Running kustomize build panics

[MikaelSmith]

Describe the bug
Panic when building a project with an entry namespace: . kubectl apply doesn't complain about this, and it's hard to debug what causes it.

panic: interface conversion: interface {} is nil, not string

goroutine 1 [running]:
sigs.k8s.io/kustomize/api/resmap.getNamespacesForRoleBinding(0xc000355270)
        sigs.k8s.io/kustomize/api@v0.10.0/resmap/reswrangler.go:439 +0x21b
sigs.k8s.io/kustomize/api/resmap.(*resWrangler).SubsetThatCouldBeReferencedByResource(0xc00000f500, 0x4735da0)
        sigs.k8s.io/kustomize/api@v0.10.0/resmap/reswrangler.go:399 +0x105
sigs.k8s.io/kustomize/api/internal/accumulator.(*nameReferenceTransformer).Transform(0xc000ac10f0, {0x475bbd0, 0xc00000f500})
        sigs.k8s.io/kustomize/api@v0.10.0/internal/accumulator/namereferencetransformer.go:55 +0xdc
sigs.k8s.io/kustomize/api/internal/accumulator.(*ResAccumulator).Transform(...)
        sigs.k8s.io/kustomize/api@v0.10.0/internal/accumulator/resaccumulator.go:142
sigs.k8s.io/kustomize/api/internal/accumulator.(*ResAccumulator).FixBackReferences(0xd0)
        sigs.k8s.io/kustomize/api@v0.10.0/internal/accumulator/resaccumulator.go:168 +0xc5
sigs.k8s.io/kustomize/api/internal/target.(*KustTarget).makeCustomizedResMap(0xc0003860d0)
        sigs.k8s.io/kustomize/api@v0.10.0/internal/target/kusttarget.go:131 +0x6f
sigs.k8s.io/kustomize/api/internal/target.(*KustTarget).MakeCustomizedResMap(...)
        sigs.k8s.io/kustomize/api@v0.10.0/internal/target/kusttarget.go:112
sigs.k8s.io/kustomize/api/krusty.(*Kustomizer).Run(0xc002327d98, {0x4755d60, 0x4b84ac8}, {0x7ffeefbff1b0, 0x1d})
        sigs.k8s.io/kustomize/api@v0.10.0/krusty/kustomizer.go:88 +0x39c
sigs.k8s.io/kustomize/kustomize/v4/commands/build.NewCmdBuild.func1(0xc000356580, {0xc000317900, 0x1, 0x1})
        sigs.k8s.io/kustomize/kustomize/v4/commands/build/build.go:80 +0x176
github.com/spf13/cobra.(*Command).execute(0xc000356580, {0xc0003178d0, 0x1, 0x1})
        github.com/spf13/cobra@v1.0.0/command.go:842 +0x60e
github.com/spf13/cobra.(*Command).ExecuteC(0xc000356000)
        github.com/spf13/cobra@v1.0.0/command.go:950 +0x3ad
github.com/spf13/cobra.(*Command).Execute(...)
        github.com/spf13/cobra@v1.0.0/command.go:887
main.main()
        sigs.k8s.io/kustomize/kustomize/v4/main.go:14 +0x1e

Resources

---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: test
---
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: test
rules: []
---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: test
subjects:
- kind: ServiceAccount
  name: test
  namespace:
roleRef:
  kind: Role
  name: test
  apiGroup: rbac.authorization.k8s.io

Kustomize version

{Version:kustomize/v4.4.0 GitCommit:63ec6bdb3d737a7c66901828c5743656c49b60e1 BuildDate:2021-09-27T16:13:36Z GoOs:darwin GoArch:amd64}

on macOS.

[natasha41575]

To clarify, is the resource stream you've provided the input to kustomize or the output? If it is the output, could you please provide the input?

If it is the input, I'm curious how does kubectl apply handle an empty namespace? Is it treated the same as default namespace?

[MikaelSmith]

It's the input, but I was paring down from several thousand lines of code and omitted the very basic kustomization.yaml associated with it.

I haven't checked what Kubernetes does with it. There's some templating that normally puts a string there, and just didn't in this particular case. So I haven't used it this way extensively. Just ended up hard to debug.

[KnVerey]

I was able to reproduce this. The input isn't valid, so we don't need to do anything fancy to accommodate it, but we definitely should not panic in this situation.

/triage accepted
/kind bug

[KnVerey]

/assign @m-Bilal

[k8s-ci-robot]

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In response to this:

/assign @m-Bilal

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[m-Bilal]

/assign