Add reproducer for #441: package_group change not detected as impacted (false negative)

[tinder-maxwellelliott]

What

Reproducer test for the under-invalidation (false-negative) half of #441.

bazel-diff only keeps targets whose query Discriminator is RULE, SOURCE_FILE, or GENERATED_FILE; every other type is dropped by BazelQueryService.toBazelTarget (it logs "Unsupported target type" and returns null). PACKAGE_GROUP is one such dropped type, so a change to a package_group's packages list is never reflected in any hash — even though it genuinely alters downstream visibility and can flip a consumer from building to failing.

As #441 puts it:

Bazel's query proto represented the package-group change, but bazel-diff v35.0.0 discarded it as an unsupported target type … v35.0.0 reported no impacted targets.

Reproducer

New fixture workspace cli/src/test/resources/workspaces/package_group_dropped/:

• //lib:consumers — a package_group created by a macro in lib/defs.bzl, gating the visibility of //lib:thing. Its allow-list lives in defs.bzl as ALLOWED.
• //lib:thing — a genrule declared directly (not via the macro), so its per-rule .bzl seed never picks up defs.bzl. This isolates this bug from the separate .bzl-provenance (over-invalidation) half of Distinguish macro source changes from changes to Bazel's loaded package state #441.
• //consumer:use_thing — depends on //lib:thing.

The only change between the two checkouts empties ALLOWED in lib/defs.bzl, revoking //consumer's visibility of //lib:thing. The BUILD files and every native rule are byte-for-byte identical across the checkouts, so the sole semantic change rides entirely on the (dropped) PACKAGE_GROUP target.

New E2E test testPackageGroupChangeIsNotImpacted_reproducerForIssue441 asserts the current (buggy) behaviour: zero impacted targets.

Verified against real Bazel (8.5.1)

	Workspace A (ALLOWED = ["//consumer"])	Workspace B (ALLOWED = [])
bazel build //consumer:use_thing	✅ builds	❌ target '//lib:thing' is not visible from //consumer:use_thing
bazel-diff get-impacted-targets	—	∅ (nothing reported)

A change that flips a real build from success to failure is completely invisible to bazel-diff.

Scope

This is a reproducer only — it pins the current behaviour so a future fix can be verified. It does not attempt the fix. The over-invalidation half of #441 (print-only macro edits marking generated native rules impacted) is a design/policy question the maintainers are still weighing, so it is intentionally left out. When the under-invalidation is fixed (e.g. by supporting PACKAGE_GROUP targets and their reverse-visibility dependents), the changed package_group and/or //consumer:use_thing should start appearing and this assertion will flag the change.

Refs #441.

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