Add support for "surrogate pairs" in unmatched characters

Author: webpro

src/index.ts

@@ -45,8 +45,6 @@ const getStringTruncatedWidth = ( input: string, truncationOptions: TruncationOp
   let truncationEnabled = false;
   let truncationIndex = length;
   let truncationLimit = Math.max ( 0, LIMIT - ELLIPSIS_WIDTH );
-  let unmatchedStart = 0;
-  let unmatchedEnd = 0;
   let width = 0;
   let widthExtra = 0;
 
@@ -57,9 +55,9 @@ const getStringTruncatedWidth = ( input: string, truncationOptions: TruncationOp
 
     /* UNMATCHED */
 
-    if ( ( unmatchedEnd > unmatchedStart ) || ( index >= length && index > indexPrev ) ) {
+    if ( index > indexPrev ) {
 
-      const unmatched = input.slice ( unmatchedStart, unmatchedEnd ) || input.slice ( indexPrev, index );
+      const unmatched = input.slice ( indexPrev, index );
 
       lengthExtra = 0;
 
@@ -78,7 +76,7 @@ const getStringTruncatedWidth = ( input: string, truncationOptions: TruncationOp
         }
 
         if ( ( width + widthExtra ) > truncationLimit ) {
-          truncationIndex = Math.min ( truncationIndex, Math.max ( unmatchedStart, indexPrev ) + lengthExtra );
+          truncationIndex = Math.min ( truncationIndex, indexPrev + lengthExtra );
         }
 
         if ( ( width + widthExtra ) > LIMIT ) {
@@ -91,8 +89,7 @@ const getStringTruncatedWidth = ( input: string, truncationOptions: TruncationOp
 
       }
 
-      unmatchedStart = unmatchedEnd = 0;
-
+      indexPrev = index;
     }
 
     /* EXITING */
@@ -118,8 +115,6 @@ const getStringTruncatedWidth = ( input: string, truncationOptions: TruncationOp
       }
 
       width += widthExtra;
-      unmatchedStart = indexPrev;
-      unmatchedEnd = index;
       index = indexPrev = LATIN_RE.lastIndex;
 
       continue;
@@ -142,8 +137,6 @@ const getStringTruncatedWidth = ( input: string, truncationOptions: TruncationOp
       }
 
       width += ANSI_WIDTH;
-      unmatchedStart = indexPrev;
-      unmatchedEnd = index;
       index = indexPrev = ANSI_RE.lastIndex;
 
       continue;
@@ -169,8 +162,6 @@ const getStringTruncatedWidth = ( input: string, truncationOptions: TruncationOp
       }
 
       width += widthExtra;
-      unmatchedStart = indexPrev;
-      unmatchedEnd = index;
       index = indexPrev = CONTROL_RE.lastIndex;
 
       continue;
@@ -196,8 +187,6 @@ const getStringTruncatedWidth = ( input: string, truncationOptions: TruncationOp
       }
 
       width += widthExtra;
-      unmatchedStart = indexPrev;
-      unmatchedEnd = index;
       index = indexPrev = TAB_RE.lastIndex;
 
       continue;
@@ -220,8 +209,6 @@ const getStringTruncatedWidth = ( input: string, truncationOptions: TruncationOp
       }
 
       width += EMOJI_WIDTH;
-      unmatchedStart = indexPrev;
-      unmatchedEnd = index;
       index = indexPrev = EMOJI_RE.lastIndex;
 
       continue;
@@ -230,8 +217,7 @@ const getStringTruncatedWidth = ( input: string, truncationOptions: TruncationOp
 
     /* UNMATCHED INDEX */
 
-    index += 1;
-
+    index += ( input.codePointAt(index) || 0 ) > 0xffff ? 2 : 1;
   }
 
   /* RETURN */

test/index.js

@@ -278,6 +278,17 @@ describe ( 'Fast String Width', () => {
 
     });
 
+    it( 'supports "surrogate pairs" in unmatched characters', (t) => {
+
+      t.is(getTruncated("██ █", { limit: 4 }), "██ █");
+      t.is(getTruncated("██ █", { limit: 3 }), "██ ");
+      t.is(getTruncated("██ █", { limit: 2 }), "██");
+
+      t.is(getTruncated("██ █", { limit: 4, ellipsis: "…" }), "██ █");
+      t.is(getTruncated("██ █", { limit: 3, ellipsis: "…" }), "██…");
+      t.is(getTruncated("██ █", { limit: 2, ellipsis: "…" }), "█…");
+
+    });
   });
 
 });