Expectation on encoding -> decoding of `None`

Hello,

I’m on a good way to make a Ruby implementation of NestedText (erikw/nestedtext-ruby, all official decode tests are passing!) and I’m currently writing unit tests for various edge-case inputs. Using the Python implementation, I’m unsure what the expectation is on encoding python’s None (and ruby’s nil in my case). I see that None is treated in different ways.

Using this base-program and just changing the obj = ... line in the different examples:

   import nestedtext as nt

    obj = ...

    dumped = nt.dumps(obj)
    print("dumped:")
    print(repr(dumped))

    loaded = nt.loads(dumped)
    print("loaded:")
    print(repr(loaded))

Just None

    obj =  None

gives the output:

dumped:
''
loaded:
{}

▶️ None encodes to empty string, but is decoded back as empty inline dict

None in list

    obj =  [None]

gives the output:

dumped:
'-'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "__main__.py", line 82, in main
    test_dump()
  File "__main__.py", line 73, in test_dump
    loaded = nt.loads(dumped)
  File "[...]/nestedtext.py", line 1088, in loads
    loader = NestedTextLoader(lines, top, source, on_dup, keymap)
  File "[...]/nestedtext.py", line 765, in __init__
    report('content must start with key or brace ({{).', lines.get_next())
  File "[...]/nestedtext.py", line 258, in report
    raise NestedTextError(template=message, *args, **kwargs)
  File "<string>", line 0
nestedtext.NestedTextError

▶️ None encodes to empty string, but can’t be decoded back to Python

None as dict value

    obj = {"key": None}

gives the output:

dumped:
'key:'
loaded:
{'key': ''}

▶️ None encodes to empty string, but is decoded back to empty string and not None

None as dict key

    obj = {None: "value"}

gives the output:

dumped:
'None: value'
loaded:
{'None': 'value'}

▶️ None encodes to the string “None”, and decodes back to the string “None”

---

Thus, None is treated different in all cases above. The encoding from Python is of course not a part of the specification for the NT data format, but it would still be nice to know the rules for None, or that None is always treated the same in all cases 😃.

Is the output above the expected? I suspect that in the case with None

• in a list, that it should be possible to decode back to Python
• as a key in a dict, that it should maybe instead render to empty string instead of the string “None”, to be more consistent with the other cases?

I’m happy to hear your thoughts!

[KenKundert]

Okay, I finally updated the GitHub version with this change.

[erikw]

Thank you for the heads-up. I will do the same in nestedtext-ruby 😃.