🐛 pkg/crd: fix type casting panic with new default *types.Alias with Go 1.23

[mtardy]

Fixes #1053

In the latest version of go, a change was made to the generation of Alias types by default. From the release notes:

By default, go/types now produces Alias type nodes for type aliases.
This behavior can be controlled by the GODEBUG gotypesalias flag. Its
default has changed from 0 in Go 1.22 to 1 in Go 1.23.

This provoked a panic in the localNamedToSchema function when processing any type alias becaused it was expecting only a *types.Named and not a *types.Alias. This can be fixed by using an anonymous interface to more broadly "ask" if the object supports the Obj() function instead of asking it to be a specific type. Types *types.Named and *types.Alias share this method so it can be used directly.

Note that it would be better (and would have made this easier to debug) to retrieve the "ok" second return value and print some error on failure to cast but this is a minimal working patch.

For example you can reproduce a panic, switching the project to use Go 1.23 (and thus gotypesalias to 1), putting the following file in repro/repro.go:

// +groupName=repro.io
package repro

import (
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
)

type Repro struct {
	metav1.TypeMeta   `json:",inline"`
	metav1.ObjectMeta `json:"metadata"`

	Reproducer StringAlias `json:"reproducer"`
}

type StringAlias = string

Then run:

go run ./cmd/controller-gen/ crd paths=./repro

You should see something similar to:

panic: interface conversion: types.Type is *types.Alias, not *types.Named

goroutine 1 [running]:
sigs.k8s.io/controller-tools/pkg/crd.localNamedToSchema(0x4001315f50, 0x40003918e0)
	/home/mtardy.linux/controller-tools/pkg/crd/schema.go:258 +0x3bc
sigs.k8s.io/controller-tools/pkg/crd.typeToSchema(0x4001315f50, {0xa391e8, 0x40003918e0})
	/home/mtardy.linux/controller-tools/pkg/crd/schema.go:197 +0xd0
sigs.k8s.io/controller-tools/pkg/crd.structToSchema(0x40009ee5f8, 0x400000e300)
	/home/mtardy.linux/controller-tools/pkg/crd/schema.go:436 +0x7d8
sigs.k8s.io/controller-tools/pkg/crd.typeToSchema(0x40009ee5f8, {0xa391b8, 0x400000e300})
	/home/mtardy.linux/controller-tools/pkg/crd/schema.go:207 +0x90
sigs.k8s.io/controller-tools/pkg/crd.infoToSchema(0x40000505f8)
	/home/mtardy.linux/controller-tools/pkg/crd/schema.go:125 +0xcc
sigs.k8s.io/controller-tools/pkg/crd.(*Parser).NeedSchemaFor(0x400009a120, {0x4000207b80, {0x40002c2540, 0x5}})
	/home/mtardy.linux/controller-tools/pkg/crd/parser.go:193 +0x1e8
sigs.k8s.io/controller-tools/pkg/crd.(*Parser).NeedFlattenedSchemaFor(0x400009a120, {0x4000207b80, {0x40002c2540, 0x5}})
	/home/mtardy.linux/controller-tools/pkg/crd/parser.go:205 +0x9c
sigs.k8s.io/controller-tools/pkg/crd.(*Parser).NeedCRDFor(0x400009a120, {{0x4000185a06, 0x8}, {0x40002c2540, 0x5}}, 0x0)
	/home/mtardy.linux/controller-tools/pkg/crd/spec.go:93 +0x3d8
sigs.k8s.io/controller-tools/pkg/crd.Generator.Generate({0x0, 0x0, 0x0, {0x0, 0x0, 0x0}, 0x0, {0x0, 0x0}, {0x0, ...}, ...}, ...)
	/home/mtardy.linux/controller-tools/pkg/crd/gen.go:182 +0x464
sigs.k8s.io/controller-tools/pkg/genall.(*Runtime).Run(0x400015cbd0)
	/home/mtardy.linux/controller-tools/pkg/genall/genall.go:272 +0x21c
main.main.func1(0x40002a2200?, {0x40002d9ad0?, 0x4?, 0x8e519c?})
	/home/mtardy.linux/controller-tools/cmd/controller-gen/main.go:176 +0x64
github.com/spf13/cobra.(*Command).execute(0x40002aec08, {0x4000136090, 0x3, 0x3})
	/home/mtardy.linux/go/pkg/mod/github.com/spf13/[email protected]/command.go:985 +0x834
github.com/spf13/cobra.(*Command).ExecuteC(0x40002aec08)
	/home/mtardy.linux/go/pkg/mod/github.com/spf13/[email protected]/command.go:1117 +0x344
github.com/spf13/cobra.(*Command).Execute(...)
	/home/mtardy.linux/go/pkg/mod/github.com/spf13/[email protected]/command.go:1041
main.main()
	/home/mtardy.linux/controller-tools/cmd/controller-gen/main.go:200 +0x290
exit status 2

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[k8s-ci-robot]

Hi @mtardy. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[sayboras]

wow this is a nice one 😲

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Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[sbueringer]

/ok-to-test

[sbueringer]

@mtardy Thank you! Especially for the explanations and code to reproduce. Feel free to ping me once #1061 (comment) is resolved