Accept multipart/form-data's part without Content-Type (#399)

Author: stakme

openapi3filter/req_resp_decoder.go

@@ -809,6 +809,11 @@ const prefixUnsupportedCT = "unsupported content type"
 // The function returns ParseError when a body is invalid.
 func decodeBody(body io.Reader, header http.Header, schema *openapi3.SchemaRef, encFn EncodingFn) (interface{}, error) {
 	contentType := header.Get(headerCT)
+	if contentType == "" {
+		if _, ok := body.(*multipart.Part); ok {
+			contentType = "text/plain"
+		}
+	}
 	mediaType := parseMediaType(contentType)
 	decoder, ok := bodyDecoders[mediaType]
 	if !ok {

openapi3filter/req_resp_decoder_test.go

@@ -974,6 +974,7 @@ func TestDecodeBody(t *testing.T) {
 		{name: "c", contentType: "text/plain", data: strings.NewReader("c2")},
 		{name: "d", contentType: "application/json", data: bytes.NewReader(d)},
 		{name: "f", contentType: "application/octet-stream", data: strings.NewReader("foo"), filename: "f1"},
+		{name: "g", data: strings.NewReader("g1")},
 	})
 	require.NoError(t, err)
 
@@ -987,10 +988,14 @@ func TestDecodeBody(t *testing.T) {
 		{name: "a", contentType: "text/plain", data: strings.NewReader("a1")},
 		{name: "x", contentType: "text/plain", data: strings.NewReader("x1")},
 	})
+	require.NoError(t, err)
+
 	multipartAdditionalProps, multipartMimeAdditionalProps, err := newTestMultipartForm([]*testFormPart{
 		{name: "a", contentType: "text/plain", data: strings.NewReader("a1")},
 		{name: "x", contentType: "text/plain", data: strings.NewReader("x1")},
 	})
+	require.NoError(t, err)
+
 	multipartAdditionalPropsErr, multipartMimeAdditionalPropsErr, err := newTestMultipartForm([]*testFormPart{
 		{name: "a", contentType: "text/plain", data: strings.NewReader("a1")},
 		{name: "x", contentType: "text/plain", data: strings.NewReader("x1")},
@@ -1075,8 +1080,9 @@ func TestDecodeBody(t *testing.T) {
 				WithProperty("b", openapi3.NewIntegerSchema()).
 				WithProperty("c", openapi3.NewArraySchema().WithItems(openapi3.NewStringSchema())).
 				WithProperty("d", openapi3.NewObjectSchema().WithProperty("d1", openapi3.NewStringSchema())).
-				WithProperty("f", openapi3.NewStringSchema().WithFormat("binary")),
-			want: map[string]interface{}{"a": "a1", "b": float64(10), "c": []interface{}{"c1", "c2"}, "d": map[string]interface{}{"d1": "d1"}, "f": "foo"},
+				WithProperty("f", openapi3.NewStringSchema().WithFormat("binary")).
+				WithProperty("g", openapi3.NewStringSchema()),
+			want: map[string]interface{}{"a": "a1", "b": float64(10), "c": []interface{}{"c1", "c2"}, "d": map[string]interface{}{"d1": "d1"}, "f": "foo", "g": "g1"},
 		},
 		{
 			name: "multipartExtraPart",