`install_github` with non-default host broken: "attempt to set an attribute on NULL"

[r-cheologist]

Consider the following:

requireNamespace("remotes")
remotes::install_github(
  repo = 'loosolab/MARMoSET', host = 'github.molgen.mpg.de/api/v3')

This fails with the error:

Error: Failed to install 'MARMoSET' from GitHub:
  attempt to set an attribute on NULL

This happens both with the current cran version and after invoking remotes::install_github("r-lib/remotes").

[dpprdan]

The error message is caused by ratelimit_reset <- .POSIXct(res_headers$x-ratelimit-reset, tz = "UTC") in github_error since this server apparently does not return a x-ratelimit-reset in its header, so res_headers$`x-ratelimit-reset = NULL`. I gather that for this server the REST API rate limit is not set. In any case, this seems to be possible according to the docs:

Note that the limits mentioned above are the default rate limits for a GitHub Enterprise Server instance. Contact your site administrator to confirm if rate limits are enabled and how they are configured.

Emphasis mine.

With my attempt to fix this applied (#413), we now get

remotes::install_github(
  repo = "loosolab/MARMoSET", host = "github.molgen.mpg.de/api/v3"
)
#> Error: Failed to install 'unknown package' from GitHub:
#>   HTTP error 401.
#>   Bad credentials

This is because install_github() uses the auth_token = github_pat() default.

Unfortunately auth_token = NULL does not help (yet).

remotes::install_github(
  repo = "loosolab/MARMoSET", host = "github.molgen.mpg.de/api/v3", 
  auth_token = NULL
)
#> Error: Failed to install 'unknown package' from GitHub:
#>   HTTP error 401.
#>   Bad credentials

This is because remote_package_name.github_remote calls github_DESCRIPTION() with pat = remote$auth_token %||% github_pat(). So since auth_token = NULL, github_DESCRIPTION() essentially tries to access the DESCRIPTION file on the github.molgen.mpg.de/api/v3 host with the PAT from the GITHUB_PAT environment variable (which is likely to be the one for github.com). Since github.molgen.mpg.de/api/v3 does not require a PAT, we get the 401 error.

Since @jimhester deliberately set %||% github_pat() in commit 203d06e, I don't know how to solve this without breaking other things at this moment.

For now, a workaround for this particular case is:

Sys.unsetenv("GITHUB_PAT")
remotes::install_github(
  repo = "loosolab/MARMoSET", host = "github.molgen.mpg.de/api/v3"
)

[reikoch]

I encountered a similar problem:
my GITHUB_PAT environment variable contained the PAT for github.com and that effectively disabled installations from our github enterprise server.

Somehow I think the PATs have to be linked to the corresponding host:

    github.com PAT1
    github.example.com PAT2
    ...

[jimhester]

Fixed by #413