🐛 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/cobra@v1.8.1/command.go:985 +0x834 github.com/spf13/cobra.(*Command).ExecuteC(0x40002aec08)	/home/mtardy.linux/go/pkg/mod/github.com/spf13/cobra@v1.8.1/command.go:1117 +0x344 github.com/spf13/cobra.(*Command).Execute(...)	/home/mtardy.linux/go/pkg/mod/github.com/spf13/cobra@v1.8.1/command.go:1041 main.main()	/home/mtardy.linux/controller-tools/cmd/controller-gen/main.go:200 +0x290 exit status 2 

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Hi @mtardy. Thanks for your PR.

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[sayboras]

wow this is a nice one 😲

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[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