Wrong Submit button detected if form$fields$type is missing

[rentrop]

Taking this example form:

require(rvest)
ses <- html_session("https://www.handelsregister.de/rp_web/mask.do?Typ=e")
form <- ses %>% html_form() %>% .[[1]]
submit_form(ses, form, submit = 'foo')

submit_form exits with the error

Error: Unknown submission name 'foo'.
Possible values: bundeslandTH, schlagwortOptionen, ort

Looking at the form all three "Possible values" are no submit-buttons:

<input checkbox> 'bundeslandTH':
<input radio> 'schlagwortOptionen':
<input text> 'ort':

digging into submit_form and submit_request it turns out that there are form$fields that do not have a form$fields$type.

rvest:::submit_request reads as follows:

is_submit <- function(x) tolower(x$type) %in% c("submit", 
    "image", "button")
  submits <- Filter(is_submit, form$fields)
  if (length(submits) == 0) {
    stop("Could not find possible submission target.", call. = FALSE)
  }
...

As the form$fields$type is missing is_submit returns logical(0) which is not at all handled by Filter

[bramtayl]

Same issue at http://stackoverflow.com/questions/39443357/rvest-trouble-post-submission/39515073#39515073

[rentrop]

Same issue at https://stackoverflow.com/questions/34830882/how-to-submit-login-form-in-rvest-package-w-o-button-argument