Re: Flycheck reports are never satisfying!?

[Sebastian Wiesner <swiesner@lunaryorn.com>]

Am 28.08.2014 um 14:05 schrieb Sebastien Vauban <sva-news@mygooglest.com>:

> Hello,
> 
> Trying to use, since short, Flycheck on all my prog modes; hence, on my
> Emacs configuration file as well.
> 
> Though, as you can see on http://screencast.com/t/gfzLGy2h6fH, it never
> is satisfying: there are always reports of errors or warnings, while my
> code is completely clean (IMO).

It’s not.  Flycheck runs the byte compiler on your init.el, and…

> Two ECM follow, showing what happens for all packages which I load and
> customize.
> 
>    Note that, here, I took an extract from Flycheck's configuration
>    itself, but the problem is the same with every third party
>    package...
> 
> 1. With an explicit package require:
> 
> --8<---------------cut here---------------start------------->8---
> ;;; .emacs-minimal.el --- Test file
> 
> ;;; Commentary:
> 
> ;;; Code:
> 
> (add-to-list 'load-path "~/.emacs.d/elpa/flycheck-20140824.731/„)

…this expression is **not** evaluated by the byte compiler, so…

(in an unrelated note, this is a *very strange thing to do*.  The path suggests that you are using package.el to install Flycheck, but in that case you should *not* set up the load-path manual.  Instead call "(package-initialize)")

> (require ‚flycheck)

…when the byte compiler tries to evaluate this expression, Flycheck is not in your load-path, hence the error below.

Top-level "require"s are a special case.  The byte compiler evaluates these to load dependencies and macros, but it will **not** generally evaluated other expressions.


> ;; modern on-the-fly syntax checking
> (when (try-require 'flycheck)
> 
>  ;; indicate errors and warnings via icons in the left fringe
>  (setq flycheck-indication-mode 'left-fringe)
> 
>  ;; enable Flycheck mode in all buffers
>  (add-hook 'after-init-hook 'global-flycheck-mode))
> 
> (provide '.emacs-minimal)
> 
> ;;; .emacs-minimal.el ends here
> --8<---------------cut here---------------end--------------->8---
> 
> Flycheck reports one ERROR:
> 
> --8<---------------cut here---------------start------------->8---
>    9   1 error    Cannot open load file: no such file or directory, flycheck (emacs-lisp)
> --8<---------------cut here---------------end--------------->8---
> 
> 2. With an implicit package require (call to function `try-require'):
> 
> --8<---------------cut here---------------start------------->8---
> ;;; .emacs-minimal2.el --- Test file
> 
> ;;; Commentary:
> 
> ;;; Internal function:
> 
> (defun try-require (feature)
>  "Attempt to load a FEATURE (or library).
> Return true if the library given as argument is successfully loaded.  If
> not, just print a message."
>  (condition-case err
>      (progn (if (stringp feature)
>                 (load-library feature)
>               (require feature)) t)
>    (file-error (message "Missing package `%s'!" feature) nil)))
> 
> ;;; Code:
> 
> (add-to-list 'load-path "~/.emacs.d/elpa/flycheck-20140824.731/")
> 
> ;; modern on-the-fly syntax checking
> (when (try-require ‚flycheck)

As said above, the byte compiler doesn’t evaluate arbitrary expressions, and it doesn’t evaluate this call either.  Hence, it never attempts to actually load Flycheck, so there’s no error, but since Flycheck isn’t loaded, you get the warnings about free variables.

>  ;; indicate errors and warnings via icons in the left fringe
>  (setq flycheck-indication-mode 'left-fringe)
> 
>  ;; enable Flycheck mode in all buffers
>  (add-hook 'after-init-hook 'global-flycheck-mode))
> 
> (provide '.emacs-minimal2)
> 
> ;;; .emacs-minimal2.el ends here
> --8<---------------cut here---------------end--------------->8---
> 
> Flycheck reports one warning:
> 
> --8<---------------cut here---------------start------------->8---
>   25   9 warning  assignment to free variable `flycheck-indication-mode' (emacs-lisp)
> --8<---------------cut here---------------end--------------->8---
> 
> How am I supposed to do, if Flycheck reports things that shouldn't be
> reported?

Generally, you should set the corresponding options of the "emacs-lisp" syntax checker [1] to set the "load-path" for Flycheck, or enable "package.el" for Flycheck.

However, as far as "init.el" is concerned, Flycheck should automatically enable package.el for syntax checking.  This doesn't seem to work in your case, and indicates that there is something unusual about your setup, so please open an issue in Flycheck's issue tracker at https://github.com/flycheck/flycheck/issues

[1]: http://flycheck.readthedocs.org/en/latest/guide/languages.html#el.flycheck-checker.emacs-lisp