Speed up directory listing in pub.

sdk/lib/_internal/pub/lib/src/io.dart

Index: sdk/lib/_internal/pub/lib/src/io.dart
diff --git a/sdk/lib/_internal/pub/lib/src/io.dart b/sdk/lib/_internal/pub/lib/src/io.dart
index 1186cdeb86f012299ca5fc7ba3663b0df7c9bb52..7a0bdb4adc4ceb06eb2fc3996c11b5e2ef00ba66 100644
--- a/sdk/lib/_internal/pub/lib/src/io.dart
+++ b/sdk/lib/_internal/pub/lib/src/io.dart
@@ -245,41 +245,16 @@ String createSystemTempDir() {
 /// The returned paths are guaranteed to begin with [dir].
 List<String> listDir(String dir, {bool recursive: false,
     bool includeHidden: false}) {
-  List<String> doList(String dir, Set<String> listedDirectories) {
-    var contents = <String>[];
+  var entities = new Directory(dir).listSync(recursive: recursive);

[nweiz, 2014/03/25 18:55:08]

Add a comment that there is a known bug with this, and reference issue 4794.
Explain why we're using it despite the bug.

[Bob Nystrom, 2014/03/25 20:04:20]

This is specified behavior now. The docs say: "If a symbolic link makes a loop
in the file system, then a recursive listing will not follow a link twice in the
same recursive descent, but will report it as a Link the second time it is
seen."

It's not the behavior I would want, but it is well-defined.

[nweiz, 2014/03/25 20:14:12]

That doesn't make it not a bug; if you want, call it a bug in the function
specification. From the perspective of a user of pub, recursive symlinks produce
unexpected output; they don't care what the documentation of some function their
tool uses says.

I'm not saying trading correctness for speed isn't worth it, I'm just saying we
should document the tradeoff we've made and why we made it.

[Bob Nystrom, 2014/03/26 00:51:38]

Absent some platonic ideal of the correct behavior, I think "does exactly what
it's documented to do" can't be fairly described as a bug. I wouldn't argue that
the behavior is *good*, but it's certainly *intentional*.
Done.

 
-    // Avoid recursive symlinks.
-    var resolvedPath = canonicalize(dir);
-    if (listedDirectories.contains(resolvedPath)) return [];
+  isHidden(part) => part.startsWith(".") && part != "." && part != "..";
 
-    listedDirectories = new Set<String>.from(listedDirectories);
-    listedDirectories.add(resolvedPath);
-
-    log.io("Listing directory $dir.");
-
-    var children = <String>[];
-    for (var entity in new Directory(dir).listSync()) {
-      if (!includeHidden && path.basename(entity.path).startsWith('.')) {
-        continue;
-      }
-
-      contents.add(entity.path);
-      if (entity is Directory) {
-        // TODO(nweiz): don't manually recurse once issue 4794 is fixed.
-        // Note that once we remove the manual recursion, we'll need to
-        // explicitly filter out files in hidden directories.
-        if (recursive) {
-          children.addAll(doList(entity.path, listedDirectories));
-        }
-      }
-    }
-
-    log.fine("Listed directory $dir:\n${contents.join('\n')}");
-    contents.addAll(children);
-    return contents;
+  if (!includeHidden) {
+    entities = entities.where(
+        (entity) => !path.split(entity.path).any(isHidden));
   }
 
-  return doList(dir, new Set<String>());
+  return entities.map((entity) => entity.path).toList();
 }
 
 /// Returns whether [dir] exists on the file system. This will return `true` for