[FR]: `check_installed0`

[mikmart]

The user-friendly errors and prompting to install are great features in check_installed(). However, as seen in #1608, the check to see if a package is in fact installed is almost 3 orders of magnitude slower than the simple requireNamespace().

Would there be scope for a check_installed0() that would retain the errors and prompting of check_installed(), but use a less featureful method of detecting whether a package is installed or not, allowing better performance? That would be useful for a package providing an optional feature in a fast but frequently called function that needs to check whether an optional dependency is available.

[lionel-]

Agreed the current situation is not ideal. We should try and optimise check_installed() first, so let's track this in #1608.

[mikmart]

That's fair. Thanks for considering!