align ignores copy

[dcherian]

Is your feature request related to a problem?

cc @benbovy

xref #7730

import numpy as np
import xarray as xr

arr = np.random.randn(10, 10, 365*30)
time = xr.date_range("2000", periods=30*365, calendar="noleap")
da = xr.DataArray(arr, dims=("y", "x", "time"), coords={"time": time})
year = da["time.year"]

xr.align(da, year, join="outer", copy=False)

This should result in no copies, but does

Describe the solution you'd like

I think we need to check aligner.copy and/or aligner.reindex (maybe?) before copying here

xarray/xarray/core/dataset.py

Lines 2805 to 2818 in f8127fc

	def _reindex_callback(
	self,
	aligner: alignment.Aligner,
	dim_pos_indexers: dict[Hashable, Any],
	variables: dict[Hashable, Variable],
	indexes: dict[Hashable, Index],
	fill_value: Any,
	exclude_dims: frozenset[Hashable],
	exclude_vars: frozenset[Hashable],
	) -> Dataset:
	"""Callback called from ``Aligner`` to create a new reindexed Dataset."""
	new_variables = variables.copy()
	new_indexes = indexes.copy()

Describe alternatives you've considered

No response

Additional context

No response

[benbovy]

@dcherian is it solved by #7736?

[dcherian]

I think I fixed it only for exact joins