[GRASS-dev] [GRASS GIS] #2895: Define dependencies for GRASS addons

[GRASS GIS]

#2895: Define dependencies for GRASS addons
-------------------------+-------------------------
 Reporter:  pmav99       |      Owner:  grass-dev@…
     Type:  enhancement  |     Status:  new
 Priority:  normal       |  Milestone:
Component:  Addons       |    Version:  unspecified
 Keywords:  g.extension  |        CPU:  Unspecified
 Platform:  Unspecified  |
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 Some addons depend on other addons. E.g. `r.lfp` depends on
 `r.stream.distance`.

 If you install `r.lfp` and you try to use it while `r.stream.distance` is
 not installed, you get the following traceback which is not particularly
 helpful; especially so if you are not familiar with Python.
 {{{
 Traceback (most recent call last):
   File "/home/grassuser/.grass7/addons/scripts/r.lfp", line 111, in
 <module>
     sys.exit(main())
   File "/home/grassuser/.grass7/addons/scripts/r.lfp", line 43, in main
     calculate_lfp(input, output, coords)
   File "/home/grassuser/.grass7/addons/scripts/r.lfp", line 67, in
 calculate_lfp
     distance=flds)
   File "/usr/lib/grass70/etc/python/grass/script/core.py", line 392, in
 run_command
     ps = start_command(*args, **kwargs)
   File "/usr/lib/grass70/etc/python/grass/script/core.py", line 361, in
 start_command
     return Popen(args, **popts)
   File "/usr/lib/grass70/etc/python/grass/script/core.py", line 64, in
 __init__
     subprocess.Popen.__init__(self, args, **kwargs)
   File "/usr/lib/python2.7/subprocess.py", line 710, in __init__
     errread, errwrite)
   File "/usr/lib/python2.7/subprocess.py", line 1335, in _execute_child
     raise child_exception
 OSError: [Errno 2] No such file or directory
 }}}
 There should be a way to define GRASS dependencies. E.g. something like
 `requirements.txt` that is being used by Python packages.

 Optimally `g.extension` should read the list of depedencies and install
 missing ones automatically. If `g.extension` does go down this road, then
 an additional flag for skipping dependency checks might also be a good
 idea.

 Perhaps this could/should also be expanded to additional non-GRASS related
 dependencies. E.g. `r.denoise` requires the existence of the `mdenoise`
 binary. In this case IMHO a graceful failure message would be preferable
 to a successful installation of a non-working addon.

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Ticket URL: <https://trac.osgeo.org/grass/ticket/2895>
GRASS GIS <https://grass.osgeo.org>