danielgtaylor · b-kamphorst · Dec 31, 2024
diff --git a/formdata.go b/formdata.go
@@ -150,6 +150,24 @@ func (m *MultipartFormFiles[T]) readMultipleFiles(key string, opMediaType *Media
 	return files, errors
 }
 
+func (m *MultipartFormFiles[T]) readSingleString(key string, opMediaType *MediaType) (string, *ErrorDetail) {
+	values := m.Form.Value[key]
+	if len(values) > 1 {
+		return "", &ErrorDetail{
+			Message:  "Multiple strings received but only one was expected",
+			Location: key,
+		}
+	}
+	if len(values) == 0 {
+		if opMediaType.Schema.requiredMap[key] {
+			return "", &ErrorDetail{Message: "String required", Location: key}
+		} else {
+			return "", nil
+		}
+	}
+	return values[0], nil
+}
+
 func (m *MultipartFormFiles[T]) Data() *T {
 	return m.data
 }
@@ -184,7 +202,13 @@ func (m *MultipartFormFiles[T]) Decode(opMediaType *MediaType) []error {
 				continue
 			}
 			field.Set(reflect.ValueOf(files))
-
+		case field.Type().Kind() == reflect.String:
+			s, err := m.readSingleString(key, opMediaType)
+			if err != nil {
+				errors = append(errors, err)
+				continue
+			}
+			field.Set(reflect.ValueOf(s))
 		default:
 			continue
 		}
@@ -221,6 +245,8 @@ func multiPartFormFileSchema(t reflect.Type) *Schema {
 				Type:  "array",
 				Items: multiPartFileSchema(f),
 			}
+		case f.Type.Kind() == reflect.String:
+			schema.Properties[name] = &Schema{Type: TypeString}
 		default:
 			// Should we panic if [T] struct defines fields with unsupported types ?
 			continue
@@ -250,9 +276,19 @@ func multiPartContentEncoding(t reflect.Type) map[string]*Encoding {
 	for i := 0; i < nFields; i++ {
 		f := t.Field(i)
 		name := formDataFieldName(f)
-		contentType := f.Tag.Get("contentType")
-		if contentType == "" {
-			contentType = "application/octet-stream"
+		var contentType string
+		switch {
+		case f.Type == reflect.TypeOf(FormFile{}):
+			fallthrough
+		case f.Type == reflect.TypeOf([]FormFile{}):
+			contentType = f.Tag.Get("contentType")
+			if contentType == "" {
+				contentType = "application/octet-stream"
+			}
+		case f.Type.Kind() == reflect.String:
+			contentType = "text/plain"
+		default:
+			continue
 		}
 		encoding[name] = &Encoding{
 			ContentType: contentType,

diff --git a/huma.go b/huma.go
@@ -1336,7 +1336,7 @@ func Register[I, O any](api API, op Operation, handler func(context.Context, *I)
 							res.Errors = append(res.Errors, &ErrorDetail{
 								Location: "body",
 								Message:  err.Error(),
-								Value:    string(body),
+								Value:    body,
 							})
 							parseErrCount++
 						} else {

diff --git a/huma_test.go b/huma_test.go
@@ -1367,6 +1367,82 @@ Content of example2.txt.
 				assert.Equal(t, http.StatusUnprocessableEntity, resp.Code)
 			},
 		},
+		{
+			Name: "request-body-multipart-file-decoded-with-strings-required",
+			Register: func(t *testing.T, api huma.API) {
+				huma.Register(api, huma.Operation{
+					Method: http.MethodPost,
+					Path:   "/upload",
+				}, func(ctx context.Context, input *struct {
+					RawBody huma.MultipartFormFiles[struct {
+						HelloWorld huma.FormFile `form:"file" contentType:"text/plain"`
+						Sender     string        `form:"sender" required:"true"`
+					}]
+				}) (*struct{}, error) {
+					fileData := input.RawBody.Data()
+
+					assert.Equal(t, "text/plain", fileData.HelloWorld.ContentType)
+					assert.Equal(t, "test.txt", fileData.HelloWorld.Filename)
+					assert.Equal(t, len("Hello, World!"), int(fileData.HelloWorld.Size))
+					assert.True(t, fileData.HelloWorld.IsSet)
+					b, err := io.ReadAll(fileData.HelloWorld)
+					require.NoError(t, err)
+					assert.Equal(t, "Hello, World!", string(b))
+
+					assert.Equal(t, "Your favorite sender", fileData.Sender)
+					return nil, nil
+				})
+
+				// Ensure OpenAPI spec is listed as a multipart/form-data upload with
+				// the appropriate schema.
+				mpContent := api.OpenAPI().Paths["/upload"].Post.RequestBody.Content["multipart/form-data"]
+				assert.Equal(t, "text/plain", mpContent.Encoding["file"].ContentType)
+				assert.Equal(t, "text/plain", mpContent.Encoding["sender"].ContentType)
+				assert.Equal(t, "string", mpContent.Schema.Properties["sender"].Type)
+				assert.Contains(t, mpContent.Schema.Required, "sender")
+			},
+			Method:  http.MethodPost,
+			URL:     "/upload",
+			Headers: map[string]string{"Content-Type": "multipart/form-data; boundary=SimpleBoundary"},
+			Body: `--SimpleBoundary
+Content-Disposition: form-data; name="file"; filename="test.txt"
+Content-Type: text/plain
+
+Hello, World!
+--SimpleBoundary
+Content-Disposition: form-data; name="sender"
+Content-Type: text/plain
+
+Your favorite sender
+--SimpleBoundary--`,
+		},
+		{
+			Name: "request-body-multipart-file-decoded-with-strings-required-missing",
+			Register: func(t *testing.T, api huma.API) {
+				huma.Register(api, huma.Operation{
+					Method: http.MethodPost,
+					Path:   "/upload",
+				}, func(ctx context.Context, input *struct {
+					RawBody huma.MultipartFormFiles[struct {
+						Sender string `form:"sender" required:"true"`
+					}]
+				}) (*struct{}, error) {
+					return nil, nil
+				})
+			},
+			Method:  http.MethodPost,
+			URL:     "/upload",
+			Headers: map[string]string{"Content-Type": "multipart/form-data; boundary=SimpleBoundary"},
+			Body:    `--SimpleBoundary--`,
+			Assert: func(t *testing.T, resp *httptest.ResponseRecorder) {
+				if ok := assert.Equal(t, http.StatusUnprocessableEntity, resp.Code); ok {
+					var errors huma.ErrorModel
+					err := json.Unmarshal(resp.Body.Bytes(), &errors)
+					require.NoError(t, err)
+					assert.Equal(t, "sender", errors.Errors[0].Location)
+				}
+			},
+		},
 		{
 			Name: "handler-error",
 			Register: func(t *testing.T, api huma.API) {