Improve PineAPPL's CLI

[cschwan]

This branch is supposed to rework the CLI to

• use clap's derive feature that makes it much easier to write an easy-to-understand subcommand and
• to make sure no regressions are introduced by testing each of the subcommands;
  • channels
  • convolute
  • diff
  • info
  • luminosity
  • merge
  • optimize
  • orders
  • pdf_uncertainty
  • plot
  • pull
  • remap
  • set
  • subgrids
  • sum
  • upgrade

[alecandido]

Are you really sure you want to test the full hardcoded docstring? If at some point you'll want to update clap version and they even change something minor (say spacing) it will break all the tests...

[cschwan]

The --help tests are just a basic implementation of the more general idea to test coverage of all subcommands. Note that the version of clap is pinned.

[alecandido]

I agree that clap won't update on its own (and that's a good thing), nevertheless at some point you might want to do it manually (and this was the meaning of the original observation).

I agree that coverage is a good thing, but nor 100% is granting to be bug free, neither any other reason exists to make 100% strictly required: for as long as you know what you are testing, and more important what not, that's perfectly fine (but this of course is only my personal point of view).

[cschwan]

My point is more that we don't have any tests for the CLI, which is potentially dangerous. While writing tests I already discovered a problem that is also present in master (fixed in commit 10c659e). I agree that the --help tests are unnecessarily fragile, but once we have proper tests we can probably remove them.

[codecov]

Codecov Report

Merging #95 (8fa4fb1) into master (38cb9f8) will decrease coverage by 0.09%.
The diff coverage is 88.47%.

@@            Coverage Diff             @@
##           master      #95      +/-   ##
==========================================
- Coverage   86.00%   85.91%   -0.10%     
==========================================
  Files          14       31      +17     
  Lines        2080     3025     +945     
==========================================
+ Hits         1789     2599     +810     
- Misses        291      426     +135     

Impacted Files	Coverage Δ
pineappl_cli/src/plot.rs	92.10% <ø> (ø)
pineappl_cli/src/merge.rs	53.33% <53.33%> (ø)
pineappl_cli/src/remap.rs	68.83% <68.83%> (ø)
pineappl_cli/src/diff.rs	69.53% <73.33%> (ø)
pineappl_cli/src/subgrids.rs	77.27% <77.27%> (ø)
pineappl_cli/src/helpers.rs	91.01% <85.71%> (ø)
pineappl_cli/src/sum.rs	94.11% <94.11%> (ø)
pineappl_cli/src/info.rs	96.96% <96.96%> (ø)
pineappl_cli/src/pull.rs	97.59% <97.59%> (ø)
pineappl_cli/src/pdfunc.rs	97.82% <97.82%> (ø)
... and 19 more

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