Cache the current working directory.

lib/path.dart

Index: lib/path.dart
diff --git a/lib/path.dart b/lib/path.dart
index af9efe54e849ded0200f1f45b469c32ac3c35bed..93fe67e4125020bfaaa446d4ec1217620c56e0e1 100644
--- a/lib/path.dart
+++ b/lib/path.dart
@@ -79,17 +79,36 @@ Style get style => context.style;
 /// In the browser, this means the current URL, without the last file segment.
 String get current {
   var uri = Uri.base;
+
+  // Converting the base URI to a file path is pretty slow, and the base URI
+  // rarely changes in practice, so we cache the result here.
+  if (uri == _currentUriBase) return _current;
+  _currentUriBase = uri;
+
   if (Style.platform == Style.url) {
-    return uri.resolve('.').toString();
+    _current = uri.resolve('.').toString();

[Lasse Reichstein Nielsen, 2015/12/01 06:52:58]

That is likely to be slower than necessary.
Instead maybe:
   var path = uri.path;
   if (path.length > 1) {
     uri = uri.replace(path: uri.path.substring(0, path.length - 1));
   }
  _current = uri.toString)(;
(That is likely to be faster, but not guaranteed, since you still reparse the
path, but you avoid the complexity of dot-normalizing a path).

[Lasse Reichstein Nielsen, 2015/12/01 06:53:54]

(That does assume that Uri.base has no query or fragment, so maybe it's not
general enough).

[nweiz, 2015/12/01 20:50:46]

Given that this is cached now, I think it's probably not worth putting a lot of
effort into optimizing the code to compute the cached value.

+    return _current;
   } else {
     var path = uri.toFilePath();
     // Remove trailing '/' or '\'.
-    int lastIndex = path.length - 1;
+    var lastIndex = path.length - 1;
     assert(path[lastIndex] == '/' || path[lastIndex] == '\\');
-    return path.substring(0, lastIndex);
+    _current = path.substring(0, lastIndex);
+    return _current;
   }
 }
 
+/// The last value returned by [Uri.base].
+///
+/// This is used to cache the current working directory.
+Uri _currentUriBase;
+
+/// The last known value of the current working directory.
+///
+/// This is cached because [current] is called frequently but rarely actually
+/// changes.
+String _current;
+
 /// Gets the path separator for the current platform. This is `\` on Windows
 /// and `/` on other platforms (including the browser).
 String get separator => context.separator;