bug#2491: 23.0.90; Flymake too aggressive when responding to unusual error combination

[Andrew Hyatt]

Thanks for the bug report, and sorry it's sat so long without any
movement.  Looking over this, I don't particularly understand the issue
(why would the check return a non-zero exit status if it was working
properly?)  It might help if you provided a simple example.

I've looked at the code in Emacs 25, though, and it still has the logic
you report.

sand@blarg.net writes:

> Background
> ----------
>
> The Flymake library shipped with CVS HEAD (and probably earlier) has
> the following code in `flymake-post-syntax-check':
>
> (defun flymake-post-syntax-check (exit-status command)
>   ;; [. . . elided . . .]
>
>   (if (and (equal 0 err-count) (equal 0 warn-count))
>       (if (equal 0 exit-status)
>           (flymake-report-status "" "")    ; PASSED
>         (if (not flymake-check-was-interrupted)
>             (flymake-report-fatal-status "CFGERR"
>               (format "Configuration error has occured while running %s" 
> command))
>           (flymake-report-status nil ""))) ; "STOPPED"
>     (flymake-report-status (format "%d/%d" err-count warn-count) "")))
>
> Depending on...
>
>  ...whether the flymake check generated errors or warnings,
>  ...whether the flymake check had a non-zero exit status, and
>  ...whether we interrupted the flymake check,
>
> we can generate any of four different statuses.  One of the statuses,
> "CFGERR" is fatal, and turns off flymake for that buffer.  The others
> are non-fatal.
>
> Problem
> -------
>
> Flymake only tracks errors that refer to the specific file being
> checked.  For example, given the following output for "foo.c",
> which includes file "bar.h"
>
> foo.c:20: warning: Type mismatch
> bar.h:30: error: Invalid syntax
>
> Flymake would "see" one warning and no errors.  The "bar.h" error is
> dropped.  Now consider the degenerate case where "bar.h" is the only
> source of errors, *and the check returns a non-zero exit status*:
>
> bar.h:30: error: Invalid syntax
>
> The error and warning counts are zero, the exit status is non-zero,
> the check was not interrupted, so we end up reporting a fatal CFGERR.
>
> Think aobut the user experience here, with the two examples shown
> above.  First, Flymake checks, and reports an warning in the current
> file "foo.c".  The user fixes the warning.  Then Flymake reports a
> fatal error (popping up a dialog box under X) and turns itself off!
>
> Solution
> --------
>
> That particular code branch is supposed to catch cases where the build
> system itself dies with an error, which is important to detect.  But
> shutting down Flymake is too excessive a response, because of errors
> in included files.
>
> The following replacement code changes the behavior to report zero
> errors and zero warnings with the file itself, but it adds a ":CFGERR"
> flag to indicate that there was some other problem with the check.
> Flymake remains enabled for the buffer.
>
> (defun flymake-post-syntax-check (exit-status command)
>   ;; [. . . elided . . .]
>
>   (if (and (equal 0 err-count) (equal 0 warn-count))
>       (if (equal 0 exit-status)
>           (flymake-report-status "" "") ; PASSED
>         (if (not flymake-check-was-interrupted)
>             (flymake-report-status "0/0" ":CFGERR")
>           (flymake-report-status nil ""))) ; "STOPPED"
>     (flymake-report-status (format "%d/%d" err-count warn-count) "")))
>
>
> Derek
>
>
>
>
> In GNU Emacs 23.0.90.1 (i486-pc-linux-gnu, GTK+ Version 2.12.11)
>  of 2009-02-07 on elegiac, modified by Debian
>  (emacs-snapshot package, version 1:20090207-1)
> Windowing system distributor `The X.Org Foundation', version 11.0.10402000
> configured using `configure  '--build' 'i486-linux-gnu' '--host' 
> 'i486-linux-gnu' '--prefix=/usr' '--sharedstatedir=/var/lib' 
> '--libexecdir=/usr/lib' '--localstatedir=/var' '--infodir=/usr/share/info' 
> '--mandir=/usr/share/man' '--with-pop=yes' 
> '--enable-locallisppath=/etc/emacs-snapshot:/etc/emacs:/usr/local/share/emacs/23.0.90/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/23.0.90/site-lisp:/usr/share/emacs/site-lisp'
>  '--with-x=yes' '--with-x-toolkit=gtk' 'build_alias=i486-linux-gnu' 
> 'host_alias=i486-linux-gnu' 'CFLAGS=-DDEBIAN -DSITELOAD_PURESIZE_EXTRA=5000 
> -g -O2' 'LDFLAGS=-g -Wl,--as-needed' 'CPPFLAGS=''