From 07487834044a1e24247d4c1631447419fdd463d2 Mon Sep 17 00:00:00 2001
From: Bojan Durdevic <bojan88@gmail.com>
Date: Sat, 21 Aug 2021 13:55:52 -0400
Subject: [PATCH] Support for line range plus syntax

---
 CHANGELOG.md            |  1 +
 assets/manual/bat.1.in  |  4 ++++
 src/bin/bat/clap_app.rs |  6 ++++--
 src/line_range.rs       | 28 +++++++++++++++++++++++++++-
 4 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9d956725..ec4d9e08 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,7 @@
 ## Features
 
 - `$BAT_CONFIG_DIR` is now a recognized environment variable. It has precedence over `$XDG_CONFIG_HOME`, see #1727 (@billrisher)
+- Support for `x:+x` syntax in line ranges (e.g. `20:+10`). See  #1810 (@bojan88)
 
 ## Bugfixes
 
diff --git a/assets/manual/bat.1.in b/assets/manual/bat.1.in
index c16b9d42..b91f7dc8 100644
--- a/assets/manual/bat.1.in
+++ b/assets/manual/bat.1.in
@@ -50,6 +50,8 @@ highlights lines 30 to 40
 highlights lines 1 to 40
 .IP "\-\-highlight\-line 40:"
 highlights lines 40 to the end of the file
+.IP "\-\-highlight\-line 30:+10"
+highlights lines 30 to 40
 .RE
 .HP
 \fB\-\-file\-name\fR <name>...
@@ -154,6 +156,8 @@ prints lines 30 to 40
 prints lines 1 to 40
 .IP "\-\-line\-range 40:"
 prints lines 40 to the end of the file
+.IP "\-\-line\-range 30:+10"
+prints lines 30 to 40
 .RE
 .HP
 \fB\-L\fR, \fB\-\-list\-languages\fR
diff --git a/src/bin/bat/clap_app.rs b/src/bin/bat/clap_app.rs
index 2ac0eba5..5e25b01a 100644
--- a/src/bin/bat/clap_app.rs
+++ b/src/bin/bat/clap_app.rs
@@ -95,7 +95,8 @@ pub fn build_app(interactive_output: bool) -> ClapApp<'static, 'static> {
                      '--highlight-line 40' highlights line 40\n  \
                      '--highlight-line 30:40' highlights lines 30 to 40\n  \
                      '--highlight-line :40' highlights lines 1 to 40\n  \
-                     '--highlight-line 40:' highlights lines 40 to the end of the file",
+                     '--highlight-line 40:' highlights lines 40 to the end of the file\n  \
+                     '--highlight-line 30:+10' highlights lines 30 to 40",
                 ),
         )
         .arg(
@@ -423,7 +424,8 @@ pub fn build_app(interactive_output: bool) -> ClapApp<'static, 'static> {
                      '--line-range 30:40' prints lines 30 to 40\n  \
                      '--line-range :40' prints lines 1 to 40\n  \
                      '--line-range 40:' prints lines 40 to the end of the file\n  \
-                     '--line-range 40' only prints line 40",
+                     '--line-range 40' only prints line 40\n  \
+                     '--line-range 30:+10' prints lines 30 to 40",
                 ),
         )
         .arg(
diff --git a/src/line_range.rs b/src/line_range.rs
index 66046500..d014d688 100644
--- a/src/line_range.rs
+++ b/src/line_range.rs
@@ -47,7 +47,16 @@ impl LineRange {
             }
             2 => {
                 new_range.lower = line_numbers[0].parse()?;
-                new_range.upper = line_numbers[1].parse()?;
+
+                new_range.upper = if line_numbers[1].bytes().next().unwrap() == b'+' {
+                    let more_lines = &line_numbers[1][1..]
+                        .parse()
+                        .map_err(|_| "Invalid line number after +")?;
+                    new_range.lower + more_lines
+                } else {
+                    line_numbers[1].parse()?
+                };
+
                 Ok(new_range)
             }
             _ => Err(
@@ -100,6 +109,23 @@ fn test_parse_fail() {
     assert!(range.is_err());
 }
 
+#[test]
+fn test_parse_plus() {
+    let range = LineRange::from("40:+10").expect("Shouldn't fail on test!");
+    assert_eq!(40, range.lower);
+    assert_eq!(50, range.upper);
+}
+
+#[test]
+fn test_parse_plus_fail() {
+    let range = LineRange::from("40:+z");
+    assert!(range.is_err());
+    let range = LineRange::from("40:+-10");
+    assert!(range.is_err());
+    let range = LineRange::from("40:+");
+    assert!(range.is_err());
+}
+
 #[derive(Copy, Clone, Debug, PartialEq)]
 pub enum RangeCheckResult {
     // Within one of the given ranges