Avoid permissions errors in _realCasePath. (#1181)

This catches permissions errors and treats them as indicating that the
path component we have so far is canonical. This also improves the
efficiency of case matching by caching results for higher directories.

CHANGELOG.md

@@ -1,3 +1,8 @@
+## 1.32.1
+
+* Don't emit permissions errors on Windows and OS X when trying to determine the
+  real case of path names.
+
 ## 1.32.0
 
 * Deprecate passing non-`%` numbers as lightness and saturation to `hsl()`,

lib/src/io.dart

@@ -8,11 +8,15 @@ import 'io/interface.dart'
     if (dart.library.io) 'io/vm.dart'
     if (dart.library.js) 'io/node.dart';
 import 'utils.dart';
+import 'util/character.dart';
 
 export 'io/interface.dart'
     if (dart.library.io) 'io/vm.dart'
     if (dart.library.js) 'io/node.dart';
 
+/// A cache of return values for directories in [_realCasePath].
+final _realCaseCache = <String, String>{};
+
 /// Returns whether the current operating system might be case-insensitive.
 ///
 /// We can't know for sure because different Mac OS systems are configured
@@ -35,18 +39,43 @@ String _realCasePath(String path) {
 
   if (!_couldBeCaseInsensitive) return path;
 
-  var realCasePath = p.rootPrefix(path);
-  for (var component in p.split(path.substring(realCasePath.length))) {
-    var matches = listDir(realCasePath)
-        .where((realPath) => equalsIgnoreCase(p.basename(realPath), component))
-        .toList();
-
-    realCasePath = matches.length != 1
-        // If the file doesn't exist, or if there are multiple options (meaning
-        // the filesystem isn't actually case-insensitive), use `component` as-is.
-        ? p.join(realCasePath, component)
-        : matches[0];
+  if (isWindows) {
+    // Drive names are *always* case-insensitive, so convert them to uppercase.
+    var prefix = p.rootPrefix(path);
+    if (prefix.isNotEmpty && isAlphabetic(prefix.codeUnitAt(0))) {
+      path = prefix.toUpperCase() + path.substring(prefix.length);
+    }
+  }
+
+  String helper(String path) {
+    var dirname = p.dirname(path);
+    if (dirname == path) return path;
+
+    return _realCaseCache.putIfAbsent(path, () {
+      var realDirname = helper(dirname);
+      var basename = p.basename(path);
+
+      try {
+        var matches = listDir(realDirname)
+            .where(
+                (realPath) => equalsIgnoreCase(p.basename(realPath), basename))
+            .toList();
+
+        return matches.length != 1
+            // If the file doesn't exist, or if there are multiple options (meaning
+            // the filesystem isn't actually case-insensitive), use `basename`
+            // as-is.
+            ? p.join(realDirname, basename)
+            : matches[0];
+      } on FileSystemException catch (_) {
+        // If there's an error listing a directory, it's likely because we're
+        // trying to reach too far out of the current directory into something
+        // we don't have permissions for. In that case, just assume we have the
+        // real path.
+        return path;
+      }
+    });
   }
 
-  return realCasePath;
+  return helper(path);
 }

pubspec.yaml

@@ -1,5 +1,5 @@
 name: sass
-version: 1.32.0
+version: 1.32.1
 description: A Sass implementation in Dart.
 author: Sass Team
 homepage: https://github.com/sass/dart-sass