Always consider newlines when diffing lines

StringIgnoringNewline caused crashes in code that assumed that two
equal values would hav the same string length.

This reverts 86612798ad. A better
approach would be to normalise line endings before diffing, but
additionally print whether files have/lack trailing newlines.

Fixes #755

CHANGELOG.md

@@ -4,6 +4,11 @@
 `~/.gitconfig` to match the manual, regardless of your difftastic
 version.**
 
+### Diffing
+
+Fixed a crash (introduced in 0.60) when the final line in a file does
+not have a trailing newline and occurs more than once in the file.
+
 ## 0.60 (released 1st August 2024)
 
 ### Diffing

sample_files/compare.expected

@@ -5,7 +5,7 @@ sample_files/ada_1.adb sample_files/ada_2.adb
 eb3b0e12e239ae33789136380e81406b  -
 
 sample_files/added_line_1.txt sample_files/added_line_2.txt
-8a1587e6b5fc53f2ec2ac665a5d00372  -
+f935214c79833318d39364145d36d8e2  -
 
 sample_files/align_footer_1.txt sample_files/align_footer_2.txt
 d640bd2de31e56a39f0efb92aff0f379  -
@@ -23,7 +23,7 @@ sample_files/bad_combine_1.rs sample_files/bad_combine_2.rs
 f5051bf7d2b8afa3a677388cbd458891  -
 
 sample_files/big_text_hunk_1.txt sample_files/big_text_hunk_2.txt
-fc26d41a5ff771670e04033b177973d2  -
+dcc22684c2a200afdd583d621b47dfa3  -
 
 sample_files/change_outer_1.el sample_files/change_outer_2.el
 2b9334a4cc72da63bba28eff958f0038  -
@@ -214,6 +214,9 @@ sample_files/r_1.R sample_files/r_2.R
 sample_files/racket_1.rkt sample_files/racket_2.rkt
 605aec93fa7b89d08e5d8ed56ad3c1be  -
 
+sample_files/repeated_line_no_eol_1.txt sample_files/repeated_line_no_eol_2.txt
+ac714893a2d28dc0204855d308972ccd  -
+
 sample_files/ruby_1.rb sample_files/ruby_2.rb
 d4d591902030355656f5c18c78f965a6  -
 

sample_files/repeated_line_no_eol_1.txt

@@ -0,0 +1 @@
+abc

sample_files/repeated_line_no_eol_2.txt

@@ -0,0 +1,2 @@
+abc
+abc

src/line_parser.rs

@@ -3,7 +3,6 @@
 use lazy_static::lazy_static;
 use line_numbers::{LinePositions, SingleLineSpan};
 use regex::Regex;
-use std::hash::Hash;
 
 use crate::words::split_words;
 use crate::{
@@ -74,66 +73,24 @@ fn merge_novel<'a>(
     res
 }
 
-#[derive(Debug, Clone)]
-struct StringIgnoringNewline<'a>(&'a str);
-
-impl PartialEq for StringIgnoringNewline<'_> {
-    fn eq(&self, other: &Self) -> bool {
-        let mut s = self.0;
-        if s.ends_with('\n') {
-            s = &s[..s.len() - 1];
-        }
-
-        let mut other_s = other.0;
-        if other_s.ends_with('\n') {
-            other_s = &other_s[..other_s.len() - 1];
-        }
-
-        s == other_s
-    }
-}
-
-impl Eq for StringIgnoringNewline<'_> {}
-
-impl Hash for StringIgnoringNewline<'_> {
-    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
-        let mut s = self.0;
-        if s.ends_with('\n') {
-            s = &s[..s.len() - 1];
-        }
-
-        s.hash(state);
-    }
-}
-
 fn changed_parts<'a>(
     src: &'a str,
     opposite_src: &'a str,
 ) -> Vec<(TextChangeKind, Vec<&'a str>, Vec<&'a str>)> {
-    let src_lines = split_lines_keep_newline(src)
-        .into_iter()
-        .map(StringIgnoringNewline)
-        .collect::<Vec<_>>();
-    let opposite_src_lines = split_lines_keep_newline(opposite_src)
-        .into_iter()
-        .map(StringIgnoringNewline)
-        .collect::<Vec<_>>();
+    let src_lines = split_lines_keep_newline(src);
+    let opposite_src_lines = split_lines_keep_newline(opposite_src);
 
     let mut res: Vec<(TextChangeKind, Vec<&'a str>, Vec<&'a str>)> = vec![];
     for diff_res in myers_diff::slice_unique_by_hash(&src_lines, &opposite_src_lines) {
         match diff_res {
             myers_diff::DiffResult::Left(line) => {
-                res.push((TextChangeKind::Novel, vec![line.0], vec![]));
+                res.push((TextChangeKind::Novel, vec![line], vec![]));
             }
             myers_diff::DiffResult::Both(line, opposite_line) => {
-                res.push((
-                    TextChangeKind::Unchanged,
-                    vec![line.0],
-                    vec![opposite_line.0],
-                ));
+                res.push((TextChangeKind::Unchanged, vec![line], vec![opposite_line]));
             }
             myers_diff::DiffResult::Right(opposite_line) => {
-                res.push((TextChangeKind::Novel, vec![], vec![opposite_line.0]));
+                res.push((TextChangeKind::Novel, vec![], vec![opposite_line]));
             }
         }
     }