Fix for issue #7479

Author: praries880

src/ResourceManager/Resources/Commands.Resources/ChangeLog.md

@@ -18,6 +18,7 @@
         - Additional information about change #1
 -->
 ## Current Release
+* Fix isssue where Get-AzureRMRoleDefinition throws an unintelligible excpetion (when the default profile has no subscription in it and no scope is specified) by adding a meaningful exception in the scenario. Also set the default param set to `RoleDefinitionNameParameterSet`.
 
 ## Version 6.6.0
 * Add missing -Mode parameter to Set-AzureRmPolicyDefinition

src/ResourceManager/Resources/Commands.Resources/RoleDefinitions/GetAzureRoleDefinitionCommand.cs

@@ -25,7 +25,7 @@ namespace Microsoft.Azure.Commands.Resources
     /// <summary>
     /// Get the available role Definitions for certain resource types.
     /// </summary>
-    [Cmdlet("Get", ResourceManager.Common.AzureRMConstants.AzureRMPrefix + "RoleDefinition"), OutputType(typeof(PSRoleDefinition))]
+    [Cmdlet("Get", ResourceManager.Common.AzureRMConstants.AzureRMPrefix + "RoleDefinition", DefaultParameterSetName = ParameterSet.RoleDefinitionName), OutputType(typeof(PSRoleDefinition))]
     public class GetAzureRoleDefinitionCommand : ResourcesBaseCmdlet
     {
         [Parameter(Position = 0, Mandatory = false, ValueFromPipelineByPropertyName = true, ParameterSetName = ParameterSet.RoleDefinitionName, HelpMessage = "Role definition name. For e.g. Reader, Contributor, Virtual Machine Contributor.")]
@@ -54,15 +54,25 @@ public override void ExecuteCmdlet()
                 Scope = Scope,
                 ResourceIdentifier = new ResourceIdentifier
                 {
-                    Subscription = DefaultProfile.DefaultContext.Subscription.Id.ToString()
+                    Subscription = (DefaultProfile.DefaultContext.Subscription.Id == null)?null:DefaultProfile.DefaultContext.Subscription.Id.ToString()
                 },
                 RoleDefinitionId = Id,
                 RoleDefinitionName = Name,
             };
 
+            if (options.Scope == null && options.ResourceIdentifier.Subscription == null)
+            {
+                WriteTerminatingError("No subscription was found in the default profile and no scope was specified. Either specify a scope or use a tenant with a subscription to run the command.");
+            }
+
             AuthorizationClient.ValidateScope(options.Scope, true);
 
             WriteObject(PoliciesClient.FilterRoleDefinitions(options), enumerateCollection: true);
         }
+
+        private void WriteTerminatingError(string message, params object[] args)
+        {
+            ThrowTerminatingError(new ErrorRecord(new Exception(String.Format(message, args)), "Error", ErrorCategory.NotSpecified, null));
+        }
     }
 }