Ignore casing in functions host config options keys (#9122)

Author: chiangvincent

src/WebJobs.Script/Config/FunctionsHostingConfigOptions.cs

@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the MIT License. See License.txt in the project root for license information.
 
+using System;
 using System.Collections.Generic;
 using Microsoft.Azure.WebJobs.Script.Workers.Rpc;
 
@@ -12,7 +13,7 @@ public class FunctionsHostingConfigOptions
 
         public FunctionsHostingConfigOptions()
         {
-            _features = new Dictionary<string, string>();
+            _features = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
         }
 
         /// <summary>

test/WebJobs.Script.Tests/Configuration/FunctionsHostingConfigOptionsTest.cs

@@ -16,6 +16,32 @@ namespace Microsoft.Azure.WebJobs.Script.Tests.Configuration
 {
     public class FunctionsHostingConfigOptionsTest
     {
+        [Theory]
+        [InlineData("FEATURE1", "value1")]
+        [InlineData("FeAtUrE1", "value1")]
+        [InlineData("feature1", "value1")]
+        [InlineData("featuree1", null)]
+        public async Task Case_Insensitive(string key, string expectedValue)
+        {
+            using (TempDirectory tempDir = new TempDirectory())
+            {
+                IHost host = GetScriptHostBuilder(Path.Combine(tempDir.Path, "settings.txt"), $"feature1=value1,feature2=value2").Build();
+                var testService = host.Services.GetService<TestService>();
+
+                _ = Task.Run(async () =>
+                {
+                    await TestHelpers.Await(() =>
+                    {
+                        return testService.Options.Value.GetFeature(key) == expectedValue;
+                    });
+                    await host.StopAsync();
+                });
+
+                await host.RunAsync();
+                Assert.Equal(testService.Options.Value.GetFeature(key), expectedValue);
+            }
+        }
+
         [Fact]
         public async Task Inject_Succeded()
         {