perf: defer windowWidth() to improve perf for non-help usage (#610)

* defer windowWidth() to improve perf for non-help usage * respond to @nexdrew's comments * add 2nd arg to maxWidth() per @nexdrew
yargs · Aug 29, 2016 · cbc3636 · cbc3636
1 parent fdb3364
commit cbc3636
Showing 1 changed file with 21 additions and 8 deletions.
diff --git a/lib/usage.js b/lib/usage.js
@@ -96,11 +96,23 @@ module.exports = function (yargs, y18n) {
     epilog = msg
   }
 
-  var wrap = windowWidth()
+  var wrapSet = false
+  var wrap
   self.wrap = function (cols) {
+    wrapSet = true
     wrap = cols
   }
 
+  function getWrap () {
+    // lazily call windowWidth() because it's very expensive,
+    // and only needs to be called if the user wants to show usage/help
+    if (!wrapSet) {
+      wrap = windowWidth()
+      wrapSet = true
+    }
+    return wrap
+  }
+
   var deferY18nLookupPrefix = '__yargsString__:'
   self.deferY18nLookup = function (str) {
     return deferY18nLookupPrefix + str
@@ -122,9 +134,10 @@ module.exports = function (yargs, y18n) {
         return acc
       }, {})
     )
+    var theWrap = getWrap()
     var ui = require('cliui')({
-      width: wrap,
-      wrap: !!wrap
+      width: theWrap,
+      wrap: !!theWrap
     })
 
     // the usage string.
@@ -140,7 +153,7 @@ module.exports = function (yargs, y18n) {
 
       commands.forEach(function (command) {
         ui.div(
-          {text: command[0], padding: [0, 2, 0, 2], width: maxWidth(commands) + 4},
+          {text: command[0], padding: [0, 2, 0, 2], width: maxWidth(commands, theWrap) + 4},
           {text: command[1]}
         )
       })
@@ -214,7 +227,7 @@ module.exports = function (yargs, y18n) {
         ].filter(Boolean).join(' ')
 
         ui.span(
-          {text: kswitch, padding: [0, 2, 0, 2], width: maxWidth(switches) + 4},
+          {text: kswitch, padding: [0, 2, 0, 2], width: maxWidth(switches, theWrap) + 4},
           desc
         )
 
@@ -235,7 +248,7 @@ module.exports = function (yargs, y18n) {
 
       examples.forEach(function (example) {
         ui.div(
-          {text: example[0], padding: [0, 2, 0, 2], width: maxWidth(examples) + 4},
+          {text: example[0], padding: [0, 2, 0, 2], width: maxWidth(examples, theWrap) + 4},
           example[1]
         )
       })
@@ -254,7 +267,7 @@ module.exports = function (yargs, y18n) {
 
   // return the maximum width of a string
   // in the left-hand column of a table.
-  function maxWidth (table) {
+  function maxWidth (table, theWrap) {
     var width = 0
 
     // table might be of the form [leftColumn],
@@ -271,7 +284,7 @@ module.exports = function (yargs, y18n) {
 
     // if we've enabled 'wrap' we should limit
     // the max-width of the left-column.
-    if (wrap) width = Math.min(width, parseInt(wrap * 0.5, 10))
+    if (theWrap) width = Math.min(width, parseInt(theWrap * 0.5, 10))
 
     return width
   }