Validation only happens one field at a time

[robertlagrant]

Currently, with the following code:

from environs import Env
env = Env()
var1 = env("VAR1")
var2 = env("VAR2")

If both env vars are missing, environs will simply display:

environs.EnvError: Environment variable "VAR1" not set

And only when that's set will it display the second error.

It'd be great to have it validate as far as possible all the required environment variables, perhaps with a manual flagging of when to start and stop such a process:

from environs import Env
env = Env(eager=False)
var1 = env("VAR1")
var2 = env("VAR2")
var3 = env.int("VAR3")
env.read()

environs.EnvError: Environment variables invalid: {"VAR1": "missing", "VAR2": "missing", "VAR3": "wrong type"]. 

[sloria]

Interesting idea. We are already generating a marshmallow schema from all the parsed envvars, so this might be straightforward.

I'm open to this if it doesn't add too much complexity. PRs welcome.

[sloria]

I took a stab at this in #94. @robertlagrant Can you take a look at the API and let me know what you think?

[robertlagrant]

@sloria I missed this in my giant numbers of Github notifications! Apologies for the large delay.

In fact, I was actually just about to fork to implement and saw this. I've had a play and it looks great to me.