Fix exception import Az.Accounts caused by env var

src/Accounts/Accounts/ChangeLog.md

@@ -19,6 +19,7 @@
 -->
 
 ## Upcoming Release
+* Fixed an issue that Az.Accounts failed to be imported if multiple environment variables, which only differ by case, are set. [#18304]
 
 ## Version 2.8.0
 * Added a preview feature allowing user to control the following configurations by using `Get-AzConfig`, `Update-AzConfig` and `Clear-AzConfig`:

src/Accounts/Authentication.Test/UnitTests/DefaultEnvironmentVariableProviderTests.cs

@@ -0,0 +1,48 @@
+// ----------------------------------------------------------------------------------
+//
+// 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.
+// ----------------------------------------------------------------------------------
+
+using Microsoft.Azure.Commands.Common.Authentication.Config;
+using Microsoft.Rest.ClientRuntime.Azure.TestFramework;
+using Xunit;
+using System;
+
+namespace Microsoft.Azure.Authentication.Test.UnitTests
+{
+    public class DefaultEnvironmentVariableProviderTests
+    {
+        [Fact]
+        [Trait(TestTraits.AcceptanceType, TestTraits.CheckIn)]
+        public void ShouldNotThrowWhen2EnvVarDifferOnlyByCase()
+        {
+            const string varName = "NameOfAnEnvVar";
+            Environment.SetEnvironmentVariable(varName, "a");
+            string varNameInUpper = varName.ToUpperInvariant();
+            Environment.SetEnvironmentVariable(varNameInUpper, "b");
+
+            try
+            {
+                DefaultEnvironmentVariableProvider provider = new DefaultEnvironmentVariableProvider();
+                var dict = provider.List();
+                Assert.True(dict.ContainsKey(varName));
+                Assert.True(dict.ContainsKey(varNameInUpper));
+                Assert.Equal(dict[varName], dict[varNameInUpper]);
+            }
+            finally
+            {
+                Environment.SetEnvironmentVariable(varName, null);
+                Environment.SetEnvironmentVariable(varNameInUpper, null);
+            }
+        }
+    }
+}

src/Accounts/Authentication/Config/Helper/DefaultEnvironmentVariableProvider.cs

@@ -16,6 +16,7 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Linq;
 
 namespace Microsoft.Azure.Commands.Common.Authentication.Config
@@ -32,9 +33,15 @@ public string Get(string variableName, EnvironmentVariableTarget target = Enviro
 
         public IReadOnlyDictionary<string, string> List(EnvironmentVariableTarget target = EnvironmentVariableTarget.Process)
         {
-            return Environment.GetEnvironmentVariables()
-                .Cast<DictionaryEntry>()
-                .ToDictionary(pair => pair.Key.ToString(), pair => pair.Value.ToString(), StringComparer.OrdinalIgnoreCase);
+            IDictionary source = Environment.GetEnvironmentVariables();
+            IDictionary<string, string> results = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
+            // cannot use ToDictionary() because keys (names of env var) may duplicate on Linux,
+            // with case being the only difference
+            foreach (var item in source.Cast<DictionaryEntry>())
+            {
+                results[item.Key.ToString()] = item.Value.ToString();
+            }
+            return new ReadOnlyDictionary<string, string>(results);
         }
 
         public void Set(string variableName, string value, EnvironmentVariableTarget target = EnvironmentVariableTarget.Process)