Add exception logging to RPS#OnStateChange and CodeMetricsAnalyst, fixes #4814

Author: Vogel612

Rubberduck.CodeAnalysis/CodeMetrics/CodeMetricsAnalyst.cs

@@ -5,11 +5,14 @@
 using System.Collections.Generic;
 using System.Linq;
 using Rubberduck.Parsing.VBA.DeclarationCaching;
+using System;
+using NLog;
 
 namespace Rubberduck.CodeAnalysis.CodeMetrics
 {
     public class CodeMetricsAnalyst : ICodeMetricsAnalyst
     {
+        private static readonly Logger Logger = LogManager.GetCurrentClassLogger();
 
         private readonly CodeMetric[] metrics;
 
@@ -49,9 +52,16 @@ private IEnumerable<ICodeMetricResult> TraverseModuleTree(IParseTree parseTree,
                 l.InjectContext((declarationFinder, moduleName));
             }
             var combinedMetricListener = new CombinedParseTreeListener(listeners);
-
-            ParseTreeWalker.Default.Walk(combinedMetricListener, parseTree);
-            return listeners.SelectMany(l => l.Results());
+            try
+            {
+                ParseTreeWalker.Default.Walk(combinedMetricListener, parseTree);
+                return listeners.SelectMany(l => l.Results());
+            }
+            catch (Exception e)
+            {
+                Logger.Warn(e, "An exception occured during parse-tree traversal or result aggregation for Code Metrics");
+                return Enumerable.Empty<ICodeMetricResult>();
+            }
         }
     }
 }

Rubberduck.Parsing/VBA/RubberduckParserState.cs

@@ -396,8 +396,21 @@ private void OnStateChanged(object requestor, CancellationToken token, ParserSta
             var handler = StateChanged;
             if (handler != null && !token.IsCancellationRequested)
             {
-                var args = new ParserStateEventArgs(state, oldStatus, token);
-                handler.Invoke(requestor, args);
+                try
+                {
+                    var args = new ParserStateEventArgs(state, oldStatus, token);
+                    handler.Invoke(requestor, args);
+                }
+                catch (Exception e)
+                {
+                    if (e is OperationCanceledException cancellation)
+                    {
+                        throw cancellation;
+                    }
+                    // Error state, because this implies consumers are not exception-safe!
+                    // this behaviour could leave us in a state where some consumers have correctly updated and some have not
+                    Logger.Error(e, "An exception occurred when notifying consumers of updated parser state.");
+                }
             }
         }