT and BAT_THEME_DARK) to configure which themes are picked. \
+                     You may also use '--theme' to set a theme that is used regardless of the terminal's colors.\n\n\
+                     Possible values:\n\
+                     * auto (default):\n     \
+                            Only query the terminals colors if the output is not redirected. \
+                            This is to prevent race conditions with pagers such as less.\n\
+                     * never\n     \
+                           Never query the terminal for its colors \
+                           and assume that the terminal has a dark background.\n\
+                     * always\n     \
+                           Always query the terminal for its colors, \
+                           regardless of whether or not the output is redirected."),
+        )
+        .arg(
+            Arg::new("theme-light")
+                .long("theme-light")
+                .overrides_with("theme-light")
+                .value_name("theme")
+                .help("Sets the color theme for syntax highlighting used for light backgrounds.")
+                .long_help(
+                    "Sets the theme name for syntax highlighting used when the terminal uses a light background. \
+                    Use '--list-themes' to see all available themes. To set a default theme, add the \
+                    '--theme-light=\"...\" option to the configuration file or export the BAT_THEME_LIGHT \
+                    environment variable (e.g. export BAT_THEME_LIGHT=\"...\")."),
+        )
+        .arg(
+            Arg::new("theme-dark")
+                .long("theme-dark")
+                .overrides_with("theme-dark")
+                .value_name("theme")
+                .help("Sets the color theme for syntax highlighting used for dark backgrounds.")
+                .long_help(
+                    "Sets the theme name for syntax highlighting used when the terminal uses a dark background. \
+                    Use '--list-themes' to see all available themes. To set a default theme, add the \
+                    '--theme-dark=\"...\" option to the configuration file or export the BAT_THEME_DARK \
+                    environment variable (e.g. export BAT_THEME_DARK=\"...\")."),
+        )
         .arg(
             Arg::new("list-themes")
                 .long("list-themes")

src/bin/bat/config.rs

@@ -141,6 +141,8 @@ pub fn get_args_from_env_vars() -> Vec<OsString> {
     [
         ("--tabs", "BAT_TABS"),
         ("--theme", "BAT_THEME"),
+        ("--theme-dark", "BAT_THEME_DARK"),
+        ("--theme-light", "BAT_THEME_LIGHT"),
         ("--pager", "BAT_PAGER"),
         ("--paging", "BAT_PAGING"),
         ("--style", "BAT_STYLE"),