Invalidate projectile-project-root-cache

[raxod502]

I find that a frequent operation is:

• Attempt to projectile-find-file
• Realize my current directory is not marked as a project
• Create .projectile file
• Attempt to projectile-find-file again
• To my surprise, Projectile still thinks the directory is not marked as a project, even though it is
• Attempt to use projectile-invalidate-cache
• To my further surprise, Projectile forces me to select a project to clear the cache for, even though what I need is just to clear projectile-project-root-cache, which is not associated with any project
• Select an unrelated project to clear the cache for, which clears projectile-project-root-cache as a side effect
• Now projectile-find-file works

Suggestions for improvement:

• Detect cases where projectile-project-root-cache should be cleared automatically to avoid user confusion
• Add a user command for clearing projectile-project-root-cache without needing to select a project
• Document the fact that this cache exists (since it affects user-visible behavior)

I could help out with this, but creating an issue first for discussion.

[bbatsov]

All good suggestions. PR welcome!

Btw, does an empty cache get created in this case when there's no project? (this definitely is a bug if so)

[raxod502]

The nil return value of the entry in projectile-project-root-functions is cached if no project is detected:

projectile/projectile.el

Lines 1335 to 1340 in 0163b33

	;; if we get here, we have failed to find a root by all
	;; conventional means, and we assume the failure isn't transient
	;; / network related, so cache the failure
	(let ((cache-key (format "projectilerootless-%s" dir)))
	(puthash cache-key 'none projectile-project-root-cache)
	'none)))))

I'm not sure if that is what you meant.

[bbatsov]

Ah, yeah - I had forgotten about this.