Don't catch all exceptions; propagate unexpected errors to trigger Watson dump

src/linker/Linker.Steps/BaseStep.cs

@@ -29,7 +29,6 @@
 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 //
 
-using System;
 using System.Diagnostics;
 using Mono.Cecil;
 
@@ -68,11 +67,7 @@ public void Process (LinkContext context)
 			Process ();
 
 			foreach (AssemblyDefinition assembly in context.GetAssemblies ()) {
-				try {
-					ProcessAssembly (assembly);
-				} catch (Exception e) {
-					throw new InternalErrorException ($"Step '{GetType ().Name}' failed when processing assembly '{assembly.FullName}'.", e);
-				}
+				ProcessAssembly (assembly);
 			}
 
 			EndProcess ();

src/linker/Linker.Steps/MarkStep.cs

@@ -554,12 +554,7 @@ void ProcessQueue ()
 		{
 			while (!QueueIsEmpty ()) {
 				(MethodDefinition method, DependencyInfo reason, MessageOrigin origin) = _methods.Dequeue ();
-				try {
-					ProcessMethod (method, reason, origin);
-				} catch (Exception e) when (!(e is LinkerFatalErrorException)) {
-					throw new LinkerFatalErrorException (
-						MessageContainer.CreateErrorMessage (origin, DiagnosticId.CouldNotFindMethodInAssembly, method.GetDisplayName (), method.Module.Name), e);
-				}
+				ProcessMethod (method, reason, origin);
 			}
 		}
 

src/linker/Linker.Steps/OutputStep.cs

@@ -133,6 +133,7 @@ protected virtual void WriteAssembly (AssemblyDefinition assembly, string direct
 			try {
 				assembly.Write (outputName, writerParameters);
 			} catch (Exception e) {
+				// We should be okay catching everything here, assembly.Write is all in Cecil and most of the state necessary to debug will be captured in assembly
 				throw new LinkerFatalErrorException (MessageContainer.CreateErrorMessage (null, DiagnosticId.FailedToWriteOutput, outputName), e);
 			}
 		}

src/linker/Linker/Driver.cs

@@ -93,7 +93,7 @@ public static bool ProcessResponseFile (string[] args, out Queue<string> result)
 						string responseFileName = arg.Substring (1);
 						using (var responseFileText = new StreamReader (responseFileName))
 							ParseResponseFile (responseFileText, result);
-					} catch (Exception e) {
+					} catch (Exception e) when (e is IOException or ObjectDisposedException) {
 						Console.Error.WriteLine ("Cannot read response file due to '{0}'", e.Message);
 						return false;
 					}
@@ -767,7 +767,7 @@ protected int SetupContext (ILogger? customLogger = null)
 		// to the error code.
 		// May propagate exceptions, which will result in the process getting an
 		// exit code determined by dotnet.
-		public int Run (ILogger? customLogger = null, bool throwOnFatalLinkerException = false)
+		public int Run (ILogger? customLogger = null)
 		{
 			int setupStatus = SetupContext (customLogger);
 			if (setupStatus > 0)
@@ -780,29 +780,37 @@ public int Run (ILogger? customLogger = null, bool throwOnFatalLinkerException =
 
 			try {
 				p.Process (Context);
-			} catch (LinkerFatalErrorException lex) {
+			} catch (Exception e) when (LogFatalError (e)) {
+				// Unreachable
+				throw;
+			}
+
+			Context.FlushCachedWarnings ();
+			Context.Tracer.Finish ();
+			return Context.ErrorsCount > 0 ? 1 : 0;
+		}
+
+		/// <summary>
+		/// This method is called in the exception filter for unexpected exceptions.
+		/// Prints error messages and returns false to avoid catching in the exception filter.
+		/// </summary>
+		bool LogFatalError (Exception e)
+		{
+			switch (e) {
+			case LinkerFatalErrorException lex:
 				Context.LogMessage (lex.MessageContainer);
-				Console.Error.WriteLine (lex.ToString ());
 				Debug.Assert (lex.MessageContainer.Category == MessageCategory.Error);
 				Debug.Assert (lex.MessageContainer.Code != null);
 				Debug.Assert (lex.MessageContainer.Code.Value != 0);
-				if (throwOnFatalLinkerException)
-					throw;
-				return lex.MessageContainer.Code ?? 1;
-			} catch (ResolutionException e) {
-				Context.LogError (null, DiagnosticId.FailedToResolveMetadataElement, e.Message);
-			} catch (Exception) {
-				// Unhandled exceptions are usually linker bugs. Ask the user to report it.
+				break;
+			case ResolutionException re:
+				Context.LogError (null, DiagnosticId.FailedToResolveMetadataElement, re.Message);
+				break;
+			default:
 				Context.LogError (null, DiagnosticId.LinkerUnexpectedError);
-				// Don't swallow the exception and exit code - rethrow it and let the surrounding tooling decide what to do.
-				// The stack trace will go to stderr, and the MSBuild task will surface it with High importance.
-				throw;
-			} finally {
-				Context.FlushCachedWarnings ();
-				Context.Tracer.Finish ();
+				break;
 			}
-
-			return Context.ErrorsCount > 0 ? 1 : 0;
+			return false;
 		}
 
 		partial void PreProcessPipeline (Pipeline pipeline);

src/tlens/TLens/Runner.cs

@@ -32,11 +32,7 @@ public void Process (List<AssemblyDefinition> assemblies)
 			bool first = true;
 			foreach (var a in analyzers) {
 				foreach (var assembly in assemblies) {
-					try {
-						a.ProcessAssembly (assembly);
-					} catch (Exception e) {
-						throw new ApplicationException ($"Internal error when analyzing '{assembly.FullName}' assembly with '{a.GetType ()}'", e);
-					}
+					a.ProcessAssembly (assembly);
 				}
 
 				if (!first)

test/Mono.Linker.Tests/TestCasesRunner/LinkerDriver.cs

@@ -28,7 +28,7 @@ public virtual void Link (string[] args, LinkerCustomizations customizations, IL
 		{
 			Driver.ProcessResponseFile (args, out var queue);
 			using (var driver = new TestDriver (queue, customizations)) {
-				driver.Run (logger, throwOnFatalLinkerException: true);
+				driver.Run (logger);
 			}
 		}
 	}