mwotton/liza

best-practices haskell template

This is a distillation of all the annoying tasks I end up setting up anyway.

controversial decisions

• top level monorepo, package directories beneath

I almost always end up structuring apps as a collection of packages anyway, so it makes sense to set it up that way from the beginning

• no default-extensions

they are convenient, but it always seems to break tooling. Put the extensions you need in the file and be done with it.

• stack

this is probably the most controversial thing here, and the one I'm least wedded to. it works well enough for now.

• ghcide-friendly

this one is rough. ghcide is great, but this bug means that you have to include test dependencies at the top level. Hopefully this will be fixed soon.

• Makefile for task-running

needs something for things like preflights and non-haskell dependency checking

TODO

• we should illustrate best practices for error handling - HasCallStack etc.
• make testwatch has some relative-path issues to do with finding sqitch plans. Use Paths.
• should deployment be gated on passing tests in github? if so, perhaps we want to deploy from github at the end of a push.
• migration testing
  • possibility for multi-prod system
    • stash databases as docker images: name schema project-YYYY-MM-DD
    • migration tester can build a new image
  • but... we don't really need that. all that we really need is a push to staging and a healthcheck
  • also staging should pull prod's db in order to migrate it?
• announce deploys somewhere
• authn
  • actually provide way to use logged-in status and identity
• authz
  • how hardcore do we want to be?
    • could use https://github.com/Simspace/avaleryar
    • should it be baked into the servant type?
    • probably needs to talk about tiers of service too
• rationing/quotas - not quite the same thing as authz.
  • could we lean on honeycomb instead? set an alert for egregious abuse?
• coverage ratchet
• payments
  • https://stripe.com/docs/billing/subscriptions/fixed-price#how-to-model-it-on-stripe
  • https://github.com/dmjio/stripe
  • can get rid of the fake endpoints and migrations now, as there will be a real User model.
  • add webhook stuff

RUMINATIONS

• property enforcement mechanisms

  • emacs save hook
  • ghc source plugin
    • cool idea, but needs to be added to the dependencies. devflag?
  • commit-hook
    • still need to run installer script
  • post-commit github action

• desirable properties

  • hlint
  • remove unused imports
  • autoformat

• current situation

  • hlint/emacs save hook
  • autoformatting via git hook

• possible replacements

  • hlint/source plugin
    • https://hackage.haskell.org/package/splint
  • unused-imports/source-plugin
    • https://github.com/kowainik/smuggler

• non-enforcement source plugins

  • https://github.com/ArturGajowy/ghc-clippy-plugin/ better error messages

• healthchecks

  • unclear what to do here.
  • Should a healthcheck failure block a release?
  • what if it's due to external circumstances?

• benchmarks