Fix null reference when no env vars defined in yml

[davidsiaw]

This PR fixes a bug introduced in #23 where if you do not define a run_env section in the barcelona.yml it would throw a null reference error.

How to test

1. Create a barcelona.yml containing this:

environments:
  hello:
    name: hello
    image_name: quay.io/dsiawdegica/hello
    scheduled_tasks: []
    services:
      - name: web
        service_type: web
        cpu: null
        memory: 256
        command: sh /start.sh
        listeners:
          - endpoint: hello
            health_check_path: /
        port_mappings:
          - lb_port: 80
            container_port: 8080
            protocol: http

2.Run ./bcn -d run -e hello -E FOO=bar ew
3. Observe that there is no segfault error, and it outputs

{"command":"ew","env_vars":{"FOO":"bar"},"interactive":true}

[degicat]

@Resonious please review this

[Resonious]

Sorry for the delay. I have a quick code question!

[Resonious]

@davidsiaw I downloaded the binary from the CI build job https://gitlab.com/degica/barcelona-cli/-/jobs/504621079 and it still seems to segfault after performing the test instructions.

[nigel@resonious testsz]$ cat barcelona.yml 
environments:
  hello:
    name: hello
    image_name: quay.io/dsiawdegica/hello
    scheduled_tasks: []
    services:
      - name: web
        service_type: web
        cpu: null
        memory: 256
        command: sh /start.sh
        listeners:
          - endpoint: hello
            health_check_path: /
        port_mappings:
          - lb_port: 80
            container_port: 8080
            protocol: http

[nigel@resonious testsz]$ ./bcn -d run -e hello -E FOO=bar ew
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x776392]

goroutine 1 [running]:
github.com/degica/barcelona-cli/cmd.loadEnvVars(0x7ffc2466a771, 0x5, 0x0, 0x0, 0xc000115b90, 0x68, 0x1)
        /go/src/github.com/degica/barcelona-cli/cmd/run.go:163 +0xa2
github.com/degica/barcelona-cli/cmd.glob..func38(0xc000136b40, 0x100, 0xc000136b40)
        /go/src/github.com/degica/barcelona-cli/cmd/run.go:52 +0x1ba
github.com/degica/barcelona-cli/vendor/github.com/urfave/cli.HandleAction(0x7c6d20, 0x85f708, 0xc000136b40, 0xc000026600, 0x0)
        /go/src/github.com/degica/barcelona-cli/vendor/github.com/urfave/cli/app.go:485 +0xc8
github.com/degica/barcelona-cli/vendor/github.com/urfave/cli.Command.Run(0x842001, 0x3, 0x0, 0x0, 0x0, 0x0, 0x0, 0x851c3b, 0x28, 0x0, ...)
        /go/src/github.com/degica/barcelona-cli/vendor/github.com/urfave/cli/command.go:193 +0x97c
github.com/degica/barcelona-cli/vendor/github.com/urfave/cli.(*App).Run(0xc00010b6c0, 0xc000012080, 0x8, 0x8, 0x0, 0x0)
        /go/src/github.com/degica/barcelona-cli/vendor/github.com/urfave/cli/app.go:250 +0x82a
main.main()
        /go/src/github.com/degica/barcelona-cli/main.go:41 +0x445
[nigel@resonious testsz]$

Let me know if there's something I'm missing.

[davidsiaw]

@Resonious That is embarassing. I must have messed up. I made a fix.

[Resonious]

@davidsiaw All good - it no longer segfaults, but I have one more code question.

[Resonious]

Looks to me like we might still need this heritageName = env.Name part.

Later in the file, it does this

api.DefaultClient.Post("/heritages/"+heritageName+"/oneoffs", bytes.NewBuffer(j))

which might not won't work right if len(envName) > 0 && len(heritageName) == 0.

Does that sound right?

[davidsiaw]

Hmm that code looks awfully suspicious. You are right. I'll try and fix it in a sane way

[davidsiaw]

@Resonious sorry it took me forever to get back to this. I legitimately thought that this was solved but it wasn't. I made a change to fix that issue. I will make an issue to refactor this into a more understandable thing later.

[davidsiaw]

@Resonious I have rebased the branch against master and fixed the ci, if you have time could you please have another look? I made an issue to fix this messiness in run.go #29

[Resonious]

No problem - just one more tiny thing, then it should be good to go

[davidsiaw]

@Resonious made some fixes to this long-overdue pr. Could you have one last look? Thanks!

[Resonious]

LGTM 👍