feat(platform-express): multer errors show 'field'

Multer errors may include a 'field' property for certain errors. Pass it
along into the error message.

packages/platform-express/multer/multer/multer.utils.ts

@@ -19,6 +19,11 @@ export function transformException(error: Error | undefined) {
     case multerExceptions.LIMIT_UNEXPECTED_FILE:
     case multerExceptions.LIMIT_PART_COUNT:
     case multerExceptions.MISSING_FIELD_NAME:
+      //@ts-expect-error: Multer may attach the fieldname to the error object
+      if (error.field) {
+        //@ts-expect-error: Multer may attach the fieldname to the error object
+        return new BadRequestException(`${error.message} - ${error.field}`);
+      }
       return new BadRequestException(error.message);
     case busboyExceptions.MULTIPART_BOUNDARY_NOT_FOUND:
       return new BadRequestException(error.message);

packages/platform-express/test/multer/multer/multer.utils.spec.ts

@@ -57,5 +57,16 @@ describe('transformException', () => {
         );
       });
     });
+    describe(`and has a 'field' property`, () => {
+      it('should return the field propery appended to the error message', () => {
+        const err = {
+          message: multerExceptions.LIMIT_UNEXPECTED_FILE,
+          field: 'foo',
+        };
+        expect(transformException(err as any).message).to.equal(
+          `${multerExceptions.LIMIT_UNEXPECTED_FILE} - foo`,
+        );
+      });
+    });
   });
 });