fix typo in accessing BlockEntryToken member

[tanmaykm]

Corrected a typo in accessing the end_mark field from span of a BlockEntryToken. Discovered issue while parsing a specification file that resulted in:

julia> github_spec = YAML.load_file("api.git.luolix.top.yaml")
ERROR: type BlockEntryToken has no field end_mark
Stacktrace:
  [1] getproperty
    @ ./Base.jl:37 [inlined]
  [2] parse_indentless_sequence_entry(stream::YAML.EventStream)
    @ YAML ~/.julia/packages/YAML/U6OOW/src/parser.jl:415
  [3] peek(stream::YAML.EventStream)
    @ YAML ~/.julia/packages/YAML/U6OOW/src/parser.jl:54
  [4] _compose_sequence_node(start_event::YAML.SequenceStartEvent, composer::YAML.Composer, anchor::Nothing)
    @ YAML ~/.julia/packages/YAML/U6OOW/src/composer.jl:137
  [5] compose_sequence_node(composer::YAML.Composer, anchor::Nothing)
...

[kescobo]

fantastic, thank you for the contribution! Can you add a test that notes this bug?

I'm a bit concerned that if someone wrote this accessor, it must have worked at some point. We don't really have a settled YAML spec that this package supports (xref #133) - was this changed at some point?

[tanmaykm]

This does look like a bug to me. I have added a MWE and test for the fix.

For comparison, this is how the python YAML parser parses the file that fails in Julia without this fix:

Python 3.10.12 (main, Nov 20 2023, 15:14:05) [GCC 11.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import yaml
>>> with open('empty_list_elem.data', 'r') as stream:
...     loaded = yaml.safe_load(stream)
... 
>>> print(loaded)
{'testlist': [None, 'one', 'two']}

With this fix, Julia parses it to a comparable:

Dict{Any,Any}("testlist" => Union{Nothing, String}[nothing, "one", "two"])

[kescobo]

OK, I think I'm happy to merge as a bug fix and then revert if someone complains 😅

I'm just going to throw a link in the #data slack for a couple of days to be sure there's nothing obvious. Please ping again if I haven't moved on this by friday

[tanmaykm]

@kescobo hope there have been no objections and we can have this merged?

[kescobo]

Thanks for the bump! JuliaRegistries/General#107585