Enable C# nullable reference types in LanguageServer project (#645)

* Enable nullable in LanguageServer.csproj

* Update nullables in Communication.cs

* Update nullables in EditorState.cs and ProjectLoader.cs

* Update nullables in FileSystemWatcher.cs

* Use SelectNotNull in FileSystemWatcher.cs

* Update nullables in LanguageServer.cs and Utils.cs

* Update nullables in Program.cs

* Fix remaining nullable errors

* Avoid extra null check

* Add LanguageServer to InternalsVisibleTo

* Fix signing

Author: bamarsha

src/Common/DelaySign.cs

@@ -1,27 +1,10 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT License.
 
+#if SIGNED
 using System.Reflection;
 
 // Attributes for delay-signing
-#if SIGNED
-[assembly:AssemblyKeyFile("..\\..\\..\\build\\267DevDivSNKey2048.snk")]
-[assembly:AssemblyDelaySign(true)]
-#endif
-
-internal static class SigningConstants
-{
-#if SIGNED
-    public const string PublicKey = ", PublicKey=" +
-        "002400000c800000140100000602000000240000525341310008000001000100613399aff18ef1" +
-        "a2c2514a273a42d9042b72321f1757102df9ebada69923e2738406c21e5b801552ab8d200a65a2" +
-        "35e001ac9adc25f2d811eb09496a4c6a59d4619589c69f5baf0c4179a47311d92555cd006acc8b" +
-        "5959f2bd6e10e360c34537a1d266da8085856583c85d81da7f3ec01ed9564c58d93d713cd0172c" +
-        "8e23a10f0239b80c96b07736f5d8b022542a4e74251a5f432824318b3539a5a087f8e53d2f135f" +
-        "9ca47f3bb2e10aff0af0849504fb7cea3ff192dc8de0edad64c68efde34c56d302ad55fd6e80f3" +
-        "02d5efcdeae953658d3452561b5f36c542efdbdd9f888538d374cef106acf7d93a4445c3c73cd9" +
-        "11f0571aaf3d54da12b11ddec375b3";
-#else
-    public const string PublicKey = "";
+[assembly: AssemblyKeyFile("..\\..\\..\\build\\267DevDivSNKey2048.snk")]
+[assembly: AssemblyDelaySign(true)]
 #endif
-}

src/Common/SigningConstants.cs

@@ -0,0 +1,19 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+internal static class SigningConstants
+{
+#if SIGNED
+    public const string PublicKey = ", PublicKey=" +
+        "002400000c800000140100000602000000240000525341310008000001000100613399aff18ef1" +
+        "a2c2514a273a42d9042b72321f1757102df9ebada69923e2738406c21e5b801552ab8d200a65a2" +
+        "35e001ac9adc25f2d811eb09496a4c6a59d4619589c69f5baf0c4179a47311d92555cd006acc8b" +
+        "5959f2bd6e10e360c34537a1d266da8085856583c85d81da7f3ec01ed9564c58d93d713cd0172c" +
+        "8e23a10f0239b80c96b07736f5d8b022542a4e74251a5f432824318b3539a5a087f8e53d2f135f" +
+        "9ca47f3bb2e10aff0af0849504fb7cea3ff192dc8de0edad64c68efde34c56d302ad55fd6e80f3" +
+        "02d5efcdeae953658d3452561b5f36c542efdbdd9f888538d374cef106acf7d93a4445c3c73cd9" +
+        "11f0571aaf3d54da12b11ddec375b3";
+#else
+    public const string PublicKey = "";
+#endif
+}

src/QsCompiler/CompilationManager/ProjectManager.cs

@@ -5,6 +5,7 @@
 using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Collections.Immutable;
+using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using System.Linq;
 using System.Reflection;
@@ -45,7 +46,7 @@ public ProjectProperties(
 
     public class ProjectInformation
     {
-        public delegate bool Loader(Uri projectFile, out ProjectInformation projectInfo);
+        public delegate bool Loader(Uri projectFile, [NotNullWhen(true)] out ProjectInformation? projectInfo);
 
         internal readonly ProjectProperties Properties;
         public readonly ImmutableArray<string> SourceFiles;
@@ -904,10 +905,9 @@ public Task ProjectChangedOnDiskAsync(
             // TODO: allow to cancel this task via cancellation token?
             return this.load.QueueForExecutionAsync(() =>
             {
-                var loaded = projectLoader(projectFile, out ProjectInformation info);
                 var existing = this.projects.TryRemove(projectFile, out Project current) ? current : null;
 
-                if (!loaded)
+                if (!projectLoader(projectFile, out var info))
                 {
                     existing?.LoadProjectAsync(
                         ImmutableDictionary<Uri, Uri?>.Empty,
@@ -986,7 +986,7 @@ public Task AssemblyChangedOnDiskAsync(Uri dllPath)
         /// if the modified file is a source file of that project and not open in the editor
         /// (i.e. openInEditor is null or returns null for that file) at the time of execution.
         /// </summary>
-        public Task SourceFileChangedOnDiskAsync(Uri sourceFile, Func<Uri, FileContentManager>? openInEditor = null)
+        public Task SourceFileChangedOnDiskAsync(Uri sourceFile, Func<Uri, FileContentManager?>? openInEditor = null)
         {
             if (sourceFile == null)
             {
@@ -1061,7 +1061,7 @@ public Task ManagerTaskAsync(Uri file, Action<CompilationUnitManager, bool> exec
         /// or if the specified position is not a valid position within the file,
         /// or if a file affected by the rename operation belongs to several compilation units.
         /// </summary>
-        public WorkspaceEdit? Rename(RenameParams param, bool versionedChanges) // versionedChanges is unused (WorkspaceEdit contains both Changes and DocumentChanges, but the version nr is null)
+        public WorkspaceEdit? Rename(RenameParams? param, bool versionedChanges) // versionedChanges is unused (WorkspaceEdit contains both Changes and DocumentChanges, but the version nr is null)
         {
             if (param?.TextDocument?.Uri == null)
             {
@@ -1111,7 +1111,7 @@ public Task ManagerTaskAsync(Uri file, Action<CompilationUnitManager, bool> exec
         /// Fails silently without logging anything if an exception occurs upon evaluating the query
         /// (occasional failures are to be expected as the evaluation is a readonly query running in parallel to the ongoing processing).
         /// </summary>
-        public Location? DefinitionLocation(TextDocumentPositionParams param) =>
+        public Location? DefinitionLocation(TextDocumentPositionParams? param) =>
             this.Manager(param?.TextDocument?.Uri)?.FileQuery(
                 param?.TextDocument, (file, c) => file.DefinitionLocation(c, param?.Position?.ToQSharp()), suppressExceptionLogging: true);
 
@@ -1125,7 +1125,7 @@ public Task ManagerTaskAsync(Uri file, Action<CompilationUnitManager, bool> exec
         /// Fails silently without logging anything if an exception occurs upon evaluating the query
         /// (occasional failures are to be expected as the evaluation is a readonly query running in parallel to the ongoing processing).
         /// </summary>
-        public SignatureHelp? SignatureHelp(TextDocumentPositionParams param, MarkupKind format = MarkupKind.PlainText) =>
+        public SignatureHelp? SignatureHelp(TextDocumentPositionParams? param, MarkupKind format = MarkupKind.PlainText) =>
             this.Manager(param?.TextDocument?.Uri)?.FileQuery(
                 param?.TextDocument, (file, c) => file.SignatureHelp(c, param?.Position?.ToQSharp(), format), suppressExceptionLogging: true);
 
@@ -1138,7 +1138,7 @@ public Task ManagerTaskAsync(Uri file, Action<CompilationUnitManager, bool> exec
         /// Fails silently without logging anything if an exception occurs upon evaluating the query
         /// (occasional failures are to be expected as the evaluation is a readonly query running in parallel to the ongoing processing).
         /// </summary>
-        public Hover? HoverInformation(TextDocumentPositionParams param, MarkupKind format = MarkupKind.PlainText) =>
+        public Hover? HoverInformation(TextDocumentPositionParams? param, MarkupKind format = MarkupKind.PlainText) =>
             this.Manager(param?.TextDocument?.Uri)?.FileQuery(
                 param?.TextDocument, (file, c) => file.HoverInformation(c, param?.Position?.ToQSharp(), format), suppressExceptionLogging: true);
 
@@ -1151,7 +1151,7 @@ public Task ManagerTaskAsync(Uri file, Action<CompilationUnitManager, bool> exec
         /// Fails silently without logging anything if an exception occurs upon evaluating the query
         /// (occasional failures are to be expected as the evaluation is a readonly query running in parallel to the ongoing processing).
         /// </summary>
-        public DocumentHighlight[]? DocumentHighlights(TextDocumentPositionParams param) =>
+        public DocumentHighlight[]? DocumentHighlights(TextDocumentPositionParams? param) =>
             this.Manager(param?.TextDocument?.Uri)?.FileQuery(
                 param?.TextDocument, (file, c) => file.DocumentHighlights(c, param?.Position?.ToQSharp()), suppressExceptionLogging: true);
 
@@ -1164,7 +1164,7 @@ public Task ManagerTaskAsync(Uri file, Action<CompilationUnitManager, bool> exec
         /// Fails silently without logging anything if an exception occurs upon evaluating the query
         /// (occasional failures are to be expected as the evaluation is a readonly query running in parallel to the ongoing processing).
         /// </summary>
-        public Location[]? SymbolReferences(ReferenceParams param) =>
+        public Location[]? SymbolReferences(ReferenceParams? param) =>
             this.Manager(param?.TextDocument?.Uri)?.FileQuery(
                 param?.TextDocument, (file, c) => file.SymbolReferences(c, param?.Position?.ToQSharp(), param?.Context), suppressExceptionLogging: true);
 
@@ -1175,7 +1175,7 @@ public Task ManagerTaskAsync(Uri file, Action<CompilationUnitManager, bool> exec
         /// Fails silently without logging anything if an exception occurs upon evaluating the query
         /// (occasional failures are to be expected as the evaluation is a readonly query running in parallel to the ongoing processing).
         /// </summary>
-        public SymbolInformation[]? DocumentSymbols(DocumentSymbolParams param) =>
+        public SymbolInformation[]? DocumentSymbols(DocumentSymbolParams? param) =>
             this.Manager(param?.TextDocument?.Uri)?.FileQuery(
                 param?.TextDocument, (file, _) => file.DocumentSymbols(), suppressExceptionLogging: true);
 
@@ -1186,7 +1186,7 @@ public Task ManagerTaskAsync(Uri file, Action<CompilationUnitManager, bool> exec
         /// Fails silently without logging anything if an exception occurs upon evaluating the query
         /// (occasional failures are to be expected as the evaluation is a readonly query running in parallel to the ongoing processing).
         /// </summary>
-        public ILookup<string, WorkspaceEdit>? CodeActions(CodeActionParams param) =>
+        public ILookup<string, WorkspaceEdit>? CodeActions(CodeActionParams? param) =>
             this.Manager(param?.TextDocument?.Uri)?.FileQuery(
                 param?.TextDocument, (file, c) => file.CodeActions(c, param?.Range?.ToQSharp(), param?.Context), suppressExceptionLogging: true);
 
@@ -1197,7 +1197,7 @@ public Task ManagerTaskAsync(Uri file, Action<CompilationUnitManager, bool> exec
         /// without logging anything if an exception occurs upon evaluating the query (occasional failures are to be
         /// expected as the evaluation is a readonly query running in parallel to the ongoing processing).
         /// </summary>
-        public CompletionList? Completions(TextDocumentPositionParams param) =>
+        public CompletionList? Completions(TextDocumentPositionParams? param) =>
             this.Manager(param?.TextDocument?.Uri)?.FileQuery(
                 param?.TextDocument,
                 (file, compilation) => file.Completions(compilation, param?.Position?.ToQSharp()),
@@ -1213,7 +1213,7 @@ public Task ManagerTaskAsync(Uri file, Action<CompilationUnitManager, bool> exec
         /// failures are to be expected as the evaluation is a read-only query running in parallel to the ongoing
         /// processing).
         /// </summary>
-        public CompletionItem? ResolveCompletion(CompletionItem item, CompletionItemData data, MarkupKind format) =>
+        public CompletionItem? ResolveCompletion(CompletionItem item, CompletionItemData? data, MarkupKind format) =>
             this.Manager(data?.TextDocument?.Uri)?.FileQuery(
                 data?.TextDocument,
                 (_, compilation) => compilation.ResolveCompletion(item, data, format),
@@ -1256,7 +1256,7 @@ public Task ManagerTaskAsync(Uri file, Action<CompilationUnitManager, bool> exec
         /// Note: this method waits for all currently running or queued tasks to finish
         /// before accumulating the diagnostics by calling FlushAndExecute.
         /// </summary>
-        public PublishDiagnosticParams[]? GetDiagnostics(Uri file)
+        public PublishDiagnosticParams[]? GetDiagnostics(Uri? file)
         {
             this.load.QueueForExecution(
                 () =>

src/QsCompiler/DocumentationParser/DocumentationParser.csproj

@@ -22,6 +22,7 @@
 
   <ItemGroup>
     <Compile Include="..\..\Common\DelaySign.cs" Link="Properties\DelaySign.cs" />
+    <Compile Include="..\..\Common\SigningConstants.cs" Link="Properties\SigningConstants.cs" />
   </ItemGroup>
 
   <ItemGroup>

src/QsCompiler/LanguageServer/Communication.cs

@@ -30,9 +30,9 @@ public static class Codes
         }
 
         public readonly int Code;
-        public readonly string Message;
+        public readonly string? Message;
 
-        public ProtocolError(int code, string message = null)
+        public ProtocolError(int code, string? message = null)
         {
             this.Code = code;
             this.Message = message;
@@ -56,20 +56,20 @@ public static class Workarounds
         public class CodeActionParams
         {
             [DataMember(Name = "textDocument")]
-            public TextDocumentIdentifier TextDocument { get; set; }
+            public TextDocumentIdentifier? TextDocument { get; set; }
 
             [DataMember(Name = "range")]
-            public VisualStudio.LanguageServer.Protocol.Range Range { get; set; }
+            public VisualStudio.LanguageServer.Protocol.Range? Range { get; set; }
 
             [DataMember(Name = "context")]
-            public CodeActionContext Context { get; set; }
+            public CodeActionContext? Context { get; set; }
 
             public VisualStudio.LanguageServer.Protocol.CodeActionParams ToCodeActionParams() =>
                 new VisualStudio.LanguageServer.Protocol.CodeActionParams
                 {
                     TextDocument = this.TextDocument,
                     Range = this.Range,
-                    Context = this.Context.ToCodeActionContext()
+                    Context = this.Context?.ToCodeActionContext()
                 };
         }
 
@@ -82,7 +82,7 @@ public VisualStudio.LanguageServer.Protocol.CodeActionParams ToCodeActionParams(
         public class CodeActionContext
         {
             [DataMember(Name = "diagnostics")]
-            public Diagnostic[] Diagnostics { get; set; }
+            public Diagnostic[]? Diagnostics { get; set; }
 
             public VisualStudio.LanguageServer.Protocol.CodeActionContext ToCodeActionContext() =>
                 new VisualStudio.LanguageServer.Protocol.CodeActionContext