From 348b54d76aad7f90206cd76f8adec3f48ccb3196 Mon Sep 17 00:00:00 2001
From: Seong Yong-ju <sei40kr@gmail.com>
Date: Thu, 29 Jan 2026 17:58:34 +0900
Subject: [PATCH] feat: add `start_line`, `end_line`, `start_column`,
 `end_column`, and `chop` methods for `Location`

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
---
 rust/ruby-prism-sys/build/main.rs       |  3 ++
 rust/ruby-prism/src/lib.rs              | 41 +++++++++++++++++++
 rust/ruby-prism/src/parse_result/mod.rs | 54 ++++++++++++++++++++++++-
 3 files changed, 97 insertions(+), 1 deletion(-)

diff --git a/rust/ruby-prism-sys/build/main.rs b/rust/ruby-prism-sys/build/main.rs
index 798d06d8ff..971b5e951e 100644
--- a/rust/ruby-prism-sys/build/main.rs
+++ b/rust/ruby-prism-sys/build/main.rs
@@ -116,6 +116,7 @@ fn generate_bindings(ruby_include_path: &Path) -> bindgen::Bindings {
         // Structs
         .allowlist_type("pm_comment_t")
         .allowlist_type("pm_diagnostic_t")
+        .allowlist_type("pm_line_column_t")
         .allowlist_type("pm_list_t")
         .allowlist_type("pm_magic_comment_t")
         .allowlist_type("pm_node_t")
@@ -140,6 +141,8 @@ fn generate_bindings(ruby_include_path: &Path) -> bindgen::Bindings {
         // Functions
         .allowlist_function("pm_list_empty_p")
         .allowlist_function("pm_list_free")
+        .allowlist_function("pm_newline_list_line")
+        .allowlist_function("pm_newline_list_line_column")
         .allowlist_function("pm_node_destroy")
         .allowlist_function("pm_pack_parse")
         .allowlist_function("pm_parse")
diff --git a/rust/ruby-prism/src/lib.rs b/rust/ruby-prism/src/lib.rs
index 6824768193..dae4cde333 100644
--- a/rust/ruby-prism/src/lib.rs
+++ b/rust/ruby-prism/src/lib.rs
@@ -160,6 +160,47 @@ mod tests {
         assert_eq!(slice, "222");
     }
 
+    #[test]
+    fn location_line_column_test() {
+        let source = "foo\nbar\nbaz";
+        let result = parse(source.as_ref());
+
+        let node = result.node();
+        let program = node.as_program_node().unwrap();
+        let statements = program.statements().body();
+        let mut iter = statements.iter();
+        let _foo = iter.next().unwrap();
+        let bar = iter.next().unwrap();
+        let baz = iter.next().unwrap();
+
+        let bar_loc = bar.location();
+        assert_eq!(bar_loc.start_line(), 2);
+        assert_eq!(bar_loc.end_line(), 2);
+        assert_eq!(bar_loc.start_column(), 0);
+        assert_eq!(bar_loc.end_column(), 3);
+
+        let baz_loc = baz.location();
+        assert_eq!(baz_loc.start_line(), 3);
+        assert_eq!(baz_loc.end_line(), 3);
+        assert_eq!(baz_loc.start_column(), 0);
+        assert_eq!(baz_loc.end_column(), 3);
+    }
+
+    #[test]
+    fn test_chop() {
+        let result = parse(b"foo");
+        let mut location = result.node().as_program_node().unwrap().location();
+
+        assert_eq!(location.chop().as_slice(), b"fo");
+        assert_eq!(location.chop().chop().chop().as_slice(), b"");
+
+        // Check that we don't go negative.
+        for _ in 0..10 {
+            location = location.chop();
+        }
+        assert_eq!(location.as_slice(), b"");
+    }
+
     #[test]
     fn visitor_test() {
         use super::{visit_interpolated_regular_expression_node, visit_regular_expression_node, InterpolatedRegularExpressionNode, RegularExpressionNode, Visit};
diff --git a/rust/ruby-prism/src/parse_result/mod.rs b/rust/ruby-prism/src/parse_result/mod.rs
index 33eb1ac9a0..447b47e460 100644
--- a/rust/ruby-prism/src/parse_result/mod.rs
+++ b/rust/ruby-prism/src/parse_result/mod.rs
@@ -8,7 +8,7 @@ mod diagnostics;
 
 use std::ptr::NonNull;
 
-use ruby_prism_sys::{pm_comment_t, pm_diagnostic_t, pm_location_t, pm_magic_comment_t, pm_node_destroy, pm_node_t, pm_parser_free, pm_parser_t};
+use ruby_prism_sys::{pm_comment_t, pm_diagnostic_t, pm_location_t, pm_magic_comment_t, pm_newline_list_line_column, pm_node_destroy, pm_node_t, pm_parser_free, pm_parser_t};
 
 pub use self::comments::{Comment, CommentType, Comments, MagicComment, MagicComments};
 pub use self::diagnostics::{Diagnostic, Diagnostics};
@@ -66,6 +66,58 @@ impl<'pr> Location<'pr> {
             })
         }
     }
+
+    /// Returns the line number where this location starts.
+    #[must_use]
+    pub fn start_line(&self) -> i32 {
+        self.line_column_at(self.start).line
+    }
+
+    /// Returns the line number where this location ends.
+    #[must_use]
+    pub fn end_line(&self) -> i32 {
+        self.line_column_at(self.end()).line
+    }
+
+    /// Returns the column number in bytes where this location starts from the
+    /// start of the line.
+    #[must_use]
+    pub fn start_column(&self) -> u32 {
+        self.line_column_at(self.start).column
+    }
+
+    /// Returns the column number in bytes where this location ends from the
+    /// start of the line.
+    #[must_use]
+    pub fn end_column(&self) -> u32 {
+        self.line_column_at(self.end()).column
+    }
+
+    /// Returns a new location that is the result of chopping off the last byte.
+    #[must_use]
+    pub const fn chop(&self) -> Self {
+        Location {
+            parser: self.parser,
+            start: self.start,
+            length: if self.length == 0 { 0 } else { self.length - 1 },
+            marker: std::marker::PhantomData,
+        }
+    }
+
+    fn line_column_at(&self, offset: u32) -> LineColumn {
+        unsafe {
+            let parser = self.parser.as_ptr();
+            let newline_list = &(*parser).newline_list;
+            let start_line = (*parser).start_line;
+            let result = pm_newline_list_line_column(newline_list, offset, start_line);
+            LineColumn { line: result.line, column: result.column }
+        }
+    }
+}
+
+struct LineColumn {
+    line: i32,
+    column: u32,
 }
 
 impl std::fmt::Debug for Location<'_> {