do not try to patch missing fs functions

Deeper fix related to #222 and #230

Author: isaacs

polyfills.js

@@ -71,13 +71,13 @@ function patch (fs) {
   fs.lstatSync = statFixSync(fs.lstatSync)
 
   // if lchmod/lchown do not exist, then make them no-ops
-  if (!fs.lchmod) {
+  if (fs.chmod && !fs.lchmod) {
     fs.lchmod = function (path, mode, cb) {
       if (cb) process.nextTick(cb)
     }
     fs.lchmodSync = function () {}
   }
-  if (!fs.lchown) {
+  if (fs.chown && !fs.lchown) {
     fs.lchown = function (path, uid, gid, cb) {
       if (cb) process.nextTick(cb)
     }
@@ -94,32 +94,38 @@ function patch (fs) {
   // CPU to a busy looping process, which can cause the program causing the lock
   // contention to be starved of CPU by node, so the contention doesn't resolve.
   if (platform === "win32") {
-    fs.rename = (function (fs$rename) { return function (from, to, cb) {
-      var start = Date.now()
-      var backoff = 0;
-      fs$rename(from, to, function CB (er) {
-        if (er
-            && (er.code === "EACCES" || er.code === "EPERM")
-            && Date.now() - start < 60000) {
-          setTimeout(function() {
-            fs.stat(to, function (stater, st) {
-              if (stater && stater.code === "ENOENT")
-                fs$rename(from, to, CB);
-              else
-                cb(er)
-            })
-          }, backoff)
-          if (backoff < 100)
-            backoff += 10;
-          return;
-        }
-        if (cb) cb(er)
-      })
-    }})(fs.rename)
+    fs.rename = typeof fs.rename !== 'function' ? fs.rename
+    : (function (fs$rename) {
+      function rename (from, to, cb) {
+        var start = Date.now()
+        var backoff = 0;
+        fs$rename(from, to, function CB (er) {
+          if (er
+              && (er.code === "EACCES" || er.code === "EPERM")
+              && Date.now() - start < 60000) {
+            setTimeout(function() {
+              fs.stat(to, function (stater, st) {
+                if (stater && stater.code === "ENOENT")
+                  fs$rename(from, to, CB);
+                else
+                  cb(er)
+              })
+            }, backoff)
+            if (backoff < 100)
+              backoff += 10;
+            return;
+          }
+          if (cb) cb(er)
+        })
+      }
+      if (Object.setPrototypeOf) Object.setPrototypeOf(rename, fs$rename)
+      return rename
+    })(fs.rename)
   }
 
   // if read() returns EAGAIN, then just try it again.
-  fs.read = (function (fs$read) {
+  fs.read = typeof fs.read !== 'function' ? fs.read
+  : (function (fs$read) {
     function read (fd, buffer, offset, length, position, callback_) {
       var callback
       if (callback_ && typeof callback_ === 'function') {
@@ -136,11 +142,12 @@ function patch (fs) {
     }
 
     // This ensures `util.promisify` works as it does for native `fs.read`.
-    if (Object.setPrototypeOf && fs$read != undefined) Object.setPrototypeOf(read, fs$read)
+    if (Object.setPrototypeOf) Object.setPrototypeOf(read, fs$read)
     return read
   })(fs.read)
 
-  fs.readSync = (function (fs$readSync) { return function (fd, buffer, offset, length, position) {
+  fs.readSync = typeof fs.readSync !== 'function' ? fs.readSync
+  : (function (fs$readSync) { return function (fd, buffer, offset, length, position) {
     var eagCounter = 0
     while (true) {
       try {
@@ -199,7 +206,7 @@ function patch (fs) {
   }
 
   function patchLutimes (fs) {
-    if (constants.hasOwnProperty("O_SYMLINK")) {
+    if (constants.hasOwnProperty("O_SYMLINK") && fs.futimes) {
       fs.lutimes = function (path, at, mt, cb) {
         fs.open(path, constants.O_SYMLINK, function (er, fd) {
           if (er) {
@@ -233,7 +240,7 @@ function patch (fs) {
         return ret
       }
 
-    } else {
+    } else if (fs.futimes) {
       fs.lutimes = function (_a, _b, _c, cb) { if (cb) process.nextTick(cb) }
       fs.lutimesSync = function () {}
     }