DiffConfig fails when provider's kubeconfig is set to file path

[mikhailshilkov]

What happened?

Reported in pulumi/pulumi#14529

A CLI version that doesn't ignore errors returned from DiffConfig fails with

error: rpc error: code = Unknown desc = failed to parse kubeconfig: couldn't get version/kind; json parse error: json: cannot unmarshal string into Go value of type struct { APIVersion string "json:"apiVersion,omitempty""; Kind string "json:"kind,omitempty"" }

when an explicit kubernetes provider points to a kubeconfig via its path.

I reproduced that the error is returned from this line:

pulumi-kubernetes/provider/pkg/provider/provider.go

Line 376 in 1944a52

return nil, err

Example

import { Provider } from '@pulumi/kubernetes'

export const provider = new Provider('***', {
  kubeconfig: join(__dirname, 'kubeconfig.yaml')
})

Output of pulumi about

CLI          
Version      3.92.0
Go Version   go1.21.3
Go Compiler  gc

Plugins
NAME            VERSION
aws             5.4.0
aws             4.38.1
aws             4.38.1
aws-apigateway  0.0.6
aws-native      0.16.1
command         0.1.0
docker          3.1.0
eks             0.36.0
kubernetes      3.12.1
nodejs          unknown
random          4.3.1

Host     
OS       darwin
Version  14.1
Arch     arm64

This project is written in nodejs: executable='/usr/local/bin/node' version='v18.17.0'

Dependencies:
NAME                              VERSION
@types/node                       17.0.5
husky                             7.0.4
deepmerge                         4.2.2
lodash                            4.17.21
@aws-sdk/client-sts               3.45.0
@pulumi/aws-apigateway            0.0.6
@pulumi/aws-native                0.16.1
@pulumi/eks                       0.36.0
@pulumi/kubernetes                3.12.1
@pulumi/pulumi                    3.18.0
eslint                            8.12.0
typescript                        4.6.3
@aws-sdk/client-kms               3.45.0
@pulumi/aws                       5.4.0
@pulumi/awsx                      0.40.0
@pulumi/command                   0.1.0
@pulumi/random                    4.3.1
@typescript-eslint/eslint-plugin  5.18.0
@types/js-yaml                    4.0.5
@types/lodash                     4.14.178
@typescript-eslint/parser         5.18.0
js-yaml                           4.1.0

Additional context

No response

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