Fix various common exceptions, log on a failed directory load (microsoft#498)

* rethrow exception after telemetry instead of disposing

* log an error instead of crashing when hitting some exceptions loading files, fix nullref when shutting down without an idle tracker

* fix short circuiting of question mark checks to prevent null from being returned

* print name of exception instead of relying on ToString

* don't use MaybeEnumerate

* upgrade message to Show

Author: jakebailey

src/Analysis/Engine/Impl/Intellisense/AnalysisQueue.cs

@@ -67,7 +67,7 @@ private async Task ConsumerLoop() {
                     return;
                 } catch (Exception ex) when (!ex.IsCriticalException()) {
                     UnhandledException?.Invoke(this, new UnhandledExceptionEventArgs(ex, false));
-                    Dispose();
+                    throw;
                 }
             }
             RaiseEventOnThreadPool(AnalysisComplete);

src/Analysis/Engine/Impl/Values/BuiltinNamespace.cs

@@ -16,6 +16,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using Microsoft.PythonTools.Analysis.Infrastructure;
 using Microsoft.PythonTools.Interpreter;
 using Microsoft.PythonTools.Parsing.Ast;
@@ -105,7 +106,7 @@ public TMemberContainer ContainedValue {
 
         public virtual ILocatedMember GetLocatedMember() => null;
 
-        public override IEnumerable<ILocationInfo> Locations => GetLocatedMember()?.Locations.MaybeEnumerate();
+        public override IEnumerable<ILocationInfo> Locations => GetLocatedMember()?.Locations ?? Enumerable.Empty<ILocationInfo>();
 
         public override bool Equals(object obj) {
             if (obj is BuiltinNamespace<TMemberContainer> bn && GetType() == bn.GetType()) {

src/Analysis/Engine/Impl/Values/SpecializedNamespace.cs

@@ -209,15 +209,15 @@ public override bool IsOfType(IAnalysisSet klass) {
             return _original.IsOfType(klass);
         }
 
-        public override IEnumerable<ILocationInfo> Locations => _original?.Locations.MaybeEnumerate();
+        public override IEnumerable<ILocationInfo> Locations => _original?.Locations ?? Enumerable.Empty<ILocationInfo>();
 
         public override string Name => _original == null ? base.Name : _original.Name;
 
-        public override IEnumerable<OverloadResult> Overloads => _original?.Overloads.MaybeEnumerate();
+        public override IEnumerable<OverloadResult> Overloads => _original?.Overloads ?? Enumerable.Empty<OverloadResult>();
 
         public override IPythonType PythonType => _original?.PythonType;
 
-        internal override IEnumerable<ILocationInfo> References => _original?.References.MaybeEnumerate();
+        internal override IEnumerable<ILocationInfo> References => _original?.References ?? Enumerable.Empty<ILocationInfo>();
 
         public override PythonMemberType MemberType => _original == null ? PythonMemberType.Unknown : _original.MemberType;
 

src/LanguageServer/Impl/LanguageServer.Lifetime.cs

@@ -64,14 +64,14 @@ public async Task Shutdown() {
             // https://microsoft.github.io/language-server-protocol/specification#shutdown
             await _server.Shutdown();
             _shutdown = true;
-            _idleTimeTracker.Dispose();
+            _idleTimeTracker?.Dispose();
         }
 
         [JsonRpcMethod("exit")]
         public async Task Exit() {
             await _server.Exit();
             _sessionTokenSource.Cancel();
-            _idleTimeTracker.Dispose();
+            _idleTimeTracker?.Dispose();
             // Per https://microsoft.github.io/language-server-protocol/specification#exit
             Environment.Exit(_shutdown ? 0 : 1);
         }

src/LanguageServer/Impl/LanguageServer.cs

@@ -17,6 +17,7 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
+using System.IO;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
@@ -164,7 +165,16 @@ public async Task DidChangeConfiguration(JToken token, CancellationToken cancell
                 await _server.DidChangeConfiguration(new DidChangeConfigurationParams { settings = settings }, cancellationToken);
 
                 if (!_filesLoaded) {
-                    await LoadDirectoryFiles();
+                    try {
+                        await LoadDirectoryFiles();
+                    } catch (Exception ex) when (
+                        ex is IOException // FileNotFoundException, DirectoryNotFoundException, PathTooLongException, etc
+                        || ex is UnauthorizedAccessException
+                    ) {
+                        // These exceptions are not caused by the LS, but by invalid/inaccessible user-specified paths.
+                        _server.ShowMessage(MessageType.Error, $"Failed to load files in {_initParams.rootPath} - {ex.GetType().Name}: {ex.Message}");
+                        return;
+                    }
                 }
                 _filesLoaded = true;
             }