Add $LESSOPEN and $LESSCLOSE support (#2444)

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();
 

src/lessopen.rs

@@ -0,0 +1,390 @@
+#![cfg(feature = "lessopen")]
+
+use std::convert::TryFrom;
+use std::env;
+use std::fs::File;
+use std::io::{BufRead, BufReader, Cursor, Read, Write};
+use std::path::PathBuf;
+use std::str;
+
+use clircle::{Clircle, Identifier};
+use os_str_bytes::RawOsString;
+use run_script::{IoOptions, ScriptOptions};
+
+use crate::error::Result;
+use crate::input::{Input, InputKind, InputReader, OpenedInput, OpenedInputKind};
+
+/// Preprocess files and/or stdin using $LESSOPEN and $LESSCLOSE
+pub(crate) struct LessOpenPreprocessor {
+    lessopen: String,
+    lessclose: Option<String>,
+    command_options: ScriptOptions,
+    kind: LessOpenKind,
+    /// Whether or not data piped via stdin is to be preprocessed
+    preprocess_stdin: bool,
+}
+
+enum LessOpenKind {
+    Piped,
+    PipedIgnoreExitCode,
+    TempFile,
+}
+
+impl LessOpenPreprocessor {
+    /// Create a new instance of LessOpenPreprocessor
+    /// Will return Ok if and only if $LESSOPEN is set
+    pub(crate) fn new() -> Result<LessOpenPreprocessor> {
+        let lessopen = env::var("LESSOPEN")?;
+
+        // "||" means pipe directly to bat without making a temporary file
+        // Also, if preprocessor output is empty and exit code is zero, use the empty output
+        // Otherwise, if output is empty and exit code is nonzero, use original file contents
+        let (kind, lessopen) = if lessopen.starts_with("||") {
+            (LessOpenKind::Piped, lessopen.chars().skip(2).collect())
+        // "|" means pipe, but ignore exit code, always using preprocessor output
+        } else if lessopen.starts_with('|') {
+            (
+                LessOpenKind::PipedIgnoreExitCode,
+                lessopen.chars().skip(1).collect(),
+            )
+        // If neither appear, write output to a temporary file and read from that
+        } else {
+            (LessOpenKind::TempFile, lessopen)
+        };
+
+        // "-" means that stdin is preprocessed along with files and may appear alongside "|" and "||"
+        let (stdin, lessopen) = if lessopen.starts_with('-') {
+            (true, lessopen.chars().skip(1).collect())
+        } else {
+            (false, lessopen)
+        };
+
+        let mut command_options = ScriptOptions::new();
+        command_options.runner = env::var("SHELL").ok();
+        command_options.input_redirection = IoOptions::Pipe;
+
+        Ok(Self {
+            lessopen: lessopen.replacen("%s", "$1", 1),
+            lessclose: env::var("LESSCLOSE")
+                .ok()
+                .map(|str| str.replacen("%s", "$1", 1).replacen("%s", "$2", 1)),
+            command_options,
+            kind,
+            preprocess_stdin: stdin,
+        })
+    }
+
+    pub(crate) fn open<'a, R: BufRead + 'a>(
+        &self,
+        input: Input<'a>,
+        mut stdin: R,
+        stdout_identifier: Option<&Identifier>,
+    ) -> Result<OpenedInput<'a>> {
+        let (lessopen_stdout, path_str, kind) = match input.kind {
+            InputKind::OrdinaryFile(ref path) => {
+                let path_str = match path.to_str() {
+                    Some(str) => str,
+                    None => return input.open(stdin, stdout_identifier),
+                };
+
+                let (exit_code, lessopen_stdout, _) = match run_script::run(
+                    &self.lessopen,
+                    &vec![path_str.to_string()],
+                    &self.command_options,
+                ) {
+                    Ok(output) => output,
+                    Err(_) => return input.open(stdin, stdout_identifier),
+                };
+
+                if self.fall_back_to_original_file(&lessopen_stdout, exit_code) {
+                    return input.open(stdin, stdout_identifier);
+                }
+
+                (
+                    RawOsString::from_string(lessopen_stdout),
+                    path_str.to_string(),
+                    OpenedInputKind::OrdinaryFile(path.to_path_buf()),
+                )
+            }
+            InputKind::StdIn => {
+                if self.preprocess_stdin {
+                    if let Some(stdout) = stdout_identifier {
+                        let input_identifier = Identifier::try_from(clircle::Stdio::Stdin)
+                            .map_err(|e| format!("Stdin: Error identifying file: {}", e))?;
+                        if stdout.surely_conflicts_with(&input_identifier) {
+                            return Err("IO circle detected. The input from stdin is also an output. Aborting to avoid infinite loop.".into());
+                        }
+                    }
+
+                    // stdin isn't Clone, so copy it to a cloneable buffer
+                    let mut stdin_buffer = Vec::new();
+                    stdin.read_to_end(&mut stdin_buffer).unwrap();
+
+                    let mut lessopen_handle = match run_script::spawn(
+                        &self.lessopen,
+                        &vec!["-".to_string()],
+                        &self.command_options,
+                    ) {
+                        Ok(handle) => handle,
+                        Err(_) => {
+                            return input.open(stdin, stdout_identifier);
+                        }
+                    };
+
+                    if lessopen_handle
+                        .stdin
+                        .as_mut()
+                        .unwrap()
+                        .write_all(&stdin_buffer.clone())
+                        .is_err()
+                    {
+                        return input.open(stdin, stdout_identifier);
+                    }
+
+                    let lessopen_output = match lessopen_handle.wait_with_output() {
+                        Ok(output) => output,
+                        Err(_) => {
+                            return input.open(Cursor::new(stdin_buffer), stdout_identifier);
+                        }
+                    };
+
+                    if lessopen_output.stdout.is_empty()
+                        && (!lessopen_output.status.success()
+                            || matches!(self.kind, LessOpenKind::PipedIgnoreExitCode))
+                    {
+                        return input.open(Cursor::new(stdin_buffer), stdout_identifier);
+                    }
+
+                    (
+                        RawOsString::assert_from_raw_vec(lessopen_output.stdout),
+                        "-".to_string(),
+                        OpenedInputKind::StdIn,
+                    )
+                } else {
+                    return input.open(stdin, stdout_identifier);
+                }
+            }
+            InputKind::CustomReader(_) => {
+                return input.open(stdin, stdout_identifier);
+            }
+        };
+
+        Ok(OpenedInput {
+            kind,
+            reader: InputReader::new(BufReader::new(
+                if matches!(self.kind, LessOpenKind::TempFile) {
+                    // Remove newline at end of temporary file path returned by $LESSOPEN
+                    let stdout = match lessopen_stdout.strip_suffix("\n") {
+                        Some(stripped) => stripped.to_owned(),
+                        None => lessopen_stdout,
+                    };
+
+                    let stdout = stdout.into_os_string();
+
+                    let file = match File::open(PathBuf::from(&stdout)) {
+                        Ok(file) => file,
+                        Err(_) => {
+                            return input.open(stdin, stdout_identifier);
+                        }
+                    };
+
+                    Preprocessed {
+                        kind: PreprocessedKind::TempFile(file),
+                        lessclose: self.lessclose.clone(),
+                        command_args: vec![path_str, stdout.to_str().unwrap().to_string()],
+                        command_options: self.command_options.clone(),
+                    }
+                } else {
+                    Preprocessed {
+                        kind: PreprocessedKind::Piped(Cursor::new(lessopen_stdout.into_raw_vec())),
+                        lessclose: self.lessclose.clone(),
+                        command_args: vec![path_str, "-".to_string()],
+                        command_options: self.command_options.clone(),
+                    }
+                },
+            )),
+            metadata: input.metadata,
+            description: input.description,
+        })
+    }
+
+    fn fall_back_to_original_file(&self, lessopen_output: &str, exit_code: i32) -> bool {
+        lessopen_output.is_empty()
+            && (exit_code != 0 || matches!(self.kind, LessOpenKind::PipedIgnoreExitCode))
+    }
+
+    #[cfg(test)]
+    /// For testing purposes only
+    /// Create an instance of LessOpenPreprocessor with specified valued for $LESSOPEN and $LESSCLOSE
+    fn mock_new(lessopen: Option<&str>, lessclose: Option<&str>) -> Result<LessOpenPreprocessor> {
+        if let Some(command) = lessopen {
+            env::set_var("LESSOPEN", command)
+        } else {
+            env::remove_var("LESSOPEN")
+        }
+
+        if let Some(command) = lessclose {
+            env::set_var("LESSCLOSE", command)
+        } else {
+            env::remove_var("LESSCLOSE")
+        }
+
+        Self::new()
+    }
+}
+
+enum PreprocessedKind {
+    Piped(Cursor<Vec<u8>>),
+    TempFile(File),
+}
+
+impl Read for PreprocessedKind {
+    fn read(&mut self, buf: &mut [u8]) -> std::result::Result<usize, std::io::Error> {
+        match self {
+            PreprocessedKind::Piped(data) => data.read(buf),
+            PreprocessedKind::TempFile(data) => data.read(buf),
+        }
+    }
+}
+
+pub struct Preprocessed {
+    kind: PreprocessedKind,
+    lessclose: Option<String>,
+    command_args: Vec<String>,
+    command_options: ScriptOptions,
+}
+
+impl Read for Preprocessed {
+    fn read(&mut self, buf: &mut [u8]) -> std::result::Result<usize, std::io::Error> {
+        self.kind.read(buf)
+    }
+}
+
+impl Drop for Preprocessed {
+    fn drop(&mut self) {
+        if let Some(ref command) = self.lessclose {
+            self.command_options.output_redirection = IoOptions::Inherit;
+
+            run_script::run(command, &self.command_args, &self.command_options)
+                .expect("failed to run $LESSCLOSE to clean up file");
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    // All tests here are serial because they all involve reading and writing environment variables
+    // Running them in parallel causes these tests and some others to randomly fail
+    use serial_test::serial;
+
+    use super::*;
+
+    /// Reset environment variables after each test as a precaution
+    fn reset_env_vars() {
+        env::remove_var("LESSOPEN");
+        env::remove_var("LESSCLOSE");
+    }
+
+    #[test]
+    #[serial]
+    fn test_just_lessopen() -> Result<()> {
+        let preprocessor = LessOpenPreprocessor::mock_new(Some("|batpipe %s"), None)?;
+
+        assert_eq!(preprocessor.lessopen, "batpipe $1");
+        assert!(preprocessor.lessclose.is_none());
+
+        reset_env_vars();
+
+        Ok(())
+    }
+
+    #[test]
+    #[serial]
+    fn test_just_lessclose() -> Result<()> {
+        let preprocessor = LessOpenPreprocessor::mock_new(None, Some("lessclose.sh %s %s"));
+
+        assert!(preprocessor.is_err());
+
+        reset_env_vars();
+
+        Ok(())
+    }
+
+    #[test]
+    #[serial]
+    fn test_both_lessopen_and_lessclose() -> Result<()> {
+        let preprocessor =
+            LessOpenPreprocessor::mock_new(Some("lessopen.sh %s"), Some("lessclose.sh %s %s"))?;
+
+        assert_eq!(preprocessor.lessopen, "lessopen.sh $1");
+        assert_eq!(preprocessor.lessclose.unwrap(), "lessclose.sh $1 $2");
+
+        reset_env_vars();
+
+        Ok(())
+    }
+
+    #[test]
+    #[serial]
+    fn test_lessopen_prefixes() -> Result<()> {
+        let preprocessor = LessOpenPreprocessor::mock_new(Some("batpipe %s"), None)?;
+
+        assert_eq!(preprocessor.lessopen, "batpipe $1");
+        assert!(matches!(preprocessor.kind, LessOpenKind::TempFile));
+        assert!(!preprocessor.preprocess_stdin);
+
+        let preprocessor = LessOpenPreprocessor::mock_new(Some("|batpipe %s"), None)?;
+
+        assert_eq!(preprocessor.lessopen, "batpipe $1");
+        assert!(matches!(
+            preprocessor.kind,
+            LessOpenKind::PipedIgnoreExitCode
+        ));
+        assert!(!preprocessor.preprocess_stdin);
+
+        let preprocessor = LessOpenPreprocessor::mock_new(Some("||batpipe %s"), None)?;
+
+        assert_eq!(preprocessor.lessopen, "batpipe $1");
+        assert!(matches!(preprocessor.kind, LessOpenKind::Piped));
+        assert!(!preprocessor.preprocess_stdin);
+
+        let preprocessor = LessOpenPreprocessor::mock_new(Some("-batpipe %s"), None)?;
+
+        assert_eq!(preprocessor.lessopen, "batpipe $1");
+        assert!(matches!(preprocessor.kind, LessOpenKind::TempFile));
+        assert!(preprocessor.preprocess_stdin);
+
+        let preprocessor = LessOpenPreprocessor::mock_new(Some("|-batpipe %s"), None)?;
+
+        assert_eq!(preprocessor.lessopen, "batpipe $1");
+        assert!(matches!(
+            preprocessor.kind,
+            LessOpenKind::PipedIgnoreExitCode
+        ));
+        assert!(preprocessor.preprocess_stdin);
+
+        let preprocessor = LessOpenPreprocessor::mock_new(Some("||-batpipe %s"), None)?;
+
+        assert_eq!(preprocessor.lessopen, "batpipe $1");
+        assert!(matches!(preprocessor.kind, LessOpenKind::Piped));
+        assert!(preprocessor.preprocess_stdin);
+
+        reset_env_vars();
+
+        Ok(())
+    }
+
+    #[test]
+    #[serial]
+    fn replace_part_of_argument() -> Result<()> {
+        let preprocessor =
+            LessOpenPreprocessor::mock_new(Some("|echo File:%s"), Some("echo File:%s Temp:%s"))?;
+
+        assert_eq!(preprocessor.lessopen, "echo File:$1");
+        assert_eq!(preprocessor.lessclose.unwrap(), "echo File:$1 Temp:$2");
+
+        reset_env_vars();
+
+        Ok(())
+    }
+}

src/lib.rs

@@ -34,6 +34,8 @@ mod diff;
 pub mod error;
 pub mod input;
 mod less;
+#[cfg(feature = "lessopen")]
+mod lessopen;
 pub mod line_range;
 pub(crate) mod nonprintable_notation;
 mod output;