private static async Task <Checksum> ComputeSourceSymbolsChecksumAsync(ProjectState projectState, CancellationToken cancellationToken)
{
// The SymbolTree for source is built from the source-symbols from the project's compilation's
// assembly. Specifically, we only get the name, kind and parent/child relationship of all the
// child symbols. So we want to be able to reuse the index as long as none of these have
// changed. The only thing that can make those source-symbols change in that manner are if
// the text of any document changes, or if options for the project change. So we build our
// checksum out of that data.
var serializer = projectState.LanguageServices.WorkspaceServices.GetService <ISerializerService>();
var projectStateChecksums = await projectState.GetStateChecksumsAsync(cancellationToken).ConfigureAwait(false);
// Order the documents by FilePath. Default ordering in the RemoteWorkspace is
// to be ordered by Guid (which is not consistent across VS sessions).
var textChecksumsTasks = projectState.DocumentStates.OrderBy(d => d.Value.FilePath, StringComparer.Ordinal).Select(async d =>
{
var documentStateChecksum = await d.Value.GetStateChecksumsAsync(cancellationToken).ConfigureAwait(false);
return(documentStateChecksum.Text);
});
var compilationOptionsChecksum = projectStateChecksums.CompilationOptions;
var parseOptionsChecksum = projectStateChecksums.ParseOptions;
var textChecksums = await Task.WhenAll(textChecksumsTasks).ConfigureAwait(false);
var allChecksums = ArrayBuilder <Checksum> .GetInstance();
try
{
allChecksums.AddRange(textChecksums);
allChecksums.Add(compilationOptionsChecksum);
allChecksums.Add(parseOptionsChecksum);
// Include serialization format version in our checksum. That way if the
// version ever changes, all persisted data won't match the current checksum
// we expect, and we'll recompute things.
allChecksums.Add(SerializationFormatChecksum);
var checksum = Checksum.Create(WellKnownSynchronizationKind.SymbolTreeInfo, allChecksums);
return(checksum);
}
finally
{
allChecksums.Free();
}
}