Hello All, Writing my first plugin that creates synthetic targets and I am wanting to provide a token to allow for http requests. Are there any patterns that could be used here?

You can read the token from an environment variable look for usages of

EnvironmentVarsRequest

https://github.com/pantsbuild/pants/blob/62828b7f56abeeea79b9249b8d97ae7d78847785/src/python/pants/backend/go/util_rules/cgo.py#L390

Have been trying to read from

EnvironmentVarsRequest

With the example seen here: https://www.pantsbuild.org/2.19/docs/writing-plugins/the-rules-api/processes#environment-variables

TOKEN=asdad pants package ::

The token is used to dynamically create synthetic targets.

just a hunch, but make sure to annotate any pants union types you have with

@union(in_scope_types=[EnvironmentName])

like so: https://github.com/pantsbuild/pants/blob/42ff1dd86a7c3b370a2802df272d27ff0bb42ce3/src/python/pants/engine/target.py#L1122

import requests
from typing import Iterable
from dataclasses import dataclass
from pants.engine.internals.synthetic_targets import (
    SyntheticTargetsRequest,
    SyntheticAddressMaps
)

from pants.engine.internals.target_adaptor import TargetAdaptor
from pants.engine.unions import UnionRule, union
from pants.engine.environment import EnvironmentName
from pants.engine.env_vars import EnvironmentVars, EnvironmentVarsRequest
from pants.engine.rules import collect_rules, Get, rule
from pants.util.logging import LogLevel

@union(in_scope_types=[EnvironmentName])
@dataclass(frozen=True)
class SynthenticFooRequest(SyntheticTargetsRequest):
    path: str = SyntheticTargetsRequest.SINGLE_REQUEST_FOR_ALL_TARGETS
    pass

def generate_some_targets(versions: Iterable[str]) -> Iterable[TargetAdaptor]:
    """_summary_

    Args:
        versions (Iterable[str]): versions eg, a.b.c

    Returns:
        Iterable[TargetAdaptor]: Iterable pants targets
    """
    target_adapters = []
    for index, version in enumerate(versions):
        adapter = TargetAdaptor(
            "docker_image", name=f"test_{index}",
            __description_of_origin__= "some origin",
            source = "Dockerfile",
            dependencies = [
                ":some-other-docker",
            ],
            tags = [
                "some-test"
            ],
            extra_build_args=[f"BASE_IMAGE=some/image:{version}"]
        )
        target_adapters.append(adapter)
    return target_adapters


def get_ids_from_url(token: str) -> list[str]:
    url = "https:/some-url/"
    headers = {"TOKEN": token}
    ids = requests.get(url=url, headers=headers, timeout=30).json()
    return ids

async def get_ids() -> list[str]:
    envs = await Get(EnvironmentVars, EnvironmentVarsRequest(["TOKEN"]))
    token = envs.get("TOKEN")
    ids = get_ids_from_url(token)
    return ids


@rule(level=LogLevel.DEBUG)
async def synthetic_targets(request: SynthenticFooRequest) -> SyntheticAddressMaps:
    iids = get_ids()

    return SyntheticAddressMaps.for_targets_request(
        request,
        [
            (
                # Address
                "somePath//BUILD.synthetic-targets",
                (
                    generate_some_targets(iids)
                ),
            ),
        ]
    )

def rules():
    return (
        *collect_rules(),
        UnionRule(SyntheticTargetsRequest, SynthenticFooRequest),
    )

@curved-television-6568 Thanks for helping out.

Aaah! this should've been called out in the docs for synthetic targets. The synthetic targets are "low level", and must work during the bootstrap phase of parsing the BUILD files, so environments are not available to rules providing synthetic targets. (in other words, my hunch previously does not apply in this case, as you can't use that) If you really need env vars, you can look for the host specific env vars using the

SessionValues

directly, indexing that using

CompleteEnvironmentVars

as here: https://github.com/pantsbuild/pants/blob/42ff1dd86a7c3b370a2802df272d27ff0bb42ce3/src/python/pants/engine/internals/platform_rules.py#L46-L72 This is on the edge of being hacky though.. as I don't think we'd consider this part of the PluginAPI, so it might break unexpectedly between pants releases if it is changed for some reason.. just beware 😉

Thanks, able to use the SessionValue directly for the time being.