Document how to negate a jsonpath conditional

[rcorre]

This is a...

• Feature Request
• Bug Report

Problem:

kubectl get ns -ojsonpath='{range .items[?(@.metadata.labels.origin)]}{.metadata.name}{"\n"}'

lists namespaces that have the label "origin". How do I list namespaces that don't have the label "origin"?

The jsonpath docs provided by kubernetes.io are very sparse, and pretty much say "we support jsonpath plus a few extra features". There's no link to the official "jsonpath" docs, so I had to search and eventually found my way to http://goessner.net/articles/JsonPath/. That pretty much says "jsonpath is like xpath" without giving a full description of the syntax, so I then found my way to https://en.wikipedia.org/wiki/XPath.

That finally seemed to be comprehensive syntax documentation, yet doesn't seem compatible with k8s. For my above example, I would expect the boolean function not to work, yet

kubectl get ns -ojsonpath='{range .items[?(not(@.metadata.labels.origin))]}{.metadata.name}{"\n"}'

fails with error: error parsing jsonpath {range .items[?(not(@.metadata.labels.origin))]}{.metadata.name}{"\n"}, unclosed array expect ].

Proposed Solution:

Include full jsonpath syntax documentation, or link to a page that documents jsonpath in a way that is compatible with k8s. Alternately, if kubectl does not really support jsonpath, the line "And we add three functions in addition to the original JSONPath syntax" should be changed to reflect that.

Page to Update:
https://kubernetes.io/docs/reference/kubectl/jsonpath/

Client Version: version.Info{Major:"1", Minor:"9", GitVersion:"v1.9.0", GitCommit:"925c127ec6b946659ad0fd596fa959be43f0cc05", GitTreeState:"clean", BuildDate:"2017-12-15T21:07:38Z", GoVersion:"go1.9.2", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"9", GitVersion:"v1.9.5", GitCommit:"f01a2bf98249a4db383560443a59bed0c13575df", GitTreeState:"clean", BuildDate:"2018-03-19T15:50:45Z", GoVersion:"go1.9.3", Compiler:"gc", Platform:"linux/amd64"}

[zacharysarah]

/assign @steveperry-53
/assign @tengqm

[tengqm]

Looks like there are many variants of jsonpath implementation. The one kubectl is using is very basic one. Regarding the filtering function, you can find the implementation here: https://github.com/kubernetes/client-go/blob/master/util/jsonpath/parser.go#L339

So ... there is currently no support to logical negation. I'm not aware of any official standard saying that JsonPath is compatible to XPath. Maybe I'm wrong.

[rcorre]

When I search for "jsonpath", my first hit is http://goessner.net/articles/JsonPath/. I guess it doesn't quite state that JsonPath is compatible with XPath, but it frequently references XPath and doesn't have a full reference of its own (e.g. it doesn't even mention ==).

The one kubectl is using is very basic one

Could the jsonpath docs include a link to whichever standard this is, or its own documentation if kubectl isn't conforming to any existing standard? As it stands right now, the docs refer to the "original JSONPath syntax" without actually stating what that is, which leaves readers to go off searching and find different things.

Thanks for the link to the source!

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[rcorre]

/remove-lifecycle stale

I think my above comment still stands:

Could the jsonpath docs include a link to whichever standard this is, or its own documentation if kubectl isn't conforming to any existing standard? As it stands right now, the docs refer to the "original JSONPath syntax" without actually stating what that is, which leaves readers to go off searching and find different things.

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[rcorre]

/remove-lifecycle rotten

Could the jsonpath docs include a link to whichever standard this is, or its own documentation if kubectl isn't conforming to any existing standard? As it stands right now, the docs refer to the "original JSONPath syntax" without actually stating what that is, which leaves readers to go off searching and find different things.

Does anyone know what "original JSONPath syntax" refers to?

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[k8s-ci-robot]

@fejta-bot: Closing this issue.

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