Ignore backup files in projectile

Question

How to ignore emacs backup (*~) files in projectile? My code does not work.

(use-package projectile
  :config
  (progn
    (setq projectile-globally-ignored-files
          (append '(
                "*.pyc"
                "*.class"
                "*~"
                )
              projectile-globally-ignored-files))
    (projectile-global-mode)
    (setq projectile-completion-system 'helm)
    (helm-projectile-on)
    (setq projectile-enable-caching t)
    (defconst projectile-mode-line-lighter " P")
    )
  )

When I call helm-projectile-find-other-file I always see backup files which is quite annoying.

Answer 1

The variable projectile-globally-ignored-files should be populated with literal filename suffixes, not glob patterns. Admittedly the variable's documentation does not make this obvious.

So your code could be rewritten as

(use-package projectile
  :config
  (setq projectile-completion-system 'helm
        projectile-enable-caching    t
        projectile-globally-ignored-files
        (append '(".pyc"
                  ".class"
                  "~")
                projectile-globally-ignored-files))
  (projectile-mode)
  (helm-projectile-on)
  (defconst projectile-mode-line-lighter " P"))

My other suggested changes to your code, as seen in my example, are the following:

• Use projectile-mode instead of obsolete projectile-global-mode.
• Call setq once.
• Do not put closing parentheses on lines by themselves, as per the Emacs Coding Conventions.
• Remove redundant progn from use-package :config clause.

By the way, is the projectile-mode-line-lighter necessary? I don't see projectile making use of it.

Answer 2

I had the same experience, finding this very confusing. Eventually, I figure out that I had to run M-x projectile-invalidate-cache for the changes to projectile-globally-ignored-* to be heeded.