[FEATURE] Add preflight that fails when zones fills are out of date

[matthijskooijman]

Is your feature request related to a problem? Please describe.
When committing changes, people sometimes forgot to do zone fills. Especially in a release this can be problematic, since then reviews might have been done on an old version of the zone fills and might miss problems the only surface when the zones are refilled, or the zone fill might be forgotten before producing fabrication outputs.

Describe the solution you'd like
Adding a preflight that does a zone fill and then fails if anything changed. This way I can add a push workflow that tests all commits to see if they were properly filled.

Note that there is already a check_zone_fills option, but that does not actually check anything, it just updates the zonefills on the in-memory pcb before doing any further processing (and also fill_zones which does the same, but also saves the result to disk). Neither of these solve my request.

Describe alternatives you've considered
Pre-commit hooks could also be used, but are opt-in on the developer's machine, so are less secure.

[set-soft]

Hi @matthijskooijman !

The name check_zone_fills is misleading, but I think it was inherited from the old kiplot tool. I have a tendency to favor compatibility instead of intuitive names.

I agree that a real check is a good idea, but I think you can solve it with the current functionality. Take a look at the following test case: tests/yaml_samples/diff_zones_1.kibot.yaml

kibot:
  version: 1

preflight:
  check_zone_fills: true

outputs:
  - name: 'diff_pcb_show'
    comment: "Show differences for the zone fill"
    type: diff
    layers: copper
    options:
      cache_dir: .cache
      old: ''
      old_type: file
      new_type: current

  - name: 'diff_pcb_check'
    comment: "Check the zone fill doesn't generate important changes"
    type: diff
    layers: copper
    options:
      cache_dir: .cache
      diff_mode: stats
      threshold: 100
      old: ''
      old_type: file
      new_type: current

This is a diff between the current file on disc and the current PCB on memory, abusing the default values ;-)
We use two outputs, one to generate a nice visual diff, and the other to measure the difference. It generates an error if the difference is above the threshold. In a workflow always saving the artifacts (even on fail) you'll get a nice PDF showing why it failed.

One think I could do is to just add internal template for this, so you just need a couple of lines in the config.

[set-soft]

Ok, I added a new internal template, so the following config will do the work:

kibot:
  version: 1

import:
  - file: CheckZoneFill

We just need to fine-tune the threshold