knitr should fail early if required libraries not present

[arencambre]

If I call knit2wp and I don't have the RWordPress library installed, I don't get an error advising me of this until after the Rmd is "compiled" into an md file. This means considerable effort has been expended all for naught. Please check for the presence of the RWordPress before the function does any heavy lifting and fail early, should it not be present.

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[cderv]

Thanks for the report.

FWIWI There is a warning now in the demo (https://yihui.org/knitr/demo/wordpress/) which is reference in the help page.
RWordPress is no more actively maintained (#1866) and we strongly advice to switch blogging with R to use blogdown (#1866 (comment))

That said, I guess we could make this warning appears in the function knit2wp and check for the package. We could also update the help page.

[arencambre]

Thank you. The appeal of knit2wp, and why I am reluctant to switch to blogdown, is it takes advantage of my existing investment in a WordPress site, instead of starting over on a whole new site. These advantages include but are not limited to:

• theming already built up
• consistency with the rest of my site
• search that includes my whole site
• not needing to manually maintain a separate site through another method
• SEO already gained through being a part of a recognized site

Since WordPress remains the most popular CMS, and there are so many ways to run it, I hope this functionality could be considered for long-term inclusion.

This is not meant as a criticism of blogdown. It also has great uses. I am only intending to highlight distinct advantages of something like knit2wp that other techniques cannot match.

[yihui]

@arencambre Totally understood. Our main point was that knit2wp() could break anytime, because we don't maintain the actual backend. If someone could continue to maintain RWordPress and XMLRPC, I'm open to support knit2wp() on my side in the foreseeable future.

[arencambre]

Understood.

Technically knit2wp is already broken. It depends on RWordPress, which depends on RCurl, the latter of which uses an obsolete version of openssl. The obsolete openssl does not support TLS 1.2 or higher, which means it only supports insecure protocols.

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