Add $LESSOPEN and $LESSCLOSE support

CHANGELOG.md

@@ -77,6 +77,7 @@
 
 - Make the default macOS theme depend on Dark Mode. See #2197, #1746 (@Enselic)
 - Support for separate system and user config files. See #668 (@patrickpichler)
+- Add support for $LESSOPEN and $LESSCLOSE. See #1597, #1739, and #2444 (@Anomalocaridid)
 
 ## Bugfixes
 

Cargo.toml

@@ -21,6 +21,7 @@ application = [
     "build-assets",
     "git",
     "minimal-application",
+    "lessopen",
 ]
 # Mainly for developers that want to iterate quickly
 # Be aware that the included features might change in the future
@@ -33,6 +34,7 @@ minimal-application = [
 ]
 git = ["git2"] # Support indicating git modifications
 paging = ["shell-words", "grep-cli"] # Support applying a pager on the output
+lessopen = ["run_script", "os_str_bytes"] # Support $LESSOPEN preprocessor
 build-assets = ["syntect/yaml-load", "syntect/plist-load", "regex", "walkdir"]
 
 # You need to use one of these if you depend on bat as a library:
@@ -64,6 +66,8 @@ regex = { version = "1.8.3", optional = true }
 walkdir = { version = "2.3", optional = true }
 bytesize = { version = "1.2.0" }
 encoding_rs = "0.8.32"
+os_str_bytes = { version = "~6.4", optional = true }
+run_script = { version = "^0.10.0", optional = true}
 
 [dependencies.git2]
 version = "0.18"

assets/completions/_bat.ps1.in

@@ -59,6 +59,7 @@ Register-ArgumentCompleter -Native -CommandName '{{PROJECT_EXECUTABLE}}' -Script
             [CompletionResult]::new('--unbuffered', 'unbuffered', [CompletionResultType]::ParameterName, 'unbuffered')
             [CompletionResult]::new('--no-config', 'no-config', [CompletionResultType]::ParameterName, 'Do not use the configuration file')
             [CompletionResult]::new('--no-custom-assets', 'no-custom-assets', [CompletionResultType]::ParameterName, 'Do not load custom assets')
+            [CompletionResult]::new('--no-lessopen', 'no-lessopen', [CompletionResultType]::ParameterName, 'Do not use the $LESSOPEN preprocessor')
             [CompletionResult]::new('--config-file', 'config-file', [CompletionResultType]::ParameterName, 'Show path to the configuration file.')
             [CompletionResult]::new('--generate-config-file', 'generate-config-file', [CompletionResultType]::ParameterName, 'Generates a default configuration file.')
             [CompletionResult]::new('--config-dir', 'config-dir', [CompletionResultType]::ParameterName, 'Show bat''s configuration directory.')

assets/completions/bat.zsh.in

@@ -46,6 +46,7 @@ _{{PROJECT_EXECUTABLE}}_main() {
         '(: --list-themes --list-languages -L)'{-L,--list-languages}'[Display all supported languages]'
         '(: --no-config)'--no-config'[Do not use the configuration file]'
         '(: --no-custom-assets)'--no-custom-assets'[Do not load custom assets]'
+        '(: --no-lessopen)'--no-lessopen'[Do not use the $LESSOPEN preprocessor]'
         '(: --config-dir)'--config-dir'[Show bat'"'"'s configuration directory]'
         '(: --config-file)'--config-file'[Show path to the configuration file]'
         '(: --generate-config-file)'--generate-config-file'[Generates a default configuration file]'

assets/manual/bat.1.in

@@ -243,6 +243,17 @@ If you ever want to remove the custom languages, you can clear the cache with `\
 Similarly to custom languages, {{PROJECT_EXECUTABLE}} supports Sublime Text \fB.tmTheme\fR themes.
 These can be installed to `\fB$({{PROJECT_EXECUTABLE}} --config-dir)/themes\fR`, and are added to the cache with
 `\fB{{PROJECT_EXECUTABLE}} cache --build`.
+
+.SH "INPUT PREPROCESSOR"
+Much like less(1) does, {{PROJECT_EXECUTABLE}} supports input preprocessors via the LESSOPEN and LESSCLOSE environment variables.
+In addition, {{PROJECT_EXECUTABLE}} attempts to be as compatible with less's preprocessor implementation as possible.
+
+To run {{PROJECT_EXECUTABLE}} without using the preprocessor, call:
+
+\fB{{PROJECT_EXECUTABLE}} --no-lessopen\fR
+
+For more information, see the "INPUT PREPROCESSOR" section of less(1).  
+
 .SH "MORE INFORMATION"
 
 For more information and up-to-date documentation, visit the {{PROJECT_EXECUTABLE}} repo:

src/bin/bat/app.rs

@@ -281,6 +281,8 @@ impl App {
                 .map(HighlightedLineRanges)
                 .unwrap_or_default(),
             use_custom_assets: !self.matches.get_flag("no-custom-assets"),
+            #[cfg(feature = "lessopen")]
+            use_lessopen: !self.matches.get_flag("no-lessopen"),
         })
     }
 

src/bin/bat/clap_app.rs

@@ -497,7 +497,20 @@ pub fn build_app(interactive_output: bool) -> Command {
                 .action(ArgAction::SetTrue)
                 .hide(true)
                 .help("Do not load custom assets"),
+        );
+
+    #[cfg(feature = "lessopen")]
+    {
+        app = app.arg(
+            Arg::new("no-lessopen")
+                .long("no-lessopen")
+                .action(ArgAction::SetTrue)
+                .hide(true)
+                .help("Do not use the $LESSOPEN preprocessor"),
         )
+    }
+
+    app = app
         .arg(
             Arg::new("config-file")
                 .long("config-file")
@@ -536,7 +549,7 @@ pub fn build_app(interactive_output: bool) -> Command {
                 .alias("diagnostics")
                 .action(ArgAction::SetTrue)
                 .hide_short_help(true)
-                .help("Show diagnostic information for bug reports.")
+                .help("Show diagnostic information for bug reports."),
         )
         .arg(
             Arg::new("acknowledgements")

src/config.rs

@@ -90,6 +90,10 @@ pub struct Config<'a> {
     /// Whether or not to allow custom assets. If this is false or if custom assets (a.k.a.
     /// cached assets) are not available, assets from the binary will be used instead.
     pub use_custom_assets: bool,
+
+    // Whether or not to use $LESSOPEN if set
+    #[cfg(feature = "lessopen")]
+    pub use_lessopen: bool,
 }
 
 #[cfg(all(feature = "minimal-application", feature = "paging"))]

src/controller.rs

@@ -6,6 +6,8 @@ use crate::config::{Config, VisibleLines};
 use crate::diff::{get_git_diff, LineChanges};
 use crate::error::*;
 use crate::input::{Input, InputReader, OpenedInput};
+#[cfg(feature = "lessopen")]
+use crate::lessopen::LessOpenPreprocessor;
 #[cfg(feature = "git")]
 use crate::line_range::LineRange;
 use crate::line_range::{LineRanges, RangeCheckResult};
@@ -19,11 +21,18 @@ use clircle::{Clircle, Identifier};
 pub struct Controller<'a> {
     config: &'a Config<'a>,
     assets: &'a HighlightingAssets,
+    #[cfg(feature = "lessopen")]
+    preprocessor: Option<LessOpenPreprocessor>,
 }
 
 impl<'b> Controller<'b> {
     pub fn new<'a>(config: &'a Config, assets: &'a HighlightingAssets) -> Controller<'a> {
-        Controller { config, assets }
+        Controller {
+            config,
+            assets,
+            #[cfg(feature = "lessopen")]
+            preprocessor: LessOpenPreprocessor::new().ok(),
+        }
     }
 
     pub fn run(
@@ -123,7 +132,18 @@ impl<'b> Controller<'b> {
         stdout_identifier: Option<&Identifier>,
         is_first: bool,
     ) -> Result<()> {
-        let mut opened_input = input.open(stdin, stdout_identifier)?;
+        let mut opened_input = {
+            #[cfg(feature = "lessopen")]
+            match self.preprocessor {
+                Some(ref preprocessor) if self.config.use_lessopen => {
+                    preprocessor.open(input, stdin, stdout_identifier)?
+                }
+                _ => input.open(stdin, stdout_identifier)?,
+            }
+
+            #[cfg(not(feature = "lessopen"))]
+            input.open(stdin, stdout_identifier)?
+        };
         #[cfg(feature = "git")]
         let line_changes = if self.config.visible_lines.diff_mode()
             || (!self.config.loop_through && self.config.style_components.changes())

src/error.rs

@@ -28,6 +28,12 @@ pub enum Error {
     InvalidPagerValueBat,
     #[error("{0}")]
     Msg(String),
+    #[cfg(feature = "lessopen")]
+    #[error(transparent)]
+    VarError(#[from] ::std::env::VarError),
+    #[cfg(feature = "lessopen")]
+    #[error(transparent)]
+    CommandParseError(#[from] ::shell_words::ParseError),
 }
 
 impl From<&'static str> for Error {

src/input.rs

@@ -256,7 +256,7 @@ pub(crate) struct InputReader<'a> {
 }
 
 impl<'a> InputReader<'a> {
-    fn new<R: BufRead + 'a>(mut reader: R) -> InputReader<'a> {
+    pub(crate) fn new<R: BufRead + 'a>(mut reader: R) -> InputReader<'a> {
         let mut first_line = vec![];
         reader.read_until(b'\n', &mut first_line).ok();