How to Copy the Link at Point -- an Undocumented Feature in EWW

If you've ever written an Emacs function only to find out that it was there all along, masquerading as something else, this post is for you.

I just finished writing an Emacs function that copies the link at point to the kill ring in EWW. It will remain unpublished. Why? Because I discovered that shr-maybe-probe-and-copy-url (bound to u and w in eww-mode) does the same thing. Just position point on a link and invoke it.

It's not obvious that pressing w will do this. In fact the major mode help for eww-mode suggests that w will not copy the link because it's bound to eww-copy-page-url. But it turns out that if point is on a link, w will invoke shr-maybe-probe-and-copy-url, "which copies this link's URL to the kill ring." The manual goes on to say, "If point is not on a link, pressing w calls eww-copy-page-url, which will copy the current page's URL to the kill ring instead."¹

Before writing my function I had been looking through the mode help (C-h m from within a EWW buffer) and the EWW source code for any function that looked like copy-link-at-point.

So how did I find out about this? I wanted to ensure that I was following the standard for capitalizing EWW, so I searched the web. This took me to the GNU Emacs manual, which has a section on EWW and shows it in all caps. But then my distractibility encouraged me to read a great deal more.

I've known that keybindings can change depending on the major mode. But it seems a keybinding can change based on context (i.e. the position of point). This idea is new to me. Maybe it's common for a function to "hand off" to another based on context. But in this case it seems irresponsible to omit documentation for the alternate behavior of a w key press. Suppose a user expects to copy the page URL and gets the URL of a link, instead?

While this was a frustrating experience, it is yet another reminder to RTFM. WDYT?

¹ GNU Emacs EWW Basic Usage