fix: provide error message for unknown provider. (#608)

* fix: provide error message for unknown provider.

If a provider is given and it is not one of the available providers, output an invalid operation message like "Provider 'foo' is not installed.

Closes #134

src/libman/Commands/CacheCleanCommand.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.IO;
+using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.Extensions.CommandLineUtils;
 using Microsoft.Web.LibraryManager.Contracts;
@@ -64,6 +65,10 @@ namespace Microsoft.Web.LibraryManager.Tools.Commands
                     Logger.Log(string.Format(Resources.Text.CacheCleanFailed, ex.Message), LogLevel.Error);
                 }
             }
+            else if (!ManifestDependencies.Providers.Any(p => p.Id == Provider.Value))
+            {
+                throw new InvalidOperationException(string.Format(Resources.Text.ProviderNotInstalled, Provider.Value));
+            }
 
             return Task.FromResult(0);
         }

test/libman.Test/LibmanCacheCleanTests.cs

@@ -4,7 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
-using System.Text;
+using System.Linq;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using Microsoft.Web.LibraryManager.Tools.Commands;
 
@@ -109,5 +109,15 @@ namespace Microsoft.Web.LibraryManager.Tools.Test
 
             Assert.IsTrue(File.Exists(Path.Combine(CacheDir, "filesystem", "abc.js")));
         }
+
+        [TestMethod]
+        public void TestCacheClean_ThrowsIfUnknownProvider()
+        {
+            var cleanCommand = new CacheCleanCommand(HostEnvironment);
+            cleanCommand.Configure();
+
+            var exception = Assert.ThrowsException<AggregateException>(() => cleanCommand.Execute("foo"));
+            Assert.IsInstanceOfType(exception.InnerExceptions.First(), typeof(InvalidOperationException));
+        }
     }
 }