improve error message for unresolved tools

src/Microsoft.DotNet.Cli.Utils/CommandResolution/ToolPathCalculator.cs

@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using System.IO;
 using System.Collections.Generic;
 using NuGet.Frameworks;
@@ -19,15 +20,39 @@ namespace Microsoft.DotNet.Cli.Utils
 
         public string GetBestLockFilePath(string packageId, VersionRange versionRange, NuGetFramework framework)
         {
+            if (versionRange == null)
+            {
+                throw new ArgumentNullException(nameof(versionRange));
+            }
+
+            if (framework == null)
+            {
+                throw new ArgumentNullException(nameof(framework));
+            }
+
             var availableToolVersions = GetAvailableToolVersions(packageId);
 
             var bestVersion = versionRange.FindBestMatch(availableToolVersions);
+            if (bestVersion == null)
+            {
+                throw new GracefulException($"Version for package `{packageId}` could not be resolved.");
+            }
 
             return GetLockFilePath(packageId, bestVersion, framework);
         }
 
         public string GetLockFilePath(string packageId, NuGetVersion version, NuGetFramework framework)
         {
+            if (version == null)
+            {
+                throw new ArgumentNullException(nameof(version));
+            }
+
+            if (framework == null)
+            {
+                throw new ArgumentNullException(nameof(framework));
+            }
+
             return Path.Combine(
                 GetBaseToolPath(packageId),
                 version.ToNormalizedString(),

src/Microsoft.DotNet.Cli.Utils/CommandUnknownException.cs

@@ -2,7 +2,7 @@
 
 namespace Microsoft.DotNet.Cli.Utils
 {
-    public class CommandUnknownException : Exception
+    public class CommandUnknownException : GracefulException
     {
         public CommandUnknownException()
         {

src/Microsoft.DotNet.Cli.Utils/GracefulEceptionException.cs

@@ -0,0 +1,19 @@
+using System;
+
+namespace Microsoft.DotNet.Cli.Utils
+{
+    public class GracefulException : Exception
+    {
+        public GracefulException()
+        {
+        }
+
+        public GracefulException(string message) : base(message)
+        {
+        }
+
+        public GracefulException(string message, Exception innerException) : base(message, innerException)
+        {
+        }
+    }
+}

src/dotnet/Program.cs

@@ -34,13 +34,11 @@ namespace Microsoft.DotNet.Cli
             {
                 return Program.ProcessArgs(args, new Telemetry());
             }
-            catch (CommandUnknownException e)
+            catch (GracefulException e)
             {
-                Console.WriteLine(e.Message);
-
+                Console.WriteLine(e.Message.Red().Bold());
                 return 1;
             }
-
         }
 
         internal static int ProcessArgs(string[] args, ITelemetry telemetryClient)