Override / interpolate of variables working incorrectly

[hectorvs]

Bug is a combination of override and interpolate.

contents of files is as follows:

foo.txt

Name=foo
Interpolate="${Name}/baz"

bar.txt

Name=bar
Interpolate="${Name}/baz"

test file:

from dotenv import load_dotenv
import os

def print_env():
    for key in os.environ.keys():
       print("{}: {}".format(key, os.getenv(key)))

load_dotenv('foo.txt', override=True)
print_env()

load_dotenv('bar.txt', override=True)
print_env()

when second print_env() runs, the values are:

Name=bar
Interpolate=foo/baz # should be bar/baz

the reason for this is that the resolve_nested_variables method looks into existing ENV vars first and then looks at the current file's loaded values. (in our case, Name was loaded in the earlier file with value foo).

I believe the correct functionality would be to first look into the loaded file's values and then on the environment in order to keep the same behavior as the first file loaded.

[elbehery95]

Totally agree. This is annoying and will always enforce that the current env defined variable will still be substituted in the .env even if its defined at .env

This line should just be reversed

python-dotenv/src/dotenv/main.py

Line 223 in e92ab1f

ret = os.getenv(name, new_values.get(name, default))

https://github.com/theskumar/python-dotenv/blame/e92ab1f18087c2ca058203f36535c43a0f824d8a/src/dotenv/main.py#L223

@bbc2 your thoughts and feedback are really appreciated

[bbc2]

This indeed looks like a problem. Thanks for reporting, I'll look into it.

[elbehery95]

I would love to have this as my first contribution in pydotenv let me know if this is possible i may submit a PR. Thanks

[bbc2]

Yes you may submit an PR. Please try to see if the change could break an existing use case. We might have been loading values in that order for a reason. Let me know if you have questions about the implementation or the tests.

[bbc2]

Fixed by #258.