Filling and submit search with rvest in R - r

Question

I am learning how to fill forms and submit with rvest in R, and I got stucked when I want to search for ggplot tag in stackoverflow. This is my code:
url<-"https://stackoverflow.com/questions"
(session<-html_session("https://stackoverflow.com/questions"))
(form<-html_form(session)[[2]])
(filled_form<-set_values(form, tagQuery = "ggplot"))
searched<-submit_form(session, filled_form)
I've got the error:
Submitting with '<unnamed>'
Error in parse_url(url) : length(url) == 1 is not TRUE
Follow this question (rvest error on form submission) I tried several things to solve this, but I couldnt:
filled_form$fields[[13]]$name<-"submit"
filled_form$fields[[14]]$name<-"submit"
filled_form$fields[[13]]$type<-"button"
filled_form$fields[[14]]$type<-"button"
Any help guys

Answer 1

The search query is in html_form(session)[[1]]
As there is no submit button in this form :
<form> 'search' (GET /search)
<input text> 'q':
this workaround seems to work :
<form> 'search' (GET /search)
<input text> 'q':
<input submit> '':
Giving the following code sequence :
library(rvest)
url<-"https://stackoverflow.com/questions"
(session<-html_session("https://stackoverflow.com/questions"))
(form<-html_form(session)[[1]])
fake_submit_button <- list(name = NULL,
type = "submit",
value = NULL,
checked = NULL,
disabled = NULL,
readonly = NULL,
required = FALSE)
attr(fake_submit_button, "class") <- "input"
form[["fields"]][["submit"]] <- fake_submit_button
(filled_form<-set_values(form, q = "ggplot"))
searched<-submit_form(session, filled_form)
the problem is that the reply has a captcha :
searched$url
[1] "https://stackoverflow.com/nocaptcha?s=7291e7e6-9b8b-4b5f-bd1c-0f6890c23573"
You won't be able to handle this with rvest, but after clicking manually on the captcha you get the query you're looking for :
https://stackoverflow.com/search?q=ggplot
Probably much easier to use my other answer with:
read_html(paste0('https://stackoverflow.com/search?tab=newest&q=',search))