fix: set format to binary for file uploads

src/Microsoft.OpenApi/Reader/V2/OpenApiParameterDeserializer.cs

@@ -18,7 +18,7 @@
     /// </summary>
     internal static partial class OpenApiV2Deserializer
     {
         private static readonly FixedFieldMap<OpenApiParameter> _parameterFixedFields =
             new()
             {
                 {
@@ -72,8 +72,13 @@
                     {
                         var type = n.GetScalarValue();
                         if (type != null)
-                        {
-                            GetOrCreateSchema(o).Type = type.ToJsonSchemaType();
+                        {                            
+                            var schema = GetOrCreateSchema(o);
+                            schema.Type = type.ToJsonSchemaType();
+                            if ("file".Equals(type, StringComparison.OrdinalIgnoreCase))
+                            {
+                                schema.Format = "binary";
+                            }
                         }
                     }
                 },
@@ -209,7 +214,7 @@
             }
         }
 
         private static void LoadParameterExamplesExtension(OpenApiParameter parameter, ParseNode node, OpenApiDocument? hostDocument)
         {
             var examples = LoadExamplesExtension(node);
             node.Context.SetTempStorage(TempStorageKeys.Examples, examples, parameter);
@@ -219,11 +224,11 @@
         {
             return p.Schema switch {
                 OpenApiSchema schema => schema,
                 _ => (OpenApiSchema)(p.Schema = new OpenApiSchema()),
             };
         }
 
         private static void ProcessIn(OpenApiParameter o, ParseNode n, OpenApiDocument hostDocument)
         {
             var value = n.GetScalarValue();
             switch (value)

test/Microsoft.OpenApi.Readers.Tests/V2Tests/OpenApiParameterTests.cs

@@ -8,6 +8,8 @@
 using Microsoft.OpenApi.Models;
 using Microsoft.OpenApi.Reader.ParseNodes;
 using Microsoft.OpenApi.Reader.V2;
+using Microsoft.OpenApi.Tests;
+using Microsoft.OpenApi.Writers;
 using Xunit;
 
 namespace Microsoft.OpenApi.Readers.Tests.V2Tests
@@ -279,5 +281,32 @@ public void ParseParameterWithEnumShouldSucceed()
                                 .Excluding((IMemberInfo memberInfo) =>
                                     memberInfo.Path.EndsWith("Parent")));
         }
+
+        [Fact]
+        public void ParseFormDataParameterShouldSucceed()
+        {
+            // Arrange
+            var expected = @"{
+  ""type"": ""string"",
+  ""description"": ""file to upload"",
+  ""format"": ""binary""
+}";
+            MapNode node;
+            using (var stream = Resources.GetStream(Path.Combine(SampleFolderPath, "formDataParameter.json")))
+            {
+                node = TestHelper.CreateYamlMapNode(stream);
+            }
+
+            // Act
+            var operation = OpenApiV2Deserializer.LoadOperation(node, new());
+            var schema = operation.RequestBody?.Content["multipart/form-data"].Schema.Properties["file"];
+            var writer = new StringWriter();
+            schema.SerializeAsV2(new OpenApiJsonWriter(writer));
+            var json = writer.ToString();
+
+            // Assert
+            Assert.Equal("binary", schema.Format);
+            Assert.Equal(expected.MakeLineBreaksEnvironmentNeutral(), json.MakeLineBreaksEnvironmentNeutral());
+        }
     }
 }

test/Microsoft.OpenApi.Readers.Tests/V2Tests/Samples/OpenApiParameter/formDataParameter.json

@@ -0,0 +1,32 @@
+{
+  "tags": [ "pet" ],
+  "summary": "uploads an image",
+  "description": "",
+  "operationId": "uploadFile",
+  "consumes": [ "multipart/form-data" ],
+  "produces": [ "application/json" ],
+  "parameters": [
+    {
+      "name": "petId",
+      "in": "path",
+      "description": "ID of pet to update",
+      "required": true,
+      "type": "integer",
+      "format": "int64"
+    },
+    {
+      "name": "additionalMetadata",
+      "in": "formData",
+      "description": "Additional data to pass to server",
+      "required": false,
+      "type": "string"
+    },
+    {
+      "name": "file",
+      "in": "formData",
+      "description": "file to upload",
+      "required": false,
+      "type": "file"
+    }
+  ]
+}