convert integer keys to strings when writing to TOML files

[lewiuberg]

Integers as keys are not supported by toml.dumps. I suggest including this capability in PyConfs since it is supported when writing to json, yaml, and ini.

Testing tomldirectly

import toml

int_as_key = {1: {2: "three"}}
str_as_key = {"1": {"2": "three"}}

print(int_as_key)
print(str_as_key)
print()

try:
    with open("with_integer.toml", "w") as f:
        formated_with_dumps = toml.dump(int_as_key, f)
except KeyError:
    print("KeyError")
    with open("with_string.toml", "w") as f:
        formated_with_dumps = toml.dump(str_as_key, f)

print()
print(formated_with_dumps)

Output:

{1: {2: 'three'}}
{'1': {'2': 'three'}}

KeyError

[1]
2 = "three"

[gahjelle]

Thanks for adding this PR, @lewiuberg

By experimenting with the current underlying libraries, I see that YAML handles int keys fine, while INI and JSON silently convert int keys to str keys. I guess implementing the latter behavior for TOML should therefore be okay.

I'm currently getting an error when I try to store a Configuration with an int key as TOML:

>>> from pyconfs import Configuration
>>> cfg = Configuration.from_dict({"answer": {42: "Everything"}})
>>> cfg.as_str(format="toml")
Traceback (most recent call last):
  File "<ipython-input-3-5906edeb1c36>", line 1, in <module>
    cfg.as_str(format="toml")
  File "/home/gahjelle/Dropbox/programmering/github/pyconfs/pyconfs/configuration.py", line 392, in as_str
    return writers.as_str(format, config=self.as_dict(), **writer_args)
  File "/home/gahjelle/miniconda3/envs/pyconfs/lib/python3.9/site-packages/pyplugs/_plugins.py", line 210, in call
    return plugin_func(*args, **kwargs)
  File "/home/gahjelle/Dropbox/programmering/github/pyconfs/pyconfs/writers/toml.py", line 39, in as_toml
    formated_config = int_keys_to_str(config)
  File "/home/gahjelle/Dropbox/programmering/github/pyconfs/pyconfs/writers/toml.py", line 23, in int_keys_to_str
    int_keys_to_str(value)
  File "/home/gahjelle/Dropbox/programmering/github/pyconfs/pyconfs/writers/toml.py", line 18, in int_keys_to_str
    for key, value in data.items():
RuntimeError: dictionary keys changed during iteration

>>> cfg.as_str(format="json")
'{"answer": {"42": "Everything"}}'

>>> cfg.as_str(format="yaml")
'answer:\n  42: Everything\n'

>>> cfg.as_str(format="ini")
'[answer]\n42 = Everything\n\n'

I believe this is because we are adding and deleting items in the dictionary while iterating over it. It might be better to create a new dictionary with string keys instead of mutating the existing one.

One possible simplification is that I think we can freely convert all keys to strings and not bother with checking whether a key is an int. Keys are always strings in TOML (https://toml.io/en/v1.0.0#keys).

Thanks for initiating this!