Why is curl not a dependency of xml2?

[anhtr]

I am not sure why curl is not a dependency of xml2. download_xml and download_html both use curl as defaults, and will give errors if that package is not installed. At this time, the error message is not very clear, and hard to trace if those download functions are used as part of a bigger code chunk or a function. I also got issues with a package that's depending on xml2, and it's even harder to track where the error came from in that instance.

install.packages("xml2")
#> Installing package into 'C:/Users/ant5152/Documents/R/win-library/3.6'
#> (as 'lib' is unspecified)
#> package 'xml2' successfully unpacked and MD5 sums checked
#> 
#> The downloaded binary packages are in
#>  C:\Users\ant5152\AppData\Local\Temp\Rtmp2xWOfd\downloaded_packages

xml2::download_xml("https://www.proteinatlas.org/ENSG00000134057.xml")
#> Error in loadNamespace(name): there is no package called 'curl'

[anhtr]

Thank you for addressing the issue.