Parameters from ENV

[haf]

Description

I'd like to use Argu to optionally take configuration from the environment. Do you think you could add that feature?

Currently writing a networked-linux tutorial and figured I wanted to showcase how to build micro-services with F#.

[eiriktsarpalis]

I'm not the biggest fan of parameterization using env vars. That said, doing it is very simple; you just pass an implementation of IConfigurationReader to the ParseConfiguration method of your parser.

[haf]

Does the GetValue : string -> string return null if it doesn't have it?

Also, what about the #if !CORE_CLR at the top of the parsers? No parsing for .Net core or is it WIP?

Also, why aren't you a fan? I'm interested to know.

[eiriktsarpalis]

Yeah, which is odd. Probably just blindly replicating ConfigurationManager behaviour.

…

On Wed, 7 Dec 2016 at 09:15, Henrik Feldt ***@***.***> wrote: Does the GetValue : string -> string return null if it doesn't have it? — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#63 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ACrts2O1xk0dIW6eLjtlCHeoL2ZiXClCks5rFnlCgaJpZM4LEi21> .

[haf]

You got a PR from me!

[eiriktsarpalis]

@haf It's just that I think using env vars for parameterization is ugly, violates referential transparency considerations and can be potentially dangerous. If completely unavoidable, I would rather just dereference the vars at the script level and pass through the CLI:

./myApp --foo=$FOO --bar=$BAR

If I am going depend on ambient state for configuration I would much rather have the ability to explicitly specify which aspects of that ambient state I want to use.

Suppose you are consuming an application that I wrote which uses Argu for environment variable parsing. Unbeknownst to you, my application is also looking for a $BAZ environment variable that triggers a functionality you're completely unaware of: let's say it drops the database it connects to once completed. Now, If you were to accidentally expose an export BAZ=true statement in one of your machines, this could carry potentially catastrophic consequences.

The above example by the way is inspired by a true story.