Opt-out the kustomize feature via go build tags

[yuwenma]

Problems:

• The k-d-p supports a kustomize hydration feature. This feature requires library kustomize/api. This library itself is commonly used by other libraries and users can encounter dependency conflicts if the other library uses a different kustomize/api release (what happened on my side and I cannot bump the other kustomize/api version).
• The k-d-p kustomize feature itself potentially causes friction issues, like fs operation, run kustomize before other transformation operations.

Description:

This PR split the kustomize hydration to 1. a generic kustomize build and 2. a no-op in different files; It adds a go build constraint without_kustomize to give users the ability to switch to opt out the kustomize feature in build time and no need to change their source code.

Test:
This PR is tested using the guestbook example by changing the make run for the following two cases

1. Preserve existing feature

make run

output

2023-01-27T23:29:57-08:00	INFO	running kustomize	{"controller": "guestbook-controller", "object": {"name":"guestbook-sample","namespace":"default"}, "namespace": "default", "name": "guestbook-sample", "reconcileID": "fbcb7051-36c0-4358-aafc-5c84c6b96e2a", "kustomizer": "EnabledKustomize"}

2. Skip kustomize

# Makefile
run: manifests generate fmt vet ## Run a controller from your host.
	go run -tags without_kustomize ./main.go

make run

output

2023-01-27T23:38:37-08:00	INFO	skip running kustomize	{"controller": "guestbook-controller", "object": {"name":"guestbook-sample","namespace":"default"}, "namespace": "default", "name": "guestbook-sample", "reconcileID": "38da0981-8143-43e5-96a4-7e551018758f", "kustomizer": "SkipKustomize"}

UPDATED

go run -tags without_kustomize ./main.go

...
2023-01-28T23:16:16-08:00	ERROR	building deployment objects	{"controller": "guestbook-controller", "object": {"name":"guestbook-sample","namespace":"default"}, "namespace": "default", "name": "guestbook-sample", "reconcileID": "b62ee9fb-be37-4094-9bb7-c3cce756c03e", "error": "error running kustomize: kustomize support is not compiled in (built with tag `without_kustomize`)"}

go run ./main.go

2023-01-28T23:19:46-08:00	INFO	running kustomize	{"controller": "guestbook-controller", "object": {"name":"guestbook-sample","namespace":"default"}, "namespace": "default", "name": "guestbook-sample", "reconcileID": "eb7c1f04-771e-45a1-b44f-d1b451357d46", "manifestPath": "channels/packages/guestbook/0.0.1"}

[justinsb]

I think you could return an error here, like fmt.Errorf("kustomize support is not compiled in (built with tag without_kustomize)")

[yuwenma]

I like the error message. Updated

[justinsb]

FYI you can have the same function with a build tag and without the build tag.

So you could declare RunKustomize in both.

One would have the build-tag //go:build without_kustomize, the other would have the build tag //go:build !without_kustomize.

Not a blocker though - and the refactoring is nice - but may be simpler in future.

[yuwenma]

Thank you for the suggestion! I'm trying to use function/struct name to make the code self-explained. But I agree the EnabledKustomize and SkipKustomize structs may give duplicate info since the go file name ("disabled" "enabled) and the build tags have already explained the rationale. Updated!

[yuwenma]

/assign @justinsb

[justinsb]

Thanks @yuwenma!

/approve
/lgtm

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[atoato88]

LGTM 😄
Should we add documentation about without_kustomize tag?

[yuwenma]

@atoato88 that's a good idea. I updated the doc here #301 Please let me know if there's anywhere else I shall update.