Error message within prefixed() context

[AGeekInside]

The error message does not prepend the prefix to error message output, when an error occurs in an env.prefixed() context. The code below illustrates the issue. The environment variable is named TEST_VAR, but the error message is showing VAR.

######@shim-dev:~/workspace/shim (environ-adoption) 
$ export TEST_VAR=-1
######@shim-dev:~/workspace/shim (environ-adoption) 
$ ipython
Python 3.6.5 (default, Aug 15 2019, 19:51:45) 
Type 'copyright', 'credits' or 'license' for more information
IPython 7.7.0 -- An enhanced Interactive Python. Type '?' for help.

In [1]: from environs import Env                                                                                                                                                                                                                                                     

In [2]: env = Env()                                                                                                                                                                                                                                                                  

In [3]: with env.prefixed("TEST_"): 
   ...:     invalid_test = env.int("VAR", validate=lambda n: n > 0) 
   ...:                                                                                                                                                                                                                                                                              
---------------------------------------------------------------------------
ValidationError                           Traceback (most recent call last)
~/.pyenv/versions/3.6.5/lib/python3.6/site-packages/environs.py in method(self, name, default, subcast, **kwargs)
     55         try:
---> 56             value = field.deserialize(value)
     57         except ma.ValidationError as error:

~/.pyenv/versions/3.6.5/lib/python3.6/site-packages/marshmallow/fields.py in deserialize(self, value, attr, data)
    265         output = self._deserialize(value, attr, data)
--> 266         self._validate(output)
    267         return output

~/.pyenv/versions/3.6.5/lib/python3.6/site-packages/marshmallow/fields.py in _validate(self, value)
    205         if errors:
--> 206             raise ValidationError(errors, **kwargs)
    207 

ValidationError: ['Invalid value.']

The above exception was the direct cause of the following exception:

EnvError                                  Traceback (most recent call last)
<ipython-input-3-be1d17efe506> in <module>
      1 with env.prefixed("TEST_"):
----> 2     invalid_test = env.int("VAR", validate=lambda n: n > 0)
      3 

~/.pyenv/versions/3.6.5/lib/python3.6/site-packages/environs.py in method(self, name, default, subcast, **kwargs)
     56             value = field.deserialize(value)
     57         except ma.ValidationError as error:
---> 58             raise EnvError('Environment variable "{}" invalid: {}'.format(name, error.args[0])) from error
     59         else:
     60             self._values[parsed_key] = value

EnvError: Environment variable "VAR" invalid: ['Invalid value.']

In [4]:  

[sloria]

Thanks for reporting. I'd certainly review/merge a PR with the fix. From the traceback, it looks lke it might be as simple as changing

 raise EnvError('Environment variable "{}" invalid: {}'.format(name, error.args[0])) from error

to

 raise EnvError('Environment variable "{}" invalid: {}'.format(parsed_key, error.args[0])) from error

[AGeekInside]

I'll take a look and see about creating a PR. Just noticed the issue as were refactoring a codebase to introduce environs, so we have an interest in a fix. :)

[sloria]

Thanks!