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

[Andrew Hyatt <ahyatt@gmail.com>]

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Thanks, Derek.

On Sun, Jan 24, 2016 at 11:19 PM Derek Upham <sand@blarg.net> wrote:

> This many years down the line I’m not in a position to reproduce it, so
> just close it out as “can’t repro”.
>
> Thanks,
>
> Derek
>
> Andrew Hyatt writes:
>
> > Got it.  So, if I understand correctly, this may or may not be fixed,
> > but in any case, it seems specific to Erlang.  Hopefully you, or another
> > Erlang user, can attempt to reproduce it so that we can move forward on
> > this bug.
> >
> > Derek Upham <sand@blarg.net> writes:
> >
> >> The situation is a flymake check for “foo.c”, where “foo.c” is
> perfectly fine but it #includes “bar.h” which has a syntax error.
> >>
> >> Flymake triggers a compilation.  The compilation fails due to the
> syntax error, returning a non-zero exit status, along with the text
> >>
> >>   bar.h:30: error: Invalid syntax
> >>
> >> Flymake quietly drops any error messages that refer to anything other
> than “foo.c”.  As far as it is concerned, the above error output is empty.
> That means...
> >>
> >> - The error and warning counts are zero
> >> - The exit status is non-zero
> >> - The check was not interrupted
> >>
> >> The nested ‘if’ clauses in ‘flymake-post-syntax-check’ route control
> through:
> >>
> >>  (flymake-report-fatal-status "CFGERR"
> >>   (format "Configuration error has occured while running %s" command))
> >>
> >> This code reports a fatal error and permanently turns off Flymake in
> the buffer.  After you fix the syntax error in “bar.h”, you have to restart
> Flymake in “foo.c” (and any other files that depended on it).  The bug is
> that we need to explicitly restart Flymake.
> >>
> >> The proposed solution in the bug report is to treat this case as a
> non-fatal situation, with a special mode line tag to indicate “there’s a
> deeper problem”.  (It would be great if we could point the user to an error
> in “bar.h” line 30, but I don’t think there’s a good way to do it in the
> UI.)  Upon reflection, I think it’s better for Flymake to keep counts of
> errors and warnings in “other” files (not ignore them) and use that to
> improve the post-syntax-check tests with another “if” clause.
> >>
> >> (I’m pretty sure this was with Erlang code, which is why no one else
> has encountered the bug.  As I recall, GCC provides enough breadcrumbs that
> the #include line in the .c file will be tagged as a problem.  The Erlang
> compiler doesn’t show that information, or didn’t back then.)
> >>
> >> Derek
> >>
> >> ahyatt@gmail.com writes:
> >>
> >>> 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=''
>
>
> --
> Derek Upham
> sand@blarg.net
>

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