#12355 Issue: Register latex to Cosmology.write - #14701

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Thanks! If this patch were to proceed, would need change log and test too. I'll let cosmology maintainer decide if it also need a what's new entry. But let's wait to hear back first.

@Mubin17, thanks for the PR. This is a very good start!
@pllim is correct that this needs a change-log and tests.
A few additional things

1. The module latex needs to be imported in __init__.py. This is to enable Cosmology.write to pick up on registered methods.
2. The write method need to be registered with Cosmology.write (see

   astropy/astropy/cosmology/io/mapping.py

   Lines 236 to 241 in b3b8295

   	# ===================================================================
   	# Register
   	convert_registry.register_reader("mapping", Cosmology, from_mapping)
   	convert_registry.register_writer("mapping", Cosmology, to_mapping)
   	convert_registry.register_identifier("mapping", Cosmology, mapping_identify)

   for example). Currently this function can only be accessed through io, which is not documented / should be private.

I'm happy to keep reviewing as the PR matures.

Hi @Mubin17, is there any way I can help with this PR? Thanks again for working on this PR!

@nstarman Apologies for being MIA the past couple of days, but I have updated the write_latex() method and it seems to be working fine now. Before I move on to tests I think I should add the read_latex() and latex_identify() methods to the Cosmology package as well. Please let me know if it is necessary or if I should jump on to tests. I came up with the code below by referencing the read_html_table().

def read_latex(filename, index=None, *, move_to_meta=False, cosmology=None,**kwargs):
    # Check that the format is 'ascii.html' (or not specified)
    format = kwargs.pop("format", "latex")
    if format != "latex":
        raise ValueError(f"format must be 'latex', not {format}")
    
    with u.add_enabled_units(cu):
        table = QTable.read(filename, format="latex", **kwargs)

    table_columns = set(table.colnames)
    for name, latex in _FORMAT_TABLE.items():
        if latex in table_columns:
            table.rename_column(latex, name)
            
    # Build the cosmology from table, using the private backend.
    return from_table(table, index=index, move_to_meta=move_to_meta, cosmology=cosmology)

However, upon execution, it throws this error:

ValueError: '.. 0.06' did not parse as unit: Syntax error parsing unit '.. 0.06' If this is meant to be a custom unit, define it with 'u.def_unit'. To have it recognized inside a file reader or other code, enable it with 'u.add_enabled_units'. For details, see https://docs.astropy.org/en/latest/units/combining_and_defining.html

@nstarman can you please review these tests before I commit text_latex.py
Please let me know if you have any suggestions.

# Licensed under a 3-clause BSD style license - see LICENSE.rst

# THIRD PARTY
import pytest

# LOCAL
import astropy.units as u
from astropy.cosmology.io.latex import _FORMAT_TABLE, write_latex
from astropy.table import QTable
from astropy.cosmology import Planck15

class TestWriteLatex:
    def setup_class(self):
        # Create a cosmology object to use for testing
        self.cosmo = Planck15

    def test_write_latex(self, tmp_path):
        # Write the cosmology to a temporary file
        filename = tmp_path / "test_write_latex.tex"
        write_latex(self.cosmo, filename)

        # Read the table back in using QTable.read() and check that the data is correct
        table = QTable.read(filename, format="latex")
        
        for column_name in table.colnames[2:]:  
            assert column_name in _FORMAT_TABLE.values()

    def test_write_latex_bad_cls(self, tmp_path):
        # Test that passing an invalid class to write_latex() raises a TypeError
        filename = tmp_path / "test_write_latex_bad_cls.tex"
        with pytest.raises(TypeError):
            write_latex(self.cosmo, filename, cls=str)

    def test_write_latex_invalid_path(self):
        # Test that passing an invalid path to write_latex() raises a IOError
        invalid_path = ""

        with pytest.raises(IOError):
            write_latex(self.cosmo, invalid_path, overwrite=True)

    def test_write_latex_invalid_format(self, tmp_path):
        filename = tmp_path / "test_write_latex_invalid_format.tex"
        # Test using non-Latex format
        with pytest.raises(ValueError):
            write_latex(self.cosmo, filename, format="ascii.html")

From a glance, these tests look good. I would try to implement them in our test suite to see how much coverage they provide!
Also take a look at the test_html file for some more tests to adapt. It's probably easiest to copy-paste-adapt from test_html.py.
Last, the test needs to be hooked up in test_connect. Ping me if anything is confusing!

@nstarman Does the merge conflict arise because my branch is 291 commits behind astropy:main? If yes, should I do sync_fork?

Please rebase on main to fix merge conflicts. We try to keep a linear history.

Thanks! @nstarman for all the help.
I am not comfortable with squashing commits, so if you can do that it would be great!
Yes, I would love to contribute to the LaTex reader. I will open a new PR soon.
Thanks again.

I already fear cosmology, but it is somehow even scarier in LaTeX! 😸

Thanks, all!