如何使用 RSelenium 从网页下载嵌入式 PDF 文件？

Question

EDIT: From the comments I received so far, I managed to use RSelenium to access the PDF files I am looking for, using the following code:

library(RSelenium)
driver <- rsDriver(browser = "firefox")
remote_driver <- driver[["client"]]
remote_driver$navigate("https://www.rad.cvm.gov.br/enetconsulta/frmGerenciaPaginaFRE.aspx?CodigoTipoInstituicao=1&NumeroSequencialDocumento=62398")
# It needs some time to load the page
option <- remote_driver$findElement(using = 'xpath', "//select[@id='cmbGrupo']/option[@value='PDF|412']")
option$clickElement()

Now, I need R to click the download button, but I could not manage to do so. I tried:

button <- remote_driver$findElement(using = "xpath", "//*[@id='download']")
button$clickElement()

But I get the following error:

Selenium message:Unable to locate element: //*[@id="download"]
For documentation on this error, please visit: https://www.seleniumhq.org/exceptions/no_such_element.html
Build info: version: '4.0.0-alpha-2', revision: 'f148142cf8', time: '2019-07-01T21:30:10'

Erro:    Summary: NoSuchElement
 Detail: An element could not be located on the page using the given search parameters.
 class: org.openqa.selenium.NoSuchElementException
 Further Details: run errorDetails method

Can someone tell what is wrong here? Thanks!

Original question:

I have several webpages from which I need to download embedded PDF files and I am looking for a way to automate it with R. This is one of the webpages: https://www.rad.cvm.gov.br/enetconsulta/frmGerenciaPaginaFRE.aspx?CodigoTipoInstituicao=1&NumeroSequencialDocumento=62398 This is a webpage from CVM ( Comissão de Valores Mobiliários , the Brazilian equivalent to the US Securities and Exchange Commission - SEC) to download Notes to Financial Statements ( Notas Explicativas ) from Brazilian companies.

I tried several options but the website seems to be built in a way that makes it difficult to extract the direct links. I tried what is suggested in here Downloading all PDFs from URL , but the html_nodes(".ms-vb2 a") %>% html_attr("href") yields an empty character vector. Similarly, when I tried the approach in here https://www.samuelworkman.org/blog/scraping-up-bits-of-helpfulness/ , the html_attr("href") generates an empty vector.

I am not used to web scraping codes in R, so I cannot figure out what is happening. I appreciate any help!

Answer 1

If someone is facing the same problem I did, I am posting the solution I used:

# set Firefox profile to download PDFs automatically
pdfprof <- makeFirefoxProfile(list(
  "pdfjs.disabled" = TRUE,
  "plugin.scan.plid.all" = FALSE,
  "plugin.scan.Acrobat" = "99.0",
  "browser.helperApps.neverAsk.saveToDisk" = 'application/pdf'))

driver <- rsDriver(browser = "firefox", extraCapabilities = pdfprof)
remote_driver <- driver[["client"]]
remote_driver$navigate("https://www.rad.cvm.gov.br/enetconsulta/frmGerenciaPaginaFRE.aspx?CodigoTipoInstituicao=1&NumeroSequencialDocumento=62398")
Sys.sleep(3) # It needs some time to load the page (set to 3 seconds)

option <- remote_driver$findElement(using = 'xpath', "//select[@id='cmbGrupo']/option[@value='PDF|412']") # select the option to open PDF file
option$clickElement()

# Find iframes in the webpage
web.elem <- remote_driver$findElements(using = "css", "iframe") # get all iframes in the webpage
sapply(web.elem, function(x){x$getElementAttribute("id")}) # see their names
remote_driver$switchToFrame(web.elem[[1]]) # Move to the first iframe (Formularios Filho)
web.elem.2 <- remote_driver$findElements(using = "css", "iframe") # get all iframes in the webpage
sapply(web.elem.2, function(x){x$getElementAttribute("id")}) # see their names
# The pdf Viewer iframe is the only one inside Formularios Filho
remote_driver$switchToFrame(web.elem.2[[1]]) # Move to the first iframe (pdf Viewer)
Sys.sleep(3) # It needs some time to load the page (set to 3 seconds)

# Download the PDF file
button <- remote_driver$findElement(using = "xpath", "//*[@id='download']")
button$clickElement() # download
Sys.sleep(3) # Need sometime to finish download and then close the window
remote_driver$close() # Close the window