[18.09] Fix panic in display only case for license

[dhiltgen]

Prior refactoring passes missed a corner case.

Signed-off-by: Daniel Hiltgen daniel.hiltgen@docker.com

[dhiltgen]

I'd like to try to build some unit test coverage for this, but the current structure is making this a bit challenging... I'll see what I can do, but if we're under the gun to get beta1.9 cut, we should consider merging this and revisit the unit coverage in a follow-up.

[codecov-io]

Codecov Report

Merging #1408 into 18.09 will increase coverage by 0.09%.
The diff coverage is 90.9%.

@@            Coverage Diff             @@
##            18.09    #1408      +/-   ##
==========================================
+ Coverage   54.12%   54.21%   +0.09%     
==========================================
  Files         290      290              
  Lines       19303    19306       +3     
==========================================
+ Hits        10447    10466      +19     
+ Misses       8192     8173      -19     
- Partials      664      667       +3

[dhiltgen]

Slightly more invasive, but now with unit coverage for the specific failure mode - confirmed running the new test case without the fix hits the panic.

[mavenugo]

LGTM

[tiborvass]

LGTM

[andrewhsu]

I'm able to reproduce the panic without this PR:

$ sudo docker engine activate --display-only
...
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x55dfe0ffe166]

goroutine 1 [running]:
github.com/docker/cli/cli/command/engine.runActivate(0x55dfe2c89860, 0xc4203adb00, 0x0, 0x0, 0x0, 0x0, 0x55dfe225ddc0, 0x16, 0x0, 0x0, ...)
        /go/src/github.com/docker/cli/cli/command/engine/activate.go:98 +0x1fd
github.com/docker/cli/cli/command/engine.newActivateCommand.func1(0xc420288c80, 0xc4200c9980, 0x0, 0x1, 0x0, 0x0)
        /go/src/github.com/docker/cli/cli/command/engine/activate.go:52 +0x6f
github.com/docker/cli/vendor/github.com/spf13/cobra.(*Command).execute(0xc420288c80, 0xc42003a0f0, 0x1, 0x1, 0xc420288c80, 0xc42003a0f0)
        /go/src/github.com/docker/cli/vendor/github.com/spf13/cobra/command.go:762 +0x46a
github.com/docker/cli/vendor/github.com/spf13/cobra.(*Command).ExecuteC(0xc4203b3680, 0xc420307f00, 0x55dfe294e2e0, 0xc420307f10)
        /go/src/github.com/docker/cli/vendor/github.com/spf13/cobra/command.go:852 +0x30c
github.com/docker/cli/vendor/github.com/spf13/cobra.(*Command).Execute(0xc4203b3680, 0xc4203b3680, 0x55dfe2c4b520)
        /go/src/github.com/docker/cli/vendor/github.com/spf13/cobra/command.go:800 +0x2d
main.main()
        /go/src/github.com/docker/cli/cmd/docker/docker.go:175 +0xde

And verify this PR fixes the issue:

$ sudo ./docker engine activate --display-only
Looking for existing licenses for andrewh5u...
NUM                 OWNER               PRODUCT ID          EXPIRES                         PRICING COMPONENTS
0                   andrewh5u           docker-ee-trial     2018-10-22 01:09:07 +0000 UTC   Nodes:10
...

[andrewhsu]

LGTM