ExecProvider errors when parsing null values

[fillbit]

When executing a command like kubectl config use-context kubectl rewrite the the kubeconfig file and adds null to optional parameters. For example a a config with

users:
- name: Name1
  user:
    exec:
      apiVersion: client.authentication.k8s.io/v1alpha1
      command: heptio-authenticator-aws

is rewritten as:

users:
- name: Name1
  user:
    exec:
      apiVersion: client.authentication.k8s.io/v1alpha1
      args: null
      command: heptio-authenticator-aws
      env: null

When the ExecParser reads this it returns the error:

ERROR: Invalid kube-config file. Expected key args in kube-config/users[name=Name1]/user/exec

This PR adds a test case and a fix for this issue.

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[codecov-io]

Codecov Report

Merging #91 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #91      +/-   ##
==========================================
+ Coverage   91.71%   91.72%   +<.01%     
==========================================
  Files          13       13              
  Lines        1135     1136       +1     
==========================================
+ Hits         1041     1042       +1     
  Misses         94       94

Impacted Files	Coverage Δ
config/exec_provider_test.py	98.38% <100%> (+0.02%)	⬆️
config/exec_provider.py	82.6% <100%> (ø)	⬆️

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[fillbit]

signed CLA?

[roycaihw]

Thanks for the contribution! I left some comments.

[roycaihw]

I suppose the test fails when exec_config is of ConfigNode class, e.g. having

exec_config = ConfigNode('test', self.input_ok)

[roycaihw]

The exception comes from ConfigNode which implements __getitem__ under the assumption that

all access keys are present in a well-formed kube-config.

Calling the __getitem__ in the if statement would also raise the exception.

To tolerate malformed config, I'd suggest using exec_config.safe_get(key) to verify if the value is null. Note that the unit test used dict for exec_config which didn't reflect the safe_get attribute.

[fillbit]

I've updated the PR to use safe_get and the unit tests to use ConfigNode instead of dict() so they work correctly. I also updated the input_ok to include a env: null value and removed my test case as it is now redundant

[roycaihw]

@fillbit Thanks. Could you also add a comment in ExecProvider documenting that __init__ expects exec_config to be of ConfigNode class, which implements the safe_get(self, key) method? Otherwise LGTM

[roycaihw]

Please fix the pycodestyle error for travis CI to pass, and squash commits before submit :)

[fillbit]

@roycaihw @mbohlool Are there any other issue that need to be addressed?

[roycaihw]

/lgtm
/approve

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: fillbit, roycaihw

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[nakulpathak3]

kubernetes-client/python#678 hi I've been seeing the error mentioned in the issue while using both 8.0.0a and 8.0.0. If anyone has any tips/ideas for what I'm doing wrong or if there is something we need to change with the way we are doing exec-provider, please let me know