Merge pull request #2999 from eth-p/strip-ansi-from-input-option

Add option to remove ANSI escape sequences from bat's input.

Author: eth-p

CHANGELOG.md

@@ -7,6 +7,7 @@
 - `bat --squeeze-limit` to set the maximum number of empty consecutive when using `--squeeze-blank`, see #1441 (@eth-p) and #2665 (@einfachIrgendwer0815)
 - `PrettyPrinter::squeeze_empty_lines` to support line squeezing for bat as a library, see #1441 (@eth-p) and #2665 (@einfachIrgendwer0815)
 - 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)
 
 ## Bugfixes
 

README.md

@@ -759,9 +759,14 @@ bat() {
 
 If an input file contains color codes or other ANSI escape sequences or control characters, `bat` will have problems
 performing syntax highlighting and text wrapping, and thus the output can become garbled.
-When displaying such files it is recommended to disable both syntax highlighting and wrapping by
+
+If your version of `bat` supports the `--strip-ansi=auto` option, it can be used to remove such sequences
+before syntax highlighting. Alternatively, you may disable both syntax highlighting and wrapping by
 passing the `--color=never --wrap=never` options to `bat`.
 
+> [!NOTE]
+> The `auto` option of `--strip-ansi` avoids removing escape sequences when the syntax is plain text.
+
 ### Terminals & colors
 
 `bat` handles terminals *with* and *without* truecolor support. However, the colors in most syntax

doc/long-help.txt

@@ -122,6 +122,11 @@ Options:
       --squeeze-limit <squeeze-limit>
           Set the maximum number of consecutive empty lines to be printed.
 
+      --strip-ansi <when>
+          Specify when to strip ANSI escape sequences from the input. The automatic mode will remove
+          escape sequences unless the syntax highlighting language is plain text. Possible values:
+          auto, always, *never*.
+
       --style <components>
           Configure which elements (line numbers, file headers, grid borders, Git modifications, ..)
           to display in addition to the file contents. The argument is a comma-separated list of

src/bin/bat/app.rs

@@ -7,6 +7,7 @@ use crate::{
     clap_app,
     config::{get_args_from_config_file, get_args_from_env_opts_var, get_args_from_env_vars},
 };
+use bat::StripAnsiMode;
 use clap::ArgMatches;
 
 use console::Term;
@@ -242,6 +243,16 @@ impl App {
                         4
                     },
                 ),
+            strip_ansi: match self
+                .matches
+                .get_one::<String>("strip-ansi")
+                .map(|s| s.as_str())
+            {
+                Some("never") => StripAnsiMode::Never,
+                Some("always") => StripAnsiMode::Always,
+                Some("auto") => StripAnsiMode::Auto,
+                _ => unreachable!("other values for --strip-ansi are not allowed"),
+            },
             theme: self
                 .matches
                 .get_one::<String>("theme")

src/bin/bat/clap_app.rs

@@ -402,6 +402,20 @@ pub fn build_app(interactive_output: bool) -> Command {
                 .long_help("Set the maximum number of consecutive empty lines to be printed.")
                 .hide_short_help(true)
         )
+        .arg(
+            Arg::new("strip-ansi")
+                .long("strip-ansi")
+                .overrides_with("strip-ansi")
+                .value_name("when")
+                .value_parser(["auto", "always", "never"])
+                .default_value("never")
+                .hide_default_value(true)
+                .help("Strip colors from the input (auto, always, *never*)")
+                .long_help("Specify when to strip ANSI escape sequences from the input. \
+                The automatic mode will remove escape sequences unless the syntax highlighting \
+                language is plain text. Possible values: auto, always, *never*.")
+                .hide_short_help(true)
+        )
         .arg(
             Arg::new("style")
                 .long("style")

src/config.rs

@@ -5,6 +5,7 @@ use crate::paging::PagingMode;
 use crate::style::StyleComponents;
 use crate::syntax_mapping::SyntaxMapping;
 use crate::wrapping::WrappingMode;
+use crate::StripAnsiMode;
 
 #[derive(Debug, Clone)]
 pub enum VisibleLines {
@@ -100,6 +101,9 @@ pub struct Config<'a> {
 
     /// The maximum number of consecutive empty lines to display
     pub squeeze_lines: Option<usize>,
+
+    // Weather or not to set terminal title when using a pager
+    pub strip_ansi: StripAnsiMode,
 }
 
 #[cfg(all(feature = "minimal-application", feature = "paging"))]

src/lib.rs

@@ -53,6 +53,7 @@ mod vscreen;
 pub(crate) mod wrapping;
 
 pub use nonprintable_notation::NonprintableNotation;
+pub use preprocessor::StripAnsiMode;
 pub use pretty_printer::{Input, PrettyPrinter, Syntax};
 pub use syntax_mapping::{MappingTarget, SyntaxMapping};
 pub use wrapping::WrappingMode;

src/preprocessor.rs

@@ -136,6 +136,27 @@ pub fn replace_nonprintable(
     output
 }
 
+/// Strips ANSI escape sequences from the input.
+pub fn strip_ansi(line: &str) -> String {
+    let mut buffer = String::with_capacity(line.len());
+
+    for seq in EscapeSequenceOffsetsIterator::new(line) {
+        if let EscapeSequenceOffsets::Text { .. } = seq {
+            buffer.push_str(&line[seq.index_of_start()..seq.index_past_end()]);
+        }
+    }
+
+    buffer
+}
+
+#[derive(Debug, PartialEq, Clone, Copy, Default)]
+pub enum StripAnsiMode {
+    #[default]
+    Never,
+    Always,
+    Auto,
+}
+
 #[test]
 fn test_try_parse_utf8_char() {
     assert_eq!(try_parse_utf8_char(&[0x20]), Some((' ', 1)));
@@ -179,3 +200,14 @@ fn test_try_parse_utf8_char() {
     assert_eq!(try_parse_utf8_char(&[0xef, 0x20]), None);
     assert_eq!(try_parse_utf8_char(&[0xf0, 0xf0]), None);
 }
+
+#[test]
+fn test_strip_ansi() {
+    // The sequence detection is covered by the tests in the vscreen module.
+    assert_eq!(strip_ansi("no ansi"), "no ansi");
+    assert_eq!(strip_ansi("\x1B[33mone"), "one");
+    assert_eq!(
+        strip_ansi("\x1B]1\x07multiple\x1B[J sequences"),
+        "multiple sequences"
+    );
+}

src/pretty_printer.rs

@@ -11,7 +11,7 @@ use crate::{
     input,
     line_range::{HighlightedLineRanges, LineRange, LineRanges},
     style::StyleComponent,
-    SyntaxMapping, WrappingMode,
+    StripAnsiMode, SyntaxMapping, WrappingMode,
 };
 
 #[cfg(feature = "paging")]
@@ -182,6 +182,15 @@ impl<'a> PrettyPrinter<'a> {
         self
     }
 
+    /// Whether to remove ANSI escape sequences from the input (default: never)
+    ///
+    /// If `Auto` is used, escape sequences will only be removed when the input
+    /// is not plain text.
+    pub fn strip_ansi(&mut self, mode: StripAnsiMode) -> &mut Self {
+        self.config.strip_ansi = mode;
+        self
+    }
+
     /// Text wrapping mode (default: do not wrap)
     pub fn wrapping_mode(&mut self, mode: WrappingMode) -> &mut Self {
         self.config.wrapping_mode = mode;

src/printer.rs

@@ -29,11 +29,13 @@ use crate::diff::LineChanges;
 use crate::error::*;
 use crate::input::OpenedInput;
 use crate::line_range::RangeCheckResult;
+use crate::preprocessor::strip_ansi;
 use crate::preprocessor::{expand_tabs, replace_nonprintable};
 use crate::style::StyleComponent;
 use crate::terminal::{as_terminal_escaped, to_ansi_color};
 use crate::vscreen::{AnsiStyle, EscapeSequence, EscapeSequenceIterator};
 use crate::wrapping::WrappingMode;
+use crate::StripAnsiMode;
 
 const ANSI_UNDERLINE_ENABLE: EscapeSequence = EscapeSequence::CSI {
     raw_sequence: "\x1B[4m",
@@ -207,6 +209,7 @@ pub(crate) struct InteractivePrinter<'a> {
     highlighter_from_set: Option<HighlighterFromSet<'a>>,
     background_color_highlight: Option<Color>,
     consecutive_empty_lines: usize,
+    strip_ansi: bool,
 }
 
 impl<'a> InteractivePrinter<'a> {
@@ -265,20 +268,41 @@ impl<'a> InteractivePrinter<'a> {
             .content_type
             .map_or(false, |c| c.is_binary() && !config.show_nonprintable);
 
-        let highlighter_from_set = if is_printing_binary || !config.colored_output {
-            None
-        } else {
+        let needs_to_match_syntax = !is_printing_binary
+            && (config.colored_output || config.strip_ansi == StripAnsiMode::Auto);
+
+        let (is_plain_text, highlighter_from_set) = if needs_to_match_syntax {
             // Determine the type of syntax for highlighting
-            let syntax_in_set =
-                match assets.get_syntax(config.language, input, &config.syntax_mapping) {
-                    Ok(syntax_in_set) => syntax_in_set,
-                    Err(Error::UndetectedSyntax(_)) => assets
-                        .find_syntax_by_name("Plain Text")?
-                        .expect("A plain text syntax is available"),
-                    Err(e) => return Err(e),
-                };
+            const PLAIN_TEXT_SYNTAX: &str = "Plain Text";
+            match assets.get_syntax(config.language, input, &config.syntax_mapping) {
+                Ok(syntax_in_set) => (
+                    syntax_in_set.syntax.name == PLAIN_TEXT_SYNTAX,
+                    Some(HighlighterFromSet::new(syntax_in_set, theme)),
+                ),
+
+                Err(Error::UndetectedSyntax(_)) => (
+                    true,
+                    Some(
+                        assets
+                            .find_syntax_by_name(PLAIN_TEXT_SYNTAX)?
+                            .map(|s| HighlighterFromSet::new(s, theme))
+                            .expect("A plain text syntax is available"),
+                    ),
+                ),
+
+                Err(e) => return Err(e),
+            }
+        } else {
+            (false, None)
+        };
 
-            Some(HighlighterFromSet::new(syntax_in_set, theme))
+        // Determine when to strip ANSI sequences
+        let strip_ansi = match config.strip_ansi {
+            _ if config.show_nonprintable => false,
+            StripAnsiMode::Always => true,
+            StripAnsiMode::Auto if is_plain_text => false, // Plain text may already contain escape sequences.
+            StripAnsiMode::Auto => true,
+            _ => false,
         };
 
         Ok(InteractivePrinter {
@@ -293,6 +317,7 @@ impl<'a> InteractivePrinter<'a> {
             highlighter_from_set,
             background_color_highlight,
             consecutive_empty_lines: 0,
+            strip_ansi,
         })
     }
 
@@ -573,7 +598,7 @@ impl<'a> Printer for InteractivePrinter<'a> {
             )
             .into()
         } else {
-            match self.content_type {
+            let mut line = match self.content_type {
                 Some(ContentType::BINARY) | None => {
                     return Ok(());
                 }
@@ -590,7 +615,14 @@ impl<'a> Printer for InteractivePrinter<'a> {
                         line
                     }
                 }
+            };
+
+            // If ANSI escape sequences are supposed to be stripped, do it before syntax highlighting.
+            if self.strip_ansi {
+                line = strip_ansi(&line).into()
             }
+
+            line
         };
 
         let regions = self.highlight_regions_for_line(&line)?;