sanity check for longer characters

dmonad · Mar 17, 2023 · 0398712 · 0398712
1 parent 629c542
commit 0398712
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Showing 2 changed files with 3 additions and 2 deletions.
diff --git a/diff.js b/diff.js
@@ -48,12 +48,12 @@ export const simpleDiffString = (a, b) => {
     left++
   }
   // If the last same character is a high surrogate, we need to rollback to the previous character
-  if (highSurrogateRegex.test(a[left - 1])) left--
+  if (left > 0 && highSurrogateRegex.test(a[left - 1])) left--
   while (right + left < a.length && right + left < b.length && a[a.length - right - 1] === b[b.length - right - 1]) {
     right++
   }
   // If the last same character is a low surrogate, we need to rollback to the previous character
-  if (lowSurrogateRegex.test(a[a.length - right])) right--
+  if (right > 0 && lowSurrogateRegex.test(a[a.length - right])) right--
   return {
     index: left,
     remove: a.length - left - right,

diff --git a/diff.test.js b/diff.test.js
@@ -38,6 +38,7 @@ export const testDiffing = tc => {
   runDiffTest('\u{d83d}\u{dea7}\u{d83d}\u{dc77}'/* '🚧👷' */, '\u{d83d}\u{dc77}'/* '👷' */, { index: 0, remove: 2, insert: '' })
   // These strings share low-surrogate characters
   runDiffTest('\u{d83d}\u{dfe6}\u{d83d}\u{dfe6}'/* '🟦🟦' */, '\u{d83c}\u{dfe6}\u{d83d}\u{dfe6}'/* '🏦🟦' */, { index: 0, remove: 2, insert: '🏦' })
+  runDiffTest('🇦🇨', '🇦🇩', { index: 2, remove: 2, insert: '🇩' })
 }
 
 /**