Require provider.credentials vars to be resolved before s3/ssm/cf vars

[dschep]

What did you implement:

Require provider.credentials vars to be resolved before s3/ssm/cf vars, similar to long standing region/stage and new profile preresolve.

test uses the service definition instead of getCredentials because
getCredentials is much more complex than getStage/getProfile/getRegion
and we only need to test that the config is updated, not all the
credential setting logic

How did you implement it:

added credentials in the prepopulate step of variable system

How can we verify it:

Create an SSM var called sls-5763 containing the value sls-5763
Create a service with the following config, replacing the key id & secret key of course:

service: sls-5763
custom:
  creds:
    sls-5763:
      accessKeyId: YOURACCESSKEYID
      secretAccessKey: YOURSECRETACCESSKEY
provider:
  credentials: ${self:custom.creds.${ssm:sls-5763}}
  name: aws
  runtime: nodejs8.10
functions:
  hello:
    handler: handler.hello

then when you run sls print with the stable version of serverless you'll get:

$ sls print
 Serverless Information ----------------------------------

  ##########################################################################################
  # 2501: 2 of 3 promises have settled
  # 2501: 1 unsettled promises:
  # 2501:   ssm:sls-4638 waited on by: ${self:custom.creds.${ssm:sls-4638}} ${ssm:sls-4638}
  # This can result from latent connections but may represent a cyclic variable dependency
  ##########################################################################################


 Serverless Information ----------------------------------

  ##########################################################################################
  # 5006: 2 of 3 promises have settled
  # 5006: 1 unsettled promises:
  # 5006:   ssm:sls-4638 waited on by: ${self:custom.creds.${ssm:sls-4638}} ${ssm:sls-4638}
  # This can result from latent connections but may represent a cyclic variable dependency
  ##########################################################################################


 Serverless Information ----------------------------------

  ##########################################################################################
  # 7507: 2 of 3 promises have settled
  # 7507: 1 unsettled promises:
  # 7507:   ssm:sls-4638 waited on by: ${self:custom.creds.${ssm:sls-4638}} ${ssm:sls-4638}
  # This can result from latent connections but may represent a cyclic variable dependency
  ##########################################################################################
^C

then install this branch with npm i -g serverless/serverless#credentials-preresolve and you should get:

$ sls print

  Error --------------------------------------------------

  Variable dependency failure: variable 'ssm:sls-4638' references service SSM but using that service requires a concrete value to be ca
lled.

     For debugging logs, run again after setting the "SLS_DEBUG=*" environment variable.

  Get Support --------------------------------------------
     Docs:          docs.serverless.com
     Bugs:          github.com/serverless/serverless/issues
     Issues:        forum.serverless.com

  Your Environment Information -----------------------------
     OS:                     darwin
     Node Version:           10.15.0
     Serverless Version:     1.36.3

Todos:

• Write tests
• n/a Write documentation
• Fix linting errors
• Make sure code coverage hasn't dropped
• Provide verification config / commands / resources
• Enable "Allow edits from maintainers" for this PR
• Update the messages below

Is this ready for review?: YES
Is it a breaking change?: NO

[pmuens]

Nice 👍 Added a comment about a function name that caught my attention.

Other than that I think it should be GTM

[pmuens]

Does this requiredConfigs above mean that those are required to be present (e.g. users need to put in region, stage, porfile, etc.)? At least it reads like that. Pretty sure that's not the case. Just want to make sure that this is not a breaking change...

[dschep]

yeah, the name is a little misleading. It works just fine when they're not set. They'r required to be prepopulated if they're set.