Merge pull request #3496 from sharkdp/decorations_auto

Restore expected behavior when piping output with styles configured and auto decorations

CHANGELOG.md

@@ -9,6 +9,7 @@
 - Fix hang when using `--list-themes` with an explicit pager, see #3457 (@abhinavcool42)
 - Fix negative values of N not being parsed in <N:M> line ranges without `=` flag value separator, see #3442 (@lmmx)
 - Fix broken Docker syntax preventing use of custom assets, see #3476 (@keith-hall)
+- Fix decorations being applied unexpectedly when piping. Now only line numbers explicitly required on the command line should be applied in auto decorations mode for `cat` compatibility. See #3496 (@keith-hall)
 
 ## Other
 - Improve README documentation on pager options passed to less, see #3443 (@injust)

README.md

@@ -540,6 +540,12 @@ variable to make these changes permanent or use `bat`'s
 > Or, if you want to override the styles completely, you use `--style=numbers` to
 > only show the line numbers.
 
+### Decorations
+
+By default, `bat` only shows decorations (such as line numbers, file headers, grid borders, etc.) when outputting to an interactive terminal. You can control this behavior with the `--decorations` option. Use `--decorations=always` to show decorations even when piping output to another command, or `--decorations=never` to disable them entirely. Possible values are `auto` (default), `never`, and `always`.
+
+There is also the `--force-colorization` option, which is an alias for `--decorations=always --color=always`. This is useful if you want to keep colorization and decorations when piping `bat`'s output to another program.
+
 ### Adding new syntaxes / language definitions
 
 Should you find that a particular syntax is not available within `bat`, you can follow these

src/bin/bat/app.rs

@@ -46,6 +46,10 @@ enum HelpType {
 pub struct App {
     pub matches: ArgMatches,
     interactive_output: bool,
+    /// True if -n / --number was passed on the command line
+    /// (not from config file or environment variables).
+    /// This is used to honor the flag when piping output, similar to `cat -n`.
+    number_from_cli: bool,
 }
 
 impl App {
@@ -54,6 +58,38 @@ impl App {
         let _ = nu_ansi_term::enable_ansi_support();
 
         let interactive_output = std::io::stdout().is_terminal();
+
+        // Check if the -n / --number option was passed on the command line
+        // (before merging with config file and environment variables).
+        // This is needed to honor the -n flag when piping output, similar to `cat -n`.
+        // We need to handle both standalone (-n, --number) and combined short flags (-pn, -An, etc.)
+        // Note: We only check if -n appears and is not overridden by -p in the same combined flag.
+        // For combined flags like -np, -p comes after -n and overrides it, so we don't count it.
+        // For combined flags like -pn, -n comes after -p and takes effect.
+        let number_from_cli = wild::args_os().any(|arg| {
+            let arg_str = arg.to_string_lossy();
+            if arg_str == "-n" || arg_str == "--number" {
+                return true;
+            }
+            // Handle combined short flags
+            // Only count -n if it's the LAST flag in the combined form (so -p doesn't override it)
+            // or if -p is not present in the combined form
+            if arg_str.starts_with('-') && !arg_str.starts_with("--") && arg_str.len() > 2 {
+                let chars: Vec<char> = arg_str.chars().skip(1).collect();
+                let n_pos = chars.iter().position(|&c| c == 'n');
+                let p_pos = chars.iter().position(|&c| c == 'p');
+                // -n is in the combined flag and either:
+                // - -p is not present, OR
+                // - -n comes after -p (so -n takes effect)
+                if let Some(n) = n_pos {
+                    if p_pos.is_none() || n > p_pos.unwrap() {
+                        return true;
+                    }
+                }
+            }
+            false
+        });
+
         let matches = Self::matches(interactive_output)?;
 
         if matches.get_flag("help") {
@@ -91,6 +127,7 @@ impl App {
         Ok(App {
             matches,
             interactive_output,
+            number_from_cli,
         })
     }
 
@@ -384,8 +421,7 @@ impl App {
                     .map(|s| s.as_str())
                     == Some("always")
                 || self.matches.get_flag("force-colorization")
-                || self.matches.get_flag("number")
-                || self.matches.contains_id("style") && !style_components.plain()),
+                || self.number_from_cli),
             tab_width: self
                 .matches
                 .get_one::<String>("tabs")

tests/integration_tests.rs

@@ -166,6 +166,53 @@ fn line_numbers() {
         .stdout("   1 line 1\n   2 line 2\n   3 line 3\n   4 line 4\n   5 line 5\n   6 line 6\n   7 line 7\n   8 line 8\n   9 line 9\n  10 line 10\n");
 }
 
+// Test that -n on command line shows line numbers even when piping (similar to `cat -n`)
+#[test]
+fn line_numbers_from_cli_in_loop_through_mode() {
+    bat()
+        .arg("multiline.txt")
+        .arg("-n")
+        .assert()
+        .success()
+        .stdout("   1 line 1\n   2 line 2\n   3 line 3\n   4 line 4\n   5 line 5\n   6 line 6\n   7 line 7\n   8 line 8\n   9 line 9\n  10 line 10\n");
+}
+
+#[test]
+fn style_from_env_var_ignored_and_line_numbers_from_cli_in_loop_through_mode() {
+    bat()
+        .env("BAT_STYLE", "full")
+        .arg("multiline.txt")
+        .arg("-n")
+        .arg("--decorations=auto")
+        .assert()
+        .success()
+        .stdout("   1 line 1\n   2 line 2\n   3 line 3\n   4 line 4\n   5 line 5\n   6 line 6\n   7 line 7\n   8 line 8\n   9 line 9\n  10 line 10\n");
+}
+
+#[test]
+fn numbers_ignored_from_cli_when_followed_by_plain_in_loop_through_mode() {
+    bat()
+        .arg("multiline.txt")
+        .arg("-np")
+        .arg("--decorations=auto")
+        .assert()
+        .success()
+        .stdout(
+            "line 1\nline 2\nline 3\nline 4\nline 5\nline 6\nline 7\nline 8\nline 9\nline 10\n",
+        );
+}
+
+#[test]
+fn numbers_honored_from_cli_when_preceeded_by_plain_in_loop_through_mode() {
+    bat()
+        .arg("multiline.txt")
+        .arg("-pn")
+        .arg("--decorations=auto")
+        .assert()
+        .success()
+        .stdout("   1 line 1\n   2 line 2\n   3 line 3\n   4 line 4\n   5 line 5\n   6 line 6\n   7 line 7\n   8 line 8\n   9 line 9\n  10 line 10\n");
+}
+
 #[test]
 fn line_range_2_3() {
     bat()
@@ -415,26 +462,18 @@ fn piped_output_with_line_numbers_style_flag() {
         .write_stdin("hello\nworld\n")
         .assert()
         .success()
-        .stdout("   1 hello\n   2 world\n");
+        .stdout("hello\nworld\n");
 }
 
 #[test]
-#[cfg(not(target_os = "windows"))]
 fn piped_output_with_line_numbers_with_header_grid_style_flag() {
+    // style ignored because non-interactive
     bat()
         .arg("--style=header,grid,numbers")
         .write_stdin("hello\nworld\n")
         .assert()
         .success()
-        .stdout(
-            "─────┬──────────────────────────────────────────────────────────────────────────
-     │ STDIN
-─────┼──────────────────────────────────────────────────────────────────────────
-   1 │ hello
-   2 │ world
-─────┴──────────────────────────────────────────────────────────────────────────
-",
-        );
+        .stdout("hello\nworld\n");
 }
 
 #[test]
@@ -452,6 +491,7 @@ fn piped_output_with_auto_style() {
 fn piped_output_with_default_style_flag() {
     bat()
         .arg("--style=default")
+        .arg("--decorations=always")
         .write_stdin("hello\nworld\n")
         .assert()
         .success()