allow warning when a env var was not overwritten

[grosser]

too many times I'm trying to debug someones issues and it's "oh you already set xyz api key in your env" 🤦
so Dotenv.load files, overwrite: :warn would tell them that it's already set.

... might also get annoying after a while 🤷 but wanted to raise an issue since this seems be a common gotcha

might want to make it set+warn instead, to keep the override is truthy behavior, lmk

FYI similar but hacky way of doing it:

Rake::Task["environment"].prerequisites << "dotenv_warning"
task :dotenv_warning do
  next if ENV["DOTENV_WARNING"] == "false"
  keys = Dotenv.parse(".env", overwrite: true).select { |k, v| ENV[k] && ENV[k] != v }.keys
  next if keys.empty?
  warn "Warning: Environment variables #{keys.join(", ")} are set in .env but overwritten by the environment" \
    "(set to the same value in .env or silence the warning with DOTENV_WARNING=false)"
end

[bkeepers]

Thanks for the pull request! I get the frustration when you realize that a local variable was set and couldn't figure out why something was not working.

Would it make sense to warn by default? I wonder if there's a clean way to say which variables were set from .env and which were already set.

[bkeepers]

Can this use the logger instead of warn? I am also hesitant about printing the values because they could contain secrets.

[grosser]

yeah good point, keys should be enough

[grosser]

... how do you suggest using the logger, in non-rails there is no logger right ?
removed the values and changed to .inspect just in case there is some escaping to be worried about

[grosser]

re "warn by default" afaik no other dotenv library does that, so I'd rather not make that the default

[grosser]

also added gem name to warning so people have a chance of knowing what is going on
once it looks good I'll start fixing tests, but did not want to waste time on that when I'm not sure if the approach is good