trigger a full rebuild when the build script changes

Author: jakemac53

lib/src/generate/build_impl.dart

@@ -4,6 +4,7 @@
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
+import 'dart:mirrors';
 
 import 'package:logging/logging.dart';
 import 'package:path/path.dart' as path;
@@ -73,8 +74,18 @@ class BuildImpl {
 
       /// Applies all [updates] to the [_assetGraph] as well as doing other
       /// necessary cleanup.
+      _logger.info('Updating dependency graph with changes since last build.');
       await _updateWithChanges(updates);
-      _assetGraph.validAsOf = validAsOf;
+
+      /// Sometimes we need to fully invalidate the graph, such as when the
+      /// build script itself is updated.
+      _logger.info('Checking if asset graph needs to be rebuilt');
+      if (await _shouldInvalidateAssetGraph()) {
+        _logger.info('Invalidating asset graph due to build script update');
+        _assetGraph.allNodes
+            .where((node) => node is GeneratedAssetNode)
+            .forEach((node) => (node as GeneratedAssetNode).needsUpdate = true);
+      }
 
       /// Wait while all inputs are collected.
       _logger.info('Initializing inputs');
@@ -89,6 +100,8 @@ class BuildImpl {
       var result = await _runPhases();
 
       /// Write out the dependency graph file.
+      _logger.info('Caching finalized dependency graph');
+      _assetGraph.validAsOf = validAsOf;
       var assetGraphAsset =
           new Asset(_assetGraphId, JSON.encode(_assetGraph.serialize()));
       await _writer.writeAsString(assetGraphAsset);
@@ -120,6 +133,55 @@ class BuildImpl {
     }
   }
 
+  /// Checks if the [_assetGraph] needs to be completely invalidated.
+  ///
+  /// For now this just means looking at the current running program, and seeing
+  /// if any of its sources are newer than the asset graph itself.
+  Future<bool> _shouldInvalidateAssetGraph() async {
+    var completer = new Completer<bool>();
+    Future.wait(currentMirrorSystem().libraries.keys.map((Uri uri) async {
+      /// Short-circuit
+      if (completer.isCompleted) return;
+      var lastModified;
+      switch (uri.scheme) {
+        case 'dart':
+          return;
+        case 'package':
+          var parts = uri.pathSegments;
+          var id = new AssetId(
+              parts[0],
+              path.url
+                  .joinAll(['lib']..addAll(parts.getRange(1, parts.length))));
+          lastModified = await _reader.lastModified(id);
+          break;
+        case 'file':
+
+          /// TODO(jakemac): Probably shouldn't use dart:io directly, but its
+          /// definitely the easiest solution and should be fine.
+          var file = new File.fromUri(uri);
+          lastModified = await file.lastModified();
+          break;
+        case 'data':
+          /// Test runner uses a `data` scheme, don't invalidate for those.
+          if (uri.path.contains('package:test')) return;
+          continue unknownUri;
+        unknownUri:
+        default:
+          _logger.info('Unrecognized uri scheme `${uri.scheme}` found for '
+              'library in build script, falling back on full rebuild.');
+          if (!completer.isCompleted) completer.complete(true);
+          return;
+      }
+      assert(lastModified != null);
+      if (lastModified.compareTo(_assetGraph.validAsOf) > 0) {
+        if (!completer.isCompleted) completer.complete(true);
+      }
+    })).then((_) {
+      if (!completer.isCompleted) completer.complete(false);
+    });
+    return completer.future;
+  }
+
   /// Creates and returns a map of updates to assets based on [_assetGraph].
   Future<Map<AssetId, ChangeType>> _getUpdates() async {
     /// Collect updates to the graph based on any changed assets.

lib/src/generate/watch_impl.dart

@@ -7,7 +7,6 @@ import 'package:logging/logging.dart';
 import 'package:path/path.dart' as path;
 import 'package:watcher/watcher.dart';
 
-import '../asset/cache.dart';
 import '../asset/id.dart';
 import '../asset/reader.dart';
 import '../asset/writer.dart';

test/common/in_memory_reader.dart

@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 import 'dart:async';
 import 'dart:convert';
+import 'dart:mirrors';
 
 import 'package:build/build.dart';
 
@@ -35,9 +36,25 @@ class InMemoryAssetReader implements AssetReader {
     }
   }
 
+  final Map<Uri, LibraryMirror> _allLibraries = currentMirrorSystem().libraries;
+
   @override
   Future<DateTime> lastModified(AssetId id) async {
-    if (!await hasInput(id)) throw new AssetNotFoundException(id);
+    if (!assets.containsKey(id)) {
+      /// Support reading files imported by the test script as well. Also
+      /// pretend like they are very old so that builds don't get invalidated.
+      ///
+      /// Overridden values in [assets] will take precedence.
+      var uri = new Uri(
+          scheme: 'package',
+          path: '${id.package}/${id.path.replaceFirst("lib/", "")}');
+      if (_allLibraries[uri] != null) {
+        return new DateTime.fromMillisecondsSinceEpoch(0);
+      }
+
+      throw new AssetNotFoundException(id);
+    }
+
     return assets[id].date;
   }
 }

test/generate/build_test.dart

@@ -265,8 +265,7 @@ main() {
         ],
       ];
 
-      var graph = new AssetGraph()
-        ..validAsOf = new DateTime.now().subtract(new Duration(days: 1));
+      var graph = new AssetGraph()..validAsOf = new DateTime.now();
 
       var aCloneNode = new GeneratedAssetNode(makeAssetId('a|lib/a.txt.copy'),
           false, true, makeAssetId('a|lib/a.txt.copy.clone'));
@@ -345,6 +344,29 @@ main() {
       expect(writer.assets.containsKey(aCopyNode.id), isFalse);
       expect(writer.assets.containsKey(aCloneNode.id), isFalse);
     });
+
+    test('invalidates graph if build script updates', () async {
+      var graph = new AssetGraph();
+      var aId = makeAssetId('a|web/a.txt');
+      var aCopyNode = new GeneratedAssetNode(
+          aId, false, true, makeAssetId('a|web/a.txt.copy'));
+      graph.add(aCopyNode);
+      var aNode = makeAssetNode('a|web/a.txt', [aCopyNode.id]);
+      graph.add(aNode);
+
+      var writer = new InMemoryAssetWriter();
+      /// Spoof the `package:test/test.dart` import and pretend its newer than
+      /// the current graph to cause a rebuild.
+      writer.writeAsString(makeAsset('test|lib/test.dart', ''),
+          lastModified: graph.validAsOf.add(new Duration(hours: 1)));
+      await testPhases(copyAPhaseGroup, {
+        'a|web/a.txt': 'a',
+        'a|web/a.txt.copy': 'a',
+        'a|.build/asset_graph.json': JSON.encode(graph.serialize()),
+      }, outputs: {
+        'a|web/a.txt.copy': 'a',
+      });
+    });
   });
 }