.Net: DefaultValue for OpenAPI payload properties (#4612)

### Motivation and Context  
Currently, the default values of parameters in OpenAPI plugins have the
'string?' type, even though their original type specified in the OpenAPI
document schema might be different. A dedicated type conversion
functionality exists to convert from the original type to a string.
However, both the string type for the parameters/arguments and the type
conversion logic are no longer necessary, as SK has moved away from
string-type arguments and recently added support for .NET primitive
types and complex types.
   
Furthermore, the `RestApiOperationPayloadProperty` class does not have a
property for default values, so a default value specified in an OpenAPI
document is lost and cannot be accessed from the code.
   
### Description  
1. The type of the `DefaultValue` property in the
`RestApiOperationParameter` class has been changed from string? to
object? to better represent the actual type of the parameter's default
value and eliminate unnecessary conversion to string.
   
2. A new `DefaultValue` property has been added to the
`RestApiOperationPayloadProperty`, making it consistent with the
RestApiOperationParameter class.

dotnet/src/Functions/Functions.OpenApi/Extensions/RestApiOperationExtensions.cs

@@ -179,6 +179,7 @@ private static List<RestApiOperationParameter> GetParametersFromPayloadMetadata(
                     expand: false,
                     RestApiOperationParameterLocation.Body,
                     RestApiOperationParameterStyle.Simple,
+                    defaultValue: property.DefaultValue,
                     description: property.Description,
                     schema: property.Schema));
             }

dotnet/src/Functions/Functions.OpenApi/Model/RestApiOperationParameter.cs

@@ -50,7 +50,7 @@ public sealed class RestApiOperationParameter
     /// <summary>
     /// The default value.
     /// </summary>
-    public string? DefaultValue { get; }
+    public object? DefaultValue { get; }
 
     /// <summary>
     /// Specifies whether arrays and objects should generate separate parameters for each array item or object property.
@@ -83,7 +83,7 @@ public RestApiOperationParameter(
         RestApiOperationParameterLocation location,
         RestApiOperationParameterStyle? style = null,
         string? arrayItemType = null,
-        string? defaultValue = null,
+        object? defaultValue = null,
         string? description = null,
         KernelJsonSchema? schema = null)
     {

dotnet/src/Functions/Functions.OpenApi/Model/RestApiOperationPayloadProperty.cs

@@ -39,28 +39,37 @@ public sealed class RestApiOperationPayloadProperty
     /// </summary>
     public KernelJsonSchema? Schema { get; }
 
+    /// <summary>
+    /// The default value.
+    /// </summary>
+    public object? DefaultValue { get; }
+
     /// <summary>
     /// Creates an instance of a <see cref="RestApiOperationPayloadProperty"/> class.
     /// </summary>
-    /// <param name="name">Property name.</param>
-    /// <param name="type">Property type.</param>
-    /// <param name="isRequired">Flag specifying if the property is required or not.</param>
-    /// <param name="properties">Properties.</param>
-    /// <param name="description">Property description.</param>
+    /// <param name="name">The name of the property.</param>
+    /// <param name="type">The type of the property.</param>
+    /// <param name="isRequired">A flag specifying if the property is required or not.</param>
+    /// <param name="properties">A list of properties for the payload property.</param>
+    /// <param name="description">A description of the property.</param>
     /// <param name="schema">The schema of the payload property.</param>
+    /// <param name="defaultValue">The default value of the property.</param>
+    /// <returns>Returns a new instance of the <see cref="RestApiOperationPayloadProperty"/> class.</returns>
     public RestApiOperationPayloadProperty(
         string name,
         string type,
         bool isRequired,
         IList<RestApiOperationPayloadProperty> properties,
         string? description = null,
-        KernelJsonSchema? schema = null)
+        KernelJsonSchema? schema = null,
+        object? defaultValue = null)
     {
         this.Name = name;
         this.Type = type;
         this.IsRequired = isRequired;
         this.Description = description;
         this.Properties = properties;
         this.Schema = schema;
+        this.DefaultValue = defaultValue;
     }
 }

dotnet/src/Functions/Functions.OpenApi/OpenApi/OpenApiDocumentParser.cs

@@ -2,7 +2,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.Globalization;
 using System.IO;
 using System.Linq;
 using System.Net.Http;
@@ -313,7 +312,8 @@ private static List<RestApiOperationPayloadProperty> GetPayloadProperties(string
                 requiredProperties.Contains(propertyName),
                 GetPayloadProperties(operationId, propertySchema, requiredProperties, level + 1),
                 propertySchema.Description,
-                propertySchema.ToJsonSchema());
+                propertySchema.ToJsonSchema(),
+                GetParameterValue(propertySchema.Default));
 
             result.Add(property);
         }
@@ -326,7 +326,7 @@ private static List<RestApiOperationPayloadProperty> GetPayloadProperties(string
     /// </summary>
     /// <param name="valueMetadata">The value metadata.</param>
     /// <returns>The parameter value.</returns>
-    private static string? GetParameterValue(IOpenApiAny valueMetadata)
+    private static object? GetParameterValue(IOpenApiAny valueMetadata)
     {
         if (valueMetadata is not IOpenApiPrimitive value)
         {
@@ -335,17 +335,17 @@ private static List<RestApiOperationPayloadProperty> GetPayloadProperties(string
 
         return value.PrimitiveType switch
         {
-            PrimitiveType.Integer => ((OpenApiInteger)value).Value.ToString(CultureInfo.InvariantCulture),
-            PrimitiveType.Long => ((OpenApiLong)value).Value.ToString(CultureInfo.InvariantCulture),
-            PrimitiveType.Float => ((OpenApiFloat)value).Value.ToString(CultureInfo.InvariantCulture),
-            PrimitiveType.Double => ((OpenApiDouble)value).Value.ToString(CultureInfo.InvariantCulture),
-            PrimitiveType.String => ((OpenApiString)value).Value.ToString(CultureInfo.InvariantCulture),
-            PrimitiveType.Byte => Convert.ToBase64String(((OpenApiByte)value).Value),
-            PrimitiveType.Binary => Encoding.UTF8.GetString(((OpenApiBinary)value).Value),
-            PrimitiveType.Boolean => ((OpenApiBoolean)value).Value.ToString(CultureInfo.InvariantCulture),
-            PrimitiveType.Date => ((OpenApiDate)value).Value.ToString("o").Substring(0, 10),
-            PrimitiveType.DateTime => ((OpenApiDateTime)value).Value.ToString(CultureInfo.InvariantCulture),
-            PrimitiveType.Password => ((OpenApiPassword)value).Value.ToString(CultureInfo.InvariantCulture),
+            PrimitiveType.Integer => ((OpenApiInteger)value).Value,
+            PrimitiveType.Long => ((OpenApiLong)value).Value,
+            PrimitiveType.Float => ((OpenApiFloat)value).Value,
+            PrimitiveType.Double => ((OpenApiDouble)value).Value,
+            PrimitiveType.String => ((OpenApiString)value).Value,
+            PrimitiveType.Byte => ((OpenApiByte)value).Value,
+            PrimitiveType.Binary => ((OpenApiBinary)value).Value,
+            PrimitiveType.Boolean => ((OpenApiBoolean)value).Value,
+            PrimitiveType.Date => ((OpenApiDate)value).Value,
+            PrimitiveType.DateTime => ((OpenApiDateTime)value).Value,
+            PrimitiveType.Password => ((OpenApiPassword)value).Value,
             _ => throw new KernelException($"The value type - {value.PrimitiveType} is not supported."),
         };
     }

dotnet/src/Functions/Functions.UnitTests/OpenApi/Extensions/RestApiOperationExtensionsTests.cs

@@ -280,18 +280,53 @@ private static RestApiOperation CreateTestOperation(string method, RestApiOperat
 
     private static RestApiOperationPayload CreateTestJsonPayload()
     {
-        var name = new RestApiOperationPayloadProperty("name", "string", true, new List<RestApiOperationPayloadProperty>(), "The name.");
-
-        var leader = new RestApiOperationPayloadProperty("leader", "string", true, new List<RestApiOperationPayloadProperty>(), "The leader.");
-
-        var landmarks = new RestApiOperationPayloadProperty("landmarks", "array", false, new List<RestApiOperationPayloadProperty>(), "The landmarks.");
-        var location = new RestApiOperationPayloadProperty("location", "object", true, new[] { landmarks }, "The location.");
-
-        var rulingCouncil = new RestApiOperationPayloadProperty("rulingCouncil", "object", true, new[] { leader }, "The ruling council.");
-
-        var population = new RestApiOperationPayloadProperty("population", "integer", true, new List<RestApiOperationPayloadProperty>(), "The population.");
-
-        var hasMagicWards = new RestApiOperationPayloadProperty("hasMagicWards", "boolean", false, new List<RestApiOperationPayloadProperty>());
+        var name = new RestApiOperationPayloadProperty(
+            name: "name",
+            type: "string",
+            isRequired: true,
+            properties: new List<RestApiOperationPayloadProperty>(),
+            description: "The name.");
+
+        var leader = new RestApiOperationPayloadProperty(
+            name: "leader",
+            type: "string",
+            isRequired: true,
+            properties: new List<RestApiOperationPayloadProperty>(),
+            description: "The leader.");
+
+        var landmarks = new RestApiOperationPayloadProperty(
+            name: "landmarks",
+            type: "array",
+            isRequired: false,
+            properties: new List<RestApiOperationPayloadProperty>(),
+            description: "The landmarks.");
+
+        var location = new RestApiOperationPayloadProperty(
+            name: "location",
+            type: "object",
+            isRequired: true,
+            properties: new[] { landmarks },
+            description: "The location.");
+
+        var rulingCouncil = new RestApiOperationPayloadProperty(
+            name: "rulingCouncil",
+            type: "object",
+            isRequired: true,
+            properties: new[] { leader },
+            description: "The ruling council.");
+
+        var population = new RestApiOperationPayloadProperty(
+            name: "population",
+            type: "integer",
+            isRequired: true,
+            properties: new List<RestApiOperationPayloadProperty>(),
+            description: "The population.");
+
+        var hasMagicWards = new RestApiOperationPayloadProperty(
+            name: "hasMagicWards",
+            type: "boolean",
+            isRequired: false,
+            properties: new List<RestApiOperationPayloadProperty>());
 
         return new RestApiOperationPayload("application/json", new[] { name, location, rulingCouncil, population, hasMagicWards });
     }

dotnet/src/Functions/Functions.UnitTests/OpenApi/OpenApiDocumentParserV20Tests.cs

@@ -175,7 +175,7 @@ public async Task ItCanExtractSimpleTypeHeaderParameterMetadataSuccessfullyAsync
         var apiVersion = GetParameterMetadata(operations, "SetSecret", RestApiOperationParameterLocation.Header, "X-API-Version");
 
         Assert.Equal("integer", apiVersion.Type);
-        Assert.Equal("10", apiVersion.DefaultValue);
+        Assert.Equal(10, apiVersion.DefaultValue);
         Assert.Equal("Requested API version.", apiVersion.Description);
         Assert.True(apiVersion.IsRequired);
     }
@@ -225,7 +225,7 @@ public async Task ItCanExtractAllPathsAsOperationsAsync()
         var operations = await this._sut.ParseAsync(this._openApiDocument);
 
         // Assert
-        Assert.Equal(3, operations.Count);
+        Assert.Equal(4, operations.Count);
     }
 
     [Fact]
@@ -293,6 +293,65 @@ public async Task ItCanParseResponsesSuccessfullyAsync()
             JsonSerializer.Serialize(response.Schema));
     }
 
+    [Fact]
+    public async Task ItCanWorkWithDefaultParametersOfVariousTypesAsync()
+    {
+        //Act
+        var operations = await this._sut.ParseAsync(this._openApiDocument);
+
+        //Assert
+        Assert.NotNull(operations);
+        Assert.True(operations.Any());
+
+        var operation = operations.Single(o => o.Id == "TestDefaultValues");
+        Assert.NotNull(operation);
+
+        var parameters = operation.GetParameters();
+        Assert.Equal(11, parameters.Count);
+
+        var stringParameter = parameters.Single(p => p.Name == "string-parameter");
+        Assert.Equal("string-value", stringParameter.DefaultValue);
+
+        var booleanParameter = parameters.Single(p => p.Name == "boolean-parameter");
+        Assert.True(booleanParameter.DefaultValue is bool value);
+
+        var integerParameter = parameters.Single(p => p.Name == "integer-parameter");
+        Assert.True(integerParameter.DefaultValue is int);
+        Assert.Equal(281, integerParameter.DefaultValue);
+
+        var longParameter = parameters.Single(p => p.Name == "long-parameter");
+        Assert.True(longParameter.DefaultValue is long);
+        Assert.Equal((long)-2814, longParameter.DefaultValue);
+
+        var floatParameter = parameters.Single(p => p.Name == "float-parameter");
+        Assert.True(floatParameter.DefaultValue is float);
+        Assert.Equal((float)12.01, floatParameter.DefaultValue);
+
+        var doubleParameter = parameters.Single(p => p.Name == "double-parameter");
+        Assert.True(doubleParameter.DefaultValue is double);
+        Assert.Equal((double)-12.01, doubleParameter.DefaultValue);
+
+        var encodedCharactersParameter = parameters.Single(p => p.Name == "encoded-characters-parameter");
+        Assert.True(encodedCharactersParameter.DefaultValue is byte[]);
+        Assert.Equal(new byte[] { 1, 2, 3, 4, 5 }, encodedCharactersParameter.DefaultValue);
+
+        var binaryDataParameter = parameters.Single(p => p.Name == "binary-data-parameter");
+        Assert.True(binaryDataParameter.DefaultValue is byte[]);
+        Assert.Equal(new byte[] { 50, 51, 52, 53, 54 }, binaryDataParameter.DefaultValue);
+
+        var dateParameter = parameters.Single(p => p.Name == "date-parameter");
+        Assert.True(dateParameter.DefaultValue is DateTime);
+        Assert.Equal(new DateTime(2017, 07, 21), dateParameter.DefaultValue);
+
+        var dateTimeParameter = parameters.Single(p => p.Name == "date-time-parameter");
+        Assert.True(dateTimeParameter.DefaultValue is DateTimeOffset);
+        Assert.Equal(new DateTimeOffset(2017, 07, 21, 17, 32, 28, TimeSpan.Zero), dateTimeParameter.DefaultValue);
+
+        var passwordParameter = parameters.Single(p => p.Name == "password-parameter");
+        Assert.True(passwordParameter.DefaultValue is string);
+        Assert.Equal("password-value", passwordParameter.DefaultValue);
+    }
+
     private static RestApiOperationParameter GetParameterMetadata(IList<RestApiOperation> operations, string operationId,
         RestApiOperationParameterLocation location, string name)
     {

dotnet/src/Functions/Functions.UnitTests/OpenApi/OpenApiDocumentParserV30Tests.cs

@@ -161,7 +161,7 @@ public async Task ItCanExtractSimpleTypeHeaderParameterMetadataSuccessfullyAsync
         var apiVersion = GetParameterMetadata(operations, "SetSecret", RestApiOperationParameterLocation.Header, "X-API-Version");
 
         Assert.Equal("integer", apiVersion.Type);
-        Assert.Equal("10", apiVersion.DefaultValue);
+        Assert.Equal(10, apiVersion.DefaultValue);
         Assert.Equal("Requested API version.", apiVersion.Description);
         Assert.True(apiVersion.IsRequired);
     }
@@ -226,7 +226,7 @@ public async Task ItCanExtractAllPathsAsOperationsAsync()
         var operations = await this._sut.ParseAsync(this._openApiDocument);
 
         // Assert
-        Assert.Equal(3, operations.Count);
+        Assert.Equal(4, operations.Count);
     }
 
     [Fact]
@@ -366,6 +366,65 @@ public async Task ItCanParseResponsesSuccessfullyAsync()
             JsonSerializer.Serialize(response.Schema));
     }
 
+    [Fact]
+    public async Task ItCanWorkWithDefaultParametersOfVariousTypesAsync()
+    {
+        //Act
+        var operations = await this._sut.ParseAsync(this._openApiDocument);
+
+        //Assert
+        Assert.NotNull(operations);
+        Assert.True(operations.Any());
+
+        var operation = operations.Single(o => o.Id == "TestDefaultValues");
+        Assert.NotNull(operation);
+
+        var parameters = operation.GetParameters();
+        Assert.Equal(11, parameters.Count);
+
+        var stringParameter = parameters.Single(p => p.Name == "string-parameter");
+        Assert.Equal("string-value", stringParameter.DefaultValue);
+
+        var booleanParameter = parameters.Single(p => p.Name == "boolean-parameter");
+        Assert.True(booleanParameter.DefaultValue is bool value);
+
+        var integerParameter = parameters.Single(p => p.Name == "integer-parameter");
+        Assert.True(integerParameter.DefaultValue is int);
+        Assert.Equal(281, integerParameter.DefaultValue);
+
+        var longParameter = parameters.Single(p => p.Name == "long-parameter");
+        Assert.True(longParameter.DefaultValue is long);
+        Assert.Equal((long)-2814, longParameter.DefaultValue);
+
+        var floatParameter = parameters.Single(p => p.Name == "float-parameter");
+        Assert.True(floatParameter.DefaultValue is float);
+        Assert.Equal((float)12.01, floatParameter.DefaultValue);
+
+        var doubleParameter = parameters.Single(p => p.Name == "double-parameter");
+        Assert.True(doubleParameter.DefaultValue is double);
+        Assert.Equal((double)-12.01, doubleParameter.DefaultValue);
+
+        var encodedCharactersParameter = parameters.Single(p => p.Name == "encoded-characters-parameter");
+        Assert.True(encodedCharactersParameter.DefaultValue is byte[]);
+        Assert.Equal(new byte[] { 1, 2, 3, 4, 5 }, encodedCharactersParameter.DefaultValue);
+
+        var binaryDataParameter = parameters.Single(p => p.Name == "binary-data-parameter");
+        Assert.True(binaryDataParameter.DefaultValue is byte[]);
+        Assert.Equal(new byte[] { 50, 51, 52, 53, 54 }, binaryDataParameter.DefaultValue);
+
+        var dateParameter = parameters.Single(p => p.Name == "date-parameter");
+        Assert.True(dateParameter.DefaultValue is DateTime);
+        Assert.Equal(new DateTime(2017, 07, 21), dateParameter.DefaultValue);
+
+        var dateTimeParameter = parameters.Single(p => p.Name == "date-time-parameter");
+        Assert.True(dateTimeParameter.DefaultValue is DateTimeOffset);
+        Assert.Equal(new DateTimeOffset(2017, 07, 21, 17, 32, 28, TimeSpan.Zero), dateTimeParameter.DefaultValue);
+
+        var passwordParameter = parameters.Single(p => p.Name == "password-parameter");
+        Assert.True(passwordParameter.DefaultValue is string);
+        Assert.Equal("password-value", passwordParameter.DefaultValue);
+    }
+
     private static MemoryStream ModifyOpenApiDocument(Stream openApiDocument, Action<JsonObject> transformer)
     {
         var json = JsonSerializer.Deserialize<JsonObject>(openApiDocument);