Compute and flush only affected transitive signatures in FileState.

pkg/analyzer/lib/src/dart/analysis/file_state.dart

Index: pkg/analyzer/lib/src/dart/analysis/file_state.dart
diff --git a/pkg/analyzer/lib/src/dart/analysis/file_state.dart b/pkg/analyzer/lib/src/dart/analysis/file_state.dart
index da38aca60b5fb54ea9731776aa7ac39e63d9cf14..93d172c5bdb2f2bde95899a4eeb3878af75471fb 100644
--- a/pkg/analyzer/lib/src/dart/analysis/file_state.dart
+++ b/pkg/analyzer/lib/src/dart/analysis/file_state.dart
@@ -93,6 +93,7 @@ class FileState {
   List<FileState> _partedFiles;
   Set<FileState> _directReferencedFiles = new Set<FileState>();
   Set<FileState> _transitiveFiles;
+  String _transitiveSignature;
 
   FileState._(this._fsState, this.path, this.uri, this.source);
 
@@ -179,6 +180,23 @@ class FileState {
   }
 
   /**
+   * Return the signature of the file, based on the [transitiveFiles].
+   */
+  String get transitiveSignature {
+    if (_transitiveSignature == null) {
+      ApiSignature signature = new ApiSignature();
+      signature.addUint32List(_fsState._salt);
+      signature.addString(_fsState._sdkApiSignature);
+      transitiveFiles

[Paul Berry, 2016/11/21 13:58:00]

It *probably* won't matter, but for safety, we should do
`signature.addUint32(transitiveFiles.length);` before this line.

(The idea is that in order to avoid accidentally producing signature collisions,
it should in theory be possible to deserialize the original data from the
signature bytes.  Adding the length means that if we were trying to deserialize
the data, we would know when to stop decoding transitive file signatures and
start decoding the URI).

[scheglov, 2016/11/21 16:51:52]

Done.

+          .map((file) => file.apiSignature)
+          .forEach(signature.addBytes);
+      signature.addString(uri.toString());
+      _transitiveSignature = signature.toHex();
+    }
+    return _transitiveSignature;
+  }
+
+  /**
    * The [UnlinkedUnit] of the file.
    */
   UnlinkedUnit get unlinked => _unlinked;
@@ -267,6 +285,16 @@ class FileState {
         !_equalByteLists(_apiSignature, newApiSignature);
     _apiSignature = newApiSignature;
 
+    // If the API signature changed, flush transitive signatures.
+    if (apiSignatureChanged) {
+      for (FileState file in _fsState._uriToFile.values) {
+        if (file._transitiveFiles != null &&
+            file._transitiveFiles.contains(this)) {
+          file._transitiveSignature = null;
+        }
+      }
+    }
+
     // This file is potentially not a library for its previous parts anymore.
     if (_partedFiles != null) {
       for (FileState part in _partedFiles) {
@@ -382,6 +410,7 @@ class FileSystemState {
   final SourceFactory _sourceFactory;
   final AnalysisOptions _analysisOptions;
   final Uint32List _salt;
+  final String _sdkApiSignature;
 
   /**
    * Mapping from a URI to the corresponding [FileState].
@@ -412,7 +441,8 @@ class FileSystemState {
       this._resourceProvider,
       this._sourceFactory,
       this._analysisOptions,
-      this._salt) {
+      this._salt,
+      this._sdkApiSignature) {
     _testView = new FileSystemStateTestView(this);
   }