Future of labgrid_run

The labgrid_run is a very thin layer on top of labgrid_genrule that uses //labgrid/run to run the provided cmd on the device.

Currently, it's trying to serve two potentially contradictory purposes:

• Be a genrule for the target
• Provide syntax sugar

Should we pick one, or have a separate macros for each? If so, what names should we use?

Genrule for the target

If we think of labgrid_run as a version of labgrid_genrule that runs on the target, then the following is already possible:

labgrid_run(
    name = "hello",
    srcs = ["@ape//ape:echo"],
    outs = ["output.txt"],
    cmd = "$(location @ape//ape:echo) world > $@",
    platform = ":platform",
)

But that quickly falls apart:

labgrid_run(
    name = "hello",
    srcs = [
        "@ape//ape:echo",
        "@ape//ape:tee",
    ],
    outs = ["output.txt"],
    cmd = "$(location @ape//ape:echo) world | @(location @ape//ape:tee) $@",
    platform = ":platform",
)

This doesn't work because labgrid_run isn't really a genrule: cmd runs on the host, so any Bash pipes or redirections will happen there.

We could possibly implement labgrid_target_genrule by running cmd inside of a hermetic Bash inside of the device. But there would be some complications, such as making sure the srcs (or possibly tools in this case) transition to the target and are transferred to the device. Or finding a way to substitute $(location) and $@ to values that make sense for the device, and making sure the output files are transferred back to the host.

Syntax sugar

If we think of labgrid_run as a convenient way to run labgrid_genrule and //labgrid/run, then we should probably add env and get attributes to it, which would translate into --env and --get flags for //labgrid/run.

So that this:

labgrid_genrule(
    name = "hello-with-env",
    srcs = ["@ape//ape:printenv"],
    outs = ["run-with-env.actual"],
    cmd = "$(location @rules_labgrid//labgrid/run) --env HELLO=world -- $(location @ape//ape:printenv) HELLO > $@",
    platform = ":platform",
    tools = ["@rules_labgrid//labgrid/run"],
)

Could be written as:

labgrid_run(
    name = "hello-with-env",
    srcs = ["@ape//ape:printenv"],
    outs = ["run-with-env.actual"],
    env = {
        "HELLO": "world",
    }
    cmd = "$(location @ape//ape:printenv) HELLO > $@",
    platform = ":platform",
)