Serverless Variables

[eahefnawy]

This PR implements the new Serverelss Variables system as described here and discussed in #1801.

• populating from env vars: ${env:my_arn}
• populating from cli options: ${opt:stage}
• populating from the self serverless.yml file: ${self:service}
• move defaults into provider with backward compatibility
• indefinite recursive nesting: ${env:${opt:stage}_arn}
• populating from another file: ${file(./config.yml):data.subProp}
• unit tests
• update docs

cc/ @serverless/vip

[nicka]

You might want to add an actual example CLI command. For example: sls deploy --stage=dev

[eahefnawy]

Sure thing. Note though that the command hasn't changed. It's still sls deploy --stage dev as usual, but what's new is that you have access to this stage CLI option in the configuration file.

[pmuens]

Just played around with it and it's really rock solid!
Great work 🎉

Here's just something I was wondering when using self. What about if we parse the file self references into JSON and use this JSON representation to find the correct value?

This way we can also e.g. access properties which are nested inside the events array like self.functions.hello.events[0].http.path. Not sure if it's necessary at all.

Another thing was that I still found several serverless.env.yml references (especially in the docs) while doing a global search (CMD + Shift + F in WebStorm). Those should be removed as well.

[eahefnawy]

@pmuens not sure I understand what you mean about JSON. The self is already accessing the parsed serverless.yml file as a Javascript Object, and we can access any value type. But just like you mention, the limitation is parsing the referencing string itself. So yeah we can't really go deep into arrays because that syntax it's not supported (not really sure if there's a need for that though), but how would JSON help here?

[pmuens]

Yes. Just something random I stumbled upon when I tried to access the path property of the http event in the serverless.yml file.

Maybe a wrong usage on my side but also not a high priority IMHO.

[pmuens]

Awesome! Will test it ASAP. Just one note. Could you do another global search for serverless.env.yml and serverless.env.yaml? There are still some references (e.g. in the root README.md file) in other files which might be removed.

[eahefnawy]

@pmuens Good catch! 👍 .... I was only searching in the docs folder

[flomotlik]

@eahefnawy please resolve conflicts

[ac360]

@eahefnawy You are so fantastic and talented, I bet you can still squeeze in support for var.myVar in populate(). Just imagine how simple and elegant var will look in serverless.yml, as an alternative to these other awesome variable sources you've implemented. It will be like art. Can you picture it?

Also, @maciej will give you a kiss.

[hellolijin]

serverless.yml
....
config: ${opt:target}
custom: ${file(./${self:config}.yml)}
...

when I run,
$ sls deploy --target dev

error happens.

Serverless Error ---------------------------------------

 Trying to populate non string value into a string for
 variable ${self:config}. Please make sure the value
 of the property is a string.

...

[hellolijin]

serverless.yml (the ./foo/function.yml is defined correctly)
...
functions:
foo: ${file(./foo/function.yml)}
...
When deploy, I got

Type Error ---------------------------------------------

 Cannot assign to read only property 'events' of ${file(./foo/function.yml)}

Could I know how to resolve it? I really want to define the functions in the sub folder.