Always display all lines in a hunk

Previously we were assuming that the first/last line pairs in a hunk
contained the earliest/latest lines on both sides. This isn't true
when there are no common items between the lines.

This fixes some display issues in load_before/after.js, but include a
new integration test that is smaller and easier to eyeball.

Fixes #133

CHANGELOG.md

@@ -10,6 +10,10 @@ incorrect diffs.
 Fixed an issue where lines were not aligned correctly after correcting
 sliders.
 
+### Display
+
+Fixed an issue where some lines in a hunk were not displayed.
+
 ## 0.22 (release 10th March 2022)
 
 Difftastic now requires Rust 1.56 to build.

sample_files/compare.expected

@@ -10,6 +10,9 @@ sample_files/clojure_before.clj sample_files/clojure_after.clj
 sample_files/comments_before.rs sample_files/comments_after.rs
 898ffdafebc08cdf4e9fe43cb3619e6c  -
 
+sample_files/context_before.rs sample_files/context_after.rs
+5f8518317cbaa2920c9d8c86d060c84f  -
+
 sample_files/contiguous_before.js sample_files/contiguous_after.js
 b5e718eb8328f8df8aff0eddf4e46d1a  -
 
@@ -53,7 +56,7 @@ sample_files/jsx_before.jsx sample_files/jsx_after.jsx
 5584ecaed7f41540d646afe39df31156  -
 
 sample_files/load_before.js sample_files/load_after.js
-c7a5800de30556a6a2cf795744fc28b9  -
+bf8527f91baff9a5f56380784b2a438e  -
 
 sample_files/modules_before.ml sample_files/modules_after.ml
 d182f73a8729211cc41e297aeab8f7a9  -

sample_files/context_after.rs

@@ -0,0 +1,14 @@
+fn print_diff_result() {
+    match () {
+        x => {
+            let opposite_to_lhs = opposite_positions(&summary.lhs_positions);
+
+            let hunks = merge_adjacent(
+                hunks,
+                opposite_to_lhs,
+            );
+
+            let lang_name;
+        }
+    }
+}

sample_files/context_before.rs

@@ -0,0 +1,15 @@
+fn print_diff_result() {
+    if summary {
+        if print_unchanged {
+        }
+    }
+
+    let opposite_to_lhs = opposite_positions(&summary.lhs_positions);
+
+    let hunks = merge_adjacent(
+        hunks,
+        opposite_to_lhs,
+    );
+
+    let lang_name;
+}

src/hunks.rs

@@ -651,13 +651,25 @@ pub fn matched_lines_for_hunk(
     matched_lines: &[(Option<LineNumber>, Option<LineNumber>)],
     hunk: &Hunk,
 ) -> Vec<(Option<LineNumber>, Option<LineNumber>)> {
-    // TODO: Use binary search instead.
-    let hunk_first = hunk.lines.first().expect("Hunks are non-empty");
-    let hunk_last = hunk.lines.last().expect("Hunks are non-empty");
+    let mut hunk_lhs_novel = hunk.novel_lhs.iter().copied().collect::<Vec<_>>();
+    hunk_lhs_novel.sort();
+
+    let mut hunk_rhs_novel = hunk.novel_rhs.iter().copied().collect::<Vec<_>>();
+    hunk_rhs_novel.sort();
 
+    let hunk_smallest = (
+        hunk_lhs_novel.first().copied(),
+        hunk_rhs_novel.first().copied(),
+    );
+    let hunk_largest = (
+        hunk_lhs_novel.last().copied(),
+        hunk_rhs_novel.last().copied(),
+    );
+
+    // TODO: Use binary search instead.
     let mut start_i = None;
     for (i, matched_line) in matched_lines.iter().enumerate() {
-        if either_side_equal(matched_line, hunk_first) {
+        if either_side_equal(matched_line, &hunk_smallest) {
             start_i = Some(i);
             break;
         }
@@ -665,7 +677,7 @@ pub fn matched_lines_for_hunk(
 
     let mut end_i = None;
     for (i, matched_line) in matched_lines.iter().enumerate().rev() {
-        if either_side_equal(matched_line, hunk_last) {
+        if either_side_equal(matched_line, &hunk_largest) {
             end_i = Some(i + 1);
             break;
         }