Properly initialize options for EnvironmentCredential sub credentials (Azure#22795)

* initialize options for EnvironmentCredential

Author: christothes

sdk/identity/Azure.Identity/src/EnvironmentCredential.cs

@@ -40,23 +40,21 @@ public class EnvironmentCredential : TokenCredential
         /// </summary>
         public EnvironmentCredential()
             : this(CredentialPipeline.GetInstance(null))
-        {
-        }
+        { }
 
         /// <summary>
         /// Creates an instance of the EnvironmentCredential class and reads client secret details from environment variables.
         /// If the expected environment variables are not found at this time, the GetToken method will return the default <see cref="AccessToken"/> when invoked.
         /// </summary>
         /// <param name="options">Options that allow to configure the management of the requests sent to the Azure Active Directory service.</param>
         public EnvironmentCredential(TokenCredentialOptions options)
-            : this(CredentialPipeline.GetInstance(options))
-        {
-            _options = options;
-        }
+            : this(CredentialPipeline.GetInstance(options), options)
+        { }
 
-        internal EnvironmentCredential(CredentialPipeline pipeline)
+        internal EnvironmentCredential(CredentialPipeline pipeline, TokenCredentialOptions options = null)
         {
             _pipeline = pipeline;
+            _options = options ?? new TokenCredentialOptions();
 
             string tenantId = EnvironmentVariables.TenantId;
             string clientId = EnvironmentVariables.ClientId;

sdk/identity/Azure.Identity/tests/EnvironmentCredentialProviderTests.cs

@@ -79,7 +79,7 @@ public void CredentialConstructionClientCertificate()
         [Test]
         public void EnvironmentCredentialUnavailableException()
         {
-            var credential = InstrumentClient(new EnvironmentCredential(CredentialPipeline.GetInstance(null), null));
+            var credential = InstrumentClient(new EnvironmentCredential(CredentialPipeline.GetInstance(null)));
             Assert.ThrowsAsync<CredentialUnavailableException>(async () => await credential.GetTokenAsync(new TokenRequestContext(MockScopes.Default)));
         }