File: Handler\References\FindUsagesLSPContext.cs
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Project: src\src\LanguageServer\Protocol\Microsoft.CodeAnalysis.LanguageServer.Protocol.csproj (Microsoft.CodeAnalysis.LanguageServer.Protocol)
// 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.Collections.Generic;
using System.Collections.Immutable;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.Classification;
using Microsoft.CodeAnalysis.Collections;
using Microsoft.CodeAnalysis.ErrorReporting;
using Microsoft.CodeAnalysis.FindSymbols;
using Microsoft.CodeAnalysis.FindSymbols.Finders;
using Microsoft.CodeAnalysis.FindUsages;
using Microsoft.CodeAnalysis.MetadataAsSource;
using Microsoft.CodeAnalysis.Options;
using Microsoft.CodeAnalysis.PooledObjects;
using Microsoft.CodeAnalysis.ReferenceHighlighting;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Microsoft.CodeAnalysis.Shared.TestHooks;
using Microsoft.CodeAnalysis.Text;
using Roslyn.LanguageServer.Protocol;
using Roslyn.Text.Adornments;
using Roslyn.Utilities;
using LSP = Roslyn.LanguageServer.Protocol;
 
namespace Microsoft.CodeAnalysis.LanguageServer.Handler
{
    internal sealed class FindUsagesLSPContext : FindUsagesContext
    {
        private readonly IProgress<SumType<VSInternalReferenceItem, LSP.Location>[]> _progress;
 
        private readonly Workspace _workspace;
        private readonly Document _document;
        private readonly int _position;
        private readonly IMetadataAsSourceFileService _metadataAsSourceFileService;
        private readonly IGlobalOptionService _globalOptions;
        private readonly bool _supportsVSExtensions;
 
        /// <summary>
        /// Methods in FindUsagesLSPContext can be called by multiple threads concurrently. We need this semaphore to
        /// ensure that we aren't making concurrent modifications to data such as _id and _definitionToId.
        /// </summary>
        private readonly SemaphoreSlim _semaphore = new(1);
 
        private readonly Dictionary<DefinitionItem, int> _definitionToId = [];
 
        /// <summary>
        /// Keeps track of definitions that cannot be reported without references and which we have
        /// not yet found a reference for.
        /// </summary>
        private readonly Dictionary<int, SumType<VSInternalReferenceItem, LSP.Location>> _definitionsWithoutReference = [];
 
        /// <summary>
        /// Set of the locations we've found references at.  We may end up with multiple references
        /// being reported for the same location.  For example, this can happen in multi-targeting 
        /// scenarios when there are symbols in files linked into multiple projects.  Those symbols
        /// may have references that themselves are in linked locations, leading to multiple references
        /// found at different virtual locations that the user considers at the same physical location.
        /// For now we filter out these duplicates to not clutter the UI.  If LSP supports the ability
        /// to override an already reported VSReferenceItem, we could also reissue the item with the
        /// additional information about all the projects it is found in.
        /// </summary>
        private readonly HashSet<(string? filePath, TextSpan span)> _referenceLocations = [];
 
        /// <summary>
        /// We report the results in chunks. A batch, if it contains results, is reported every 0.5s.
        /// </summary>
        private readonly AsyncBatchingWorkQueue<SumType<VSInternalReferenceItem, LSP.Location>> _workQueue;
 
        // Unique identifier given to each definition and reference.
        private int _id = 0;
 
        public FindUsagesLSPContext(
            IProgress<SumType<VSInternalReferenceItem, LSP.Location>[]> progress,
            Workspace workspace,
            Document document,
            int position,
            IMetadataAsSourceFileService metadataAsSourceFileService,
            IAsynchronousOperationListener asyncListener,
            IGlobalOptionService globalOptions,
            ClientCapabilities clientCapabilities,
            CancellationToken cancellationToken)
        {
            _progress = progress;
            _workspace = workspace;
            _document = document;
            _position = position;
            _metadataAsSourceFileService = metadataAsSourceFileService;
            _globalOptions = globalOptions;
            _supportsVSExtensions = clientCapabilities.HasVisualStudioLspCapability();
            _workQueue = new AsyncBatchingWorkQueue<SumType<VSInternalReferenceItem, LSP.Location>>(
                DelayTimeSpan.Medium, ReportReferencesAsync, asyncListener, cancellationToken);
        }
 
        // After all definitions/references have been found, wait here until all results have been reported.
        public override async ValueTask OnCompletedAsync(CancellationToken cancellationToken)
            => await _workQueue.WaitUntilCurrentBatchCompletesAsync().ConfigureAwait(false);
 
        public override async ValueTask OnDefinitionFoundAsync(DefinitionItem definition, CancellationToken cancellationToken)
        {
            using (await _semaphore.DisposableWaitAsync(cancellationToken).ConfigureAwait(false))
            {
                if (_definitionToId.ContainsKey(definition))
                {
                    return;
                }
 
                // Assigning a new id to the definition
                _id++;
                _definitionToId.Add(definition, _id);
 
                // Creating a new VSReferenceItem for the definition
                var definitionItem = await GenerateVSReferenceItemAsync(
                    definitionId: _id, id: _id, definition.SourceSpans.FirstOrNull(),
                    definition.DisplayableProperties, definition.GetClassifiedText(),
                    definition.Tags.GetFirstGlyph(), symbolUsageInfo: null, isWrittenTo: false, cancellationToken).ConfigureAwait(false);
 
                if (definitionItem != null)
                {
                    // If a definition shouldn't be included in the results list if it doesn't have references, we
                    // have to hold off on reporting it until later when we do find a reference.
                    if (definition.DisplayIfNoReferences)
                    {
                        _workQueue.AddWork(definitionItem.Value);
                    }
                    else
                    {
                        _definitionsWithoutReference.Add(_id, definitionItem.Value);
                    }
                }
            }
        }
 
        public override async ValueTask OnReferencesFoundAsync(IAsyncEnumerable<SourceReferenceItem> references, CancellationToken cancellationToken)
        {
            await foreach (var reference in references)
            {
                using (await _semaphore.DisposableWaitAsync(cancellationToken).ConfigureAwait(false))
                {
                    // Each reference should be associated with a definition. If this somehow isn't the
                    // case, we bail out early.
                    if (!_definitionToId.TryGetValue(reference.Definition, out var definitionId))
                        continue;
 
                    var documentSpan = reference.SourceSpan;
                    var document = documentSpan.Document;
 
                    // If this is reference to the same physical location we've already reported, just
                    // filter this out.  it will clutter the UI to show the same places.
                    if (!_referenceLocations.Add((document.FilePath, reference.SourceSpan.SourceSpan)))
                        continue;
 
                    // If the definition hasn't been reported yet, add it to our list of references to report.
                    if (_definitionsWithoutReference.TryGetValue(definitionId, out var definition))
                    {
                        _workQueue.AddWork(definition);
                        _definitionsWithoutReference.Remove(definitionId);
                    }
 
                    // give this reference a fresh id.
                    _id++;
 
                    // Creating a new VSReferenceItem for the reference
                    var referenceItem = await GenerateVSReferenceItemAsync(
                        definitionId, _id, reference.SourceSpan,
                        reference.AdditionalProperties, definitionText: null,
                        definitionGlyph: Glyph.None, reference.SymbolUsageInfo, reference.IsWrittenTo, cancellationToken).ConfigureAwait(false);
 
                    if (referenceItem != null)
                        _workQueue.AddWork(referenceItem.Value);
                }
            }
        }
 
        private async Task<SumType<VSInternalReferenceItem, LSP.Location>?> GenerateVSReferenceItemAsync(
            int definitionId,
            int id,
            DocumentSpan? documentSpan,
            ImmutableArray<(string key, string value)> properties,
            ClassifiedTextElement? definitionText,
            Glyph definitionGlyph,
            SymbolUsageInfo? symbolUsageInfo,
            bool isWrittenTo,
            CancellationToken cancellationToken)
        {
            // Getting the text for the Text property. If we somehow can't compute the text, that means we're probably dealing with a metadata
            // reference, and those don't show up in the results list in Roslyn FAR anyway.
            var text = await ComputeTextAsync(definitionId, documentSpan, definitionText, isWrittenTo, cancellationToken).ConfigureAwait(false);
            if (text == null)
                return null;
 
            var location = await ComputeLocationAsync(documentSpan, cancellationToken).ConfigureAwait(false);
 
            return _supportsVSExtensions
                ? CreateVsReference(definitionId, id, text, documentSpan, properties, definitionText, definitionGlyph, symbolUsageInfo, location)
                : location;
        }
 
        private static SumType<VSInternalReferenceItem, LSP.Location>? CreateVsReference(
            int definitionId,
            int id,
            ClassifiedTextElement text,
            DocumentSpan? documentSpan,
            ImmutableArray<(string key, string value)> properties,
            ClassifiedTextElement? definitionText,
            Glyph definitionGlyph,
            SymbolUsageInfo? symbolUsageInfo,
            LSP.Location? location)
        {
            // TO-DO: The Origin property should be added once Rich-Nav is completed.
            // https://github.com/dotnet/roslyn/issues/42847
            var result = new VSInternalReferenceItem
            {
                DefinitionId = definitionId,
                DefinitionText = definitionText,    // Only definitions should have a non-null DefinitionText
                DefinitionIcon = new ImageElement(definitionGlyph.ToLSPImageId()),
                Location = location,
                DisplayPath = location?.Uri.LocalPath,
                Id = id,
                Kind = symbolUsageInfo.HasValue ? ProtocolConversions.SymbolUsageInfoToReferenceKinds(symbolUsageInfo.Value) : [],
                ResolutionStatus = VSInternalResolutionStatusKind.ConfirmedAsReference,
                Text = text,
            };
 
            if (documentSpan is var (document, _))
            {
                result.DocumentName = document.Name;
                result.ProjectName = document.Project.Name;
            }
 
            foreach (var (key, value) in properties)
            {
                if (key == AbstractReferenceFinder.ContainingMemberInfoPropertyName)
                    result.ContainingMember = value;
                else if (key == AbstractReferenceFinder.ContainingTypeInfoPropertyName)
                    result.ContainingType = value;
            }
 
            return result;
        }
 
        private async Task<LSP.Location?> ComputeLocationAsync(DocumentSpan? documentSpan, CancellationToken cancellationToken)
        {
            // If we have no document span, our location may be in metadata.
            if (documentSpan != null)
            {
                // We do have a document span, so compute location normally.
                return await ProtocolConversions.DocumentSpanToLocationAsync(documentSpan.Value, cancellationToken).ConfigureAwait(false);
            }
 
            // If we have no document span, our location may be in metadata or may be a namespace.
            var symbol = await SymbolFinder.FindSymbolAtPositionAsync(_document, _position, cancellationToken).ConfigureAwait(false);
            if (symbol == null || symbol.Locations.IsEmpty || symbol.Kind == SymbolKind.Namespace)
            {
                // Either:
                // (1) We couldn't find the location in metadata and it's not in any of our known documents.
                // (2) The symbol is a namespace (and therefore has no location).
                return null;
            }
 
            var options = _globalOptions.GetMetadataAsSourceOptions();
            var declarationFile = await _metadataAsSourceFileService.GetGeneratedFileAsync(
                _workspace, _document.Project, symbol, signaturesOnly: true, options: options, cancellationToken: cancellationToken).ConfigureAwait(false);
 
            var linePosSpan = declarationFile.IdentifierLocation.GetLineSpan().Span;
 
            if (string.IsNullOrEmpty(declarationFile.FilePath))
            {
                return null;
            }
 
            try
            {
                return new LSP.Location
                {
                    Uri = ProtocolConversions.CreateAbsoluteUri(declarationFile.FilePath),
                    Range = ProtocolConversions.LinePositionToRange(linePosSpan),
                };
            }
            catch (UriFormatException e) when (FatalError.ReportAndCatch(e))
            {
                // We might reach this point if the file path is formatted incorrectly.
                return null;
            }
        }
 
        private async Task<ClassifiedTextElement?> ComputeTextAsync(
            int? definitionId,
            DocumentSpan? documentSpan,
            ClassifiedTextElement? definitionText,
            bool isWrittenTo,
            CancellationToken cancellationToken)
        {
            // General case
            if (documentSpan != null)
            {
                var document = documentSpan.Value.Document;
                var options = _globalOptions.GetClassificationOptions(document.Project.Language);
 
                var classifiedSpansAndHighlightSpan = await ClassifiedSpansAndHighlightSpanFactory.ClassifyAsync(
                    documentSpan.Value, classifiedSpans: null, options, cancellationToken).ConfigureAwait(false);
 
                var classifiedSpans = classifiedSpansAndHighlightSpan.ClassifiedSpans;
                var docText = await document.GetValueTextAsync(cancellationToken).ConfigureAwait(false);
                var classifiedTextRuns = GetClassifiedTextRuns(_id, definitionId, documentSpan.Value, isWrittenTo, classifiedSpans, docText);
 
                return new ClassifiedTextElement([.. classifiedTextRuns]);
            }
 
            // Certain definitions may not have a DocumentSpan, such as namespace and metadata definitions
            if (_id == definitionId)
            {
                return definitionText;
            }
 
            return null;
        }
 
        private static ClassifiedTextRun[] GetClassifiedTextRuns(
            int id,
            int? definitionId,
            DocumentSpan documentSpan,
            bool isWrittenTo,
            ImmutableArray<ClassifiedSpan> classifiedSpans,
            SourceText docText)
        {
            using var _ = ArrayBuilder<ClassifiedTextRun>.GetInstance(out var classifiedTextRuns);
            foreach (var span in classifiedSpans)
            {
                // Default case: Don't highlight. For example, if the user invokes FAR on 'x' in 'var x = 1', then 'var',
                // '=', and '1' should not be highlighted.
                string? markerTagType = null;
 
                // Case 1: Highlight this span of text. For example, if the user invokes FAR on 'x' in 'var x = 1',
                // then 'x' should be highlighted.
                if (span.TextSpan == documentSpan.SourceSpan)
                {
                    // Case 1a: Highlight a definition
                    if (id == definitionId)
                    {
                        markerTagType = ReferenceHighlightingConstants.DefinitionTagId;
                    }
                    // Case 1b: Highlight a written reference
                    else if (isWrittenTo)
                    {
                        markerTagType = ReferenceHighlightingConstants.WrittenReferenceTagId;
                    }
                    // Case 1c: Highlight a read reference
                    else
                    {
                        markerTagType = ReferenceHighlightingConstants.ReferenceTagId;
                    }
                }
 
                classifiedTextRuns.Add(new ClassifiedTextRun(
                    span.ClassificationType, docText.ToString(span.TextSpan), ClassifiedTextRunStyle.Plain, markerTagType));
            }
 
            return classifiedTextRuns.ToArray();
        }
 
        private ValueTask ReportReferencesAsync(ImmutableSegmentedList<SumType<VSInternalReferenceItem, LSP.Location>> referencesToReport, CancellationToken cancellationToken)
        {
            // We can report outside of the lock here since _progress is thread-safe.
            _progress.Report([.. referencesToReport]);
            return ValueTaskFactory.CompletedTask;
        }
    }
}