From 95cc2c97b5913309e283aa03131fbe7c72130215 Mon Sep 17 00:00:00 2001
From: Ivan Babak <babak.john@gmail.com>
Date: Sun, 1 Jul 2018 19:47:55 -0700
Subject: [PATCH] fix(perf): shortcut getStringWidth for ASCII-only strings
 (#4776) (#4790)

---
 src/common/util.js     | 8 ++++++++
 src/doc/doc-printer.js | 6 +++---
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/src/common/util.js b/src/common/util.js
index 4ec2f0e3..fece2904 100644
--- a/src/common/util.js
+++ b/src/common/util.js
@@ -6,6 +6,9 @@ const escapeStringRegexp = require("escape-string-regexp");
 const getCjkRegex = require("cjk-regex");
 const getUnicodeRegex = require("unicode-regex");
 
+// eslint-disable-next-line no-control-regex
+const notAsciiRegex = /[^\x20-\x7F]/;
+
 const cjkPattern = getCjkRegex().source;
 
 // http://spec.commonmark.org/0.25/#ascii-punctuation-character
@@ -713,6 +716,11 @@ function getStringWidth(text) {
     return 0;
   }
 
+  // shortcut to avoid needless string `RegExp`s, replacements, and allocations within `string-width`
+  if (!notAsciiRegex.test(text)) {
+    return text.length;
+  }
+
   // emojis are considered 2-char width for consistency
   // see https://github.com/sindresorhus/string-width/issues/11
   // for the reason why not implemented in `string-width`
diff --git a/src/doc/doc-printer.js b/src/doc/doc-printer.js
index cc3ecfe0..72e2be2f 100644
--- a/src/doc/doc-printer.js
+++ b/src/doc/doc-printer.js
@@ -1,6 +1,6 @@
 "use strict";
 
-const util = require("../common/util");
+const { getStringWidth } = require("../common/util");
 const { concat, fill, cursor } = require("./doc-builders");
 
 /** @type {{[groupId: PropertyKey]: MODE}} */
@@ -130,7 +130,7 @@ function fits(next, restCommands, width, options, mustBeFlat) {
     const doc = x[2];
 
     if (typeof doc === "string") {
-      width -= util.getStringWidth(doc);
+      width -= getStringWidth(doc);
     } else {
       switch (doc.type) {
         case "concat":
@@ -224,7 +224,7 @@ function printDocToString(doc, options) {
     if (typeof doc === "string") {
       out.push(doc);
 
-      pos += util.getStringWidth(doc);
+      pos += getStringWidth(doc);
     } else {
       switch (doc.type) {
         case "cursor":