Add code to ProcessedOptions to fetch the SDK summary bundle.

pkg/front_end/lib/src/base/processed_options.dart

Index: pkg/front_end/lib/src/base/processed_options.dart
diff --git a/pkg/front_end/lib/src/base/processed_options.dart b/pkg/front_end/lib/src/base/processed_options.dart
index 360b5fa6a48807aa65938d2b484e679b18469555..be1783a318d203eee72745e4a449848c82f53538 100644
--- a/pkg/front_end/lib/src/base/processed_options.dart
+++ b/pkg/front_end/lib/src/base/processed_options.dart
@@ -4,6 +4,7 @@
 
 import 'dart:async';
 
+import 'package:analyzer/src/summary/idl.dart';
 import 'package:front_end/compiler_options.dart';
 import 'package:front_end/file_system.dart';
 import 'package:front_end/src/base/uri_resolver.dart';
@@ -29,6 +30,13 @@ class ProcessedOptions {
   /// been computed yet.
   UriResolver _uriResolver;
 
+  /// The summary bundle for the SDK, or `null` if it has not been read yet.
+  PackageBundle _sdkSummary;
+
+  /// The location of the SDK, or `null` if the location hasn't been determined
+  /// yet.
+  Uri _sdkLocation;

[danrubel, 2017/01/09 22:01:23]

Is this the same as the sdkRoot in
https://codereview.chromium.org/2614063007/diff/60001/pkg/front_end/lib/compi...
? If so, should we rename one or the other so they match?

[Paul Berry, 2017/01/11 14:12:45]

Done.

+
   /// Initializes a [ProcessedOptions] object wrapping the given [rawOptions].
   ProcessedOptions(CompilerOptions rawOptions) : this._raw = rawOptions;
 
@@ -47,6 +55,30 @@ class ProcessedOptions {
     return _raw.fileSystem;
   }
 
+  /// Get the summary bundle for the SDK.
+  ///
+  /// This is an asynchronous getter since file system operations are required.
+  Future<PackageBundle> getSdkSummary() async {
+    if (_sdkSummary == null) {
+      Uri summaryLocation;
+      if (_raw.sdkSummary != null) {
+        // Options sdkSummary and sdkRoot are mutually exclusive.
+        assert(_raw.sdkRoot == null);
+        // No need to look for the SDK; we were told where the SDK summary is.
+        summaryLocation = _raw.sdkSummary;
+      } else {
+        // Need to look for the SDK summary inside the SDK.
+        var sdkLocation = await _getSdkLocation();
+        summaryLocation = sdkLocation.resolve(
+            'lib/_internal/' + (_raw.strongMode ? 'strong.sum' : 'spec.sum'));
+      }
+      var summaryBytes =
+          await fileSystem.entityForUri(summaryLocation).readAsBytes();
+      _sdkSummary = new PackageBundle.fromBuffer(summaryBytes);
+    }
+    return _sdkSummary;
+  }
+
   /// Get the [UriResolver] which resolves "package:" and "dart:" URIs.
   ///
   /// This is an asynchronous getter since file system operations may be
@@ -79,4 +111,26 @@ class ProcessedOptions {
     }
     return _packages;
   }
+
+  /// Get the location of the SDK.
+  ///
+  /// This is an asynchronous getter since file system operations may be
+  /// required to locate the SDK.
+  Future<Uri> _getSdkLocation() async {
+    if (_sdkLocation == null) {
+      // If an SDK summary location was provided, the SDK itself should not be
+      // needed.
+      assert(_raw.sdkSummary == null);
+      if (_raw.sdkRoot == null) {
+        // TODO(paulberry): implement the algorithm for finding the SDK
+        // automagically.
+        throw new UnimplementedError();
+      }
+      _sdkLocation = _raw.sdkRoot;
+      if (!_sdkLocation.path.endsWith('/')) {
+        _sdkLocation = _sdkLocation.replace(path: _sdkLocation.path + '/');
+      }
+    }
+    return _sdkLocation;
+  }
 }