Panic when diffing an invalid kubeconfig

[rraval]

A mixture of 2 space indents in YAML and 4 space indents in Typescript caused my editor to malform the kubeconfig during unrelated refactoring.

This causes pulumi up to panic when computing the diff: ~kubeconfig

Expected behavior

Some reasonable error reporting instead of process crash.

Current behavior

pulumi up crashes with:

  pulumi:pulumi:Stack (pulumi-kubernetes-segfault-dev):
    panic: runtime error: invalid memory address or nil pointer dereference
    [signal SIGSEGV: segmentation violation code=0x1 addr=0x10 pc=0x1d21d22]
    goroutine 29 [running]:
    github.com/pulumi/pulumi-kubernetes/provider/v3/pkg/provider.getActiveClusterFromConfig(0xc0004a86c0, 0xc00024ad20, 0xc000697380)
    	/home/runner/work/pulumi-kubernetes/pulumi-kubernetes/provider/pkg/provider/util.go:118 +0xe2
    github.com/pulumi/pulumi-kubernetes/provider/v3/pkg/provider.(*kubeProvider).DiffConfig(0xc0009a7a40, 0x2507808, 0xc00024ac00, 0xc0001e8000, 0xc0009a7a40, 0x1f0d501, 0xc000834180)
    	/home/runner/work/pulumi-kubernetes/pulumi-kubernetes/provider/pkg/provider/provider.go:345 +0xcb8
    github.com/pulumi/pulumi/sdk/v3/proto/go._ResourceProvider_DiffConfig_Handler.func1(0x2507808, 0xc00024ac00, 0x20b3780, 0xc0001e8000, 0x20c8ca0, 0x3561868, 0x2507808, 0xc00024ac00)
    	/home/runner/go/pkg/mod/github.com/pulumi/pulumi/sdk/v3@v3.0.0/proto/go/provider.pb.go:2158 +0x89
    github.com/grpc-ecosystem/grpc-opentracing/go/otgrpc.OpenTracingServerInterceptor.func1(0x2507808, 0xc000120ab0, 0x20b3780, 0xc0001e8000, 0xc00013e0c0, 0xc0004020d8, 0x0, 0x0, 0x24c19e0, 0xc00007d790)
    	/home/runner/go/pkg/mod/github.com/grpc-ecosystem/grpc-opentracing@v0.0.0-20180507213350-8e809c8a8645/go/otgrpc/server.go:57 +0x30a
    github.com/pulumi/pulumi/sdk/v3/proto/go._ResourceProvider_DiffConfig_Handler(0x214f4a0, 0xc0009a7a40, 0x2507808, 0xc000120ab0, 0xc0004a84e0, 0xc000622d80, 0x2507808, 0xc000120ab0, 0xc000577300, 0x127a)
    	/home/runner/go/pkg/mod/github.com/pulumi/pulumi/sdk/v3@v3.0.0/proto/go/provider.pb.go:2160 +0x150
    google.golang.org/grpc.(*Server).processUnaryRPC(0xc00079ce00, 0x25235b8, 0xc000582600, 0xc000538100, 0xc00070de60, 0x34ff1d0, 0x0, 0x0, 0x0)
    	/home/runner/go/pkg/mod/google.golang.org/grpc@v1.34.0/server.go:1210 +0x52b
    google.golang.org/grpc.(*Server).handleStream(0xc00079ce00, 0x25235b8, 0xc000582600, 0xc000538100, 0x0)
    	/home/runner/go/pkg/mod/google.golang.org/grpc@v1.34.0/server.go:1533 +0xd0c
    google.golang.org/grpc.(*Server).serveStreams.func1.2(0xc000532080, 0xc00079ce00, 0x25235b8, 0xc000582600, 0xc000538100)
    	/home/runner/go/pkg/mod/google.golang.org/grpc@v1.34.0/server.go:871 +0xab
    created by google.golang.org/grpc.(*Server).serveStreams.func1
    	/home/runner/go/pkg/mod/google.golang.org/grpc@v1.34.0/server.go:869 +0x1fd

Steps to reproduce

I've minimized the problem: https://github.com/rraval/pulumi-kubernetes-segfault

1. Check out the initial commit: index.ts.
2. Run pulumi up with no issues.
3. Move to the second commit: index.ts, Diff. This commit corrupts the indentation of kubeconfig, making it invalid.
4. Run pulumi up again, see panic from above.

Context (Environment)

Refactoring some code to move the provider creation from top level into a function (hence the change in indentation).

Affected feature

[lblackstone]

Thanks for the detailed repro! I tracked down the panic and have a PR open to fix that should go out with tomorrow's release.