Add the noChmod option

This allows a way to suppress the call to process.umask() while
still being as compliant as possible with the modes as defined
in the tarball entries.

Re: npm/cli#1103

PR-URL: #270
Credit: @isaacs
Close: #270
Reviewed-by: @ruyadorno

README.md

@@ -302,7 +302,6 @@ The following options are supported:
 - `mtime` Set to a `Date` object to force a specific `mtime` for
   everything added to the archive.  Overridden by `noMtime`.
 
-
 The following options are mostly internal, but can be modified in some
 advanced use cases, such as re-using caches between runs.
 
@@ -396,6 +395,13 @@ The following options are supported:
   the `filter` option described above.)
 - `onentry` A function that gets called with `(entry)` for each entry
   that passes the filter.
+- `onwarn` A function that will get called with `(code, message, data)` for
+  any warnings encountered.  (See "Warnings and Errors")
+- `noChmod` Set to true to omit calling `fs.chmod()` to ensure that the
+  extracted file matches the entry mode.  This also suppresses the call to
+  `process.umask()` to determine the default umask value, since tar will
+  extract with whatever mode is provided, and let the process `umask` apply
+  normally.
 
 The following options are mostly internal, but can be modified in some
 advanced use cases, such as re-using caches between runs.
@@ -451,6 +457,8 @@ The following options are supported:
   the call to `onentry`.  Set `noResume: true` to suppress this
   behavior.  Note that by opting into this, the stream will never
   complete until the entry data is consumed.
+- `onwarn` A function that will get called with `(code, message, data)` for
+  any warnings encountered.  (See "Warnings and Errors")
 
 ### tar.u(options, fileList, callback) [alias: tar.update]
 
@@ -708,6 +716,11 @@ Most unpack errors will cause a `warn` event to be emitted.  If the
   that passes the filter.
 - `onwarn` A function that will get called with `(code, message, data)` for
   any warnings encountered.  (See "Warnings and Errors")
+- `noChmod` Set to true to omit calling `fs.chmod()` to ensure that the
+  extracted file matches the entry mode.  This also suppresses the call to
+  `process.umask()` to determine the default umask value, since tar will
+  extract with whatever mode is provided, and let the process `umask` apply
+  normally.
 
 ### class tar.Unpack.Sync
 

lib/unpack.js

@@ -169,11 +169,14 @@ class Unpack extends Parser {
 
     this.cwd = path.resolve(opt.cwd || process.cwd())
     this.strip = +opt.strip || 0
-    this.processUmask = process.umask()
+    // if we're not chmodding, then we don't need the process umask
+    this.processUmask = opt.noChmod ? 0 : process.umask()
     this.umask = typeof opt.umask === 'number' ? opt.umask : this.processUmask
+
     // default mode for dirs created as parents
     this.dmode = opt.dmode || (0o0777 & (~this.umask))
     this.fmode = opt.fmode || (0o0666 & (~this.umask))
+
     this.on('entry', entry => this[ONENTRY](entry))
   }
 
@@ -299,6 +302,7 @@ class Unpack extends Parser {
       cache: this.dirCache,
       cwd: this.cwd,
       mode: mode,
+      noChmod: this.noChmod,
     }, cb)
   }
 
@@ -475,7 +479,7 @@ class Unpack extends Parser {
 
         else if (st.isDirectory()) {
           if (entry.type === 'Directory') {
-            if (!entry.mode || (st.mode & 0o7777) === entry.mode)
+            if (!this.noChmod && (!entry.mode || (st.mode & 0o7777) === entry.mode))
               this[MAKEFS](null, entry, done)
             else {
               fs.chmod(entry.absolute, entry.mode,
@@ -538,7 +542,7 @@ class UnpackSync extends Unpack {
         try {
           if (st.isDirectory()) {
             if (entry.type === 'Directory') {
-              if (entry.mode && (st.mode & 0o7777) !== entry.mode)
+              if (!this.noChmod && entry.mode && (st.mode & 0o7777) !== entry.mode)
                 fs.chmodSync(entry.absolute, entry.mode)
             } else
               fs.rmdirSync(entry.absolute)

test/unpack.js

@@ -1916,6 +1916,48 @@ t.test('use explicit chmod when required by umask', t => {
   })
 })
 
+t.test('dont use explicit chmod if noChmod flag set', t => {
+  process.umask(0o022)
+  const { umask } = process
+  t.teardown(() => process.umask = umask)
+  process.umask = () => {
+    throw new Error('should not call process.umask()')
+  }
+
+  const basedir = path.resolve(unpackdir, 'umask-no-chmod')
+
+  const data = makeTar([
+    {
+      path: 'x/y/z',
+      mode: 0o775,
+      type: 'Directory',
+    },
+    '',
+    '',
+  ])
+
+  const check = t => {
+    const st = fs.statSync(basedir + '/x/y/z')
+    t.equal(st.mode & 0o777, 0o755)
+    rimraf.sync(basedir)
+    t.end()
+  }
+
+  t.test('async', t => {
+    mkdirp.sync(basedir)
+    const unpack = new Unpack({ cwd: basedir, noChmod: true })
+    unpack.on('close', _ => check(t))
+    unpack.end(data)
+  })
+
+  return t.test('sync', t => {
+    mkdirp.sync(basedir)
+    const unpack = new Unpack.Sync({ cwd: basedir, noChmod: true})
+    unpack.end(data)
+    check(t)
+  })
+})
+
 t.test('chown implicit dirs and also the entries', t => {
   const basedir = path.resolve(unpackdir, 'chownr')