Enforce import order

[barrettj12]

Apparently there is an implicit rule that Pebble imports should be arranged into three groups:

• standard library imports
• 3rd-party / non-Pebble imports
• Pebble imports (i.e. those beginning with github.com/canonical/pebble)

This rule was not being enforced anywhere except code review, and there were many Go files not following this convention.

I've fixed up all Go files so that they now follow this convention. I used the gci tool to enforce the import order. Unfortunately goimports is not strict enough - it will only make sure that imports from the same group are not together. It will allow a group to be split up, so e.g. the following still passes:

import (
  "github.com/canonical/pebble/internals/plan"

  "github.com/canonical/pebble/internals/servicelog"
)

The easiest way to use gci is via golangci-lint (which gci is bundled inside). Run

golangci-lint run -c .github/.golangci.yml

to do the linting. If you add the --fix flag, gci will fix all the imports for you.

While I'm here, I resolved a stale TODO in daemon_test.go by changing the import of gocheck to use ., following the convention observed in (most) other test files.

Finally, I've added a Lint GitHub workflow to enforce this import order on future PRs.

[benhoyt]

Thanks! Definitely nice to enforce this via tooling rather than (clearly error-prone) human eyeballs. And nice to make daemon_test.go consistent and get rid of that TODO too.

[flotter]

Just an idea for the future: I like the idea of having a single script (like snapd and others : run-checks) that can perform the same checks the CI will in advance to save time iterating. Right now things are still simple, but I think it would soon be really useful to start adding spread like tests as well, and this means the turnaround time of a failed CI run can be painfully long.

[jnsgruk]

Looks good, thanks Jordan. Merging this as it's just an enforcement of agreed code style.