/// <summary>
/// Get the text changes between this document and a prior version of the same document.
/// The changes, when applied to the text of the old document, will produce the text of the current document.
/// </summary>
public async Task <IEnumerable <TextChange> > GetTextChangesAsync(Document oldDocument, CancellationToken cancellationToken = default(CancellationToken))
{
try
{
using (Logger.LogBlock(FeatureId.Document, FunctionId.Document_GetTextChanges, this.Name, cancellationToken))
{
if (oldDocument == this)
{
// no changes
return(SpecializedCollections.EmptyEnumerable <TextChange>());
}
if (this.Id != oldDocument.Id)
{
throw new ArgumentException(WorkspacesResources.DocumentVersionIsDifferent);
}
// first try to see if text already knows its changes
IList <TextChange> textChanges = null;
SourceText text;
SourceText oldText;
if (this.TryGetText(out text) && oldDocument.TryGetText(out oldText))
{
if (text == oldText)
{
return(SpecializedCollections.EmptyEnumerable <TextChange>());
}
var container = text.Container;
if (container != null)
{
textChanges = text.GetTextChanges(oldText).ToList();
// if changes are significant (not the whole document being replaced) then use these changes
if (textChanges.Count > 1 || (textChanges.Count == 1 && textChanges[0].Span != new TextSpan(0, oldText.Length)))
{
return(textChanges);
}
}
}
// get changes by diffing the trees
SyntaxTree tree = await this.GetSyntaxTreeAsync(cancellationToken).ConfigureAwait(false);
SyntaxTree oldTree = await oldDocument.GetSyntaxTreeAsync(cancellationToken).ConfigureAwait(false);
return(tree.GetChanges(oldTree));
}
}
catch (Exception e) if (ExceptionHelpers.CrashUnlessCanceled(e))
{
throw ExceptionUtilities.Unreachable;
}
}
/// <summary>
/// Generates Diff results for each change that occurred from the ancestor to the changed
/// </summary>
/// <param name="ancestor">
/// The abstract syntax tree that the changed version originated from
/// </param>
/// <param name="changed">The abstract syntax tree that resulted from changing the ancestor</param>
/// <returns>Changes between the ancestor and changed</returns>
public static IEnumerable<Diff> Compare(SyntaxTree ancestor, SyntaxTree changed)
{
var offset = 0; //Tracks differences in indexes moving through the changed syntax tree
foreach (var change in changed.GetChanges(ancestor))
{ //Assumes that this list is sorted by place in file
var origLength = change.Span.Length;
var offsetChange = (change.NewText.Length - origLength);
var chanStart = change.Span.Start + offset;
var chanLength = origLength + offsetChange;
offset += offsetChange;
var d = new Diff
{
Ancestor = SpanDetails.Create(change.Span, ancestor),
Changed = SpanDetails.Create(new TextSpan(chanStart, chanLength), changed)
};
yield return d;
}
}
private static bool TryGetChangesIgnoringWhiteSpace(SyntaxTree oldTree, SyntaxTree newTree, out IEnumerable<string> textchanges)
{
#region CodeContracts
Contract.Requires(oldTree != null);
Contract.Requires(newTree != null);
Contract.Ensures(!Contract.Result<bool>() || Contract.ValueAtReturn<IEnumerable<string>>(out textchanges) != null);
#endregion CodeContracts
var workspace = MSBuildWorkspace.Create();
oldTree = Formatter.Format(oldTree.GetRoot(), workspace).SyntaxTree;
newTree = Formatter.Format(newTree.GetRoot(), workspace).SyntaxTree;
textchanges = null;
if (oldTree == newTree)
{
return false;
}
var changes = newTree.GetChanges(oldTree);
if (!changes.Any()) {
return false;
}
textchanges = changes.Select(x => x.NewText.Trim());
//textchanges = changes.Select(x => x.NewText.Trim());
if (textchanges.All(x => x == ""))
{
return false;
}
return true;
}