Check dimensions in given context

[khansson]

I have a function which needs to use a quantity that can energy units. I can check that the units are correct using check

import pint
ureg = pint.UnitRegistry()
q = 500 * ureg.eV
q.check('[energy]') #returns True

this is all good. However, I have some data coming in as cm^-1 or cm_1 in pint. This will not work.

import pint
ureg = pint.UnitRegistry()
q = 500 * ureg.cm_1
q.check('[energy]') #returns False

However, it will also not work in a context

import pint
ureg = pint.UnitRegistry()
q = 500 * ureg.cm_1
with ureg.context('sp'):
     q.check('[energy]') #returns False

I can use is_compatible_with but not with a dimension (i.e. I can do q.is_compatible_with('eV') not q.is_compatible_with('[energy]'))

I am not sure this is a design decision or not, or if there is a more correct way of going about this. Otherwise, it would be great if this capability were added.

[khansson]

I made a function that more or less works, but is not very elegant

def check_dimensions(registry : pint.UnitRegistry,  src :QuantityOrUnitLike, dimensions : UnitLike, *contexts , **ctx_kwargs):
    if contexts:
        src_dim = registry.get_dimensionality(src)
        dst_dim = registry.get_dimensionality(dimensions)
        with registry.context(*contexts, **ctx_kwargs):
            path = find_shortest_path(registry._active_ctx.graph, src_dim, dst_dim)
            return bool(path)
    elif registry._active_ctx:
        src_dim = registry.get_dimensionality(src)
        dst_dim = registry.get_dimensionality(dimensions)
        path = find_shortest_path(registry._active_ctx.graph, src_dim, dst_dim)
        return bool(path)  
    return src.check(dimensions)

ideally this would be a member function of the UnitRegistry?

BTW this works with 0.22, the master branch has the function _get_conversion_factor which may be better, or at least simpler