Kubectl: Kubectl user exec should accept zero-length environment values

[mb-m]

Is this a request for help? (If yes, you should use our troubleshooting guide and community support channels, see http://kubernetes.io/docs/troubleshooting/.): No

What keywords did you search in Kubernetes issues before filing this one? (If you have found any duplicates, you should instead reply there.): Searched through current open issues

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Is this a BUG REPORT or FEATURE REQUEST? (choose one): BUG REPORT

Kubernetes version (use kubectl version):

Client Version: version.Info{Major:"1", Minor:"14", GitVersion:"v1.14.1", GitCommit:"b7394102d6ef778017f2ca4046abbaa23b88c290", GitTreeState:"clean", BuildDate:"2019-04-19T22:12:47Z", GoVersion:"go1.12.4", Compiler:"gc", Platform:"darwin/amd64"}
Server Version: version.Info{Major:"1", Minor:"12+", GitVersion:"v1.12.6-eks-d69f1b", GitCommit:"d69f1bf3669bf00b7f4a758e978e0e7a1e3a68f7", GitTreeState:"clean", BuildDate:"2019-02-28T20:26:10Z", GoVersion:"go1.10.8", Compiler:"gc", Platform:"linux/amd64"}

Environment:

• Cloud provider or hardware configuration: AWS
• OS (e.g. from /etc/os-release): MacOS
• Kernel (e.g. uname -a):
• Install tools: brew
• Others:

What happened:

Error in configuration: 
* env variable AWS_SECURITY_TOKEN value must be specified for eks-staging to use exec authentication plugin
* env variable AWS_SESSION_TOKEN value must be specified for eks-staging to use exec authentication plugin
* env variable AWS_SECRET_ACCESS_KEY value must be specified for eks-staging to use exec authentication plugin
* env variable AWS_ACCESS_KEY_ID value must be specified for eks-staging to use exec authentication plugin

What you expected to happen:
empty environment variable should be allowed

How to reproduce it (as minimally and precisely as possible):
Kubernetes config users.[].user.exec.env.[].value = ""

Anything else we need to know:
https://github.com/kubernetes/kubectl/blob/master/vendor/k8s.io/client-go/tools/clientcmd/validation.go#L253-L255 - these lines cause the problem. While it's totally reasonable to force a non-zero-length environment name (the lines immediately preceding, an empty environment value (overriding a value in the shell, for example) has utility and shouldn't be blocked. Asserting that value is present is reasonable, asserting that it's not empty is not.

[pswica]

I tried to address here: https://github.com/kubernetes/kubernetes/pull/78875

[seans3]

/sig cli
/area kubectl
/kind bug

[mb-m]

Thank you so much, @pswica!

[seans3]

/assign @pswica

[k8s-ci-robot]

@seans3: GitHub didn't allow me to assign the following users: pswica.

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In response to this:

/assign @pswica

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