I’m working on a plugin for

import-linter

, and trying to debug rule graph errors in the integration tests. I basically copy-paste-adjusted the setups from

mypy

and

flake8

to set things up. the errors I’m seeing look like:

No source of dependency ImportLinter for @rule(pants.backend.python.lint.import_linter.rules:88:import_linter_lint_partition(ImportLinterPartition, ImportLinterConfigFile, ImportLinterCustomContracts, ImportLinter) -> LintResult, gets=[Get(PythonSourceFiles, PythonSourceFilesRequest), Get(Pex, RequirementsPexRequest), Get(VenvPex, PexRequest), Get(Digest, MergeDigests), Get(FallibleProcessResult, VenvPexProcess)]). All potential sources were eliminated: []

there’s a separate error like ^^^ for every input type to

import_linter_lint_partition

. the stacktrace is coming out of my

pytest.fixture

for setting up a rule runner:

@pytest.fixture
def rule_runner() -> RuleRunner:
    return RuleRunner(
        rules=[
            *import_linter_rules(),
            *import_linter_subsystem_rules(),
            *dependency_inference_rules.rules(),
            *config_files.rules(),
            *target_types_rules.rules(),
            QueryRule(LintResults, [ImportLinterRequest]),
        ],
        target_types=[PythonSourcesGeneratorTarget, PythonRequirementTarget, PythonSourceTarget],
    )

any tips to help me debug what’s wrong with the setup? I keep wondering if the empty array in

All potential sources were eliminated: []

is a sign that the rules aren’t getting collected properly

and

ImportLinter

is a subsystem that you’re expecting to be able to consume? is it registered with

SubsystemRule

…? that’s sometimes necessary when it’s in its own file.

yes, it’s the new subsystem I’m adding for the plugin. will check that

SubsystemRule

👀

yea, there is some (annoying) magic around subsystems. they’re supposed to be registered if they’re in the argument list of a

@rule

without the

SubsystemRule

, but that can fail

I think it might be a bigger-picture problem because there are a handful of other errors, including for types that pre-exist my changes (i.e.

Get(VenvPex, PexRequest)

). will make the draft

(this confusingly named ticket covers improving rule graph error messages: https://github.com/pantsbuild/pants/issues/11269)

there were some missing dependency rules: have pushed a fix. sorry for the trouble there. will definitely be working on the errors before stabilization

Thank you!