Case-sensitive comparison of HTTP header string causes resp_link_url() to fail and can break response pagination

[DavidRLovell]

I think I may have found a problem in resp_link_url() at line 177:

link_headers <- headers[names(headers) == "Link"]

Here's why I think there is an issue

• I had been successfully retrieving paginated responses from the Canvas Learning Management System via their API
• Today, I noticed that I was only getting the first 100 elements of a request that had (last year) been returning 184
  • The request relates to a class I teach and I have been on a break... writing an R package to access Canvas using httr2
• The Pagination page of the Canvas API documentation notes:

Because HTTP header names are case-insensitive, please be sure you are not parsing the Link header in a case-sensitive way. The capitalization of the header name is not guaranteed.

• I can sucessfully retrieve paginated responses when I change line 177 of resp_link_url() to make a case-insensitive comparison:

link_headers <- headers[tolower(names(headers)) == "link"]

• Seeing that resp_header_exists() does case-insensitve comparison lends weight to the idea that there is a problem.

@hadley: I think this may have happened here perhaps?

[hadley]

Ah yes good catch. Do you want to do a PR? I’ll probably do another patch release in the next few weeks.

[DavidRLovell]

Sorted... I hope... this is my first ever PR... please let me know if there are any issues.