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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
using System;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.Collections;
using Microsoft.CodeAnalysis.Editor.Shared.Extensions;
using Microsoft.CodeAnalysis.Editor.Shared.Tagging;
using Microsoft.CodeAnalysis.Editor.Tagging;
using Microsoft.CodeAnalysis.ErrorReporting;
using Microsoft.CodeAnalysis.Host;
using Microsoft.CodeAnalysis.Internal.Log;
using Microsoft.CodeAnalysis.Shared.TestHooks;
using Microsoft.CodeAnalysis.Text;
using Microsoft.CodeAnalysis.Text.Shared.Extensions;
using Microsoft.VisualStudio.Text;
using Microsoft.VisualStudio.Text.Tagging;
using Microsoft.VisualStudio.Utilities;
using Roslyn.LanguageServer.Protocol;
using Roslyn.Utilities;
namespace Microsoft.CodeAnalysis.Classification;
internal partial class SyntacticClassificationTaggerProvider
{
/// <summary>
/// A classifier that operates only on the syntax of the source and not the semantics. Note:
/// this class operates in a hybrid sync/async manner. Specifically, while classification
/// happens synchronously, it may be synchronous over a parse tree which is out of date. Then,
/// asynchronously, we will attempt to get an up to date parse tree for the file. When we do, we
/// will determine which sections of the file changed and we will use that to notify the editor
/// about what needs to be reclassified.
/// </summary>
internal sealed partial class TagComputer
{
private sealed record CachedServices(
Workspace Workspace,
IContentType ContentType,
SolutionServices SolutionServices,
IClassificationService ClassificationService);
private static readonly object s_uniqueKey = new();
private readonly SyntacticClassificationTaggerProvider _taggerProvider;
private readonly ITextBuffer2 _subjectBuffer;
private readonly WorkspaceRegistration _workspaceRegistration;
private readonly CancellationTokenSource _disposalCancellationSource = new();
/// <summary>
/// Work queue we use to batch up notifications about changes that will cause
/// us to classify. This ensures that if we hear a flurry of changes, we don't
/// kick off an excessive amount of background work to process them.
/// </summary>
private readonly AsyncBatchingWorkQueue<ITextSnapshot> _workQueue;
/// <summary>
/// Timeout before we cancel the work to diff and return whatever we have.
/// </summary>
private readonly TimeSpan _diffTimeout;
private Workspace? _workspace;
/// <summary>
/// Cached values for the last services we computed for a particular <see cref="Workspace"/> and <see
/// cref="IContentType"/>. These rarely change, and are expensive enough to show up in very hot scenarios (like
/// scrolling) where we are going to be called in at a very high volume.
/// </summary>
private CachedServices? _lastCachedServices;
// The latest data about the document being classified that we've cached. objects can
// be accessed from both threads, and must be obtained when this lock is held.
//
// SyntaxNode is the preferred storage here because it doesn't GC-root a Solution instance.
// For languages that do not support syntax, this field offers fallback storage for a Document.
// it allows computing the root, and changed-spans, in the background so that we can
// report a smaller change range, and have the data ready for classifying with GetTags
// get called.
private readonly object _gate = new();
private (ITextSnapshot lastSnapshot, Document document, SyntaxNode? root)? _lastProcessedData;
/// <summary>
/// This will cache previous classification information for a span, so that we can avoid digging into same tree
/// again and again to find exactly same answer
/// </summary>
private readonly ClassifiedLineCache _lineCache;
private int _taggerReferenceCount;
public TagComputer(
SyntacticClassificationTaggerProvider taggerProvider,
ITextBuffer2 subjectBuffer,
TimeSpan diffTimeout)
{
_taggerProvider = taggerProvider;
_subjectBuffer = subjectBuffer;
_diffTimeout = diffTimeout;
_workQueue = new AsyncBatchingWorkQueue<ITextSnapshot>(
DelayTimeSpan.NearImmediate,
ProcessChangesAsync,
equalityComparer: null,
taggerProvider._listener,
_disposalCancellationSource.Token);
_lineCache = new ClassifiedLineCache(taggerProvider.ThreadingContext);
_workspaceRegistration = Workspace.GetWorkspaceRegistration(subjectBuffer.AsTextContainer());
_workspaceRegistration.WorkspaceChanged += OnWorkspaceRegistrationChanged;
if (_workspaceRegistration.Workspace != null)
ConnectToWorkspace(_workspaceRegistration.Workspace);
_subjectBuffer.ChangedOnBackground += this.OnSubjectBufferChanged;
}
public static TagComputer GetOrCreate(
SyntacticClassificationTaggerProvider taggerProvider, ITextBuffer2 subjectBuffer)
{
taggerProvider.ThreadingContext.ThrowIfNotOnUIThread();
var tagComputer = subjectBuffer.Properties.GetOrCreateSingletonProperty(
s_uniqueKey, () => new TagComputer(taggerProvider, subjectBuffer, TaggerDelay.NearImmediate.ComputeTimeDelay()));
tagComputer.IncrementReferenceCount();
return tagComputer;
}
private void DisconnectTagComputer()
=> _subjectBuffer.Properties.RemoveProperty(s_uniqueKey);
public event EventHandler<SnapshotSpanEventArgs>? TagsChanged;
private (SolutionServices solutionServices, IClassificationService classificationService)? TryGetClassificationService(ITextSnapshot snapshot)
{
var workspace = _workspace;
var contentType = snapshot.ContentType;
var lastCachedServices = _lastCachedServices;
if (lastCachedServices is null ||
lastCachedServices.Workspace != workspace ||
lastCachedServices.ContentType != contentType)
{
if (workspace?.Services.SolutionServices is not { } solutionServices)
return null;
if (solutionServices.GetProjectServices(contentType)?.GetService<IClassificationService>() is not { } classificationService)
return null;
lastCachedServices = new(workspace, contentType, solutionServices, classificationService);
_lastCachedServices = lastCachedServices;
}
return (lastCachedServices.SolutionServices, lastCachedServices.ClassificationService);
}
#region Workspace Hookup
private void OnWorkspaceRegistrationChanged(object? sender, EventArgs e)
{
var token = _taggerProvider._listener.BeginAsyncOperation(nameof(OnWorkspaceRegistrationChanged));
var task = SwitchToMainThreadAndHookupWorkspaceAsync();
task.CompletesAsyncOperation(token);
}
private async Task SwitchToMainThreadAndHookupWorkspaceAsync()
{
try
{
await _taggerProvider.ThreadingContext.JoinableTaskFactory.SwitchToMainThreadAsync(_disposalCancellationSource.Token);
// We both try to connect synchronously, and register for workspace registration events.
// It's possible (particularly in tests), to connect in the startup path, but then get a
// previously scheduled, but not yet delivered event. Don't bother connecting to the
// same workspace again in that case.
var newWorkspace = _workspaceRegistration.Workspace;
if (newWorkspace == _workspace)
return;
DisconnectFromWorkspace();
if (newWorkspace != null)
ConnectToWorkspace(newWorkspace);
}
catch (OperationCanceledException)
{
// can happen if we were disposed of.
}
catch (Exception e) when (FatalError.ReportAndCatch(e))
{
// We were in a fire and forget task. So just report the NFW and do not let
// this bleed out to an unhandled exception.
}
}
internal void IncrementReferenceCount()
{
_taggerProvider.ThreadingContext.ThrowIfNotOnUIThread();
_taggerReferenceCount++;
}
internal void DecrementReferenceCount()
{
_taggerProvider.ThreadingContext.ThrowIfNotOnUIThread();
_taggerReferenceCount--;
if (_taggerReferenceCount == 0)
{
// stop any bg work we're doing.
_disposalCancellationSource.Cancel();
_subjectBuffer.ChangedOnBackground -= this.OnSubjectBufferChanged;
DisconnectFromWorkspace();
_workspaceRegistration.WorkspaceChanged -= OnWorkspaceRegistrationChanged;
DisconnectTagComputer();
}
}
private void ConnectToWorkspace(Workspace workspace)
{
_taggerProvider.ThreadingContext.ThrowIfNotOnUIThread();
_workspace = workspace;
_workspace.WorkspaceChanged += this.OnWorkspaceChanged;
_workspace.DocumentActiveContextChanged += this.OnDocumentActiveContextChanged;
// Now that we've connected to the workspace, kick off work to reclassify this buffer.
_workQueue.AddWork(_subjectBuffer.CurrentSnapshot);
}
public void DisconnectFromWorkspace()
{
_taggerProvider.ThreadingContext.ThrowIfNotOnUIThread();
_lastCachedServices = null;
lock (_gate)
{
_lastProcessedData = null;
}
if (_workspace != null)
{
_workspace.WorkspaceChanged -= this.OnWorkspaceChanged;
_workspace.DocumentActiveContextChanged -= this.OnDocumentActiveContextChanged;
_workspace = null;
// Now that we've disconnected to the workspace, kick off work to reclassify this buffer.
_workQueue.AddWork(_subjectBuffer.CurrentSnapshot);
}
}
#endregion
#region Event Handling
private void OnSubjectBufferChanged(object? sender, TextContentChangedEventArgs args)
{
// we know a change to our buffer is always affecting this document. So we can
// just enqueue the work to reclassify things unilaterally.
_workQueue.AddWork(args.After);
}
private void OnDocumentActiveContextChanged(object? sender, DocumentActiveContextChangedEventArgs args)
{
if (_workspace == null)
return;
var documentId = args.NewActiveContextDocumentId;
var bufferDocumentId = _workspace.GetDocumentIdInCurrentContext(_subjectBuffer.AsTextContainer());
if (bufferDocumentId != documentId)
return;
_workQueue.AddWork(_subjectBuffer.CurrentSnapshot);
}
private void OnWorkspaceChanged(object? sender, WorkspaceChangeEventArgs args)
{
// We may be getting an event for a workspace we already disconnected from. If so,
// ignore them. We won't be able to find the Document corresponding to our text buffer,
// so we can't reasonably classify this anyways.
if (args.NewSolution.Workspace != _workspace)
return;
if (args.Kind != WorkspaceChangeKind.ProjectChanged)
return;
var documentId = _workspace.GetDocumentIdInCurrentContext(_subjectBuffer.AsTextContainer());
if (args.ProjectId != documentId?.ProjectId)
return;
var oldProject = args.OldSolution.GetProject(args.ProjectId);
var newProject = args.NewSolution.GetProject(args.ProjectId);
// In case of parse options change reclassify the doc as it may have affected things
// like preprocessor directives.
if (Equals(oldProject?.ParseOptions, newProject?.ParseOptions))
return;
_workQueue.AddWork(_subjectBuffer.CurrentSnapshot);
}
#endregion
/// <summary>
/// Parses the document in the background and determines what has changed to report to
/// the editor. Calls to <see cref="ProcessChangesAsync"/> are serialized by <see cref="AsyncBatchingWorkQueue{TItem}"/>
/// so we don't need to worry about multiple calls to this happening concurrently.
/// </summary>
private async ValueTask ProcessChangesAsync(ImmutableSegmentedList<ITextSnapshot> snapshots, CancellationToken cancellationToken)
{
// We have potentially heard about several changes to the subject buffer. However
// we only need to process the latest once.
Contract.ThrowIfTrue(snapshots.IsDefault || snapshots.IsEmpty);
var currentSnapshot = GetLatest(snapshots);
if (TryGetClassificationService(currentSnapshot) is not (var solutionServices, var classificationService))
return;
var currentDocument = currentSnapshot.GetOpenDocumentInCurrentContextWithChanges();
if (currentDocument == null)
return;
var lastProcessedData = GetLastProcessedData();
// Optionally pre-calculate the root of the doc so that it is ready to classify once GetTags is called.
// Also, attempt to determine a smaller change range span for this document so that we can avoid reporting
// the entire document as changed.
var currentRoot = await currentDocument.GetSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
var changeRange = await ComputeChangedRangeAsync(
solutionServices, classificationService,
currentDocument, currentRoot,
lastProcessedData?.document, lastProcessedData?.root,
cancellationToken).ConfigureAwait(false);
var changedSpan = changeRange != null
? currentSnapshot.GetSpan(changeRange.Value.Span.Start, changeRange.Value.NewLength)
: currentSnapshot.GetFullSpan();
lock (_gate)
{
_lastProcessedData = (currentSnapshot, currentDocument, currentRoot);
}
// Notify the editor now that there were changes. Note: we do not need to go the
// UI to do this. The editor supports TagsChanged being called on any thread.
this.TagsChanged?.Invoke(this, new SnapshotSpanEventArgs(changedSpan));
return;
static ITextSnapshot GetLatest(ImmutableSegmentedList<ITextSnapshot> snapshots)
{
var latest = snapshots[0];
for (var i = 1; i < snapshots.Count; i++)
{
var snapshot = snapshots[i];
if (snapshot.Version.VersionNumber > latest.Version.VersionNumber)
latest = snapshot;
}
return latest;
}
}
private ValueTask<TextChangeRange?> ComputeChangedRangeAsync(
SolutionServices solutionServices,
IClassificationService classificationService,
Document currentDocument,
SyntaxNode? currentRoot,
Document? lastProcessedDocument,
SyntaxNode? lastProcessedRoot,
CancellationToken cancellationToken)
{
if (lastProcessedDocument is null)
return ValueTaskFactory.FromResult<TextChangeRange?>(null);
if (lastProcessedRoot != null)
{
// If we have syntax available fast path the change computation without async or blocking.
if (currentRoot is not null)
return new(classificationService.ComputeSyntacticChangeRange(solutionServices, lastProcessedRoot, currentRoot, _diffTimeout, cancellationToken));
else
return ValueTaskFactory.FromResult<TextChangeRange?>(null);
}
else
{
// Otherwise, fall back to the language to compute the difference based on the document contents.
return classificationService.ComputeSyntacticChangeRangeAsync(lastProcessedDocument, currentDocument, _diffTimeout, cancellationToken);
}
}
private (ITextSnapshot lastSnapshot, Document document, SyntaxNode? root)? GetLastProcessedData()
{
lock (_gate)
return _lastProcessedData;
}
public void AddTags(NormalizedSnapshotSpanCollection spans, SegmentedList<TagSpan<IClassificationTag>> tags)
{
_taggerProvider.ThreadingContext.ThrowIfNotOnUIThread();
using (Logger.LogBlock(FunctionId.Tagger_SyntacticClassification_TagComputer_GetTags, CancellationToken.None))
AddTagsWorker(spans, tags);
}
private void AddTagsWorker(NormalizedSnapshotSpanCollection spans, SegmentedList<TagSpan<IClassificationTag>> tags)
{
_taggerProvider.ThreadingContext.ThrowIfNotOnUIThread();
if (spans.Count == 0 || _workspace == null)
return;
var snapshot = spans[0].Snapshot;
if (TryGetClassificationService(snapshot) is not (var solutionServices, var classificationService))
return;
using var _ = Classifier.GetPooledList(out var classifiedSpans);
foreach (var span in spans)
AddClassifications(span);
var typeMap = _taggerProvider._typeMap;
foreach (var classifiedSpan in classifiedSpans)
tags.Add(ClassificationUtilities.Convert(typeMap, snapshot, classifiedSpan));
return;
void AddClassifications(SnapshotSpan span)
{
_taggerProvider.ThreadingContext.ThrowIfNotOnUIThread();
// First, get the tree and snapshot that we'll be operating over.
if (GetLastProcessedData() is not (var lastProcessedSnapshot, var lastProcessedDocument, var lastProcessedRoot))
{
// We don't have a syntax tree yet. Just do a lexical classification of the document.
AddLexicalClassifications(classificationService, span, classifiedSpans);
return;
}
// We have a tree. However, the tree may be for an older version of the snapshot.
// If it is for an older version, then classify that older version and translate
// the classifications forward. Otherwise, just classify normally.
if (lastProcessedSnapshot.Version.ReiteratedVersionNumber != span.Snapshot.Version.ReiteratedVersionNumber)
{
// Slightly more complicated. We have a parse tree, it's just not for the snapshot we're being asked for.
AddClassifiedSpansForPreviousDocument(solutionServices, classificationService, span, lastProcessedSnapshot, lastProcessedDocument, lastProcessedRoot, classifiedSpans);
return;
}
// Mainline case. We have the corresponding document for the snapshot we're classifying.
AddSyntacticClassificationsForDocument(solutionServices, classificationService, span, lastProcessedDocument, lastProcessedRoot, classifiedSpans);
}
}
private void AddLexicalClassifications(IClassificationService classificationService, SnapshotSpan span, SegmentedList<ClassifiedSpan> classifiedSpans)
{
_taggerProvider.ThreadingContext.ThrowIfNotOnUIThread();
classificationService.AddLexicalClassifications(
span.Snapshot.AsText(), span.Span.ToTextSpan(), classifiedSpans, CancellationToken.None);
}
private void AddSyntacticClassificationsForDocument(
SolutionServices solutionServices,
IClassificationService classificationService,
SnapshotSpan span,
Document lastProcessedDocument,
SyntaxNode? lastProcessedRoot,
SegmentedList<ClassifiedSpan> classifiedSpans)
{
_taggerProvider.ThreadingContext.ThrowIfNotOnUIThread();
var cancellationToken = CancellationToken.None;
// Pass in the doc-id and parse options so that if those change between the last cached values and now, we
// don't try to reuse them.
if (_lineCache.TryUseCache(lastProcessedDocument.Id, lastProcessedDocument.Project.ParseOptions, span, classifiedSpans))
return;
using var _ = Classifier.GetPooledList(out var tempList);
// If we have a syntax root ready, use it. Otherwise, get the root synchronously. We do not want to do
// anything async here as we'd have to block on that, potentially starving the UI thread while the
// threadpool does work.
//
// If this is a language that does not support syntax, we have no choice but to try to get the
// classifications asynchronously, blocking on that result.
var root = lastProcessedRoot != null
? lastProcessedRoot
: lastProcessedDocument.SupportsSyntaxTree
? lastProcessedDocument.GetSyntaxRootSynchronously(cancellationToken)
: null;
if (root != null)
classificationService.AddSyntacticClassifications(solutionServices, root, span.Span.ToTextSpan(), tempList, cancellationToken);
else
classificationService.AddSyntacticClassificationsAsync(lastProcessedDocument, span.Span.ToTextSpan(), tempList, cancellationToken).Wait(cancellationToken);
_lineCache.Update(span, tempList);
classifiedSpans.AddRange(tempList);
}
private void AddClassifiedSpansForPreviousDocument(
SolutionServices solutionServices,
IClassificationService classificationService,
SnapshotSpan span,
ITextSnapshot lastProcessedSnapshot,
Document lastProcessedDocument,
SyntaxNode? lastProcessedRoot,
SegmentedList<ClassifiedSpan> classifiedSpans)
{
_taggerProvider.ThreadingContext.ThrowIfNotOnUIThread();
// Slightly more complicated case. They're asking for the classifications for a
// different snapshot than what we have a parse tree for. So we first translate the span
// that they're asking for so that is maps onto the tree that we have spans for. We then
// get the classifications from that tree. We then take the results and translate them
// back to the snapshot they want. Finally, as some of the classifications may have
// changed, we check for some common cases and touch them up manually so that things
// look right for the user.
// 1) translate the requested span onto the right span for the snapshot that corresponds
// to the syntax tree.
var translatedSpan = span.TranslateTo(lastProcessedSnapshot, SpanTrackingMode.EdgeExclusive);
if (translatedSpan.IsEmpty)
{
// well, there is no information we can get from previous tree, use lexer to
// classify given span. soon we will re-classify the region.
AddLexicalClassifications(classificationService, span, classifiedSpans);
}
else
{
using var _ = Classifier.GetPooledList(out var tempList);
AddSyntacticClassificationsForDocument(
solutionServices, classificationService, translatedSpan, lastProcessedDocument, lastProcessedRoot, tempList);
var currentSnapshot = span.Snapshot;
var currentText = currentSnapshot.AsText();
foreach (var lastClassifiedSpan in tempList)
{
// 2) Translate those classifications forward so that they correspond to the true
// requested snapshot.
var lastSnapshotSpan = lastClassifiedSpan.TextSpan.ToSnapshotSpan(lastProcessedSnapshot);
var currentSnapshotSpan = lastSnapshotSpan.TranslateTo(currentSnapshot, SpanTrackingMode.EdgeInclusive);
var currentClassifiedSpan = new ClassifiedSpan(lastClassifiedSpan.ClassificationType, currentSnapshotSpan.Span.ToTextSpan());
// 3) The classifications may be incorrect due to changes in the text. For example,
// if "clss" becomes "class", then we want to changes the classification from
// 'identifier' to 'keyword'.
currentClassifiedSpan = classificationService.AdjustStaleClassification(currentText, currentClassifiedSpan);
classifiedSpans.Add(currentClassifiedSpan);
}
}
}
}
}
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