Clean up code that locates SDK and SDK version.

pkg/path/lib/path.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /// A comprehensive, cross-platform path manipulation library.
 library path;
 
 import 'dart:io' as io;
 
 /// An internal builder for the current OS so we can provide a straight
@@ skipping 145 matching lines @@
 ///
 ///     path.relative(r'D:\other', from: r'C:\home'); // -> 'D:\other'
 String relative(String path, {String from}) =>
     _builder.relative(path, from: from);
 
 /// Removes a trailing extension from the last part of [path].
 ///
 ///     withoutExtension('path/to/foo.dart'); // -> 'path/to/foo'
 String withoutExtension(String path) => _builder.withoutExtension(path);
 
+/// Validates that there are no non-null arguments following a null one and
+/// throws an appropriate [ArgumentError] on failure.
+_validateArgList(String method, List<String> args) {
+  for (var i = 1; i < args.length; i++) {
+    if (args[i] != null && args[i - 1] == null) {

[nweiz, 2013/01/19 00:35:47]

Short-circuit?

[Bob Nystrom, 2013/01/22 23:53:19]

Done.

+      // Ignore nulls hanging off the end.
+      var numArgs;
+      for (numArgs = args.length; numArgs >= 1; numArgs--) {
+        if (args[numArgs - 1] != null) break;
+      }
+
+      // Show the arguments.
+      var message = new StringBuffer();
+      message.add("$method(");
+      message.add(args.take(numArgs)
+          .mappedBy((arg) => arg == null ? "null" : '"$arg"')

[nweiz, 2013/01/19 00:35:47]

I really wish we had a better way of dumping strings than '"$arg"'. That's so
hard to read if it contains a newline or a quote or anything.

[Bob Nystrom, 2013/01/22 23:53:19]

Agreed. But until then, this should cover most cases.

+          .join(", "));
+      message.add("): part ${i - 1} was null, but part $i was not.");
+      throw new ArgumentError(message.toString());
+    }
+  }
+}
+
 /// An instantiable class for manipulating paths. Unlike the top-level
 /// functions, this lets you explicitly select what platform the paths will use.
 class Builder {
   /// Creates a new path builder for the given style and root directory.
   ///
   /// If [style] is omitted, it uses the host operating system's path style. If
   /// [root] is omitted, it defaults to the current working directory. If [root]
   /// is relative, it is considered relative to the current working directory.
   factory Builder({Style style, String root}) {
     if (style == null) {
@@ skipping 119 matching lines @@
   /// If a part is an absolute path, then anything before that will be ignored:
   ///
   ///     builder.join('path', '/to', 'foo'); // -> '/to/foo'
   ///
   String join(String part1, [String part2, String part3, String part4,
               String part5, String part6, String part7, String part8]) {
     var buffer = new StringBuffer();
     var needsSeparator = false;
 
     var parts = [part1, part2, part3, part4, part5, part6, part7, part8];
-    for (var i = 1; i < parts.length; i++) {
-      if (parts[i] != null && parts[i - 1] == null) {
-        throw new ArgumentError("join(): part ${i - 1} was null, but part $i "
-            "was not.");
-      }
-    }
+    _validateArgList("join", parts);
 
     for (var part in parts) {
       if (part == null) continue;
 
       if (this.isAbsolute(part)) {
         // An absolute path discards everything before it.
         buffer.clear();
         buffer.add(part);
       } else {
         if (part.length > 0 && part[0].contains(style.separatorPattern)) {
@@ skipping 52 matching lines @@
     return parsed.toString();
   }
 
   /// Creates a new path by appending the given path parts to the [root].
   /// Equivalent to [join()] with [root] as the first argument. Example:
   ///
   ///     var builder = new Builder(root: 'root');
   ///     builder.resolve('path', 'to', 'foo'); // -> 'root/path/to/foo'
   String resolve(String part1, [String part2, String part3, String part4,
               String part5, String part6, String part7]) {
-    if (!?part2) return join(root, part1);
-    if (!?part3) return join(root, part1, part2);
-    if (!?part4) return join(root, part1, part2, part3);
-    if (!?part5) return join(root, part1, part2, part3, part4);
-    if (!?part6) return join(root, part1, part2, part3, part4, part5);
-    if (!?part7) return join(root, part1, part2, part3, part4, part5, part6);
     return join(root, part1, part2, part3, part4, part5, part6, part7);
   }
 
   /// Attempts to convert [path] to an equivalent relative path relative to
   /// [root].
   ///
   ///     var builder = new Builder(root: '/root/path');
   ///     builder.relative('/root/path/a/b.dart'); // -> 'a/b.dart'
   ///     builder.relative('/root/other.dart'); // -> '../other.dart'
   ///
@@ skipping 281 matching lines @@
     // If there is no dot, or it's the first character, like '.bashrc', it
     // doesn't count.
     if (lastDot <= 0) return [file, ''];
 
     return [file.substring(0, lastDot), file.substring(lastDot)];
   }
 
   _ParsedPath clone() => new _ParsedPath(
       style, root, new List.from(parts), new List.from(separators));
 }