api: Generate enum consts with Values funcs

akutz commented 2 months ago

Description

This patch ensures enum types are generated with Values functions that make it trivial to discover all values for a given enum.

@dougm, I am not sure if this is something we want or not. I propose it to make it simpler for projects like VM Operator to generate a list of all constant values for enums like GuestOSID. I checked, and while it is possible to use unsafe code to list all types in a given package, Go's compiler makes it impossible to list all exported constants at the package level. Other than AST with source analysis, this is the only way for a downstream project to get a list of all an "enum"'s values. The question is -- is it worth the increase in memory?

cc @dilyar85 as I was doing this so you could create a pkg/gen/guestosids/guestosids.go file in VM Operator that is effectively a main.go and could be used with //go:generate in the ./api/v1alpha3/virtualmachine_types.go file to automatically generate a type with the correct kubebuilder comments for an enum.

Closes: NA

Type of change

Please mark options that are relevant:

[ ] Bug fix (non-breaking change which fixes an issue)
[x] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
[ ] This change requires a documentation update
[ ] Build related change

How Has This Been Tested?

NA

Checklist:

[x] My code follows the CONTRIBUTION guidelines of this project
[x] I have commented my code, particularly in hard-to-understand areas
[x] I have made corresponding changes to the documentation
[x] I have added tests that prove my fix is effective or that my feature works
[x] New and existing unit tests pass locally with my changes
[x] Any dependent changes have been merged

akutz commented 2 months ago

Thanks @akutz , very nice. This would also be quite useful within govmomi, we can replace this: https://github.com/vmware/govmomi/blob/main/simulator/guest_id.sh#L29

And lists of enum consts are sprinkled all over govc, e.g.

https://github.com/vmware/govmomi/blob/ae5fd928c9958968b1b4055edbd09e904f76860c/govc/cluster/change.go#L30-L34

I have replaced the aforementioned guest_id.sh with the new work.

akutz commented 2 months ago

Hey @dougm, it needs another review. Please see the updates I made to it to make it a little more useful.

vmware / govmomi