PackageMapUriResolver for Dart server.

pkg/analysis_server/lib/src/package_uri_resolver.dart

+// Copyright (c) 2014, 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.
+
+library resolver.package;
+
+import 'package:analysis_server/src/resource.dart';
+import 'package:analyzer/src/generated/source_io.dart';
+
+
+/**
+ * A [UriResolver] implementation for the `package:` scheme that uses a map of
+ * package names to their directories.
+ */
+class PackageMapUriResolver extends UriResolver {
+  /**
+   * The name of the `package` scheme.
+   */
+  static const String PACKAGE_SCHEME = "package";
+
+  /**
+   * A table mapping package names to the path of the directory containing
+   * the package.
+   */
+  final Map<String, Folder> packageMap;
+
+  /**
+   * The [ResourceProvider] for this resolver.
+   */
+  final ResourceProvider resourceProvider;
+
+  /**
+   * Create a new [PackageMapUriResolver].
+   *
+   * [packageMap] is a table mapping package names to the path of the directory
+   * containing the package
+   */
+  PackageMapUriResolver(this.resourceProvider, this.packageMap);
+
+  @override
+  Source fromEncoding(UriKind kind, Uri uri) {
+    if (kind == UriKind.PACKAGE_SELF_URI || kind == UriKind.PACKAGE_URI) {
+      Resource resource = resourceProvider.getResource(uri.path);
+      if (resource is File) {
+        return resource.createSource(kind);
+      }
+    }
+    return null;
+  }
+
+  @override
+  Source resolveAbsolute(Uri uri) {
+    if (!isPackageUri(uri)) {
+      return null;
+    }
+    // Prepare path.
+    String path = uri.path;
+    // Prepare path components.
+    String pkgName;
+    String relPath;
+    int index = path.indexOf('/');
+    if (index == -1 || index == 0) {
+      return null;
+    } else {
+      // <pkgName>/<relPath>
+      pkgName = path.substring(0, index);
+      relPath = path.substring(index + 1);
+    }
+    // Try to find an existing file.
+    Folder packageDir = packageMap[pkgName];
+    if (packageDir != null && packageDir.exists) {
+      Resource result = packageDir.getChild(relPath);
+      if (result is File && result.exists) {
+        return result.createSource(UriKind.PACKAGE_URI);
+      }
+    }
+    // Return a NonExistingSource instance.
+    // This helps provide more meaningful error messages to users
+    // (a missing file error, as opposed to an invalid URI error).
+    // TODO(scheglov) move NonExistingSource to "source.dart"
+    return new NonExistingSource(uri.toString(), UriKind.PACKAGE_URI);
+  }
+
+  /**
+   * Returns `true` if [uri] is a `package` URI.
+   */
+  static bool isPackageUri(Uri uri) {
+    return uri.scheme == PACKAGE_SCHEME;
+  }
+}