Add intermediate netrc struct and custom JSON marshaling methods to Netrc

[jackspirou]

This PR attempts to fix a bug with the Netrc JSON struct tag being named "user" instead of "password" while maintaining compatibility with current plugins that rely on the "user" syntax.

You can find the problematic line here: https://github.com/drone/drone-go/blob/master/drone/types.go#L124

More information about .netrc the file format here: https://www-01.ibm.com/support/knowledgecenter/ssw_aix_71/com.ibm.aix.files/netrc.htm

[tboerger]

LGTM

[jackspirou]

You can play with the implementation at http://play.golang.org/p/nyjvgCsUBV

[jackspirou]

After reading through the codebase I realized a JSON Unmarshal interface is needed as well. I have added it. You can play with an example here http://play.golang.org/p/-IkM7KTf8W.

Tested and working!

[tboerger]

Still LGTM

[jackspirou]

@bradrydzewski and @gtaylor any thoughts?

[bradrydzewski]

few thoughts ... first is to add some unit tests just to ensure we have all our edge cases covered. Also although slightly less efficient (it will allocate an intermediary struct) what if we simplify with something like this:

type netrc struct {
    Machine  string `json:"machine"`
    Login    string `json:"login"`
    Password string `json:"password"`
    PasswordOld string `json:"user"`
}

func (n *Netrc) UnmarshalJSON(b []byte) error {
  x := &netrc{}
  err := json.Unmarhsal(b, x)
  if err != nil {
    return 
  }
  n.Machine = x.Machine
  n.Login = x.Login
  n.Password = x.Password
  if x.PasswordOld != "" {
    n.Password = x.PasswordOld
  }
  return nil
}

func (n Netrc) MarshalJSON() ([]byte, error) {
  x := &netrc{
    Machine: x.Machine,
    Login: x.Login,
    Password: x.Password,
    PaswordOld: x.Password
  }
  return json.Marshal(x)
}

[jackspirou]

@bradrydzewski I started with a similar approach, but then ran into known issues around creating an endless recursion calls with json.Marshal -> MarshalJSON -> json.Marshal -> MarshalJSON etc... This creates an overflow error:

runtime: goroutine stack exceeds 250000000-byte limit
fatal error: stack overflow

I made some updates to your example above and you can see the results at http://play.golang.org/p/rYFGu5jglg.

I can def add unit tests and change DeprecatedUser to PasswordOld if you prefer that name.

[bradrydzewski]

@jackspirou we can have Netrc and netrc to avoid the loop. Check out http://play.golang.org/p/-SkUAiCk23

[jackspirou]

@bradrydzewski absolutely. Sorry if that was what you meant by:

it will allocate an intermediary struct

and I was too thick go get it. 😞

[bradrydzewski]

no worries! I have a bit of an unfair advantage because I spent about two weeks playing with custom yaml marshaling code and working around Go static typing limitations. It stretched my mind 😄

[jackspirou]

K, made changes and added tests.

[jackspirou]

@bradrydzewski does this look good now with the suggested changes?