private Model SetModelExplicitlySelectedItemInBackground(
Model model,
Func<Model, SignatureHelpItem> selector)
{
AssertIsBackground();
if (model == null)
{
return null;
}
var selectedItem = selector(model);
Contract.ThrowIfFalse(model.Items.Contains(selectedItem));
return model.WithSelectedItem(selectedItem);
}
private async Task<Model> ComputeModelInBackgroundAsync(
Model currentModel,
IList<ISignatureHelpProvider> matchedProviders,
IList<ISignatureHelpProvider> unmatchedProviders,
SnapshotPoint caretPosition,
DisconnectedBufferGraph disconnectedBufferGraph,
SignatureHelpTriggerInfo triggerInfo,
CancellationToken cancellationToken)
{
try
{
using (Logger.LogBlock(FunctionId.SignatureHelp_ModelComputation_ComputeModelInBackground, cancellationToken))
{
AssertIsBackground();
cancellationToken.ThrowIfCancellationRequested();
var document = await Controller.DocumentProvider.GetDocumentAsync(caretPosition.Snapshot, cancellationToken).ConfigureAwait(false);
if (document == null)
{
return currentModel;
}
if (triggerInfo.TriggerReason == SignatureHelpTriggerReason.RetriggerCommand)
{
if (currentModel == null ||
(triggerInfo.TriggerCharacter.HasValue && !currentModel.Provider.IsRetriggerCharacter(triggerInfo.TriggerCharacter.Value)))
{
return currentModel;
}
}
// first try to query the providers that can trigger on the specified character
var result = await ComputeItemsAsync(matchedProviders, caretPosition, triggerInfo, document, cancellationToken).ConfigureAwait(false);
var provider = result.Item1;
var items = result.Item2;
if (provider == null)
{
// no match, so now query the other providers
result = await ComputeItemsAsync(unmatchedProviders, caretPosition, triggerInfo, document, cancellationToken).ConfigureAwait(false);
provider = result.Item1;
items = result.Item2;
if (provider == null)
{
// the other providers didn't produce items either, so we don't produce a model
return null;
}
}
if (currentModel != null &&
currentModel.Provider == provider &&
currentModel.GetCurrentSpanInSubjectBuffer(disconnectedBufferGraph.SubjectBufferSnapshot).Span.Start == items.ApplicableSpan.Start &&
currentModel.ArgumentIndex == items.ArgumentIndex &&
currentModel.ArgumentCount == items.ArgumentCount &&
currentModel.ArgumentName == items.ArgumentName)
{
// The new model is the same as the current model. Return the currentModel
// so we keep the active selection.
return currentModel;
}
var selectedItem = GetSelectedItem(currentModel, items, provider);
var model = new Model(disconnectedBufferGraph, items.ApplicableSpan, provider,
items.Items, selectedItem, items.ArgumentIndex, items.ArgumentCount, items.ArgumentName,
selectedParameter: 0);
var syntaxFactsService = document.GetLanguageService<ISyntaxFactsService>();
var isCaseSensitive = syntaxFactsService == null || syntaxFactsService.IsCaseSensitive;
var selection = DefaultSignatureHelpSelector.GetSelection(model.Items,
model.SelectedItem, model.ArgumentIndex, model.ArgumentCount, model.ArgumentName, isCaseSensitive);
return model.WithSelectedItem(selection.SelectedItem)
.WithSelectedParameter(selection.SelectedParameter);
}
}
catch (Exception e) when (FatalError.ReportUnlessCanceled(e))
{
throw ExceptionUtilities.Unreachable;
}
}
private static SignatureHelpItem GetSelectedItem(Model currentModel, SignatureHelpItems items, ISignatureHelpProvider provider)
{
// Try to find the most appropriate item in the list to select by default.
// If the provider specified one a selected item, then always stick with that one.
if (items.SelectedItemIndex.HasValue)
{
return items.Items[items.SelectedItemIndex.Value];
}
// If the provider did not pick a default, and it's the same provider as the previous
// model we have, then try to return the same item that we had before.
if (currentModel != null && currentModel.Provider == provider)
{
return items.Items.FirstOrDefault(i => DisplayPartsMatch(i, currentModel.SelectedItem)) ?? items.Items.First();
}
// Otherwise, just pick the first item we have.
return items.Items.First();
}