Try out using msgpack for asset graph

Towards #41

See if this makes a meaningful difference for performance.

build_runner/bin/graph_inspector.dart

@@ -30,7 +30,7 @@ Future<void> main(List<String> args) async {
 
   final argParser = ArgParser()
     ..addOption('graph-file',
-        abbr: 'g', help: 'Specify the asset_graph.json file to inspect.')
+        abbr: 'g', help: 'Specify the asset_graph.msgpack file to inspect.')
     ..addOption('build-script',
         abbr: 'b',
         help: 'Specify the build script to find the asset graph for.',

build_runner/test/generate/watch_test.dart

@@ -231,7 +231,7 @@ a:file://fake/pkg/path
             decodedMatches('b'));
       });
 
-      test('rebuilds properly update asset_graph.json', () async {
+      test('rebuilds properly update asset_graph.msgpack', () async {
         var buildState = await startWatch([copyABuildApplication],
             {'a|web/a.txt': 'a', 'a|web/b.txt': 'b'}, writer);
         var results = StreamQueue(buildState.buildResults);

build_runner_core/lib/src/asset_graph/graph.dart

@@ -6,13 +6,15 @@ import 'dart:async';
 import 'dart:collection';
 import 'dart:convert';
 import 'dart:io';
+import 'dart:typed_data';
 
 import 'package:build/build.dart';
 import 'package:build/experiments.dart' as experiments_zone;
 import 'package:convert/convert.dart';
 import 'package:crypto/crypto.dart';
 import 'package:glob/glob.dart';
 import 'package:meta/meta.dart';
+import 'package:msgpack_dart/msgpack_dart.dart' as msgpack;
 import 'package:package_config/package_config.dart';
 import 'package:watcher/watcher.dart';
 
@@ -48,7 +50,8 @@ class AssetGraph {
 
   /// Deserializes this graph.
   factory AssetGraph.deserialize(List<int> serializedGraph) =>
-      _AssetGraphDeserializer(serializedGraph).deserialize();
+      _AssetGraphDeserializer(Uint8List.fromList(serializedGraph))
+          .deserialize();
 
   static Future<AssetGraph> build(
       List<BuildPhase> buildPhases,

build_runner_core/lib/src/asset_graph/serialization.dart

@@ -8,7 +8,7 @@ part of 'graph.dart';
 ///
 /// This should be incremented any time the serialize/deserialize formats
 /// change.
-const _version = 24;
+const _version = 1;
 
 /// Deserializes an [AssetGraph] from a [Map].
 class _AssetGraphDeserializer {
@@ -18,10 +18,10 @@ class _AssetGraphDeserializer {
 
   _AssetGraphDeserializer._(this._serializedGraph);
 
-  factory _AssetGraphDeserializer(List<int> bytes) {
+  factory _AssetGraphDeserializer(Uint8List bytes) {
     dynamic decoded;
     try {
-      decoded = jsonDecode(utf8.decode(bytes));
+      decoded = msgpack.deserialize(bytes);
     } on FormatException {
       throw AssetGraphCorruptedException();
     }
@@ -211,7 +211,7 @@ class _AssetGraphSerializer {
   _AssetGraphSerializer(this._graph);
 
   /// Perform the serialization, should only be called once.
-  List<int> serialize() {
+  Uint8List serialize() {
     var pathId = 0;
     // [path0, packageId0, path1, packageId1, ...]
     var assetPaths = <dynamic>[];
@@ -233,7 +233,7 @@ class _AssetGraphSerializer {
           .map((pkg, version) => MapEntry(pkg, version?.toString())),
       'enabledExperiments': _graph.enabledExperiments,
     };
-    return utf8.encode(json.encode(result));
+    return msgpack.serialize(result);
   }
 
   List _serializeNode(AssetNode node) {

build_runner_core/lib/src/util/constants.dart

@@ -13,7 +13,7 @@ final String assetGraphPath = assetGraphPathFor(_scriptPath);
 
 /// Relative path to the asset graph for a build script at [path]
 String assetGraphPathFor(String path) =>
-    '$cacheDir/${_scriptHashFor(path)}/asset_graph.json';
+    '$cacheDir/${_scriptHashFor(path)}/asset_graph.msgpack';
 
 /// Relative path to the directory which holds serialized versions of errors
 /// reported during previous builds.

build_runner_core/pubspec.yaml

@@ -26,6 +26,7 @@ dependencies:
   timing: ^0.1.1
   watcher: ^0.9.7
   yaml: ^2.1.0
+  msgpack_dart: ^0.0.7
 
 dev_dependencies:
   build_test: ^1.0.0

build_runner_core/test/generate/build_test.dart

@@ -842,7 +842,7 @@ void main() {
     });
   });
 
-  test('tracks dependency graph in a asset_graph.json file', () async {
+  test('tracks dependency graph in a asset_graph.msgpack file', () async {
     final writer = InMemoryRunnerAssetWriter();
     await testBuilders([
       requiresPostProcessBuilderApplication,
@@ -1019,7 +1019,7 @@ void main() {
         outputs: {}, writer: writer);
   });
 
-  test('can recover from a deleted asset_graph.json cache', () async {
+  test('can recover from a deleted asset_graph.msgpack cache', () async {
     final writer = InMemoryRunnerAssetWriter();
     var inputs = <String, String>{'a|web/a.txt': 'a', 'a|lib/b.txt': 'b'};
     var outputs = <String, String>{
@@ -1030,7 +1030,7 @@ void main() {
     await testBuilders([copyABuilderApplication], inputs,
         outputs: outputs, writer: writer);
 
-    // Delete the `asset_graph.json` file!
+    // Delete the `asset_graph.msgpack` file!
     var outputId = makeAssetId('a|$assetGraphPath');
     await writer.delete(outputId);