File: Navigation\AbstractDefinitionLocationService.cs
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Project: src\src\EditorFeatures\Core\Microsoft.CodeAnalysis.EditorFeatures.csproj (Microsoft.CodeAnalysis.EditorFeatures)
// 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.Collections.Generic;
using System.Collections.Immutable;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.Classification;
using Microsoft.CodeAnalysis.Editor.Host;
using Microsoft.CodeAnalysis.Editor.Shared.Utilities;
using Microsoft.CodeAnalysis.FindUsages;
using Microsoft.CodeAnalysis.GoToDefinition;
using Microsoft.CodeAnalysis.LanguageService;
using Microsoft.CodeAnalysis.PooledObjects;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Microsoft.CodeAnalysis.Shared.Utilities;
using Microsoft.CodeAnalysis.Text;
 
namespace Microsoft.CodeAnalysis.Navigation;
 
internal abstract partial class AbstractDefinitionLocationService(
    IThreadingContext threadingContext,
    IStreamingFindUsagesPresenter streamingPresenter) : IDefinitionLocationService
{
    private readonly IThreadingContext _threadingContext = threadingContext;
    private readonly IStreamingFindUsagesPresenter _streamingPresenter = streamingPresenter;
 
    private static Task<INavigableLocation?> GetNavigableLocationAsync(
        Document document, int position, CancellationToken cancellationToken)
    {
        var solution = document.Project.Solution;
        var workspace = solution.Workspace;
        var service = workspace.Services.GetRequiredService<IDocumentNavigationService>();
 
        return service.GetLocationForPositionAsync(
            workspace, document.Id, position, cancellationToken);
    }
 
    public async Task<DefinitionLocation?> GetDefinitionLocationAsync(Document document, int position, CancellationToken cancellationToken)
    {
        var symbolService = document.GetRequiredLanguageService<IGoToDefinitionSymbolService>();
 
        // We want to compute this as quickly as possible so that the symbol be squiggled and navigated to.  We
        // don't want to wait on expensive operations like computing source-generators or skeletons if we can avoid
        // it.  So first try with a frozen document, then fallback to a normal document.  This mirrors how go-to-def
        // works as well.
        return await GetDefinitionLocationWorkerAsync(document.WithFrozenPartialSemantics(cancellationToken)).ConfigureAwait(false) ??
               await GetDefinitionLocationWorkerAsync(document).ConfigureAwait(false);
 
        async ValueTask<DefinitionLocation?> GetDefinitionLocationWorkerAsync(Document document)
        {
            // We don't need nullable information to compute the symbol.  So avoid expensive work computing this.
            var semanticModel = await document.GetRequiredNullableDisabledSemanticModelAsync(cancellationToken).ConfigureAwait(false);
            return await GetControlFlowTargetLocationAsync(document, semanticModel).ConfigureAwait(false) ??
                   await GetSymbolLocationAsync(document, semanticModel).ConfigureAwait(false);
        }
 
        async ValueTask<DefinitionLocation?> GetControlFlowTargetLocationAsync(
            Document document, SemanticModel semanticModel)
        {
            var (controlFlowTarget, controlFlowSpan) = await symbolService.GetTargetIfControlFlowAsync(
                document, semanticModel, position, cancellationToken).ConfigureAwait(false);
            if (controlFlowTarget == null)
                return null;
 
            var location = await GetNavigableLocationAsync(
                document, controlFlowTarget.Value, cancellationToken).ConfigureAwait(false);
            return location is null ? null : new DefinitionLocation(location, new DocumentSpan(document, controlFlowSpan));
        }
 
        async ValueTask<DefinitionLocation?> GetSymbolLocationAsync(
            Document document, SemanticModel semanticModel)
        {
            // Try to compute the referenced symbol and attempt to go to definition for the symbol.
            var (symbol, project, span) = await symbolService.GetSymbolProjectAndBoundSpanAsync(
                document, semanticModel, position, cancellationToken).ConfigureAwait(false);
            if (symbol is null)
                return null;
 
            // if the symbol only has a single source location, and we're already on it,
            // try to see if there's a better symbol we could navigate to.
            var remappedLocation = await GetAlternativeLocationIfAlreadyOnDefinitionAsync(
                project, position, symbol, originalDocument: document, cancellationToken).ConfigureAwait(false);
            if (remappedLocation != null)
                return new DefinitionLocation(remappedLocation, new DocumentSpan(document, span));
 
            var isThirdPartyNavigationAllowed = await IsThirdPartyNavigationAllowedAsync(
                symbol, position, document, cancellationToken).ConfigureAwait(false);
 
            var solution = project.Solution;
            var regularDefinitions = await GoToDefinitionFeatureHelpers.GetDefinitionsAsync(
                symbol, solution, isThirdPartyNavigationAllowed, cancellationToken).ConfigureAwait(false);
            var interceptorDefinitions = await GetInterceptorDefinitionsAsync(
                solution, document, span, cancellationToken).ConfigureAwait(false);
 
            var symbolDisplayName = FindUsagesHelpers.GetDisplayName(symbol);
            var title = interceptorDefinitions.Length == 0
                ? string.Format(EditorFeaturesResources._0_declarations, symbolDisplayName)
                : string.Format(EditorFeaturesResources._0_declarations_and_interceptors, symbolDisplayName);
 
            var allDefinitions = regularDefinitions.Concat(interceptorDefinitions);
            var location = await _streamingPresenter.GetStreamingLocationAsync(
                _threadingContext, solution.Workspace, title, allDefinitions, cancellationToken).ConfigureAwait(false);
 
            if (location is null)
                return null;
 
            return new DefinitionLocation(location, new DocumentSpan(document, span));
        }
 
        async ValueTask<ImmutableArray<DefinitionItem>> GetInterceptorDefinitionsAsync(
            Solution solution, Document document, TextSpan span, CancellationToken cancellationToken)
        {
            var semanticFacts = document.GetRequiredLanguageService<ISemanticFactsService>();
 
            var interceptorSymbol = await semanticFacts.GetInterceptorSymbolAsync(document, span.Start, cancellationToken).ConfigureAwait(false);
            return await GoToDefinitionFeatureHelpers.GetDefinitionsAsync(
                interceptorSymbol, solution, thirdPartyNavigationAllowed: false, cancellationToken).ConfigureAwait(false);
        }
    }
 
    /// <summary>
    /// Attempts to find a better definition for the symbol, if the user is already on the definition of it.
    /// </summary>
    /// <param name="project">The project context to use for finding symbols</param>
    /// <param name="originalDocument">The document the user is navigating from. This may not be part of the project supplied.</param>
    private async Task<INavigableLocation?> GetAlternativeLocationIfAlreadyOnDefinitionAsync(
        Project project, int position, ISymbol symbol, Document originalDocument, CancellationToken cancellationToken)
    {
        var solution = project.Solution;
 
        if (symbol.DeclaringSyntaxReferences is not [{ SyntaxTree: { } definitionTree, Span: var definitionSpan }])
            return null;
 
        if (!definitionSpan.IntersectsWith(position))
            return null;
 
        var definitionDocument = solution.GetDocument(definitionTree);
        if (definitionDocument != originalDocument)
            return null;
 
        // Ok, we were already on the definition. Look for better symbols we could show results for instead. This can be
        // expanded with other mappings in the future if appropriate.
        return await TryGetExplicitInterfaceLocationAsync().ConfigureAwait(false) ??
               await TryGetInterceptedLocationAsync().ConfigureAwait(false) ??
               await TryGetOtherPartOfPartialAsync().ConfigureAwait(false);
 
        async ValueTask<INavigableLocation?> TryGetExplicitInterfaceLocationAsync()
        {
            var interfaceImpls = symbol.ExplicitOrImplicitInterfaceImplementations();
            if (interfaceImpls.Length == 0)
                return null;
 
            var title = string.Format(EditorFeaturesResources._0_implemented_members,
                FindUsagesHelpers.GetDisplayName(symbol));
 
            using var _ = ArrayBuilder<DefinitionItem>.GetInstance(out var builder);
            foreach (var impl in interfaceImpls)
            {
                builder.AddRange(await GoToDefinitionFeatureHelpers.GetDefinitionsAsync(
                    impl, solution, thirdPartyNavigationAllowed: false, cancellationToken).ConfigureAwait(false));
            }
 
            var definitions = builder.ToImmutable();
 
            return await _streamingPresenter.GetStreamingLocationAsync(
                _threadingContext, solution.Workspace, title, definitions, cancellationToken).ConfigureAwait(false);
        }
 
        async ValueTask<INavigableLocation?> TryGetInterceptedLocationAsync()
        {
            if (symbol is not IMethodSymbol method)
                return null;
 
            // Find attributes of the form: [InterceptsLocationAttribute(version: 1, data: "...")];
 
            var attributes = method.GetAttributes();
            var interceptsLocationDatas = InterceptsLocationUtilities.GetInterceptsLocationData(attributes);
            if (interceptsLocationDatas.Length == 0)
                return null;
 
            using var _ = ArrayBuilder<DocumentSpan>.GetInstance(out var documentSpans);
 
            foreach (var (contentHash, position) in interceptsLocationDatas)
            {
                var document = await project.GetDocumentAsync(contentHash, cancellationToken).ConfigureAwait(false);
 
                if (document != null)
                {
                    var root = await document.GetRequiredSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
 
                    if (position >= 0 && position < root.FullSpan.Length)
                    {
                        var token = root.FindToken(position);
                        documentSpans.Add(new DocumentSpan(document, token.Span));
                    }
                }
            }
 
            documentSpans.RemoveDuplicates();
 
            if (documentSpans.Count == 0)
            {
                return null;
            }
            else if (documentSpans.Count == 1)
            {
                // Just one document span this mapped to.  Navigate directly do that.
                return await documentSpans[0].GetNavigableLocationAsync(cancellationToken).ConfigureAwait(false);
            }
            else
            {
                var title = string.Format(EditorFeaturesResources._0_intercepted_locations,
                    FindUsagesHelpers.GetDisplayName(method));
 
                var definitionItem = method.ToNonClassifiedDefinitionItem(solution, includeHiddenLocations: true);
 
                var referenceItems = new List<SourceReferenceItem>(capacity: documentSpans.Count);
                var classificationOptions = ClassificationOptions.Default with { ClassifyObsoleteSymbols = false };
                foreach (var documentSpan in documentSpans)
                {
                    var classifiedSpans = await ClassifiedSpansAndHighlightSpanFactory.ClassifyAsync(
                        documentSpan, classifiedSpans: null, classificationOptions, cancellationToken).ConfigureAwait(false);
 
                    referenceItems.Add(new SourceReferenceItem(
                        definitionItem, documentSpan, classifiedSpans, SymbolUsageInfo.None, additionalProperties: []));
                }
 
                // Multiple document spans this mapped to.  Show them all.
                return new NavigableLocation(async (options, cancellationToken) =>
                {
                    // Can only navigate or present items on UI thread.
                    await _threadingContext.JoinableTaskFactory.SwitchToMainThreadAsync(cancellationToken);
 
                    // We have multiple definitions, or we have definitions with multiple locations. Present this to the
                    // user so they can decide where they want to go to.
                    //
                    // We ignore the cancellation token returned by StartSearch as we're in a context where
                    // we've computed all the results and we're synchronously populating the UI with it.
                    var (context, _) = _streamingPresenter.StartSearch(title, new StreamingFindUsagesPresenterOptions(SupportsReferences: true));
                    try
                    {
                        await context.OnDefinitionFoundAsync(definitionItem, cancellationToken).ConfigureAwait(false);
                        await context.OnReferencesFoundAsync(referenceItems.AsAsyncEnumerable(), cancellationToken).ConfigureAwait(false);
                    }
                    finally
                    {
                        await context.OnCompletedAsync(cancellationToken).ConfigureAwait(false);
                    }
 
                    return true;
                });
            }
        }
        async ValueTask<INavigableLocation?> TryGetOtherPartOfPartialAsync()
        {
            ISymbol? otherPart = symbol is IMethodSymbol method ? method.PartialDefinitionPart ?? method.PartialImplementationPart : null;
            otherPart ??= symbol is IPropertySymbol property ? property.PartialDefinitionPart ?? property.PartialImplementationPart : null;
 
            if (otherPart is null || Equals(symbol, otherPart))
                return null;
 
            if (otherPart.Locations is not [{ SourceTree: { } sourceTree, SourceSpan: var span }])
                return null;
 
            var document = solution.GetDocument(sourceTree);
            if (document is null)
                return null;
 
            var documentSpan = new DocumentSpan(document, span);
            return await documentSpan.GetNavigableLocationAsync(cancellationToken).ConfigureAwait(false);
        }
    }
 
    private static async Task<bool> IsThirdPartyNavigationAllowedAsync(
        ISymbol symbolToNavigateTo, int caretPosition, Document document, CancellationToken cancellationToken)
    {
        var syntaxRoot = document.GetRequiredSyntaxRootSynchronously(cancellationToken);
        var syntaxFactsService = document.GetRequiredLanguageService<ISyntaxFactsService>();
        var containingTypeDeclaration = syntaxFactsService.GetContainingTypeDeclaration(syntaxRoot, caretPosition);
 
        if (containingTypeDeclaration != null)
        {
            var semanticModel = await document.GetRequiredNullableDisabledSemanticModelAsync(cancellationToken).ConfigureAwait(false);
 
            // Allow third parties to navigate to all symbols except types/constructors
            // if we are navigating from the corresponding type.
 
            if (semanticModel.GetDeclaredSymbol(containingTypeDeclaration, cancellationToken) is ITypeSymbol containingTypeSymbol &&
                (symbolToNavigateTo is ITypeSymbol || symbolToNavigateTo.IsConstructor()))
            {
                var candidateTypeSymbol = symbolToNavigateTo is ITypeSymbol
                    ? symbolToNavigateTo
                    : symbolToNavigateTo.ContainingType;
 
                if (Equals(containingTypeSymbol, candidateTypeSymbol))
                {
                    // We are navigating from the same type, so don't allow third parties to perform the navigation.
                    // This ensures that if we navigate to a class from within that class, we'll stay in the same file
                    // rather than navigate to, say, XAML.
                    return false;
                }
            }
        }
 
        return true;
    }
}