fix(v2): map OpenAPI 2.0 response schema type file to binary format (#3150) (#3151)

* test(v2): add unit test for OpenAPI 2.0 schema type file mapping to binary format

* fix(v2): set format binary when reading OpenAPI 2.0 schema with type file

* test(v2): add response schema integration test for type file

* docs(v2): document OpenAPI 2.0 file type to binary format mapping in schema deserializer

* test(v2): parse enclosing operation with produces to populate response content schema

Co-authored-by: Hardik K <hardikkaurani1@gmail.com>

Author: baywet

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

@@ -1,4 +1,4 @@
-// Copyright (c) Microsoft Corporation. All rights reserved.
+// Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT license.
 
 using System;
@@ -170,6 +170,11 @@ internal static partial class OpenApiV2Deserializer
                     if (type != null)
                     {
                         o.Type = type.ToJsonSchemaType();
+                        // OpenAPI 2.0 response schema allows type: file, which maps to format: binary in OpenAPI 3.x
+                        if ("file".Equals(type, StringComparison.OrdinalIgnoreCase))
+                        {
+                            o.Format = "binary";
+                        }
                     }
                 }
             },

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

@@ -1,4 +1,4 @@
-// Copyright (c) Microsoft Corporation. All rights reserved.
+// Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT license.
 
 using System.Collections.Generic;
@@ -186,5 +186,40 @@ public async Task SerializeSchemaWithOnlyNullableShouldSucceed()
 
             Assert.Equal(expected.MakeLineBreaksEnvironmentNeutral(), schemaString.MakeLineBreaksEnvironmentNeutral());
         }
+
+        [Fact]
+        public void ParseSchemaWithTypeFileShouldSetTypeStringAndFormatBinary()
+        {
+            // Arrange
+            var node = JsonNode.Parse("{\"type\": \"file\"}");
+
+            // Act
+            var schema = OpenApiV2Deserializer.LoadSchema(node, new(), new ParsingContext(new()));
+
+            // Assert
+            Assert.NotNull(schema);
+            Assert.Equal(JsonSchemaType.String, schema.Type);
+            Assert.Equal("binary", schema.Format);
+        }
+
+        [Fact]
+        public void ParseResponseSchemaWithTypeFileShouldSetTypeStringAndFormatBinary()
+        {
+            // Arrange
+            var node = JsonNode.Parse("{\"produces\": [\"application/octet-stream\"], \"responses\": {\"200\": {\"description\": \"File response\", \"schema\": {\"type\": \"file\"}}}}");
+
+            // Act
+            var operation = OpenApiV2Deserializer.LoadOperation(node, new(), new ParsingContext(new()));
+
+            // Assert
+            Assert.NotNull(operation);
+            Assert.NotNull(operation.Responses);
+            var response = Assert.IsType<OpenApiResponse>(operation.Responses["200"]);
+            Assert.NotNull(response.Content);
+            var mediaType = Assert.Single(response.Content.Values);
+            Assert.NotNull(mediaType.Schema);
+            Assert.Equal(JsonSchemaType.String, mediaType.Schema.Type);
+            Assert.Equal("binary", mediaType.Schema.Format);
+        }
     }
 }