Fallback to first available context as DefaultContext if current default context key is 'Default' (#14281)

* Fallback to first available context as DefaultContext if current default context key is 'Default'

* address comment

Author: erich-wang

src/Accounts/Accounts/ChangeLog.md

@@ -17,7 +17,9 @@
     * Overview of change #1
         - Additional information about change #1
 -->
+
 ## Upcoming Release
+* Fallback to first valid context if current default context key is "Default" which is invalid
 
 ## Version 2.2.7
 * Fixed incorrect warning message on Windows PowerShell [#14556]

src/Accounts/Authentication.ResourceManager/AzureRmProfile.cs

@@ -71,10 +71,11 @@ public virtual IAzureContext DefaultContext
                 }
 
                 IAzureContext result = null;
-                if (DefaultContextKey == "Default" && Contexts.Any(c => c.Key != "Default"))
+                if (DefaultContextKey == Constants.DefaultValue && Contexts.Any(c => c.Key != Constants.DefaultValue))
                 {
-                    // If the default context is "Default", but there are other contexts set, remove the "Default" context to throw the below exception
-                    TryCacheRemoveContext("Default");
+                    // If the default context is "Default", but there are other contexts set, remove the "Default" context and select first avaiable context as default
+                    EnqueueDebugMessage($"Incorrect default context key '{DefaultContextKey}' found. Trying to remove it and falling back to the first available context.");
+                    TryRemoveContext(Constants.DefaultValue);
                 }
 
                 if (!string.IsNullOrEmpty(DefaultContextKey) && Contexts != null && Contexts.ContainsKey(DefaultContextKey))
@@ -292,6 +293,7 @@ public void Save(IFileProvider provider, bool serializeCache = true)
 
             try
             {
+                TryRemoveContext(Constants.DefaultValue);
                 string contents = ToString(serializeCache);
                 string diskContents = string.Empty;
                 diskContents = provider.CreateReader().ReadToEnd();

src/Accounts/Authentication.ResourceManager/Constants.cs

@@ -0,0 +1,21 @@
+// ----------------------------------------------------------------------------------
+//
+// Copyright Microsoft Corporation
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+// ----------------------------------------------------------------------------------
+
+namespace Microsoft.Azure.Commands.Common.Authentication.ResourceManager
+{
+    internal static class Constants
+    {
+        public const string DefaultValue = "Default";
+    }
+}