Defaults shouldn't override previously set variables

[kdonovan]

In our application we set the rollbar_token from environmental variables for security, but when rollbar loads itself up it blows away the already-set variables with it's defaults.

[brianr]

Thanks @kdonovan! This looks good to me. @jondeandres can you review as well?

[jondeandres]

@brianr it's nice for me.

[brianr]

Merge, thanks @kdonovan! Will get this out in the next release.

[brianr]

Released in 1.4.3 (now on rubygems)

[shaneog]

This is breaking deploys for me. The problem is that by the time the Rollbar load:defaults task is run, the deploy.rb file has not been parsed, and thus my set :rollbar_token, ENV['ROLLBAR_ACCESS_TOKEN'] has not been run.
So I'm consistently getting the message Please specify the Rollbar access token, set :rollbar_token, 'your token'

@kdonovan How/where are you loading the Rollbar access token ENV variable?

[jondeandres]

I've detected the problem here.

fetch is not so safe cause it evaluates the default value if it's callable, https://github.com/capistrano/capistrano/blob/master/lib/capistrano/configuration.rb#L41.

We can do something crazy like Proc.new { Proc.new { ... } }, but is really ugly.

@kdonovan could you provide us the loading order you have when setting :rollbar_token, require 'rollbar/capistrano3 and others?

It seems you are setting :rollbar_token before `require 'rollbar/capistrano3' is executed, could be?

My suggestion is change that order, and we'll then revert this PR since it's being a problem for most of the users.

[jondeandres]

@kdonovan I could reproduce your problem with this code

task :foo do
  set :rollbar_token, proc { 'foo' }
end

before 'load:defaults', 'foo'

Are you using something similar? In that case 'load:defaults' will override your values.

We can fix this for everybody with this code:

namespace :load do
  task :defaults do
    set :rollbar_user,  Proc.new { ENV['USER'] || ENV['USERNAME'] } unless fetch(:rollbar_user)
    set :rollbar_env,   Proc.new { fetch :rails_env, 'production' } unless fetch(:rollbar_env)
    set :rollbar_token, Proc.new { abort "Please specify the Rollbar access token, set :rollbar_token, 'your token'" } unless fetch(:rollbar_token)
    set :rollbar_role,  Proc.new { :app } unless fetch(:rollbar_role)
  end
end

But probably the best is just not set anything before 'load:defaults' is executed, https://github.com/capistrano/capistrano/blob/master/lib/capistrano/setup.rb#L13.