fix: perf regression on hot string munging path

lib/normalize-unicode.js

@@ -0,0 +1,11 @@
+// warning: extremely hot code path.
+// This has been meticulously optimized for use
+// within npm install on large package trees.
+// Do not edit without careful benchmarking.
+const normalizeCache = Object.create(null)
+const {hasOwnProperty} = Object.prototype
+module.exports = s => {
+  if (!hasOwnProperty.call(normalizeCache, s))
+    normalizeCache[s] = s.normalize('NFKD')
+  return normalizeCache[s]
+}

lib/path-reservations.js

@@ -7,7 +7,7 @@
 // while still allowing maximal safe parallelization.
 
 const assert = require('assert')
-const normPath = require('./normalize-windows-path.js')
+const normalize = require('./normalize-unicode.js')
 const stripSlashes = require('./strip-trailing-slashes.js')
 const { join } = require('path')
 
@@ -28,7 +28,7 @@ module.exports = () => {
   const getDirs = path => {
     const dirs = path.split('/').slice(0, -1).reduce((set, path) => {
       if (set.length)
-        path = normPath(join(set[set.length - 1], path))
+        path = join(set[set.length - 1], path)
       set.push(path || '/')
       return set
     }, [])
@@ -116,9 +116,8 @@ module.exports = () => {
     // So, we just pretend that every path matches every other path here,
     // effectively removing all parallelization on windows.
     paths = isWindows ? ['win32 parallelization disabled'] : paths.map(p => {
-      return stripSlashes(normPath(join(p)))
-        .normalize('NFKD')
-        .toLowerCase()
+      // don't need normPath, because we skip this entirely for windows
+      return normalize(stripSlashes(join(p))).toLowerCase()
     })
 
     const dirs = new Set(

lib/strip-trailing-slashes.js

@@ -1,24 +1,13 @@
-// this is the only approach that was significantly faster than using
-// str.replace(/\/+$/, '') for strings ending with a lot of / chars and
-// containing multiple / chars.
-const batchStrings = [
-  '/'.repeat(1024),
-  '/'.repeat(512),
-  '/'.repeat(256),
-  '/'.repeat(128),
-  '/'.repeat(64),
-  '/'.repeat(32),
-  '/'.repeat(16),
-  '/'.repeat(8),
-  '/'.repeat(4),
-  '/'.repeat(2),
-  '/',
-]
-
+// warning: extremely hot code path.
+// This has been meticulously optimized for use
+// within npm install on large package trees.
+// Do not edit without careful benchmarking.
 module.exports = str => {
-  for (const s of batchStrings) {
-    while (str.length >= s.length && str.slice(-1 * s.length) === s)
-      str = str.slice(0, -1 * s.length)
+  let i = str.length - 1
+  let slashesStart = -1
+  while (i > -1 && str.charAt(i) === '/') {
+    slashesStart = i
+    i--
   }
-  return str
+  return slashesStart === -1 ? str : str.slice(0, slashesStart)
 }

lib/unpack.js

@@ -17,6 +17,7 @@ const pathReservations = require('./path-reservations.js')
 const stripAbsolutePath = require('./strip-absolute-path.js')
 const normPath = require('./normalize-windows-path.js')
 const stripSlash = require('./strip-trailing-slashes.js')
+const normalize = require('./normalize-unicode.js')
 
 const ONENTRY = Symbol('onEntry')
 const CHECKFS = Symbol('checkFs')
@@ -101,8 +102,7 @@ const uint32 = (a, b, c) =>
 // Note that on windows, we always drop the entire cache whenever a
 // symbolic link is encountered, because 8.3 filenames are impossible
 // to reason about, and collisions are hazards rather than just failures.
-const cacheKeyNormalize = path => stripSlash(normPath(path))
-  .normalize('NFKD')
+const cacheKeyNormalize = path => normalize(stripSlash(normPath(path)))
   .toLowerCase()
 
 const pruneCache = (cache, abs) => {

test/create.js

@@ -154,7 +154,13 @@ t.test('gzipped tarball that makes some drain/resume stuff', t => {
   const cwd = path.dirname(__dirname)
   const out = path.resolve(dir, 'package.tgz')
 
-  c({ z: true, C: cwd }, ['node_modules'])
+  // don't include node_modules/.cache, since that gets written to
+  // by nyc during tests, and can result in spurious errors.
+  const entries = fs.readdirSync(`${cwd}/node_modules`)
+    .filter(e => !/^\./.test(e))
+    .map(e => `node_modules/${e}`)
+
+  c({ z: true, C: cwd }, entries)
     .pipe(fs.createWriteStream(out))
     .on('finish', _ => {
       const child = spawn('tar', ['tf', out], {

test/normalize-unicode.js

@@ -0,0 +1,12 @@
+const t = require('tap')
+const normalize = require('../lib/normalize-unicode.js')
+
+// café
+const cafe1 = Buffer.from([0x63, 0x61, 0x66, 0xc3, 0xa9]).toString()
+
+// cafe with a `
+const cafe2 = Buffer.from([0x63, 0x61, 0x66, 0x65, 0xcc, 0x81]).toString()
+
+t.equal(normalize(cafe1), normalize(cafe2), 'matching unicodes')
+t.equal(normalize(cafe1), normalize(cafe2), 'cached')
+t.equal(normalize('foo'), 'foo', 'non-unicdoe string')

test/strip-trailing-slashes.js

@@ -3,5 +3,6 @@ const stripSlash = require('../lib/strip-trailing-slashes.js')
 const short = '///a///b///c///'
 const long = short.repeat(10) + '/'.repeat(1000000)
 
+t.equal(stripSlash('no slash'), 'no slash')
 t.equal(stripSlash(short), '///a///b///c')
 t.equal(stripSlash(long), short.repeat(9) + '///a///b///c')