Fix optional parameter ordering in generated TS/CS clients (#5135)

Author: lahma

src/NSwag.CodeGeneration.CSharp.Tests/OptionalParameterTests.cs

@@ -37,8 +37,8 @@ public enum MyEnum
             Two,
             Three,
             Four
-
         }
+
         public class MyClass
         {
 #pragma warning disable IDE0051
@@ -145,5 +145,66 @@ public async Task When_setting_is_enabled_then_parameters_are_reordered()
             // Assert
             Assert.Contains("TestAsync(string a, string b, string c = null, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken))", code);
         }
+
+        [Fact]
+        public async Task When_optional_parameter_comes_before_required()
+        {
+            // Arrange
+            const string specification = """
+                                         {
+                                           "openapi": "3.0.0",
+                                           "paths": {
+                                             "/": {
+                                               "get": {
+                                                 "operationId": "Get",
+                                                 "parameters": [
+                                                   {
+                                                     "name": "firstname",
+                                                     "in": "query",
+                                                     "schema": {
+                                                       "type": "string",
+                                                       "nullable": true
+                                                     },
+                                                     "x-position": 1
+                                                   },
+                                                   {
+                                                     "name": "lastname",
+                                                     "in": "query",
+                                                     "required": true,
+                                                     "schema": {
+                                                       "type": "string"
+                                                     },
+                                                     "x-position": 2
+                                                   }
+                                                 ],
+                                                 "responses": {
+                                                   "200": {
+                                                     "description": "",
+                                                     "content": {
+                                                       "application/json": {
+                                                         "schema": {
+                                                           "type": "string"
+                                                         }
+                                                       }
+                                                     }
+                                                   }
+                                                 }
+                                               }
+                                             }
+                                           }
+                                         }
+                                         """;
+
+            // Act
+            var document = await OpenApiDocument.FromJsonAsync(specification, "", SchemaType.OpenApi3);
+            var generator = new CSharpClientGenerator(document, new CSharpClientGeneratorSettings
+            {
+                GenerateOptionalParameters = true
+            });
+            var code = generator.GenerateFile();
+
+            // Assert
+            Assert.Contains("GetAsync(string lastname, string firstname = null,", code);
+        }
     }
 }

src/NSwag.CodeGeneration.CSharp/Models/CSharpOperationModel.cs

@@ -55,16 +55,22 @@ public CSharpOperationModel(
                 // TODO: Move to CSharpControllerOperationModel
                 if (generator is CSharpControllerGenerator)
                 {
-                    parameters = [.. parameters
-                        .OrderBy(p => p.Position ?? 0)
-                        .ThenBy(p => !p.IsRequired)
-                        .ThenBy(p => p.Default == null)];
+                    parameters =
+                    [
+                        .. parameters
+                            .OrderBy(p => !p.IsRequired)
+                            .ThenBy(p => p.Default == null)
+                            .ThenBy(p => p.Position ?? 0)
+                    ];
                 }
                 else
                 {
-                    parameters = [.. parameters
-                        .OrderBy(p => p.Position ?? 0)
-                        .ThenBy(p => !p.IsRequired)];
+                    parameters =
+                    [
+                        .. parameters
+                            .OrderBy(p => !p.IsRequired)
+                            .ThenBy(p => p.Position ?? 0)
+                    ];
                 }
             }
 

src/NSwag.CodeGeneration.TypeScript.Tests/OptionalParameterTests.cs

@@ -0,0 +1,69 @@
+using NJsonSchema;
+using Xunit;
+
+namespace NSwag.CodeGeneration.TypeScript.Tests
+{
+    public class OptionalParameterTests
+    {
+        [Fact]
+        public async Task When_optional_parameter_comes_before_required()
+        {
+            // Arrange
+            const string specification = """
+                                         {
+                                           "openapi": "3.0.0",
+                                           "paths": {
+                                             "/": {
+                                               "get": {
+                                                 "operationId": "Get",
+                                                 "parameters": [
+                                                   {
+                                                     "name": "firstname",
+                                                     "in": "query",
+                                                     "schema": {
+                                                       "type": "string",
+                                                       "nullable": true
+                                                     },
+                                                     "x-position": 1
+                                                   },
+                                                   {
+                                                     "name": "lastname",
+                                                     "in": "query",
+                                                     "required": true,
+                                                     "schema": {
+                                                       "type": "string"
+                                                     },
+                                                     "x-position": 2
+                                                   }
+                                                 ],
+                                                 "responses": {
+                                                   "200": {
+                                                     "description": "",
+                                                     "content": {
+                                                       "application/json": {
+                                                         "schema": {
+                                                           "type": "string"
+                                                         }
+                                                       }
+                                                     }
+                                                   }
+                                                 }
+                                               }
+                                             }
+                                           }
+                                         }
+                                         """;
+
+            // Act
+            var document = await OpenApiDocument.FromJsonAsync(specification, "", SchemaType.OpenApi3);
+            var generator = new TypeScriptClientGenerator(document, new TypeScriptClientGeneratorSettings
+            {
+                GenerateOptionalParameters = true
+            });
+            var code = generator.GenerateFile();
+
+            // Assert
+            Assert.Contains("get(lastname: string, firstname?: string | null | undefined)", code);
+        }
+    }
+}

src/NSwag.CodeGeneration.TypeScript/Models/TypeScriptOperationModel.cs

@@ -39,7 +39,12 @@ public TypeScriptOperationModel(
 
             if (settings.GenerateOptionalParameters)
             {
-                parameters = [.. parameters.OrderBy(p => p.Position ?? 0).ThenBy(p => !p.IsRequired)];
+                parameters =
+                [
+                    .. parameters
+                        .OrderBy(p => !p.IsRequired)
+                        .ThenBy(p => p.Position ?? 0)
+                ];
             }
 
             Parameters = parameters