private static async Task <(ProjectChanges, IEnumerable <TextChange>)> GetChangesForCodeActionAsync(
Document document,
CodeAction codeAction,
ProgressTracker progressTracker,
IDocumentTextDifferencingService textDiffingService,
CancellationToken cancellationToken)
{
// CodeAction.GetChangedSolutionAsync is only implemented for code actions that can fully compute the new
// solution without deferred computation or taking a dependency on the main thread. In other cases, the
// implementation of GetChangedSolutionAsync will throw an exception and the code action application is
// expected to apply the changes by executing the operations in GetOperationsAsync (which may have other
// side effects). This code cannot assume the input CodeAction supports GetChangedSolutionAsync, so it first
// attempts to apply text changes obtained from GetOperationsAsync. Two forms are supported:
//
// 1. GetOperationsAsync returns an empty list of operations (i.e. no changes are required)
// 2. GetOperationsAsync returns a list of operations, where the first change is an ApplyChangesOperation to
// change the text in the solution, and any remaining changes are deferred computation changes.
//
// If GetOperationsAsync does not adhere to one of these patterns, the code falls back to calling
// GetChangedSolutionAsync since there is no clear way to apply the changes otherwise.
var operations = await codeAction.GetOperationsAsync(cancellationToken).ConfigureAwait(false);
Solution newSolution;
if (operations.Length == 0)
{
newSolution = document.Project.Solution;
}
else if (operations.Length == 1 && operations[0] is ApplyChangesOperation applyChangesOperation)
{
newSolution = applyChangesOperation.ChangedSolution;
}
else
{
newSolution = await codeAction.GetRequiredChangedSolutionAsync(
progressTracker, cancellationToken : cancellationToken).ConfigureAwait(false);
}
var newDocument = newSolution.GetRequiredDocument(document.Id);
// Use Line differencing to reduce the possibility of changes that overwrite existing code.
var textChanges = await textDiffingService.GetTextChangesAsync(
document, newDocument, TextDifferenceTypes.Line, cancellationToken).ConfigureAwait(false);
var projectChanges = newDocument.Project.GetChanges(document.Project);
return(projectChanges, textChanges);
}