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Merge changes from a single DidChange notification #74268

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Jul 25, 2024
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15 changes: 15 additions & 0 deletions src/LanguageServer/Protocol/Extensions/Extensions.cs
Original file line number Diff line number Diff line change
Expand Up @@ -243,5 +243,20 @@ private static bool TryGetVSCompletionListSetting(ClientCapabilities clientCapab

return true;
}

public static int CompareTo(this Position p1, Position p2)
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CompareTo

I'm sure there is a similar method implemented somewhere in Roslyn, but I couldn't find it

{
if (p1.Line > p2.Line)
return 1;
else if (p1.Line < p2.Line)
return -1;

if (p1.Character > p2.Character)
return 1;
else if (p1.Character < p2.Character)
return -1;

return 0;
}
}
}
Original file line number Diff line number Diff line change
Expand Up @@ -4,9 +4,11 @@

using System;
using System.Composition;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.Host.Mef;
using Microsoft.CodeAnalysis.Text;
using Roslyn.LanguageServer.Protocol;
using Roslyn.Utilities;

Expand All @@ -28,15 +30,52 @@ public TextDocumentIdentifier GetTextDocumentIdentifier(DidChangeTextDocumentPar
{
var text = context.GetTrackedDocumentSourceText(request.TextDocument.Uri);

text = GetUpdatedSourceText(request.ContentChanges, text);

context.UpdateTrackedDocument(request.TextDocument.Uri, text);

return SpecializedTasks.Default<object>();
}

private static SourceText GetUpdatedSourceText(TextDocumentContentChangeEvent[] contentChanges, SourceText text)
{
var areChangesOrdered = true;

// Per the LSP spec, each text change builds upon the previous, so we don't need to translate any text
// positions between changes, which makes this quite easy. See
// positions between changes. See
// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#didChangeTextDocumentParams
// for more details.
foreach (var change in request.ContentChanges)
text = text.WithChanges(ProtocolConversions.ContentChangeEventToTextChange(change, text));
//
// If the host sends us changes in a way such that no earlier change can affect the position of a later change,
// then we can merge the changes into a single TextChange, allowing creation of only a single new
// source text.
for (var i = 1; i < contentChanges.Length; i++)
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can we add some tests for this (e.g. sending changes that overlap and don't overlap and verifying that the server ends up with the correct source text?

Probably here - https://github.com/dotnet/roslyn/blob/fa05fe407b8b41eeade24e75f6e3746720bda927/src/LanguageServer/ProtocolUnitTests/DocumentChanges/DocumentChangesTests.cs

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Added some unit tests, they aren't as clean as I had hoped, but it should at least give some coverage

{
var prevChange = contentChanges[i - 1];
var curChange = contentChanges[i];

context.UpdateTrackedDocument(request.TextDocument.Uri, text);
if (prevChange.Range.Start.CompareTo(curChange.Range.End) < 0)
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Its early and I'm not 100% sure of this. Is it possible we need to compare against all previous changes? For example we have two disparate changes, then one afterwards that overlaps just the first one?

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Chatted in person, let me know if you still have concerns.

{
areChangesOrdered = false;
break;
}
}

return SpecializedTasks.Default<object>();
if (!areChangesOrdered)
{
// The host didn't send us the items ordered, so we'll apply each one independently.
foreach (var change in contentChanges)
text = text.WithChanges(ProtocolConversions.ContentChangeEventToTextChange(change, text));
}
else
{
// The changes were ordered, so we can merge them into a single operation on the source text. Note that
// the original change ordering was in reverse document order, whereas the WithChanges implementation works
// more efficiently with them in forward document order.
var newChanges = contentChanges.Reverse().SelectAsArray(change => ProtocolConversions.ContentChangeEventToTextChange(change, text));
text = text.WithChanges(newChanges);
}

return text;
}
}
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