path: add path.isAbsolute(path)

An absolute path will always open the same location regardless of your
current working directory. For posix, this just means path.charAt(0) ===
'/', but on Windows it's a little more complicated.

Fixes joyent/node#5299.

1 files changed, 16 insertions, 4 deletions

diff --git a/lib/path.js b/lib/path.js
index db0cdea2dd..5cef72fac7 100644
--- a/lib/path.js
+++ b/lib/path.js
@@ -121,7 +121,7 @@ if (isWindows) {
       var result = splitDeviceRe.exec(path),
           device = result[1] || '',
           isUnc = device && device.charAt(1) !== ':',
-          isAbsolute = !!result[2] || isUnc, // UNC paths are always absolute
+          isAbsolute = exports.isAbsolute(path),
           tail = result[3];
 
       if (device &&
@@ -172,7 +172,7 @@ if (isWindows) {
     var result = splitDeviceRe.exec(path),
         device = result[1] || '',
         isUnc = device && device.charAt(1) !== ':',
-        isAbsolute = !!result[2] || isUnc, // UNC paths are always absolute
+        isAbsolute = exports.isAbsolute(path),
         tail = result[3],
         trailingSlash = /[\\\/]$/.test(tail);
 
@@ -203,6 +203,15 @@ if (isWindows) {
   };
 
   // windows version
+  exports.isAbsolute = function(path) {
+    var result = splitDeviceRe.exec(path),
+        device = result[1] || '',
+        isUnc = device && device.charAt(1) !== ':';
+    // UNC paths are always absolute
+    return !!result[2] || isUnc;
+  };
+
+  // windows version
   exports.join = function() {
     function f(p) {
       if (typeof p !== 'string') {
@@ -338,7 +347,7 @@ if (isWindows) {
   // path.normalize(path)
   // posix version
   exports.normalize = function(path) {
-    var isAbsolute = path.charAt(0) === '/',
+    var isAbsolute = exports.isAbsolute(path),
         trailingSlash = path.substr(-1) === '/';
 
     // Normalize the path
@@ -356,6 +365,10 @@ if (isWindows) {
     return (isAbsolute ? '/' : '') + path;
   };
 
+  // posix version
+  exports.isAbsolute = function(path) {
+    return path.charAt(0) === '/';
+  };
 
   // posix version
   exports.join = function() {
@@ -416,7 +429,6 @@ if (isWindows) {
   exports.delimiter = ':';
 }
 
-
 exports.dirname = function(path) {
   var result = splitPath(path),
       root = result[0],