Add support for Cookie Parameter style

src/Microsoft.OpenApi/Models/OpenApiParameter.cs

@@ -44,7 +44,7 @@ public ParameterStyle? Style
         /// <inheritdoc/>
         public bool Explode
         {
-            get => _explode ?? Style == ParameterStyle.Form;
+            get => _explode ?? (Style is ParameterStyle.Form or ParameterStyle.Cookie);
             set => _explode = value;
         }
 
@@ -115,6 +115,12 @@ internal void SerializeInternal(IOpenApiWriter writer, OpenApiSpecVersion versio
             Action<IOpenApiWriter, IOpenApiSerializable> callback)
         {
             Utils.CheckArgumentNull(writer);
+
+            // Validate that Cookie style is only used in OpenAPI 3.2 and later
+            if (Style == ParameterStyle.Cookie && version < OpenApiSpecVersion.OpenApi3_2)
+            {
+                throw new OpenApiException($"Parameter style 'cookie' is only supported in OpenAPI 3.2 and later versions. Current version: {version}");
+            }
 
             writer.WriteStartObject();
 
@@ -143,7 +149,7 @@ internal void SerializeInternal(IOpenApiWriter writer, OpenApiSpecVersion versio
             }
 
             // explode
-            writer.WriteProperty(OpenApiConstants.Explode, _explode, Style is ParameterStyle.Form);
+            writer.WriteProperty(OpenApiConstants.Explode, _explode, Style is ParameterStyle.Form or ParameterStyle.Cookie);
 
             // allowReserved
             writer.WriteProperty(OpenApiConstants.AllowReserved, AllowReserved, false);
@@ -251,6 +257,12 @@ internal virtual void WriteRequestBodySchemaForV2(IOpenApiWriter writer, Diction
         public virtual void SerializeAsV2(IOpenApiWriter writer)
         {
             Utils.CheckArgumentNull(writer);
+
+            // Validate that Cookie style is only used in OpenAPI 3.2 and later
+            if (Style == ParameterStyle.Cookie)
+            {
+                throw new OpenApiException($"Parameter style 'cookie' is only supported in OpenAPI 3.2 and later versions. Current version: {OpenApiSpecVersion.OpenApi2_0}");
+            }
 
             writer.WriteStartObject();
 

src/Microsoft.OpenApi/Models/ParameterStyle.cs

@@ -41,6 +41,11 @@ public enum ParameterStyle
         /// <summary>
         /// Provides a simple way of rendering nested objects using form parameters.
         /// </summary>
-        [Display("deepObject")] DeepObject
+        [Display("deepObject")] DeepObject,
+
+        /// <summary>
+        /// Cookie style parameters. Introduced in OpenAPI 3.2.
+        /// </summary>
+        [Display("cookie")] Cookie
     }
 }

test/Microsoft.OpenApi.Tests/Models/OpenApiParameterCookieStyleTests.SerializeCookieParameterAsV32JsonWorksAsync_produceTerseOutput=False.verified.txt

@@ -0,0 +1,9 @@
+{
+  "name": "sessionId",
+  "in": "cookie",
+  "description": "Session identifier stored in cookie",
+  "style": "cookie",
+  "schema": {
+    "type": "string"
+  }
+}

test/Microsoft.OpenApi.Tests/Models/OpenApiParameterCookieStyleTests.SerializeCookieParameterAsV32JsonWorksAsync_produceTerseOutput=True.verified.txt

@@ -0,0 +1 @@
+{"name":"sessionId","in":"cookie","description":"Session identifier stored in cookie","style":"cookie","schema":{"type":"string"}}

test/Microsoft.OpenApi.Tests/Models/OpenApiParameterCookieStyleTests.cs

@@ -0,0 +1,251 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT license.
+
+using System;
+using System.Globalization;
+using System.IO;
+using System.Threading.Tasks;
+using Xunit;
+using VerifyXunit;
+
+namespace Microsoft.OpenApi.Tests.Models
+{
+    [Collection("DefaultSettings")]
+    public class OpenApiParameterCookieStyleTests
+    {
+        private static OpenApiParameter CookieParameter => new()
+        {
+            Name = "sessionId",
+            In = ParameterLocation.Cookie,
+            Style = ParameterStyle.Cookie,
+            Description = "Session identifier stored in cookie",
+            Schema = new OpenApiSchema()
+            {
+                Type = JsonSchemaType.String
+            }
+        };
+
+        private static OpenApiParameter CookieParameterWithDefault => new()
+        {
+            Name = "preferences",
+            In = ParameterLocation.Cookie,
+            Description = "User preferences stored in cookie",
+            Schema = new OpenApiSchema()
+            {
+                Type = JsonSchemaType.String
+            }
+        };
+
+        [Fact]
+        public void CookieParameterStyleIsAvailable()
+        {
+            // Arrange & Act
+            var parameter = CookieParameter;
+
+            // Assert
+            Assert.Equal(ParameterStyle.Cookie, parameter.Style);
+            Assert.Equal(ParameterLocation.Cookie, parameter.In);
+        }
+
+        [Fact]
+        public void CookieParameterHasCorrectDefaultStyle()
+        {
+            // Arrange & Act
+            var parameter = CookieParameterWithDefault;
+
+            // Assert
+            Assert.Equal(ParameterStyle.Form, parameter.Style); // Default for cookie location should be Form
+        }
+
+        [Fact]
+        public void CookieParameterStyleDisplayNameIsCookie()
+        {
+            // Arrange & Act
+            var displayName = ParameterStyle.Cookie.GetDisplayName();
+
+            // Assert
+            Assert.Equal("cookie", displayName);
+        }
+
+        [Fact]
+        public async Task SerializeCookieParameterAsV32JsonWorks()
+        {
+            // Arrange
+            var expected =
+                """
+                {
+                  "name": "sessionId",
+                  "in": "cookie",
+                  "description": "Session identifier stored in cookie",
+                  "style": "cookie",
+                  "schema": {
+                    "type": "string"
+                  }
+                }
+                """;
+
+            // Act
+            var actual = await CookieParameter.SerializeAsJsonAsync(OpenApiSpecVersion.OpenApi3_2);
+
+            // Assert
+            actual = actual.MakeLineBreaksEnvironmentNeutral();
+            expected = expected.MakeLineBreaksEnvironmentNeutral();
+            Assert.Equal(expected, actual);
+        }
+
+        [Fact]
+        public async Task SerializeCookieParameterWithDefaultStyleAsV32JsonWorks()
+        {
+            // Arrange
+            var expected =
+                """
+                {
+                  "name": "preferences",
+                  "in": "cookie",
+                  "description": "User preferences stored in cookie",
+                  "schema": {
+                    "type": "string"
+                  }
+                }
+                """;
+
+            // Act
+            var actual = await CookieParameterWithDefault.SerializeAsJsonAsync(OpenApiSpecVersion.OpenApi3_2);
+
+            // Assert
+            actual = actual.MakeLineBreaksEnvironmentNeutral();
+            expected = expected.MakeLineBreaksEnvironmentNeutral();
+            Assert.Equal(expected, actual);
+        }
+
+        [Theory]
+        [InlineData(OpenApiSpecVersion.OpenApi2_0)]
+        [InlineData(OpenApiSpecVersion.OpenApi3_0)]
+        [InlineData(OpenApiSpecVersion.OpenApi3_1)]
+        public void SerializeCookieParameterStyleThrowsForEarlierVersions(OpenApiSpecVersion version)
+        {
+            // Arrange
+            var outputStringWriter = new StringWriter(CultureInfo.InvariantCulture);
+            var writer = new OpenApiJsonWriter(outputStringWriter);
+
+            // Act & Assert
+            var exception = Assert.Throws<OpenApiException>(() =>
+            {
+                switch (version)
+                {
+                    case OpenApiSpecVersion.OpenApi2_0:
+                        CookieParameter.SerializeAsV2(writer);
+                        break;
+                    case OpenApiSpecVersion.OpenApi3_0:
+                        CookieParameter.SerializeAsV3(writer);
+                        break;
+                    case OpenApiSpecVersion.OpenApi3_1:
+                        CookieParameter.SerializeAsV31(writer);
+                        break;
+                }
+            });
+
+            Assert.Contains("Parameter style 'cookie' is only supported in OpenAPI 3.2 and later versions", exception.Message);
+            Assert.Contains($"Current version: {version}", exception.Message);
+        }
+
+        [Theory]
+        [InlineData(OpenApiSpecVersion.OpenApi2_0)]
+        [InlineData(OpenApiSpecVersion.OpenApi3_0)]
+        [InlineData(OpenApiSpecVersion.OpenApi3_1)]
+        public async Task SerializeCookieParameterWithDefaultStyleWorksForEarlierVersions(OpenApiSpecVersion version)
+        {
+            // Arrange & Act
+            string actual = version switch
+            {
+                OpenApiSpecVersion.OpenApi2_0 => await CookieParameterWithDefault.SerializeAsJsonAsync(OpenApiSpecVersion.OpenApi2_0),
+                OpenApiSpecVersion.OpenApi3_0 => await CookieParameterWithDefault.SerializeAsJsonAsync(OpenApiSpecVersion.OpenApi3_0),
+                OpenApiSpecVersion.OpenApi3_1 => await CookieParameterWithDefault.SerializeAsJsonAsync(OpenApiSpecVersion.OpenApi3_1),
+                _ => throw new ArgumentOutOfRangeException()
+            };
+
+            // Assert - Should not throw because default style (Form) is being used
+            Assert.NotEmpty(actual);
+            Assert.DoesNotContain("\"style\"", actual); // Style should not be emitted when it's the default
+        }
+
+        [Theory]
+        [InlineData(true)]
+        [InlineData(false)]
+        public async Task SerializeCookieParameterAsV32JsonWorksAsync(bool produceTerseOutput)
+        {
+            // Arrange
+            var outputStringWriter = new StringWriter(CultureInfo.InvariantCulture);
+            var writer = new OpenApiJsonWriter(outputStringWriter, new() { Terse = produceTerseOutput });
+
+            // Act
+            CookieParameter.SerializeAsV32(writer);
+            await writer.FlushAsync();
+
+            // Assert
+            await Verifier.Verify(outputStringWriter).UseParameters(produceTerseOutput);
+        }
+
+        [Fact]
+        public void CookieParameterStyleEnumValueExists()
+        {
+            // Arrange & Act
+            var cookieStyleExists = Enum.IsDefined(typeof(ParameterStyle), ParameterStyle.Cookie);
+
+            // Assert
+            Assert.True(cookieStyleExists);
+        }
+
+        [Fact]
+        public void CookieParameterStyleCanBeDeserialized()
+        {
+            // Arrange
+            var cookieStyleString = "cookie";
+
+            // Act
+            var success = cookieStyleString.TryGetEnumFromDisplayName<ParameterStyle>(out var parameterStyle);
+
+            // Assert
+            Assert.True(success);
+            Assert.Equal(ParameterStyle.Cookie, parameterStyle);
+        }
+
+        [Fact]
+        public async Task SerializeCookieParameterAsYamlV32Works()
+        {
+            // Arrange
+            var expected = """
+                name: sessionId
+                in: cookie
+                description: Session identifier stored in cookie
+                style: cookie
+                schema:
+                  type: string
+                """;
+
+            // Act
+            var actual = await CookieParameter.SerializeAsYamlAsync(OpenApiSpecVersion.OpenApi3_2);
+
+            // Assert
+            Assert.Equal(expected.MakeLineBreaksEnvironmentNeutral(), actual.MakeLineBreaksEnvironmentNeutral());
+        }
+
+        [Theory]
+        [InlineData(ParameterStyle.Form, true)]
+        [InlineData(ParameterStyle.SpaceDelimited, false)]
+        [InlineData(ParameterStyle.Cookie, true)]
+        public void WhenStyleIsFormOrCookieTheDefaultValueOfExplodeShouldBeTrueOtherwiseFalse(ParameterStyle? style, bool expectedExplode)
+        {
+            // Arrange
+            var parameter = new OpenApiParameter
+            {
+                Name = "name1",
+                In = ParameterLocation.Query,
+                Style = style
+            };
+
+            // Act & Assert
+            Assert.Equal(expectedExplode, parameter.Explode);
+        }
+    }
+}

test/Microsoft.OpenApi.Tests/PublicApi/PublicApi.approved.txt

@@ -1753,6 +1753,8 @@ namespace Microsoft.OpenApi
         PipeDelimited = 5,
         [Microsoft.OpenApi.Display("deepObject")]
         DeepObject = 6,
+        [Microsoft.OpenApi.Display("cookie")]
+        Cookie = 7,
     }
     public sealed class PathExpression : Microsoft.OpenApi.SourceExpression
     {