270 replacer casts

[cdent]

This is an effort to provide the functionality described in #270 by implementing optional "casts" on the $ENVIRON and $REPLACER replacers by appending a :cast (int, str, bool, float) to the replacer name (e.g., $ENVIRON:int['FOOBAR']).

This only works when the replacer is the entirety of the message being replaced:

data:
    foo: $ENVIRON:int['FOOBAR']

not mixed in:

data:
    foo: boom $ENVIRON:int['FOOBAR'] boom

We can't do this for two reasons:

• in part, the surrounding context may conflict with the intended value of the cast
• but more, the way the repl function inre.sub works, they can only return strings, thus the casting has to happen after the re.sub

While the code is present to make it possible to do casts of other replacers, for the moment any cast will be ignored, mostly because it doesn't make sense for most of them.

It might, however, make sense for $COOKIE so input on that desired.

This isn't done, it needs to be confirmed as having grammatical sense, and it also needs doc update, but I'm putting it up here for some initial feedback on the format and implementation.

[cdent]

@jd I suspect you might have some input on this if you can cast (ha!) your mind back to gnocchi time.

[jd]

I think we mostly used ENVIRON in headers not in data, so we were cool with strings only.

Now I understand why you'd need this feature in data. I did not check the implementation, but the principle LGTM.

[FND]

The concept seems sound, though I'm not sure I can grok all the implications (also WRT the implementation).

As mentioned before, I'm a little wary because this feels like special-casing, but that's quite possibly unjustified or simply irrelevant (as you're solving an actual problem here).

[FND]

minor nit:

return {
    "true": True,
    "false": False,
    "null": None
}.get(value.lower(), value)

seems more readable/idiomatic?

[cdent]

Perhaps, but code was already there in the previous way and changing it now would be an unrelated change.

Also that looks icky.

[cdent]

@taget have you had a chance to try this out?

[cdent]

@taget I'm still hoping you can verify that this solves the problems you were trying to solve

[taget]

@cdent
hi Chris, sorry to not response you for long time.

I tried in my test environment, works for me when cast a integer to string

yaml:

  POST: /api/cgi
  request_headers:
    content-type: application/json
  data:
    params:
      content:
        requestInfo:
          requestKey: mx_ksdionuj3djfk
          caller: vs-api
          seqId: ''
          requestId: ''
        version: '1.0'
        type: json
        requestItem:
          data:
            detail:
            - uuid: $ENVIRON['VS_UUID']
              hostIpList:
                  - $ENVIRON['VS_HOSTIP']
              migrateBandwidth: 20
              migrateTimeout: 3600
              pauseTime: $ENVIRON:str['PAUSE_TIME']
              schedulerDebug: 'on'
              compression:
                compression: mt
          method: instance_live_migrate

VS_HOSTIP="101" VS_UUID="100" PAUSE_TIME=122 gabbi-run http://127.0.0.1:8000 < a.yaml

result

{
  "params": {
    "content": {
      "type": "json",
      "requestInfo": {
        "seqId": "",
        "requestId": "",
        "caller": "vs-api",
        "requestKey": "mx_ksdionuj3djfk"
      },
      "requestItem": {
        "method": "instance_live_migrate",
        "data": {
          "detail": [
            {
              "schedulerDebug": "on",
              "migrateBandwidth": 20,
              "uuid": 100,
              "compression": {
                "compression": "mt"
              },
              "pauseTime": "122",
              "migrateTimeout": 3600,
              "hostIpList": [
                101
              ]
            }
          ]
        }
      },
      "version": "1.0"
    }
  }
}

thanks for your help :)