add workaround to support yaml anchors

[jmccann]

Adding a workaround to allow yaml anchors to work with drone-cli. They have been working fine with Drone 0.8.6 server/agents.

This works by unmarshalling from []byte yaml to a map[string]interface{} and then back to a []byte yaml. During this process the anchors are "compiled". So

some-anchor: &some-anchor
  image: alpine:3.7
  commands:
    - echo "hello world"

pipeline:
  foo:
    <<: *some-anchor

Then becomes:

pipeline:
  foo:
    commands:
    - echo "hello world"
    image: alpine:3.7

some-anchor:
  commands:
  - echo "hello world"
  image: alpine:3.7

[bradrydzewski]

I wonder if we apply this patch to go-yaml if it will work?

[[constraint]]
  branch = "fix-for-issue-91"
  name = "gopkg.in/yaml.v2"
  source = "https://github.com/vinzenz/yaml.git"

[bradrydzewski]

also just a heads up that the CLI in master changed to support 0.9 (some deprecated API calls were removed, some structures changed). So we probably need to branch 0.8.6 and update.

[jmccann]

You think the issue is with that package? I'm not sure since I'm using that package to "fix" this.

And yes, would love to be able to fix in 0.8.6 also. The "patch" I PM'd you earlier was against the 0.8.6 code.

[bradrydzewski]

I think it could be at the package level. This is the particular issue that seems similar to what you are describing: go-yaml/yaml#91

[jmccann]

So I added the following to Gopkg.toml:

+[[override]]
+  branch = "fix-for-issue-91"
+  name = "gopkg.in/yaml.v2"
+  source = "https://github.com/vinzenz/yaml.git"

And did a dep ensure to update local vendor.

I then ran and got:

» go build -o drone.bin github.com/drone/drone-cli/drone && ./drone.bin exec           
panic: reflect.Value.Addr of unaddressable value [recovered]
	panic: reflect.Value.Addr of unaddressable value [recovered]
	panic: reflect.Value.Addr of unaddressable value

goroutine 1 [running]:
github.com/drone/drone-cli/vendor/gopkg.in/yaml%2ev2.handleErr(0xc42022f420)
	/Users/z087177/go/src/github.com/drone/drone-cli/vendor/gopkg.in/yaml.v2/yaml.go:164 +0x99
panic(0x14a9ca0, 0x15f3580)
	/usr/local/Cellar/go/1.10.3/libexec/src/runtime/panic.go:502 +0x229
github.com/drone/drone-cli/vendor/gopkg.in/yaml%2ev2.handleErr(0xc42022ec98)
	/Users/z087177/go/src/github.com/drone/drone-cli/vendor/gopkg.in/yaml.v2/yaml.go:164 +0x99
panic(0x14a9ca0, 0x15f3580)
	/usr/local/Cellar/go/1.10.3/libexec/src/runtime/panic.go:502 +0x229
reflect.Value.Addr(0x14d45a0, 0xc42035e7e0, 0x15, 0xb, 0xc42039e268, 0x1)
	/usr/local/Cellar/go/1.10.3/libexec/src/reflect/value.go:245 +0x94
github.com/drone/drone-cli/vendor/gopkg.in/yaml%2ev2.(*decoder).alias(0xc420360cc0, 0xc420396700, 0x14d45a0, 0xc42035e7e0, 0x15, 0x1012089)
	/Users/z087177/go/src/github.com/drone/drone-cli/vendor/gopkg.in/yaml.v2/decode.go:400 +0x47c
...

So it didn't seem happy ...

[bradrydzewski]

0.9 supports multi-document yaml files which would be problematic here. But we can definitely backport this to 0.8. I will create an 0.8 branch tomorrow morning that we can use.

[jmccann]

Is there documentation around that so I can try to understand the issue. Looking at the cli source it seems it looks for a single file, defaulting to .drone.yml, and reads the file and starts using it.

Thanks for the help on this!

[bradrydzewski]

yes, the yaml.Unmarshal will not work with a multi-document yaml like this https://github.com/drone/drone-git/blob/master/.drone.yml :)