CredentialsPlugin should support more than username/password credentials

[kmanning]

• This issue was broken out of Issue CredentialsPlugin should be applied to every Stage, not just BuildStage #192

[kmanning]

From @dkolb :

Overview

Currently Credentials Plugin only supports the build stage and Username/Password credentail types.

The current use case I have requires mapping credentials onto TF_VAR_blah environment variables in the environment stages. Furthermore, some of these credentials are of the string() type of DSL call. Finally, some of these credentials differ between individual environment stage.

Current Workarounds

Currently I'm moving to decorating each stage directly in the Jenkinsfile for now.

def validate   = new TerraformValidateStage()
def deployDev  = new TerraformEnvironmentStage('dev')

deployDev.decorate(TerraformEnvironmentStage.ALL, { closure ->
  withCredentials([
    usernamePassword(
      credentialsId: 'some-user'
      usernameVariable: 'TF_VAR_some_user',
      passwordVariable: 'TF_VAR_some_passord'
    ),
    string(
      credentialsId: 'some-secret',
      variable: 'TF_VAR_some_secret'
    )
  ]) {
    closure()
  }
})

validate
  .then(deployDev)
  .build()

[kmanning]

CredentialsPlugin currently offers

CredentialsPlugin.withBuildCredentials('my-credentials').init()

That's way too specific, and does not indicate that it's using username/password credentials. Part of what makes this complicated is that Jenkinsfile uses specific DSL to generate binding configuration.

Seems like there are 2 options:

1. Offer binding-specific methods
2. Offer a binding method

Both options could be provided, without conflicting. Either way, the existing withBuildCredentials should probably be deprecated and replaced.

To sketch out what option 2 could look like:

CredentialsPlugin.withBinding {
        usernamePassword(
            credentialsId: 'some-user'
            usernameVariable: 'TF_VAR_some_user',
            passwordVariable: 'TF_VAR_some_password'
        )
    }.init()

^-- that would be the equivalent of:

...
  withCredentials([
    usernamePassword(
      credentialsId: 'some-user'
      usernameVariable: 'TF_VAR_some_user',
      passwordVariable: 'TF_VAR_some_passord'
    )] {
        ... // your pipeline
  }
...

We could make the method cumulative. So using your example above:

CredentialsPlugin.withBinding {
        usernamePassword(
            credentialsId: 'some-user'
            usernameVariable: 'TF_VAR_some_user',
            passwordVariable: 'TF_VAR_some_password'
        ) 
    }.withBinding {
        string(
            credentialsId: 'some-secret',
            variable: 'TF_VAR_some_secret'
        )
    }.init()

^--- that would produce the equivalent:

...
  withCredentials([
    usernamePassword(
      credentialsId: 'some-user'
      usernameVariable: 'TF_VAR_some_user',
      passwordVariable: 'TF_VAR_some_passord'
    ),
    string(
      credentialsId: 'some-secret',
      variable: 'TF_VAR_some_secret'
    )
  ]) {
       .... // your pipeline
  }
...

[kmanning]

Let's deprecate withBuildCredentials as part of this issue.
Then remove withBuildCredentials in the next major release - Issue #404