[GRASS-dev] Re: [GRASS GIS] #429: Add option to disable warnings in modules

[GRASS GIS]

#429: Add option to disable warnings in modules
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  Reporter:  kyngchaos    |       Owner:  grass-dev at lists.osgeo.org
      Type:  enhancement  |      Status:  new                      
  Priority:  minor        |   Milestone:  6.4.0                    
 Component:  default      |     Version:  svn-develbranch6         
Resolution:               |    Keywords:                           
  Platform:  Unspecified  |         Cpu:  Unspecified              
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Comment (by glynn):

 Replying to [ticket:429 kyngchaos]:

 > I would like to be able to suppress warning messages in commands, yet
 keep messages based on the GRASS_VERBOSE level, especially in raster
 projection (r.proj) where is possible to get thousands of "pj_transform()
 failed: tolerance condition error" warnings, depending on the projection,
 that are expected but clutter the progress output and slow down the
 process.

 The correct solution here is as others have suggested: limit the number of
 warnings from a single source rather than disabling them completely.

 The main problem with pj_do_proj() and pj_do_transform() is that the same
 G_warning() call is used to report any and all error conditions from
 pj_transform(). Some may be more serious than others, so printing a fixed
 number of warnings could result in harmless warnings being shown but more
 serious ones being suppressed.

 A more robust solution is to record the last error code, and suppress
 multiple consecutive occurrences of the same error. If you get a different
 error, you generate a warning for it.

 This will still produce a flood if you get alternating errors, but
 avoiding that is awkward, requiring e.g. an array containing a flag for
 each error code.

 > I see that G_warning() has a companion G_suppress_warnings(), so this at
 least was an intended possibility at one time (but maybe deprecated or
 discouraged now?).

 It's a band-aid for library functions which generate too many warnings. I
 suggest removing it in 7.0. If there are cases where the library should
 normally produce a warning (because it's unrealistic to require
 programmers to manually check for rare errors) but cases where it needs to
 be disabled, there should either be a "nowarn" flag or a corresponding
 function to suppress a specific warning.

 The existing usage means that code which uses G_suppress_warnings() around
 e.g. G_read_colors() to suppress the "colour support ... missing" warning
 (which is harmless; you just get the default rainbow colour table) could
 also suppress more significant warnings.

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Ticket URL: <http://trac.osgeo.org/grass/ticket/429#comment:7>
GRASS GIS <http://grass.osgeo.org>