Flymake creates a ton of file handles and processes

[jakub-w]

With emacs -q when editing in haskell-mode and having flymake-mode enabled, flymake frequently creates a new process and a handle for the temporary file, quickly exhausting the limit for open files.

It seems to create a new process whenever a newline is inserted or file is saved.

Can anyone reproduce it or is it just me?

[purcell]

I haven't use the built-in flymake support tbh, so I don't know if there's a mechanism for throttling that checking, or aborting overlapping checks. I use dante myself, where the checking is cheaper, but it hooks into flycheck rather than flymake. ghcide works with eglot, fwiw, which is a less over-engineered LSP front-end than lsp-mode and it uses flymake.

[jakub-w]

It looks like it can be reproduced easily and is not specific to my environment. I checked with a clean docker setup. Also it doesn't matter if it's built-in or elpa flymake.

Will this be investigated? I've seen some similar reported issues and it seems like the consensus was pretty much this:

Lets agree to use flycheck instead of flymake, flycheck is better at handling temporary files.

Originally posted by @gracjan in #130 (comment)

@purcell I used eglot with hie and this is how I stumbled upon this problem. Listing alternatives doesn't solve anything. If the official stance is to use flycheck the broken code specific to flymake should be removed.

Eglot with flymake happily work in haskell-mode buffer after the workaround is applied:

(eval-after-load 'haskell-mode
    '(setq flymake-allowed-file-name-masks
	   (remove '("\\.l?hs\\'" haskell-flymake-init)
		   flymake-allowed-file-name-masks)))

[purcell]

Will this be investigated?

Listing alternatives doesn't solve anything.

If the official stance is to use flycheck the broken code specific to flymake should be removed.

There are no very active maintainers here, and I dip in as and when I have a little time. If you would like this to be investigated, your help would be appreciated. In theory the flymake support in recent Emacsen is comparable to flycheck, but I have not tried it out enough to diagnose whether this is the case or to have any particular recommendations on this issue.

[harinath]

I found that running 'M-x haskell-check' once in the buffer solved the issue. Seemingly in

(defun haskell-flymake-init ()
  "Flymake init function for Haskell."
  (let ((checker-elts (and haskell-saved-check-command
                           (split-string haskell-saved-check-command))))
    (list (car checker-elts)
          (append (cdr checker-elts)
                  (list (haskell-flymake-create-temp-buffer-copy
                         'flymake-create-temp-inplace))))))

'haskell-saved-check-command' is usually null, unless 'haskell-check' is run. Maybe the '(and haskell-saved-check-command' clause should be moved outside the 'let', so that flymake-init will return null instead?

[purcell]

Good find, @harinath - I made this change in 6e8e947.

[purcell]

Since I have added the fix which @harinath reported, I'll go ahead and close this.