Merge branch 'master' into bat_config_dir_docs

.gitignore

@@ -2,6 +2,7 @@
 **/*.rs.bk
 
 # Generated files
+/assets/completions/_bat.ps1
 /assets/completions/bat.bash
 /assets/completions/bat.fish
 /assets/completions/bat.zsh

CHANGELOG.md

@@ -9,6 +9,7 @@
 - Syntax highlighting for JavaScript files that start with `#!/usr/bin/env bun` #2913 (@sharunkumar)
 - `bat --strip-ansi={never,always,auto}` to remove ANSI escape sequences from bat's input, see #2999 (@eth-p)
 - Add or remove individual style components without replacing all styles #2929 (@eth-p)
+- Automatically choose theme based on the terminal's color scheme, see #2896 (@bash)
 - Add option `--binary=as-text` for printing binary content, see issue #2974 and PR #2976 (@einfachIrgendwer0815)
 
 ## Bugfixes
@@ -78,6 +79,9 @@
   - [BREAKING] `SyntaxMapping::mappings` is replaced by `SyntaxMapping::{builtin,custom,all}_mappings`
 - Make `Controller::run_with_error_handler`'s error handler `FnMut`, see #2831 (@rhysd)
 - Improve compile time by 20%, see #2815 (@dtolnay)
+- Add `theme::theme` for choosing an appropriate theme based on the
+  terminal's color scheme, see #2896 (@bash)
+  - [BREAKING] Remove `HighlightingAssets::default_theme`. Use `theme::default_theme` instead.
 
 # v0.24.0
 

Cargo.lock

@@ -149,6 +149,7 @@ dependencies = [
  "shell-words",
  "syntect",
  "tempfile",
+ "terminal-colorsaurus",
  "thiserror",
  "toml",
  "unicode-width",
@@ -625,6 +626,12 @@ version = "0.14.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7dfda62a12f55daeae5015f81b0baea145391cb4520f86c248fc615d72640d12"
 
+[[package]]
+name = "hermit-abi"
+version = "0.3.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d231dfb89cfffdbc30e7fc41579ed6066ad03abda9e567ccafae602b97ec5024"
+
 [[package]]
 name = "home"
 version = "0.5.9"
@@ -751,9 +758,9 @@ checksum = "b5e6163cb8c49088c2c36f57875e58ccd8c87c7427f7fbd50ea6710b2f3f2e8f"
 
 [[package]]
 name = "memchr"
-version = "2.6.4"
+version = "2.7.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f665ee40bc4a3c5590afb1e9677db74a508659dfd71e126420da8274909a0167"
+checksum = "78ca9ab1a0babb1e7d5695e3530886289c18cf2f87ec19a575a0abdce112e3a3"
 
 [[package]]
 name = "miniz_oxide"
@@ -764,6 +771,18 @@ dependencies = [
  "adler2",
 ]
 
+[[package]]
+name = "mio"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4929e1f84c5e54c3ec6141cd5d8b5a5c055f031f80cf78f2072920173cb4d880"
+dependencies = [
+ "hermit-abi",
+ "libc",
+ "wasi",
+ "windows-sys 0.52.0",
+]
+
 [[package]]
 name = "nix"
 version = "0.29.0"
@@ -1308,6 +1327,30 @@ dependencies = [
  "winapi-util",
 ]
 
+[[package]]
+name = "terminal-colorsaurus"
+version = "0.4.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5f99bb1dc5cde9eada5a8f466641240f9d5b9f55291d675df4160b097fbfa42e"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "memchr",
+ "mio",
+ "terminal-trx",
+]
+
+[[package]]
+name = "terminal-trx"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6d4c86910e10c782a02d3b7606de43cf7ebd80e1fafdca8e49a0db2b0d4611f0"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "windows-sys 0.52.0",
+]
+
 [[package]]
 name = "terminal_size"
 version = "0.3.0"

Cargo.toml

@@ -68,6 +68,7 @@ bytesize = { version = "1.3.0" }
 encoding_rs = "0.8.35"
 os_str_bytes = { version = "~7.0", optional = true }
 run_script = { version = "^0.10.1", optional = true}
+terminal-colorsaurus = "0.4"
 
 [dependencies.git2]
 version = "0.19"

README.md

@@ -482,8 +482,10 @@ the following command (you need [`fzf`](https://github.com/junegunn/fzf) for thi
 bat --list-themes | fzf --preview="bat --theme={} --color=always /path/to/file"
 ```
 
-`bat` looks good on a dark background by default. However, if your terminal uses a
+`bat` automatically picks a fitting theme depending on your terminal's background color.
-light background, some themes like `GitHub` or `OneHalfLight` will work better for you.
+You can use the `--theme-light` / `--theme-light` options or the `BAT_THEME_DARK` / `BAT_THEME_LIGHT` environment variables
+to customize the themes used. This is especially useful if you frequently switch between dark and light mode.
+
 You can also use a custom theme by following the
 ['Adding new themes' section below](https://github.com/sharkdp/bat#adding-new-themes).
 

assets/completions/_bat.ps1.in

@@ -37,6 +37,8 @@ Register-ArgumentCompleter -Native -CommandName '{{PROJECT_EXECUTABLE}}' -Script
             [CompletionResult]::new('-m', 'm', [CompletionResultType]::ParameterName, 'Use the specified syntax for files matching the glob pattern (''*.cpp:C++'').')
             [CompletionResult]::new('--map-syntax', 'map-syntax', [CompletionResultType]::ParameterName, 'Use the specified syntax for files matching the glob pattern (''*.cpp:C++'').')
             [CompletionResult]::new('--theme', 'theme', [CompletionResultType]::ParameterName, 'Set the color theme for syntax highlighting.')
+            [CompletionResult]::new('--theme-dark', 'theme', [CompletionResultType]::ParameterName, 'Set the color theme for syntax highlighting for dark backgrounds.')
+            [CompletionResult]::new('--theme-light', 'theme', [CompletionResultType]::ParameterName, 'Set the color theme for syntax highlighting for light backgrounds.')
             [CompletionResult]::new('--style', 'style', [CompletionResultType]::ParameterName, 'Comma-separated list of style elements to display (*default*, auto, full, plain, changes, header, header-filename, header-filesize, grid, rule, numbers, snip).')
             [CompletionResult]::new('-r', 'r', [CompletionResultType]::ParameterName, 'Only print the lines from N to M.')
             [CompletionResult]::new('--line-range', 'line-range', [CompletionResultType]::ParameterName, 'Only print the lines from N to M.')

assets/completions/bat.bash.in

@@ -113,6 +113,13 @@ _bat() {
 		return 0
 		;;
 	--theme)
+    	local IFS=$'\n'
+    	COMPREPLY=($(compgen -W "auto${IFS}auto:always${IFS}auto:system${IFS}dark${IFS}light${IFS}$("$1" --list-themes)" -- "$cur"))
+                    __bat_escape_completions
+    	return 0
+    	;;
+	--theme-dark | \
+	--theme-light)
 		local IFS=$'\n'
 		COMPREPLY=($(compgen -W "$("$1" --list-themes)" -- "$cur"))
                 __bat_escape_completions
@@ -170,6 +177,8 @@ _bat() {
 			--map-syntax
 			--ignored-suffix
 			--theme
+			--theme-dark
+			--theme-light
 			--list-themes
 			--squeeze-blank
 			--squeeze-limit

assets/completions/bat.fish.in

@@ -129,6 +129,14 @@ set -l tabs_opts '
     8\t
 '
 
+set -l special_themes '
+    auto\tdefault,\ Choose\ a\ theme\ based\ on\ dark\ or\ light\ mode
+    auto:always\tChoose\ a\ theme\ based\ on\ dark\ or\ light\ mode
+    auto:system\tChoose\ a\ theme\ based\ on\ dark\ or\ light\ mode
+    dark\tUse\ the\ theme\ specified\ by\ --theme-dark
+    light\tUse\ the\ theme\ specified\ by\ --theme-light
+'
+
 # Completions:
 
 complete -c $bat -l acknowledgements -d "Print acknowledgements" -n __fish_is_first_arg
@@ -203,7 +211,11 @@ complete -c $bat -l tabs -x -a "$tabs_opts" -d "Set tab width" -n __bat_no_excl_
 
 complete -c $bat -l terminal-width -x -d "Set terminal <width>, +<offset>, or -<offset>" -n __bat_no_excl_args
 
-complete -c $bat -l theme -x -a "(command $bat --list-themes | command cat)" -d "Set the syntax highlighting theme" -n __bat_no_excl_args
+complete -c $bat -l theme -x -a "$special_themes(command $bat --list-themes | command cat)" -d "Set the syntax highlighting theme" -n __bat_no_excl_args
+
+complete -c $bat -l theme-dark -x -a "(command $bat --list-themes | command cat)" -d "Set the syntax highlighting theme for dark backgrounds" -n __bat_no_excl_args
+
+complete -c $bat -l theme-light -x -a "(command $bat --list-themes | command cat)" -d "Set the syntax highlighting theme for light backgrounds" -n __bat_no_excl_args
 
 complete -c $bat -s V -l version -f -d "Show version information" -n __fish_is_first_arg
 

assets/completions/bat.zsh.in

@@ -42,7 +42,9 @@ _{{PROJECT_EXECUTABLE}}_main() {
         --decorations='[specify when to show the decorations]:when:(auto never always)'
         --paging='[specify when to use the pager]:when:(auto never always)'
         '(-m --map-syntax)'{-m+,--map-syntax=}'[map a glob pattern to an existing syntax name]: :->syntax-maps'
-        '(--theme)'--theme='[set the color theme for syntax highlighting]:theme:->themes'
+        '(--theme)'--theme='[set the color theme for syntax highlighting]:theme:->theme_preferences'
+        '(--theme-dark)'--theme-dark='[set the color theme for syntax highlighting for dark backgrounds]:theme:->themes'
+        '(--theme-light)'--theme-light='[set the color theme for syntax highlighting for light backgrounds]:theme:->themes'
         '(: --list-themes --list-languages -L)'--list-themes'[show all supported highlighting themes]'
         --style='[comma-separated list of style elements to display]: : _values "style [default]"
             default auto full plain changes header header-filename header-filesize grid rule numbers snip'
@@ -84,6 +86,12 @@ _{{PROJECT_EXECUTABLE}}_main() {
             local -a themes expl
             themes=(${(f)"$(_call_program themes {{PROJECT_EXECUTABLE}} --list-themes)"} )
 
+            _wanted themes expl 'theme' compadd -a themes && ret=0
+        ;;
+        theme_preferences)
+            local -a themes expl
+            themes=(auto dark light auto:always auto:system ${(f)"$(_call_program themes {{PROJECT_EXECUTABLE}} --list-themes)"} )
+
             _wanted themes expl 'theme' compadd -a themes && ret=0
         ;;
     esac

assets/manual/bat.1.in

@@ -152,9 +152,38 @@ will use JSON syntax, and ignore '.dev'
 .HP
 \fB\-\-theme\fR <theme>
 .IP
-Set the theme for syntax highlighting. Use '\-\-list\-themes' to see all available themes.
+Set the theme for syntax highlighting. Use \fB\-\-list\-themes\fP to see all available themes.
-To set a default theme, add the '\-\-theme="..."' option to the configuration file or
+To set a default theme, add the \fB\-\-theme="..."\fP option to the configuration file or
-export the BAT_THEME environment variable (e.g.: export BAT_THEME="...").
+export the \fBBAT_THEME\fP environment variable (e.g.: \fBexport BAT_THEME="..."\fP).
+
+Special values:
+.RS
+.IP "auto (\fIdefault\fR)"
+Picks a dark or light theme depending on the terminal's colors.
+Use \fB-\-theme\-light\fR and \fB-\-theme\-dark\fR to customize the selected theme.
+.IP "auto:always"
+Variation of \fBauto\fR where where the terminal's colors are detected even when the output is redirected.
+.IP "auto:system (macOS only)"
+Variation of \fBauto\fR where the color scheme is detected from the system-wide preference instead.
+.IP "dark"
+Use the dark theme specified by \fB-\-theme-dark\fR.
+.IP "light"
+Use the light theme specified by \fB-\-theme-light\fR.
+.RE
+.HP
+\fB\-\-theme\-dark\fR <theme>
+.IP
+Sets the theme name for syntax highlighting used when the terminal uses a dark background.
+To set a default theme, add the \fB\-\-theme-dark="..."\fP option to the configuration file or
+export the \fBBAT_THEME_DARK\fP environment variable (e.g. \fBexport BAT_THEME_DARK="..."\fP).
+This option only has an effect when \fB\-\-theme\fP option is set to \fBauto\fR or \fBdark\fR.
+.HP
+\fB\-\-theme\-light\fR <theme>
+.IP
+Sets the theme name for syntax highlighting used when the terminal uses a dark background.
+To set a default theme, add the \fB\-\-theme-dark="..."\fP option to the configuration file or
+export the \fBBAT_THEME_LIGHT\fP environment variable (e.g. \fBexport BAT_THEME_LIGHT="..."\fP).
+This option only has an effect when \fB\-\-theme\fP option is set to \fBauto\fR or \fBlight\fR.
 .HP
 \fB\-\-list\-themes\fR
 .IP

doc/long-help.txt

@@ -120,6 +120,27 @@ Options:
           set a default theme, add the '--theme="..."' option to the configuration file or export
           the BAT_THEME environment variable (e.g.: export BAT_THEME="...").
           
+          Special values:
+          
+            * auto: Picks a dark or light theme depending on the terminal's colors (default).
+                    Use '--theme-light' and '--theme-dark' to customize the selected theme.
+              * auto:always: Detect the terminal's colors even when the output is redirected.
+              * auto:system: Detect the color scheme from the system-wide preference (macOS only).
+            * dark: Use the dark theme specified by '--theme-dark'.
+            * light: Use the light theme specified by '--theme-light'.
+
+      --theme-light <theme>
+          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="...").
+
+      --theme-dark <theme>
+          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="...").
+
       --list-themes
           Display a list of supported themes for syntax highlighting.
 

doc/short-help.txt

@@ -43,6 +43,10 @@ Options:
           Use the specified syntax for files matching the glob pattern ('*.cpp:C++').
       --theme <theme>
           Set the color theme for syntax highlighting.
+      --theme-light <theme>
+          Sets the color theme for syntax highlighting used for light backgrounds.
+      --theme-dark <theme>
+          Sets the color theme for syntax highlighting used for dark backgrounds.
       --list-themes
           Display all supported highlighting themes.
   -s, --squeeze-blank

src/assets.rs

@@ -13,6 +13,7 @@ use crate::error::*;
 use crate::input::{InputReader, OpenedInput};
 use crate::syntax_mapping::ignored_suffixes::IgnoredSuffixes;
 use crate::syntax_mapping::MappingTarget;
+use crate::theme::{default_theme, ColorScheme};
 use crate::{bat_warning, SyntaxMapping};
 
 use lazy_theme_set::LazyThemeSet;
@@ -69,57 +70,6 @@ impl HighlightingAssets {
         }
     }
 
-    /// The default theme.
-    ///
-    /// ### Windows and Linux
-    ///
-    /// Windows and most Linux distributions has a dark terminal theme by
-    /// default. On these platforms, this function always returns a theme that
-    /// looks good on a dark background.
-    ///
-    /// ### macOS
-    ///
-    /// On macOS the default terminal background is light, but it is common that
-    /// Dark Mode is active, which makes the terminal background dark. On this
-    /// platform, the default theme depends on
-    /// ```bash
-    /// defaults read -globalDomain AppleInterfaceStyle
-    /// ```
-    /// To avoid the overhead of the check on macOS, simply specify a theme
-    /// explicitly via `--theme`, `BAT_THEME`, or `~/.config/bat`.
-    ///
-    /// See <https://github.com/sharkdp/bat/issues/1746> and
-    /// <https://github.com/sharkdp/bat/issues/1928> for more context.
-    pub fn default_theme() -> &'static str {
-        #[cfg(not(target_os = "macos"))]
-        {
-            Self::default_dark_theme()
-        }
-        #[cfg(target_os = "macos")]
-        {
-            if macos_dark_mode_active() {
-                Self::default_dark_theme()
-            } else {
-                Self::default_light_theme()
-            }
-        }
-    }
-
-    /**
-     * The default theme that looks good on a dark background.
-     */
-    fn default_dark_theme() -> &'static str {
-        "Monokai Extended"
-    }
-
-    /**
-     * The default theme that looks good on a light background.
-     */
-    #[cfg(target_os = "macos")]
-    fn default_light_theme() -> &'static str {
-        "Monokai Extended Light"
-    }
-
     pub fn from_cache(cache_path: &Path) -> Result<Self> {
         Ok(HighlightingAssets::new(
             SerializedSyntaxSet::FromFile(cache_path.join("syntaxes.bin")),
@@ -248,7 +198,10 @@ impl HighlightingAssets {
                     bat_warning!("Unknown theme '{}', using default.", theme)
                 }
                 self.get_theme_set()
-                    .get(self.fallback_theme.unwrap_or_else(Self::default_theme))
+                    .get(
+                        self.fallback_theme
+                            .unwrap_or_else(|| default_theme(ColorScheme::Dark)),
+                    )
                     .expect("something is very wrong if the default theme is missing")
             }
         }
@@ -399,26 +352,6 @@ fn asset_from_cache<T: serde::de::DeserializeOwned>(
         .map_err(|_| format!("Could not parse cached {description}").into())
 }
 
-#[cfg(target_os = "macos")]
-fn macos_dark_mode_active() -> bool {
-    const PREFERENCES_FILE: &str = "Library/Preferences/.GlobalPreferences.plist";
-    const STYLE_KEY: &str = "AppleInterfaceStyle";
-
-    let preferences_file = home::home_dir()
-        .map(|home| home.join(PREFERENCES_FILE))
-        .expect("Could not get home directory");
-
-    match plist::Value::from_file(preferences_file).map(|file| file.into_dictionary()) {
-        Ok(Some(preferences)) => match preferences.get(STYLE_KEY).and_then(|val| val.as_string()) {
-            Some(value) => value == "Dark",
-            // If the key does not exist, then light theme is currently in use.
-            None => false,
-        },
-        // Unreachable, in theory. All macOS users have a home directory and preferences file setup.
-        Ok(None) | Err(_) => true,
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;

src/bin/bat/app.rs

@@ -9,6 +9,7 @@ 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, ThemeName, ThemeOptions, ThemePreference};
 use bat::BinaryBehavior;
 use bat::StripAnsiMode;
 use clap::ArgMatches;
@@ -17,7 +18,6 @@ use console::Term;
 
 use crate::input::{new_file_input, new_stdin_input};
 use bat::{
-    assets::HighlightingAssets,
     bat_warning,
     config::{Config, VisibleLines},
     error::*,
@@ -278,18 +278,7 @@ impl App {
                 Some("auto") => StripAnsiMode::Auto,
                 _ => unreachable!("other values for --strip-ansi are not allowed"),
             },
-            theme: self
+            theme: theme(self.theme_options()).to_string(),
-                .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())),
             visible_lines: match self.matches.try_contains_id("diff").unwrap_or_default()
                 && self.matches.get_flag("diff")
             {
@@ -448,4 +437,25 @@ impl App {
 
         Ok(styled_components)
     }
+
+    fn theme_options(&self) -> ThemeOptions {
+        let theme = self
+            .matches
+            .get_one::<String>("theme")
+            .map(|t| ThemePreference::from_str(t).unwrap())
+            .unwrap_or_default();
+        let theme_dark = self
+            .matches
+            .get_one::<String>("theme-dark")
+            .map(|t| ThemeName::from_str(t).unwrap());
+        let theme_light = self
+            .matches
+            .get_one::<String>("theme-light")
+            .map(|t| ThemeName::from_str(t).unwrap());
+        ThemeOptions {
+            theme,
+            theme_dark,
+            theme_light,
+        }
+    }
 }

src/bin/bat/clap_app.rs

@@ -393,9 +393,40 @@ pub fn build_app(interactive_output: bool) -> Command {
                      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=\"...\").",
+                     BAT_THEME=\"...\").\n\n\
+                     Special values:\n\n  \
+                     * auto: Picks a dark or light theme depending on the terminal's colors (default).\n          \
+                     Use '--theme-light' and '--theme-dark' to customize the selected theme.\n    \
+                     * auto:always: Detect the terminal's colors even when the output is redirected.\n    \
+                     * auto:system: Detect the color scheme from the system-wide preference (macOS only).\n  \
+                     * dark: Use the dark theme specified by '--theme-dark'.\n  \
+                     * light: Use the light theme specified by '--theme-light'.",
                 ),
         )
+        .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

@@ -140,7 +140,9 @@ fn get_args_from_str(content: &str) -> Result<Vec<OsString>, shell_words::ParseE
 pub fn get_args_from_env_vars() -> Vec<OsString> {
     [
         ("--tabs", "BAT_TABS"),
-        ("--theme", "BAT_THEME"),
+        ("--theme", bat::theme::env::BAT_THEME),
+        ("--theme-dark", bat::theme::env::BAT_THEME_DARK),
+        ("--theme-light", bat::theme::env::BAT_THEME_LIGHT),
         ("--pager", "BAT_PAGER"),
         ("--paging", "BAT_PAGING"),
         ("--style", "BAT_STYLE"),

src/bin/bat/main.rs

@@ -14,6 +14,7 @@ use std::io::{BufReader, Write};
 use std::path::Path;
 use std::process;
 
+use bat::theme::DetectColorScheme;
 use nu_ansi_term::Color::Green;
 use nu_ansi_term::Style;
 
@@ -30,12 +31,12 @@ use directories::PROJECT_DIRS;
 use globset::GlobMatcher;
 
 use bat::{
-    assets::HighlightingAssets,
     config::Config,
     controller::Controller,
     error::*,
     input::Input,
     style::{StyleComponent, StyleComponents},
+    theme::{color_scheme, default_theme, ColorScheme},
     MappingTarget, PagingMode,
 };
 
@@ -189,7 +190,12 @@ fn theme_preview_file<'a>() -> Input<'a> {
     Input::from_reader(Box::new(BufReader::new(THEME_PREVIEW_DATA)))
 }
 
-pub fn list_themes(cfg: &Config, config_dir: &Path, cache_dir: &Path) -> Result<()> {
+pub fn list_themes(
+    cfg: &Config,
+    config_dir: &Path,
+    cache_dir: &Path,
+    detect_color_scheme: DetectColorScheme,
+) -> Result<()> {
     let assets = assets_from_cache_or_binary(cfg.use_custom_assets, cache_dir)?;
     let mut config = cfg.clone();
     let mut style = HashSet::new();
@@ -200,10 +206,14 @@ pub fn list_themes(cfg: &Config, config_dir: &Path, cache_dir: &Path) -> Result<
     let stdout = io::stdout();
     let mut stdout = stdout.lock();
 
-    let default_theme = HighlightingAssets::default_theme();
+    let default_theme_name = default_theme(color_scheme(detect_color_scheme).unwrap_or_default());
     for theme in assets.themes() {
-        let default_theme_info = if !config.loop_through && default_theme == theme {
+        let default_theme_info = if !config.loop_through && default_theme_name == theme {
             " (default)"
+        } else if default_theme(ColorScheme::Dark) == theme {
+            " (default dark)"
+        } else if default_theme(ColorScheme::Light) == theme {
+            " (default light)"
         } else {
             ""
         };
@@ -371,7 +381,7 @@ fn run() -> Result<bool> {
                 };
                 run_controller(inputs, &plain_config, cache_dir)
             } else if app.matches.get_flag("list-themes") {
-                list_themes(&config, config_dir, cache_dir)?;
+                list_themes(&config, config_dir, cache_dir, DetectColorScheme::default())?;
                 Ok(true)
             } else if app.matches.get_flag("config-file") {
                 println!("{}", config_file().to_string_lossy());

src/lib.rs

@@ -49,6 +49,7 @@ pub(crate) mod printer;
 pub mod style;
 pub(crate) mod syntax_mapping;
 mod terminal;
+pub mod theme;
 mod vscreen;
 pub(crate) mod wrapping;
 

src/pretty_printer.rs

@@ -245,7 +245,9 @@ impl<'a> PrettyPrinter<'a> {
         self
     }
 
-    /// Specify the highlighting theme
+    /// Specify the highlighting theme.
+    /// You can use [`crate::theme::theme`] to pick a theme based on user preferences
+    /// and the terminal's background color.
     pub fn theme(&mut self, theme: impl AsRef<str>) -> &mut Self {
         self.config.theme = theme.as_ref().to_owned();
         self

src/theme.rs

@@ -0,0 +1,571 @@
+//! Utilities for choosing an appropriate theme for syntax highlighting.
+
+use std::convert::Infallible;
+use std::fmt;
+use std::io::IsTerminal as _;
+use std::str::FromStr;
+
+/// Environment variable names.
+pub mod env {
+    /// See [`crate::theme::ThemeOptions::theme`].
+    pub const BAT_THEME: &str = "BAT_THEME";
+    /// See [`crate::theme::ThemeOptions::theme_dark`].
+    pub const BAT_THEME_DARK: &str = "BAT_THEME";
+    /// See [`crate::theme::ThemeOptions::theme_light`].
+    pub const BAT_THEME_LIGHT: &str = "BAT_THEME";
+}
+
+/// Chooses an appropriate theme or falls back to a default theme
+/// based on the user-provided options and the color scheme of the terminal.
+///
+/// Intentionally returns a [`ThemeResult`] instead of a simple string so
+/// that downstream consumers such as `delta` can easily apply their own
+/// default theme and can use the detected color scheme elsewhere.
+pub fn theme(options: ThemeOptions) -> ThemeResult {
+    theme_impl(options, &TerminalColorSchemeDetector)
+}
+
+/// The default theme, suitable for the given color scheme.
+/// Use [`theme`] if you want to automatically detect the color scheme from the terminal.
+pub const fn default_theme(color_scheme: ColorScheme) -> &'static str {
+    match color_scheme {
+        ColorScheme::Dark => "Monokai Extended",
+        ColorScheme::Light => "Monokai Extended Light",
+    }
+}
+
+/// Detects the color scheme from the terminal.
+pub fn color_scheme(when: DetectColorScheme) -> Option<ColorScheme> {
+    color_scheme_impl(when, &TerminalColorSchemeDetector)
+}
+
+/// Options for configuring the theme used for syntax highlighting.
+/// Used together with [`theme`].
+#[derive(Debug, Clone, Default, PartialEq, Eq)]
+pub struct ThemeOptions {
+    /// Configures how the theme is chosen. If set to a [`ThemePreference::Fixed`] value,
+    /// then the given theme is used regardless of the terminal's background color.
+    /// This corresponds with the `BAT_THEME` environment variable and the `--theme` option.
+    pub theme: ThemePreference,
+    /// The theme to use in case the terminal uses a dark background with light text.
+    /// This corresponds with the `BAT_THEME_DARK` environment variable and the `--theme-dark` option.
+    pub theme_dark: Option<ThemeName>,
+    /// The theme to use in case the terminal uses a light background with dark text.
+    /// This corresponds with the `BAT_THEME_LIGHT` environment variable and the `--theme-light` option.
+    pub theme_light: Option<ThemeName>,
+}
+
+/// What theme should `bat` use?
+///
+/// The easiest way to construct this is from a string:
+/// ```
+/// # use bat::theme::{ThemePreference, DetectColorScheme};
+/// let preference = ThemePreference::new("auto:system");
+/// assert_eq!(ThemePreference::Auto(DetectColorScheme::System), preference);
+/// ```
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub enum ThemePreference {
+    /// Choose between [`ThemeOptions::theme_dark`] and [`ThemeOptions::theme_light`]
+    /// based on the terminal's color scheme.
+    Auto(DetectColorScheme),
+    /// Always use the same theme regardless of the terminal's color scheme.
+    Fixed(ThemeName),
+    /// Use a dark theme.
+    Dark,
+    /// Use a light theme.
+    Light,
+}
+
+impl Default for ThemePreference {
+    fn default() -> Self {
+        ThemePreference::Auto(Default::default())
+    }
+}
+
+impl ThemePreference {
+    /// Creates a theme preference from a string.
+    pub fn new(s: impl Into<String>) -> Self {
+        use ThemePreference::*;
+        let s = s.into();
+        match s.as_str() {
+            "auto" => Auto(Default::default()),
+            "auto:always" => Auto(DetectColorScheme::Always),
+            "auto:system" => Auto(DetectColorScheme::System),
+            "dark" => Dark,
+            "light" => Light,
+            _ => Fixed(ThemeName::new(s)),
+        }
+    }
+}
+
+impl FromStr for ThemePreference {
+    type Err = Infallible;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        Ok(ThemePreference::new(s))
+    }
+}
+
+impl fmt::Display for ThemePreference {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        use ThemePreference::*;
+        match self {
+            Auto(DetectColorScheme::Auto) => f.write_str("auto"),
+            Auto(DetectColorScheme::Always) => f.write_str("auto:always"),
+            Auto(DetectColorScheme::System) => f.write_str("auto:system"),
+            Fixed(theme) => theme.fmt(f),
+            Dark => f.write_str("dark"),
+            Light => f.write_str("light"),
+        }
+    }
+}
+
+/// The name of a theme or the default theme.
+///
+/// ```
+/// # use bat::theme::ThemeName;
+/// assert_eq!(ThemeName::Default, ThemeName::new("default"));
+/// assert_eq!(ThemeName::Named("example".to_string()), ThemeName::new("example"));
+/// ```
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub enum ThemeName {
+    Named(String),
+    Default,
+}
+
+impl ThemeName {
+    /// Creates a theme name from a string.
+    pub fn new(s: impl Into<String>) -> Self {
+        let s = s.into();
+        if s == "default" {
+            ThemeName::Default
+        } else {
+            ThemeName::Named(s)
+        }
+    }
+}
+
+impl FromStr for ThemeName {
+    type Err = Infallible;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        Ok(ThemeName::new(s))
+    }
+}
+
+impl fmt::Display for ThemeName {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            ThemeName::Named(t) => f.write_str(t),
+            ThemeName::Default => f.write_str("default"),
+        }
+    }
+}
+
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum DetectColorScheme {
+    /// Only query the terminal for its colors when appropriate (i.e. when the the output is not redirected).
+    #[default]
+    Auto,
+    /// Always query the terminal for its colors.
+    Always,
+    /// Detect the system-wide dark/light preference (macOS only).
+    System,
+}
+
+/// The color scheme used to pick a fitting theme. Defaults to [`ColorScheme::Dark`].
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum ColorScheme {
+    #[default]
+    Dark,
+    Light,
+}
+
+/// The resolved theme and the color scheme as determined from
+/// the terminal, OS or fallback.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ThemeResult {
+    /// The theme selected according to the [`ThemeOptions`].
+    pub theme: ThemeName,
+    /// Either the user's chosen color scheme, the terminal's color scheme, the OS's
+    /// color scheme or `None` if the color scheme was not detected because the user chose a fixed theme.
+    pub color_scheme: Option<ColorScheme>,
+}
+
+impl fmt::Display for ThemeResult {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match &self.theme {
+            ThemeName::Named(name) => f.write_str(name),
+            ThemeName::Default => f.write_str(default_theme(self.color_scheme.unwrap_or_default())),
+        }
+    }
+}
+
+fn theme_impl(options: ThemeOptions, detector: &dyn ColorSchemeDetector) -> ThemeResult {
+    // Implementation note: This function is mostly pure (i.e. it has no side effects) for the sake of testing.
+    // All the side effects (e.g. querying the terminal for its colors) are performed in the detector.
+    match options.theme {
+        ThemePreference::Fixed(theme) => ThemeResult {
+            theme,
+            color_scheme: None,
+        },
+        ThemePreference::Dark => choose_theme_opt(Some(ColorScheme::Dark), options),
+        ThemePreference::Light => choose_theme_opt(Some(ColorScheme::Light), options),
+        ThemePreference::Auto(when) => choose_theme_opt(color_scheme_impl(when, detector), options),
+    }
+}
+
+fn choose_theme_opt(color_scheme: Option<ColorScheme>, options: ThemeOptions) -> ThemeResult {
+    ThemeResult {
+        color_scheme,
+        theme: color_scheme
+            .and_then(|c| choose_theme(options, c))
+            .unwrap_or(ThemeName::Default),
+    }
+}
+
+fn choose_theme(options: ThemeOptions, color_scheme: ColorScheme) -> Option<ThemeName> {
+    match color_scheme {
+        ColorScheme::Dark => options.theme_dark,
+        ColorScheme::Light => options.theme_light,
+    }
+}
+
+fn color_scheme_impl(
+    when: DetectColorScheme,
+    detector: &dyn ColorSchemeDetector,
+) -> Option<ColorScheme> {
+    let should_detect = match when {
+        DetectColorScheme::Auto => detector.should_detect(),
+        DetectColorScheme::Always => true,
+        DetectColorScheme::System => return color_scheme_from_system(),
+    };
+    should_detect.then(|| detector.detect()).flatten()
+}
+
+trait ColorSchemeDetector {
+    fn should_detect(&self) -> bool;
+
+    fn detect(&self) -> Option<ColorScheme>;
+}
+
+struct TerminalColorSchemeDetector;
+
+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(target_os = "macos"))]
+fn color_scheme_from_system() -> Option<ColorScheme> {
+    crate::bat_warning!(
+        "Theme 'auto:system' is only supported on macOS, \
+        using default."
+    );
+    None
+}
+
+#[cfg(target_os = "macos")]
+fn color_scheme_from_system() -> Option<ColorScheme> {
+    const PREFERENCES_FILE: &str = "Library/Preferences/.GlobalPreferences.plist";
+    const STYLE_KEY: &str = "AppleInterfaceStyle";
+
+    let preferences_file = home::home_dir()
+        .map(|home| home.join(PREFERENCES_FILE))
+        .expect("Could not get home directory");
+
+    match plist::Value::from_file(preferences_file).map(|file| file.into_dictionary()) {
+        Ok(Some(preferences)) => match preferences.get(STYLE_KEY).and_then(|val| val.as_string()) {
+            Some("Dark") => Some(ColorScheme::Dark),
+            // If the key does not exist, then light theme is currently in use.
+            Some(_) | None => Some(ColorScheme::Light),
+        },
+        // Unreachable, in theory. All macOS users have a home directory and preferences file setup.
+        Ok(None) | Err(_) => None,
+    }
+}
+
+#[cfg(test)]
+impl ColorSchemeDetector for Option<ColorScheme> {
+    fn should_detect(&self) -> bool {
+        true
+    }
+
+    fn detect(&self) -> Option<ColorScheme> {
+        *self
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::ColorScheme::*;
+    use super::*;
+    use std::cell::Cell;
+    use std::iter;
+
+    mod color_scheme_detection {
+        use super::*;
+
+        #[test]
+        fn not_called_for_dark_or_light() {
+            for theme in [ThemePreference::Dark, ThemePreference::Light] {
+                let detector = DetectorStub::should_detect(Some(Dark));
+                let options = ThemeOptions {
+                    theme,
+                    ..Default::default()
+                };
+                _ = theme_impl(options, &detector);
+                assert!(!detector.was_called.get());
+            }
+        }
+
+        #[test]
+        fn called_for_always() {
+            let detectors = [
+                DetectorStub::should_detect(Some(Dark)),
+                DetectorStub::should_not_detect(),
+            ];
+            for detector in detectors {
+                let options = ThemeOptions {
+                    theme: ThemePreference::Auto(DetectColorScheme::Always),
+                    ..Default::default()
+                };
+                _ = theme_impl(options, &detector);
+                assert!(detector.was_called.get());
+            }
+        }
+
+        #[test]
+        fn called_for_auto_if_should_detect() {
+            let detector = DetectorStub::should_detect(Some(Dark));
+            _ = theme_impl(ThemeOptions::default(), &detector);
+            assert!(detector.was_called.get());
+        }
+
+        #[test]
+        fn not_called_for_auto_if_not_should_detect() {
+            let detector = DetectorStub::should_not_detect();
+            _ = theme_impl(ThemeOptions::default(), &detector);
+            assert!(!detector.was_called.get());
+        }
+    }
+
+    mod precedence {
+        use super::*;
+
+        #[test]
+        fn theme_is_preferred_over_light_or_dark_themes() {
+            for color_scheme in optional(color_schemes()) {
+                for options in [
+                    ThemeOptions {
+                        theme: ThemePreference::Fixed(ThemeName::Named("Theme".to_string())),
+                        ..Default::default()
+                    },
+                    ThemeOptions {
+                        theme: ThemePreference::Fixed(ThemeName::Named("Theme".to_string())),
+                        theme_dark: Some(ThemeName::Named("Dark Theme".to_string())),
+                        theme_light: Some(ThemeName::Named("Light Theme".to_string())),
+                        ..Default::default()
+                    },
+                ] {
+                    let detector = ConstantDetector(color_scheme);
+                    assert_eq!("Theme", theme_impl(options, &detector).to_string());
+                }
+            }
+        }
+
+        #[test]
+        fn detector_is_not_called_if_theme_is_present() {
+            let options = ThemeOptions {
+                theme: ThemePreference::Fixed(ThemeName::Named("Theme".to_string())),
+                ..Default::default()
+            };
+            let detector = DetectorStub::should_detect(Some(Dark));
+            _ = theme_impl(options, &detector);
+            assert!(!detector.was_called.get());
+        }
+    }
+
+    mod default_theme {
+        use super::*;
+
+        #[test]
+        fn default_dark_if_unable_to_detect_color_scheme() {
+            let detector = ConstantDetector(None);
+            assert_eq!(
+                default_theme(ColorScheme::Dark),
+                theme_impl(ThemeOptions::default(), &detector).to_string()
+            );
+        }
+
+        // For backwards compatibility, if the default theme is requested
+        // explicitly through BAT_THEME, we always pick the default dark theme.
+        #[test]
+        fn default_dark_if_requested_explicitly_through_theme() {
+            for color_scheme in optional(color_schemes()) {
+                let options = ThemeOptions {
+                    theme: ThemePreference::Fixed(ThemeName::Default),
+                    ..Default::default()
+                };
+                let detector = ConstantDetector(color_scheme);
+                assert_eq!(
+                    default_theme(ColorScheme::Dark),
+                    theme_impl(options, &detector).to_string()
+                );
+            }
+        }
+
+        #[test]
+        fn varies_depending_on_color_scheme() {
+            for color_scheme in color_schemes() {
+                for options in [
+                    ThemeOptions::default(),
+                    ThemeOptions {
+                        theme_dark: Some(ThemeName::Default),
+                        theme_light: Some(ThemeName::Default),
+                        ..Default::default()
+                    },
+                ] {
+                    let detector = ConstantDetector(Some(color_scheme));
+                    assert_eq!(
+                        default_theme(color_scheme),
+                        theme_impl(options, &detector).to_string()
+                    );
+                }
+            }
+        }
+    }
+
+    mod choosing {
+        use super::*;
+
+        #[test]
+        fn chooses_default_theme_if_unknown() {
+            let options = ThemeOptions {
+                theme_dark: Some(ThemeName::Named("Dark".to_string())),
+                theme_light: Some(ThemeName::Named("Light".to_string())),
+                ..Default::default()
+            };
+            let detector = ConstantDetector(None);
+            assert_eq!(
+                default_theme(ColorScheme::default()),
+                theme_impl(options, &detector).to_string()
+            );
+        }
+
+        #[test]
+        fn chooses_dark_theme_if_dark_or_unknown() {
+            let options = ThemeOptions {
+                theme_dark: Some(ThemeName::Named("Dark".to_string())),
+                theme_light: Some(ThemeName::Named("Light".to_string())),
+                ..Default::default()
+            };
+            let detector = ConstantDetector(Some(ColorScheme::Dark));
+            assert_eq!("Dark", theme_impl(options, &detector).to_string());
+        }
+
+        #[test]
+        fn chooses_light_theme_if_light() {
+            let options = ThemeOptions {
+                theme_dark: Some(ThemeName::Named("Dark".to_string())),
+                theme_light: Some(ThemeName::Named("Light".to_string())),
+                ..Default::default()
+            };
+            let detector = ConstantDetector(Some(ColorScheme::Light));
+            assert_eq!("Light", theme_impl(options, &detector).to_string());
+        }
+    }
+
+    mod theme_preference {
+        use super::*;
+
+        #[test]
+        fn values_roundtrip_via_display() {
+            let prefs = [
+                ThemePreference::Auto(DetectColorScheme::Auto),
+                ThemePreference::Auto(DetectColorScheme::Always),
+                ThemePreference::Auto(DetectColorScheme::System),
+                ThemePreference::Fixed(ThemeName::Default),
+                ThemePreference::Fixed(ThemeName::new("foo")),
+                ThemePreference::Dark,
+                ThemePreference::Light,
+            ];
+            for pref in prefs {
+                assert_eq!(pref, ThemePreference::new(&pref.to_string()));
+            }
+        }
+    }
+
+    struct DetectorStub {
+        should_detect: bool,
+        color_scheme: Option<ColorScheme>,
+        was_called: Cell<bool>,
+    }
+
+    impl DetectorStub {
+        fn should_detect(color_scheme: Option<ColorScheme>) -> Self {
+            DetectorStub {
+                should_detect: true,
+                color_scheme,
+                was_called: Cell::default(),
+            }
+        }
+
+        fn should_not_detect() -> Self {
+            DetectorStub {
+                should_detect: false,
+                color_scheme: None,
+                was_called: Cell::default(),
+            }
+        }
+    }
+
+    impl ColorSchemeDetector for DetectorStub {
+        fn should_detect(&self) -> bool {
+            self.should_detect
+        }
+
+        fn detect(&self) -> Option<ColorScheme> {
+            self.was_called.set(true);
+            self.color_scheme
+        }
+    }
+
+    struct ConstantDetector(Option<ColorScheme>);
+
+    impl ColorSchemeDetector for ConstantDetector {
+        fn should_detect(&self) -> bool {
+            true
+        }
+
+        fn detect(&self) -> Option<ColorScheme> {
+            self.0
+        }
+    }
+
+    fn optional<T>(value: impl Iterator<Item = T>) -> impl Iterator<Item = Option<T>> {
+        value.map(Some).chain(iter::once(None))
+    }
+
+    fn color_schemes() -> impl Iterator<Item = ColorScheme> {
+        [Dark, Light].into_iter()
+    }
+}

tests/integration_tests.rs

@@ -273,11 +273,8 @@ fn squeeze_limit_line_numbers() {
 
 #[test]
 fn list_themes_with_colors() {
-    #[cfg(target_os = "macos")]
-    let default_theme_chunk = "Monokai Extended Light\x1B[0m (default)";
-
-    #[cfg(not(target_os = "macos"))]
     let default_theme_chunk = "Monokai Extended\x1B[0m (default)";
+    let default_light_theme_chunk = "Monokai Extended Light\x1B[0m (default light)";
 
     bat()
         .arg("--color=always")
@@ -286,16 +283,14 @@ fn list_themes_with_colors() {
         .success()
         .stdout(predicate::str::contains("DarkNeon").normalize())
         .stdout(predicate::str::contains(default_theme_chunk).normalize())
+        .stdout(predicate::str::contains(default_light_theme_chunk).normalize())
         .stdout(predicate::str::contains("Output the square of a number.").normalize());
 }
 
 #[test]
 fn list_themes_without_colors() {
-    #[cfg(target_os = "macos")]
-    let default_theme_chunk = "Monokai Extended Light (default)";
-
-    #[cfg(not(target_os = "macos"))]
     let default_theme_chunk = "Monokai Extended (default)";
+    let default_light_theme_chunk = "Monokai Extended Light (default light)";
 
     bat()
         .arg("--color=never")
@@ -304,7 +299,8 @@ fn list_themes_without_colors() {
         .assert()
         .success()
         .stdout(predicate::str::contains("DarkNeon").normalize())
-        .stdout(predicate::str::contains(default_theme_chunk).normalize());
+        .stdout(predicate::str::contains(default_theme_chunk).normalize())
+        .stdout(predicate::str::contains(default_light_theme_chunk).normalize());
 }
 
 #[test]
@@ -414,6 +410,7 @@ fn no_args_doesnt_break() {
     // as the slave end of a pseudo terminal. Although both point to the same "file", bat should
     // not exit, because in this case it is safe to read and write to the same fd, which is why
     // this test exists.
+
     let OpenptyResult { master, slave } = openpty(None, None).expect("Couldn't open pty.");
     let mut master = File::from(master);
     let stdin_file = File::from(slave);
@@ -424,6 +421,7 @@ fn no_args_doesnt_break() {
     let mut child = bat_raw_command()
         .stdin(stdin)
         .stdout(stdout)
+        .env("TERM", "dumb") // Suppresses color detection
         .spawn()
         .expect("Failed to start.");