""" Os detection facilities. """

def os_select(

ctx = None,

*,

linux = None,

windows = None,

macos = None,

default = None):

"""

This can work both in a macro and a rule context to choose something based on the current OS.

If used in a rule implementation, you need to pass `ctx` and add `OS_DETECTION_ATTRS` to the

rule attributes.

"""

choices = {

"linux": linux or default,

"windows": windows or default,

"macos": macos or default,

}

if not ctx:

return select({

"@platforms//os:%s" % os: v

for os, v in choices.items()

if v != None

})

for os, v in choices.items():

if ctx.target_platform_has_constraint(getattr(ctx.attr, "_%s_constraint" % os)[platform_common.ConstraintValueInfo]):

if v == None:

fail("%s not supported by %s" % (os, ctx.label))

return v

fail("Unknown OS detected")

OS_DETECTION_ATTRS = {

"_windows_constraint": attr.label(default = "@platforms//os:windows"),

"_macos_constraint": attr.label(default = "@platforms//os:macos"),

"_linux_constraint": attr.label(default = "@platforms//os:linux"),

}