With 4.0.0 table indices became Null, not numeric indexes

[kabenin]

Hello,

Thank you for your work and great product you maintain for a lot of users like me!

I get some code that started to fail after upgrading to v 4.0.0. I see there are some breaking changes in (https://github.com/boolangery/py-lua-parser/releases/tag/4.0.0). I'm not sure I hit one of those cases, and wanted to ask if the parsing I see is expected.

We are talking about tables initializers for lists or sequences:

t = {"a", "b"}

this creates a table with numeric indexes, 1, 2. We can iterate on this table using pairs or ipairs (while example in this test that is expected to fail fails indeed standalone-tests/failing/luau-table-iteration.lua)

for k, v in pairs(t) do
    print(k.." => "..v)
end

In version 4.0.0 Field keys of the table in the example above are all None:
For slightly modified code from the example in docs:

from luaparser import ast
from luaparser import astnodes


src = open('t.lua', 'r').read()
print(src)

class StrVisitor(ast.ASTVisitor):
    def visit_Field(self, node):
        print('Field key = ' + str(node.key))

tree = ast.parse(src)
StrVisitor().visit(tree)

output is:

Field key = None
Field key = None

Is this expected, and I should expect the same behavior in future versions?

There is also a bug in command line tool, while parsing code t = {"a", "b"}:

 luaparser t.lua
Traceback (most recent call last):
  File "/private/tmp/luaparser/.venv/lib/python3.14/site-packages/luaparser/ast.py", line 86, in default
    to_json = getattr(o, "to_json")
AttributeError: 'bytes' object has no attribute 'to_json'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/private/tmp/luaparser/.venv/bin/luaparser", line 7, in <module>
    sys.exit(main())
             ~~~~^^
  File "/private/tmp/luaparser/.venv/lib/python3.14/site-packages/luaparser/__main__.py", line 73, in main
    output = ast.to_pretty_json(tree)
  File "/private/tmp/luaparser/.venv/lib/python3.14/site-packages/luaparser/ast.py", line 95, in to_pretty_json
    return json.dumps(root, cls=JSONEncoder, indent=4)
           ~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/Cellar/python@3.14/3.14.2/Frameworks/Python.framework/Versions/3.14/lib/python3.14/json/__init__.py", line 242, in dumps
    **kw).encode(obj)
          ~~~~~~^^^^^
  File "/opt/homebrew/Cellar/python@3.14/3.14.2/Frameworks/Python.framework/Versions/3.14/lib/python3.14/json/encoder.py", line 202, in encode
    chunks = self.iterencode(o, _one_shot=True)
  File "/opt/homebrew/Cellar/python@3.14/3.14.2/Frameworks/Python.framework/Versions/3.14/lib/python3.14/json/encoder.py", line 263, in iterencode
    return _iterencode(o, 0)
  File "/private/tmp/luaparser/.venv/lib/python3.14/site-packages/luaparser/ast.py", line 91, in default
    return {k: v for k, v in o.__dict__.items() if not k.startswith("_")}
                             ^^^^^^^^^^
AttributeError: 'bytes' object has no attribute '__dict__'. Did you mean: '__dir__'?
when serializing dict item 's'
when serializing luaparser.astnodes.String object
when serializing dict item 'value'
when serializing luaparser.astnodes.Field object
when serializing list item 0
when serializing dict item 'fields'
when serializing luaparser.astnodes.Table object
when serializing list item 0
when serializing dict item 'values'
when serializing luaparser.astnodes.Assign object
when serializing list item 0
when serializing dict item 'body'
when serializing luaparser.astnodes.Block object
when serializing dict item 'body'
when serializing luaparser.astnodes.Chunk object

Thank you!

[boolangery]

I fixed the json printer on main can you test?
For table field key, yes this is expected to make the AST better reflect how the code is written (#70), because in some context adding implicit indices when printing the AST back to lua code change the semantic