Support inlay hints

build/Settings.props

@@ -2,7 +2,7 @@
 <Project ToolsVersion="14.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
 
   <PropertyGroup>
-    <LangVersion>9.0</LangVersion>
+    <LangVersion>10.0</LangVersion>
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
     <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
     <GenerateAssemblyInfo>true</GenerateAssemblyInfo>

src/OmniSharp.Abstractions/LoggingExtensions/LoggingExtensions.cs

@@ -0,0 +1,77 @@
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Text;
+
+#nullable enable
+
+namespace Microsoft.Extensions.Logging
+{
+    public static class LoggingExtensions
+    {
+        public static void Log(this ILogger logger, LogLevel logLevel, [InterpolatedStringHandlerArgument("logger", "logLevel")] LoggerInterpolatedStringHandler handler)
+        {
+            logger.Log(logLevel, handler.ToString());
+        }
+    }
+
+    [InterpolatedStringHandler]
+    public struct LoggerInterpolatedStringHandler
+    {
+        private readonly StringBuilder? _builder;
+        public LoggerInterpolatedStringHandler(int literalLength, int formattedCount, ILogger logger, LogLevel level, out bool shouldAppend)
+        {
+            if (logger.IsEnabled(level))
+            {
+                shouldAppend = true;
+                _builder = new(literalLength);
+            }
+            else
+            {
+                shouldAppend = false;
+                _builder = null;
+            }
+        }
+
+        public void AppendLiteral(string literal)
+        {
+            Debug.Assert(_builder != null);
+            _builder!.Append(literal);
+        }
+
+        public void AppendFormatted<T>(T t)
+        {
+            Debug.Assert(_builder != null);
+            _builder!.Append(t?.ToString());
+        }
+
+        public void AppendFormatted<T>(T t, int alignment, string format)
+        {
+            Debug.Assert(_builder != null);
+            _builder!.Append(string.Format($"{{0,{alignment}:{format}}}", t));
+        }
+
+        public override string ToString()
+        {
+            return _builder?.ToString() ?? string.Empty;
+        }
+    }
+}
+
+#if !NET6_0_OR_GREATER
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct, AllowMultiple = false, Inherited = false)]
+    internal sealed class InterpolatedStringHandlerAttribute : Attribute
+    {
+    }
+    [AttributeUsage(AttributeTargets.Parameter, AllowMultiple = false, Inherited = false)]
+    internal sealed class InterpolatedStringHandlerArgumentAttribute : Attribute
+    {
+        public InterpolatedStringHandlerArgumentAttribute(string argument) => Arguments = new string[] { argument };
+
+        public InterpolatedStringHandlerArgumentAttribute(params string[] arguments) => Arguments = arguments;
+
+        public string[] Arguments { get; }
+    }
+}
+#endif

src/OmniSharp.Abstractions/Models/v1/InlayHints/InlayHint.cs

@@ -0,0 +1,35 @@
+using OmniSharp.Models.V2;
+
+#nullable enable annotations
+
+namespace OmniSharp.Models.v1.InlayHints;
+
+public sealed record InlayHint
+{
+    public Point Position { get; set; }
+    public string Label { get; set; }
+    public string? Tooltip { get; set; }
+    public (string SolutionVersion, int Position) Data { get; set; }
+
+#nullable enable
+    public override string ToString()
+    {
+        return $"InlineHint {{ {nameof(Position)} = {Position}, {nameof(Label)} = {Label}, {nameof(Tooltip)} = {Tooltip} }}";
+    }
+
+    public bool Equals(InlayHint? other)
+    {
+        if (ReferenceEquals(this, other)) return true;
+        if (other is null) return false;
+
+        return Position == other.Position && Label == other.Label && Tooltip == other.Tooltip;
+    }
+
+    public override int GetHashCode() => (Position, Label, Tooltip).GetHashCode();
+}
+
+public enum InlayHintKind
+{
+    Type = 1,
+    Parameter = 2,
+}

src/OmniSharp.Abstractions/Models/v1/InlayHints/InlayHintRequest.cs

@@ -0,0 +1,13 @@
+using OmniSharp.Mef;
+using OmniSharp.Models.V2;
+
+#nullable enable annotations
+
+namespace OmniSharp.Models.v1.InlayHints;
+
+
+[OmniSharpEndpoint(OmniSharpEndpoints.InlayHint, typeof(InlayHintRequest), typeof(InlayHintResponse))]
+public record InlayHintRequest : IRequest
+{
+    public Location Location { get; set; }
+}

src/OmniSharp.Abstractions/Models/v1/InlayHints/InlayHintResolveRequest.cs

@@ -0,0 +1,9 @@
+using OmniSharp.Mef;
+
+namespace OmniSharp.Models.v1.InlayHints;
+
+[OmniSharpEndpoint(OmniSharpEndpoints.InlayHintResolve, typeof(InlayHintResolveRequest), typeof(InlayHint))]
+public record InlayHintResolveRequest : IRequest
+{
+    public InlayHint Hint { get; set; }
+}

src/OmniSharp.Abstractions/Models/v1/InlayHints/InlayHintResponse.cs

@@ -0,0 +1,11 @@
+#nullable enable annotations
+
+using System.Collections.Generic;
+
+namespace OmniSharp.Models.v1.InlayHints;
+
+public record InlayHintResponse
+{
+    public static readonly InlayHintResponse None = new() { InlayHints = new() };
+    public List<InlayHint> InlayHints { get; set; }
+}

src/OmniSharp.Abstractions/OmniSharpEndpoints.cs

@@ -56,6 +56,9 @@ public static class OmniSharpEndpoints
         public const string UpdateSourceGeneratedFile = "/updatesourcegeneratedfile";
         public const string SourceGeneratedFileClosed = "/sourcegeneratedfileclosed";
 
+        public const string InlayHint = "/inlayHint";
+        public const string InlayHintResolve = "/inlayHint/resolve";
+
         public static class V2
         {
             public const string GetCodeActions = "/v2/getcodeactions";

src/OmniSharp.Roslyn.CSharp/Services/InlayHints/InlayHintService.cs

@@ -0,0 +1,186 @@
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Composition;
+using System.Diagnostics.CodeAnalysis;
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.ExternalAccess.OmniSharp.InlineHints;
+using Microsoft.CodeAnalysis.Text;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
+using OmniSharp.Extensions;
+using OmniSharp.Mef;
+using OmniSharp.Models.v1.InlayHints;
+using OmniSharp.Options;
+using OmniSharp.Roslyn.CSharp.Helpers;
+
+#nullable enable
+
+namespace OmniSharp.Roslyn.CSharp.Services.InlayHints;
+
+[Shared]
+[OmniSharpHandler(OmniSharpEndpoints.InlayHint, LanguageNames.CSharp)]
+[OmniSharpHandler(OmniSharpEndpoints.InlayHintResolve, LanguageNames.CSharp)]
+internal class InlayHintService :
+    IRequestHandler<InlayHintRequest, InlayHintResponse>,
+    IRequestHandler<InlayHintResolveRequest, InlayHint>
+{
+    private readonly OmniSharpWorkspace _workspace;
+    private readonly IOptionsMonitor<OmniSharpOptions> _omniSharpOptions;
+    private readonly ILogger _logger;
+    private readonly InlineHintCache _cache;
+    private readonly FormattingOptions _formattingOptions;
+
+    [ImportingConstructor]
+    public InlayHintService(OmniSharpWorkspace workspace, FormattingOptions formattingOptions, ILoggerFactory loggerFactory, IOptionsMonitor<OmniSharpOptions> omniSharpOptions)
+    {
+        _workspace = workspace;
+        _formattingOptions = formattingOptions;
+        _logger = loggerFactory.CreateLogger<InlayHintService>();
+        _omniSharpOptions = omniSharpOptions;
+        _cache = new(_logger);
+    }
+    public async Task<InlayHintResponse> Handle(InlayHintRequest request)
+    {
+        var document = _workspace.GetDocument(request.Location.FileName);
+        if (document == null)
+        {
+            _logger.Log(LogLevel.Warning, $"Inlay hints requested for document not in workspace {request.Location}");
+            return InlayHintResponse.None;
+        }
+
+        var sourceText = await document.GetTextAsync();
+        var mappedSpan = sourceText.GetSpanFromRange(request.Location.Range);
+
+        var inlayHintsOptions = _omniSharpOptions.CurrentValue.RoslynExtensionsOptions.InlayHintsOptions;
+        var options = new OmniSharpInlineHintsOptions
+        {
+            ParameterOptions = new()
+            {
+                EnabledForParameters = inlayHintsOptions.EnableForParameters,
+                ForIndexerParameters = inlayHintsOptions.ForIndexerParameters,
+                ForLiteralParameters = inlayHintsOptions.ForLiteralParameters,
+                ForObjectCreationParameters = inlayHintsOptions.ForObjectCreationParameters,
+                ForOtherParameters = inlayHintsOptions.ForOtherParameters,
+                SuppressForParametersThatDifferOnlyBySuffix = inlayHintsOptions.SuppressForParametersThatDifferOnlyBySuffix,
+                SuppressForParametersThatMatchArgumentName = inlayHintsOptions.SuppressForParametersThatMatchArgumentName,
+                SuppressForParametersThatMatchMethodIntent = inlayHintsOptions.SuppressForParametersThatMatchMethodIntent,
+            },
+            TypeOptions = new()
+            {
+                EnabledForTypes = inlayHintsOptions.EnableForTypes,
+                ForImplicitObjectCreation = inlayHintsOptions.ForImplicitObjectCreation,
+                ForImplicitVariableTypes = inlayHintsOptions.ForImplicitVariableTypes,
+                ForLambdaParameterTypes = inlayHintsOptions.ForLambdaParameterTypes,
+            }
+        };
+
+        var hints = await OmniSharpInlineHintsService.GetInlineHintsAsync(document, mappedSpan, options, CancellationToken.None);
+
+        var solutionVersion = _workspace.CurrentSolution.Version;
+
+        return new()
+        {
+            InlayHints = _cache.MapAndCacheHints(hints, document, solutionVersion, sourceText)
+        };
+    }
+
+    public async Task<InlayHint> Handle(InlayHintResolveRequest request)
+    {
+        if (!_cache.TryGetFromCache(request.Hint, out var roslynHint, out var document))
+        {
+            return request.Hint;
+        }
+
+        var descriptionTags = await roslynHint.GetDescrptionAsync(document, CancellationToken.None);
+        StringBuilder stringBuilder = new StringBuilder();
+        MarkdownHelpers.TaggedTextToMarkdown(
+            descriptionTags,
+            stringBuilder,
+            _formattingOptions,
+            MarkdownFormat.FirstLineAsCSharp,
+            out _);
+
+        return request.Hint with
+        {
+            Tooltip = stringBuilder.ToString(),
+        };
+    }
+
+    private class InlineHintCache
+    {
+        private readonly object _lock = new();
+        private string? _currentVersionString;
+        private List<(OmniSharpInlineHint Hint, Document Document)>? _hints;
+        private readonly ILogger _logger;
+
+        public InlineHintCache(ILogger logger)
+        {
+            _logger = logger;
+        }
+
+        public List<InlayHint> MapAndCacheHints(ImmutableArray<OmniSharpInlineHint> roslynHints, Document document, VersionStamp solutionVersion, SourceText text)
+        {
+            var resultList = new List<InlayHint>();
+            var solutionVersionString = solutionVersion.ToString();
+            lock (_lock)
+            {
+                var hintsList = _currentVersionString == solutionVersionString
+                    ? _hints
+                    : new();
+
+                foreach (var hint in roslynHints)
+                {
+                    var position = hintsList!.Count;
+                    resultList.Add(new InlayHint()
+                    {
+                        Label = string.Concat(hint.DisplayParts),
+                        Position = text.GetPointFromPosition(hint.Span.End),
+                        Data = (solutionVersionString, position)
+                    });
+
+                    hintsList.Add((hint, document));
+                }
+
+                _currentVersionString = solutionVersionString;
+                _hints = hintsList;
+            }
+
+            return resultList;
+        }
+
+        public bool TryGetFromCache(InlayHint hint, out OmniSharpInlineHint roslynHint, [NotNullWhen(true)] out Document? document)
+        {
+            (roslynHint, document) = (default, null);
+            lock (_lock)
+            {
+                if (_hints is null)
+                {
+                    _logger.LogWarning("Attempted to resolve hint before hints were requested");
+                    return false;
+                }
+
+                if (_currentVersionString == hint.Data.SolutionVersion)
+                {
+                    if (hint.Data.Position >= _hints.Count)
+                    {
+                        _logger.LogWarning("Hint position is not found in the list");
+                        roslynHint = default;
+                        return false;
+                    }
+
+                    (roslynHint, document) = _hints[hint.Data.Position];
+                    return true;
+                }
+                else
+                {
+                    _logger.LogInformation("Requested hint for outdated solution version");
+                    roslynHint = default;
+                    return false;
+                }
+            }
+        }
+    }
+}

src/OmniSharp.Shared/Options/InlayHintsOptions.cs

@@ -0,0 +1,35 @@
+namespace OmniSharp.Options
+{
+    public struct InlayHintsOptions
+    {
+        public static readonly InlayHintsOptions AllOn = new()
+        {
+            EnableForParameters = true,
+            ForLiteralParameters = true,
+            ForIndexerParameters = true,
+            ForObjectCreationParameters = true,
+            ForOtherParameters = true,
+            SuppressForParametersThatDifferOnlyBySuffix = true,
+            SuppressForParametersThatMatchMethodIntent = true,
+            SuppressForParametersThatMatchArgumentName = true,
+            EnableForTypes = true,
+            ForImplicitVariableTypes = true,
+            ForLambdaParameterTypes = true,
+            ForImplicitObjectCreation = true
+        };
+
+        public bool EnableForParameters { get; set; }
+        public bool ForLiteralParameters { get; set; }
+        public bool ForIndexerParameters { get; set; }
+        public bool ForObjectCreationParameters { get; set; }
+        public bool ForOtherParameters { get; set; }
+        public bool SuppressForParametersThatDifferOnlyBySuffix { get; set; }
+        public bool SuppressForParametersThatMatchMethodIntent { get; set; }
+        public bool SuppressForParametersThatMatchArgumentName { get; set; }
+
+        public bool EnableForTypes { get; set; }
+        public bool ForImplicitVariableTypes { get; set; }
+        public bool ForLambdaParameterTypes { get; set; }
+        public bool ForImplicitObjectCreation { get; set; }
+    }
+}

src/OmniSharp.Shared/Options/RoslynExtensionsOptions.cs

@@ -14,6 +14,7 @@ public class RoslynExtensionsOptions : OmniSharpExtensionsOptions
         public int DocumentAnalysisTimeoutMs { get; set; } = 30 * 1000;
         public int DiagnosticWorkersThreadCount { get; set; } = Math.Max(1, (int)(Environment.ProcessorCount * 0.75)); // Use 75% of available processors by default (but at least one)
         public bool AnalyzeOpenDocumentsOnly { get; set; }
+        public InlayHintsOptions InlayHintsOptions { get; set; } = new();
     }
 
     public class OmniSharpExtensionsOptions