fix(http-client-csharp): exclude custom constructors with settings parameter from property discovery (#10260)

## Problem

When building settings properties from custom constructors, we consider
all public constructors on the client. If a custom constructor takes the
client's settings type as a parameter, it doesn't make sense to consider
that constructor — the settings type is the thing we're building, so its
constructor parameters aren't meaningful inputs for configuration
binding.

## Fix

Skip custom constructors that have a parameter whose type matches
\ClientProvider.ClientSettings.Type\ when discovering parameters for
settings properties, \BindCore\ bindings, and \ConfigurationSchema.json\
generation.

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: JoshLove-msft

packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/src/ConfigurationSchemaGenerator.cs

@@ -127,7 +127,8 @@ private static JsonObject BuildClientEntry(ClientProvider client, string options
                 knownProps.Add("Options");
                 foreach (var ctor in customConstructors)
                 {
-                    if (!ctor.Signature.Modifiers.HasFlag(MethodSignatureModifiers.Public))
+                    if (!ctor.Signature.Modifiers.HasFlag(MethodSignatureModifiers.Public) ||
+                        settings.HasSettingsParameter(ctor))
                     {
                         continue;
                     }

packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/src/Providers/ClientSettingsProvider.cs

@@ -117,7 +117,8 @@ protected override PropertyProvider[] BuildProperties()
                 knownProps.Add("Options");
                 foreach (var ctor in customConstructors)
                 {
-                    if (!ctor.Signature.Modifiers.HasFlag(MethodSignatureModifiers.Public))
+                    if (!ctor.Signature.Modifiers.HasFlag(MethodSignatureModifiers.Public) ||
+                        HasSettingsParameter(ctor))
                     {
                         continue;
                     }
@@ -190,7 +191,8 @@ protected override MethodProvider[] BuildMethods()
                 knownProps.Add("Options");
                 foreach (var ctor in customConstructors)
                 {
-                    if (!ctor.Signature.Modifiers.HasFlag(MethodSignatureModifiers.Public))
+                    if (!ctor.Signature.Modifiers.HasFlag(MethodSignatureModifiers.Public) ||
+                        HasSettingsParameter(ctor))
                     {
                         continue;
                     }
@@ -498,5 +500,14 @@ internal static bool IsStandardParameterType(CSharpType type)
 
             return false;
         }
+
+        /// <summary>
+        /// Returns true if the constructor has a parameter whose type matches this client's
+        /// settings type.
+        /// </summary>
+        internal bool HasSettingsParameter(ConstructorProvider ctor)
+        {
+            return ctor.Signature.Parameters.Any(p => p.Type.Equals(Type));
+        }
     }
 }

packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/ClientSettingsProviderTests.cs

@@ -964,5 +964,39 @@ await MockHelpers.LoadMockGeneratorAsync(
             Assert.IsTrue(bodyString.Contains("ConnectionString"),
                 "BindCore should bind the custom constructor parameter 'ConnectionString' from configuration");
         }
+
+        [Test]
+        public void TestSettingsType_DoesNotContainSelfReferentialSettingsProperty()
+        {
+            var client = InputFactory.Client("TestClient");
+            var clientProvider = new ClientProvider(client);
+            var settingsProvider = clientProvider.ClientSettings;
+
+            Assert.IsNotNull(settingsProvider);
+
+            // The settings type should not have a property named "Settings" that references itself.
+            // This would happen if the generated settings constructor (which takes the settings type
+            // as a parameter) is incorrectly treated as a custom constructor.
+            var settingsProperty = settingsProvider!.Properties.FirstOrDefault(p => p.Name == "Settings");
+            Assert.IsNull(settingsProperty,
+                "Settings type should not contain a self-referential 'Settings' property");
+        }
+
+        [Test]
+        public void TestBindCoreMethod_DoesNotBindSettingsParameter()
+        {
+            var client = InputFactory.Client("TestClient");
+            var clientProvider = new ClientProvider(client);
+            var settingsProvider = clientProvider.ClientSettings;
+
+            Assert.IsNotNull(settingsProvider);
+
+            var bindCoreMethod = settingsProvider!.Methods.FirstOrDefault(m => m.Signature.Name == "BindCore");
+            Assert.IsNotNull(bindCoreMethod);
+
+            var bodyString = bindCoreMethod!.BodyStatements!.ToDisplayString();
+            Assert.IsFalse(bodyString.Contains("GetSection(\"Settings\")"),
+                "BindCore should not bind a self-referential Settings section");
+        }
     }
 }