#17354 Improve safety of using `environments` during `BUILD` evaluation time New issue created by stuhood Currently, build graph calculations and

BUILD

file evaluation are pinned to the

__local__

environment (see #17129), meaning that it will not run in a

docker

, or

remote

environment. This is accomplished by "masking" the environment at graph and

BUILD

file evaluation boundaries, and then explicit injecting the

ChosenLocalEnvironmentName

as the current

EnvironmentName

. While that process is enforced (by the

masked_type

annotations) and fairly safe, it is not type safe for

@rule

authors who might think that they can use the

Platform

or

EnvironmentVars

during

BUILD

file evaluation time or dependency inference. Because they can access those types in those locations, but they will not get the appropriate values to use at runtime: they will instead get the values for the

__local__

environment. If you know that, then you can manually avoid consuming environment-specific types in those

@rules

, and defer the work to, say, codegen (as @thejcannon demonstrates here), but making this type safe instead would definitely be preferable. * * * One way to help guide users would be to overload all of the environment-aware intrinsics (

Process

running,

Platform

calculation,

EnvironmentVars

calculation, etc) to consume _either_: • an

EnvironmentName

(as they do today in

2.15.x

), representing the runtime environment of a target • a type specific to build graph evaluation, or explicitly for the local environment, maybe called

LocalEnvironmentName

or

BuildGraphEnvironmentName

. The latter type would be available to

@rules

which were part of

BUILD

file evaluation and dependency calculation, while the former type would be available to codegen and etc. This would bifurcate

@rules

by type, and maybe help to guide @rule authors to avoid consuming the "wrong"

Platform

. But because dependency inference still needs to be able to run processes, it would not represent true type safety. pantsbuild/pants