Remove pint dependency from Datasette 1.0

[simonw]

Pint still hasn't made itself compatible with Python 3.13. More importantly, the functionality that it supports in Datasette (unit conversions) is not at all widely used, and adds up to some gnarly complexity in the codebase.

I've decided to remove unit functionality and Pint prior to Datasette 1.0

If there's demand for that functionality to come back I'd like to do that as a plugin, adding extra plugin hooks if needed to support it. Those hooks could be added in a post 1.0 version without breaking backwards compatibility, so I don't think we need to solve those prior to the 1.0 release.

[simonw]

Some relevant parts of the code and docs:

datasette/docs/metadata.rst

Lines 267 to 277 in d444b6a

	Units are interpreted using Pint_, and you can see the full list of available units in
	Pint's `unit registry`_. You can also add `custom units`_ to the metadata, which will be
	registered with Pint:
	.. [[[cog
	metadata_example(cog, {
	"custom_units": [
	"decibel = [] = dB"
	]
	})
	.. ]]]

datasette/datasette/views/table.py

Lines 295 to 302 in d444b6a

	elif column in table_config.get("units", {}) and value != "":
	# Interpret units using pint
	value = value * ureg(table_config["units"][column])
	# Pint uses floating point which sometimes introduces errors in the compact
	# representation, which we have to round off to avoid ugliness. In the vast
	# majority of cases this rounding will be inconsequential. I hope.
	value = round(value.to_compact(), 6)
	display_value = markupsafe.Markup(f"{value:~P}".replace(" ", " "))

datasette/datasette/views/table.py

Line 1032 in d444b6a

filters = Filters(sorted(filter_args), units, ureg)

datasette/datasette/filters.py

Lines 416 to 428 in d444b6a

	def convert_unit(self, column, value):
	"""If the user has provided a unit in the query, convert it into the column unit, if present."""
	if column not in self.units:
	return value
	# Try to interpret the value as a unit
	value = self.ureg(value)
	if isinstance(value, numbers.Number):
	# It's just a bare number, assume it's the column unit
	return value
	column_unit = self.ureg(self.units[column])
	return value.to(column_unit).magnitude

[simonw]

Look for ureg and units.

[simonw]

This unblocks:

• Test fail against Python 3.13-dev with a Pint error #2320