Re: [GRASS-dev] Parser checking output maps but not input maps
Vaclav Petras wrote: For scripts which use g.parser for argument parsing, if G_parser() fails g.parser itself fails, which in turn causes the script to fail. Python scripts should normally terminate on an exception if a spawned command fails, whereas shell scripts normally ignore the status of any spanwed commands. For Python this is ensured by checking @ARGS_PARSED@ in g.parser output in grass.script.core.parse() [1]. For Bash I have no idea how it is/was done (e.g. in version 6). bash scripts exec g.parser in the current process, in place of bash. g.parser then re-executes the calling script with the option values stored in environment variables. If g.parser fails, the script never gets re-executed, and the exit status of g.parser is the exit status of the process which was originally running the script. However, my problem is that in C if you have an input map, you don't have to check that whether it exists. While in Python you have to check if it exists otherwise the first module (subprocess) you call with it will unexpectedly fail. I hit this issue when I was trying to write documentation for writing scripts and I wanted to do it the right way (as opposed to hopping that some random script I pick in the source code follows well the undocumented API). The question now is if we want to fix the inconsistency in between writing C and Python (and error reporting with overwrite). Or if we say that the current state is good enough as long as it is documented and there is some convenient function to check existence of a map. I don't think I exhausted all options, so if somebody has an idea or is willing to implement something, that would be great. If you consider GRASS modules as being the Python equivalent of GRASS API functions in C, then there isn't an inconsistency. Rather than explicitly checking for a map, we rely upon whatever tries to use generating a fatal error if it doesn't exist. If you want to directly check for the existence of a map, use grass.script.find_file() (a wrapper around g.findfile, which in turn is a wrapper around G_find_file2(), which is what C code would use for that purpose). -- Glynn Clements gl...@gclements.plus.com ___ grass-dev mailing list grass-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-dev
Re: [GRASS-dev] Parser checking output maps but not input maps
Vaclav Petras wrote: is there some reason for GRASS parser not checking if the input map exists? It checks if the output map exists and if it it does it ends execution with an error. If an input map (or file) doesn't exist, you'll get an error when the module tries to open it. If I understand correctly, this applies only for C modules not Python or Bash modules, right? For scripts which use g.parser for argument parsing, if G_parser() fails g.parser itself fails, which in turn causes the script to fail. Python scripts should normally terminate on an exception if a spawned command fails, whereas shell scripts normally ignore the status of any spanwed commands. In both cases the error is not associated with the given option while in case of overwrite it is (which is nice). Correct. -- Glynn Clements gl...@gclements.plus.com ___ grass-dev mailing list grass-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-dev
Re: [GRASS-dev] Parser checking output maps but not input maps
On Mon, Jul 6, 2015 at 7:56 PM, Glynn Clements gl...@gclements.plus.com wrote: is there some reason for GRASS parser not checking if the input map exists? It checks if the output map exists and if it it does it ends execution with an error. If an input map (or file) doesn't exist, you'll get an error when the module tries to open it. If I understand correctly, this applies only for C modules not Python or Bash modules, right? For scripts which use g.parser for argument parsing, if G_parser() fails g.parser itself fails, which in turn causes the script to fail. Python scripts should normally terminate on an exception if a spawned command fails, whereas shell scripts normally ignore the status of any spanwed commands. For Python this is ensured by checking @ARGS_PARSED@ in g.parser output in grass.script.core.parse() [1]. For Bash I have no idea how it is/was done (e.g. in version 6). However, my problem is that in C if you have an input map, you don't have to check that whether it exists. While in Python you have to check if it exists otherwise the first module (subprocess) you call with it will unexpectedly fail. I hit this issue when I was trying to write documentation for writing scripts and I wanted to do it the right way (as opposed to hopping that some random script I pick in the source code follows well the undocumented API). The question now is if we want to fix the inconsistency in between writing C and Python (and error reporting with overwrite). Or if we say that the current state is good enough as long as it is documented and there is some convenient function to check existence of a map. I don't think I exhausted all options, so if somebody has an idea or is willing to implement something, that would be great. Vaclav [1] https://trac.osgeo.org/grass/browser/grass/trunk/lib/python/script/core.py#L712 ___ grass-dev mailing list grass-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-dev
Re: [GRASS-dev] Parser checking output maps but not input maps
Vaclav Petras wrote: is there some reason for GRASS parser not checking if the input map exists? It checks if the output map exists and if it it does it ends execution with an error. If an input map (or file) doesn't exist, you'll get an error when the module tries to open it. If an output map exists, it would just get silently overwritten if it wasn't for the checks performed by G_parser(). -- Glynn Clements gl...@gclements.plus.com ___ grass-dev mailing list grass-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-dev
Re: [GRASS-dev] Parser checking output maps but not input maps
On Sat, Jul 4, 2015 at 12:55 PM, Glynn Clements gl...@gclements.plus.com wrote: Vaclav Petras wrote: is there some reason for GRASS parser not checking if the input map exists? It checks if the output map exists and if it it does it ends execution with an error. If an input map (or file) doesn't exist, you'll get an error when the module tries to open it. If I understand correctly, this applies only for C modules not Python or Bash modules, right? In both cases the error is not associated with the given option while in case of overwrite it is (which is nice). If an output map exists, it would just get silently overwritten if it wasn't for the checks performed by G_parser(). -- Glynn Clements gl...@gclements.plus.com ___ grass-dev mailing list grass-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-dev
[GRASS-dev] Parser checking output maps but not input maps
Hi,
is there some reason for GRASS parser not checking if the input map exists?
It checks if the output map exists and if it it does it ends execution with
an error.
Having this interface definition (full script attached):
#%option G_OPT_R_INPUT
#% key: elevation
#%end
#%option G_OPT_R_OUTPUT
#% key: aspect
#%end
I now get this:
$ r.mapcalc aaa = 1
$ g.list rast m=.
aaa
$ test_parser_inputs.py elevation=bbb aspect=aaa
ERROR: option aspect: aaa exists.
$ test_parser_inputs.py elevation=bbb aspect=ccc
('bbb', 'ccc') [i.e., no error]
But I would expect to get the error also in the second case:
$ test_parser_inputs.py elevation=bbb aspect=ccc
ERROR: option elevation: bbb doesn't exist.
Is there some advantage in checking the existence of the input maps and
files manually?
Vaclav
#!/usr/bin/env python
#%module
#% description: Test inputs and outputs in parser
#% keyword: test
#% keyword: raster
#%end
#%option G_OPT_R_INPUT
#% key: elevation
#%end
#%option G_OPT_R_OUTPUT
#% key: aspect
#%end
import grass.script as gscript
def main():
options, flags = gscript.parser()
elevation = options['elevation']
aspect = options['aspect']
print(elevation, aspect)
if __name__ == '__main__':
main()
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