Fix string.insert with negative indices

sass · Jan 12, 2022 · 0d4f420 · 0d4f420
1 parent 720c358
commit 0d4f420
Show file tree

Hide file tree

Showing 2 changed files with 4 additions and 2 deletions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,5 +1,7 @@
 ## 1.47.1
 
+* Fix a bug in `string.insert` with certain negative indices.
+
 ### JS API
 
 * **Potentially breaking bug fix:** Match the specification of the new JS API by
@@ -19,7 +21,7 @@
 
 * **Potentially breaking bug fix:** Match the specification of the new JS API by
   passing `undefined` rather than `null` to `Logger.warn()` for an unset `span`.
-  
+
 #### TypeScript Declarations
 
 * Add a declaration for the `LegacyPluginThis.options.context` field.

diff --git a/lib/src/functions/string.dart b/lib/src/functions/string.dart
@@ -66,7 +66,7 @@ final _insert = _function("insert", r"$string, $insert, $index", (arguments) {
   if (indexInt < 0) {
     // +1 because negative indexes start counting from -1 rather than 0, and
     // another +1 because we want to insert *after* that index.
-    indexInt = string.sassLength + indexInt + 2;
+    indexInt = math.max(string.sassLength + indexInt + 2, 0);
   }
 
   var codepointIndex = _codepointForIndex(indexInt, string.sassLength);