add support for resolving all constants

Author: jakemac53

lib/src/analyzer/resolver.dart

@@ -26,10 +26,15 @@ class Resolver {
   ///
   /// [release] must be called when done handling this [Resolver] to allow it
   /// to be used by later phases.
+  ///
+  /// If you pass a value of [false] for [resolveAllConstants], then constants
+  /// will only be resolved in [entryPoints], and not any other libraries. This
+  /// gives a significant speed boost, at the cost of not being able to assume
+  /// all constants are already resolved.
   Future<Resolver> resolve(BuildStep buildStep,
-      [List<AssetId> entryPoints]) async {
+      {List<AssetId> entryPoints, bool resolveAllConstants}) async {
     return new Resolver(await resolver.resolve(toBarbackTransform(buildStep),
-        entryPoints?.map(toBarbackAssetId)?.toList()));
+        entryPoints?.map(toBarbackAssetId)?.toList(), resolveAllConstants));
   }
 
   /// Release this resolver so it can be updated by following build steps.

lib/src/builder/build_step.dart

@@ -31,5 +31,10 @@ abstract class BuildStep {
 
   /// Gives a [Resolver] for [id]. This must be released when it is done being
   /// used.
-  Future<Resolver> resolve(AssetId id);
+  ///
+  /// If you pass a value of [false] for [resolveAllConstants], then constants
+  /// will only be resolved in [id], and not any other libraries. This gives a
+  /// significant speed boost, at the cost of not being able to assume all
+  /// constants are already resolved.
+  Future<Resolver> resolve(AssetId id, {bool resolveAllConstants});
 }

lib/src/builder/build_step_impl.dart

@@ -99,8 +99,10 @@ class BuildStepImpl implements BuildStep {
   }
 
   /// Resolves [id] and returns a [Future<Resolver>] once that is done.
-  Future<Resolver> resolve(AssetId id) async => new Resolver(
-      await _resolvers.get(toBarbackTransform(this), [toBarbackAssetId(id)]));
+  @override
+  Future<Resolver> resolve(AssetId id, {bool resolveAllConstants}) async =>
+      new Resolver(await _resolvers.get(toBarbackTransform(this),
+          [toBarbackAssetId(id)], resolveAllConstants));
 
   /// Should be called after `build` has completed. This will wait until for
   /// [_outputsCompleted].