readline: properly handle 0-width characters

PR-URL: #13918
Reviewed-By: James M Snell <[email protected]>

Author: TimothyGu

lib/readline.js

@@ -670,13 +670,14 @@ Interface.prototype._getDisplayPos = function(str) {
       row += 1;
       continue;
     }
-    if (isFullWidthCodePoint(code)) {
+    const width = getStringWidth(code);
+    if (width === 0 || width === 1) {
+      offset += width;
+    } else { // width === 2
       if ((offset + 1) % col === 0) {
         offset++;
       }
       offset += 2;
-    } else {
-      offset++;
     }
   }
   var cols = offset % col;

test/parallel/test-readline-position.js

@@ -0,0 +1,31 @@
+'use strict';
+require('../common');
+const { PassThrough } = require('stream');
+const readline = require('readline');
+const assert = require('assert');
+
+const ctrlU = { ctrl: true, name: 'u' };
+
+{
+  const input = new PassThrough();
+  const rl = readline.createInterface({
+    terminal: true,
+    input: input,
+    prompt: ''
+  });
+
+  for (const [cursor, string] of [
+    [1, 'a'],
+    [2, 'ab'],
+    [2, '丁'],
+    [0, '\u0301'],   // COMBINING ACUTE ACCENT
+    [1, 'a\u0301'],  // á
+    [0, '\u20DD'],   // COMBINING ENCLOSING CIRCLE
+    [2, 'a\u20DDb'], // a⃝b
+    [0, '\u200E']    // LEFT-TO-RIGHT MARK
+  ]) {
+    rl.write(string);
+    assert.strictEqual(rl._getCursorPos().cols, cursor);
+    rl.write(null, ctrlU);
+  }
+}