pkg/cli: only allow one default plugin per project version

[estroz]

A CLI's default plugins now contain only one plugin per project version, and the Option returned by WithDefaultPlugins will return an error if multiple are found. The one-to-one mapping identifies which plugin that should be run when no plugin key is passed via layout or --plugins.

• pkg/cli: change the type of cli.defaultPluginsFromOptions such that
  it maps one project version to one plugin.

Relates to #1536.

/cc @joelanford @camilamacedo86 @DirectXMan12

[camilamacedo86]

Hi @estroz,

Currently, KB has just 1 plugin version which makes these changes pass successfully in the CI. However, if we apply here the changes made in the commit e38b06b from the PR #1498 where we are adding a new plugin version it will NOT work well as expected. See:

$ make generate
rm -rf /Users/camilamacedo/go/bin/controller-gen
make generate-testdata
make[1]: Entering directory '/Users/camilamacedo/go/src/sigs.k8s.io/kubebuilder'
GO111MODULE=on ./generate_testdata.sh
~/go/src/sigs.k8s.io/kubebuilder ~/go/src/sigs.k8s.io/kubebuilder
Starting to generate projects with version 2
Generating project-v2
go: creating new go.mod: module sigs.k8s.io/kubebuilder/testdata/project-v2
initializing project-v2 ...
2020/06/01 14:08:26 broken pre-set default plugins: project version "3-alpha" already has plugin "go.kubebuilder.io/v2.0.0"
make[1]: *** [Makefile:63: generate-testdata] Error 1
make[1]: Leaving directory '/Users/camilamacedo/go/src/sigs.k8s.io/kubebuilder'
make: *** [Makefile:58: generate] Error 2

So, IMO let's merge the PR #1498 and the fix #1538 and then, we will have the KB with more the 1 plugin version implemented and checked by the CI. After that will be easier to do improvements and changes as you are suggesting without the risk to introduce new issues for this scenario.

[estroz]

@camilamacedo86 #1498 should fail with this PR because both v2 and v3 plugins from that PR support an overlapping set of project versions, which this PR aims to avoid. The goal of this PR is to say "a user will use this plugin if they have not specified one for their project's version". Right now, having more than one is ambiguous given how a CLI is constructed.

[camilamacedo86]

Hi @estroz,

So, you are saying that the following scenario is invalid?

// When has more than one supportable plugin. E.g:
// - go.kubebuilder.io/v2.0.0 which is supported by V2 and V3
// - go.kubebuilder.io/v3.0.0 which is supported by V3

If yes, should we not change the var supportedProjectVersions = []string{config.Version2, config.Version3Alpha}. I mean, should it really be an array? Or is your idea that the following scenario would be valid and because of this we should keep the array?

// - go.kubebuilder.io/v2.0.0 which is supported by V2 and V3
// - go.kubebuilder.io/v3.0.0 which is supported by V4

[estroz]

Project versions 2 and 3 should have different default plugins. Realistically the plugin for version 2 should be “special” since there is no layout key for that project scheme. See #1537 for an example.

[camilamacedo86]

Hi @estroz,

I thought that we would allow the multi-project version. However, thinking about keeping it simple and reduce the complexity I agree with you. It shows the best approach to move forward.

[camilamacedo86]

Checked that it worked as proposed to work. See:

2020/06/01 14:08:26 broken pre-set default plugins: project version "3-alpha" already has plugin "go.kubebuilder.io/v2.0.0"
make[1]: *** [Makefile:63: generate-testdata] Error 1
make[1]: Leaving directory '/Users/camilamacedo/go/src/sigs.k8s.io/kubebuilder'
make: *** [Makefile:58: generate] Error 2

/lgtm
/approve

[k8s-ci-robot]

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