Exposes publicly override of AadIssuerValidator factory taking a delegate

src/Microsoft.IdentityModel.Validators/AadIssuerValidator/AadIssuerValidator.cs

@@ -323,14 +323,15 @@ public static AadIssuerValidator GetAadIssuerValidator(string aadAuthority)
         /// </summary>
         /// <param name="aadAuthority">The authority to create the validator for, e.g. https://login.microsoftonline.com/. </param>
         /// <param name="httpClient">Optional HttpClient to use to retrieve the endpoint metadata (can be null).</param>
-        /// <param name="configurationManagerProvider">Configuration manager provider. Injection point for metadata managed outside of the class.</param>
+        /// <param name="configurationManagerProvider">Configuration manager provider. Injection point for metadata managed outside
+        /// of the class. The delegate needs to return a configuration manager for a given authority.</param>
         /// <example><code>
         /// AadIssuerValidator aadIssuerValidator = AadIssuerValidator.GetAadIssuerValidator(authority, configurationManagerProvider);
         /// TokenValidationParameters.IssuerValidator = aadIssuerValidator.Validate;
         /// </code></example>
         /// <returns>A <see cref="AadIssuerValidator"/> for the aadAuthority.</returns>
         /// <exception cref="ArgumentNullException">if <paramref name="aadAuthority"/> is null or empty.</exception>
-        internal static AadIssuerValidator GetAadIssuerValidator(string aadAuthority, HttpClient httpClient, Func<string, BaseConfigurationManager> configurationManagerProvider)
+        public static AadIssuerValidator GetAadIssuerValidator(string aadAuthority, HttpClient httpClient, Func<string, BaseConfigurationManager> configurationManagerProvider)
         {
             if (string.IsNullOrEmpty(aadAuthority))
                 throw LogHelper.LogArgumentNullException(nameof(aadAuthority));

src/Microsoft.IdentityModel.Validators/PublicAPI.Unshipped.txt

@@ -0,0 +1 @@
+static Microsoft.IdentityModel.Validators.AadIssuerValidator.GetAadIssuerValidator(string aadAuthority, System.Net.Http.HttpClient httpClient, System.Func<string, Microsoft.IdentityModel.Tokens.BaseConfigurationManager> configurationManagerProvider) -> Microsoft.IdentityModel.Validators.AadIssuerValidator

test/Microsoft.IdentityModel.Validators.Tests/AadIssuerValidatorTests.cs

@@ -1,6 +1,9 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT License.
 
+using System;
+using System.Net.Http;
+using Microsoft.IdentityModel.Tokens;
 using Microsoft.IdentityModel.TestUtils;
 using Xunit;
 
@@ -21,6 +24,35 @@ public static void IsValidIssuer_ValidatesIssuersCorrectly(AadIssuerValidatorThe
             Assert.Equal(theoryData.ExpectedResult, validationResult);
         }
 
+        [Fact]
+        public void GetAadIssuerValidator_ThrowsOnNullOrEmptyAuthority()
+        {
+            Assert.Throws<ArgumentNullException>(() =>
+                AadIssuerValidator.GetAadIssuerValidator(null, null, null));
+            Assert.Throws<ArgumentNullException>(() =>
+                AadIssuerValidator.GetAadIssuerValidator("", null, null));
+        }
+
+        [Fact]
+        public void GetAadIssuerValidator_ReturnsInstance_WithAndWithoutProvider()
+        {
+            string authority = "https://login.microsoftonline.com/common";
+            HttpClient httpClient = new HttpClient();
+
+            // Without provider
+            var validator1 = AadIssuerValidator.GetAadIssuerValidator(authority, httpClient, null);
+            Assert.NotNull(validator1);
+
+            // With provider
+            Func<string, BaseConfigurationManager> provider = (auth) => new MockBaseConfigurationManager();
+            var validator2 = AadIssuerValidator.GetAadIssuerValidator(authority, httpClient, provider);
+            Assert.NotNull(validator2);
+
+            // Should return the same instance for the same authority when provider is null
+            var validator3 = AadIssuerValidator.GetAadIssuerValidator(authority, httpClient, null);
+            Assert.Same(validator1, validator3);
+        }
+
         public static TheoryData<AadIssuerValidatorTheoryData> AadIssuerValidationTestCases()
         {
             var theoryData = new TheoryData<AadIssuerValidatorTheoryData>
@@ -109,6 +141,11 @@ public static TheoryData<AadIssuerValidatorTheoryData> AadIssuerValidationTestCa
 
             return theoryData;
         }
+
+        private class MockBaseConfigurationManager : BaseConfigurationManager
+        {
+            public override void RequestRefresh() { }
+        }
     }
 
     public class AadIssuerValidatorTheoryData : TheoryDataBase