feat: skip kit-repo-only tests instead of failing a sized-down adopter

scripts/tests/conftest.py

@@ -25,9 +25,68 @@
 
 from __future__ import annotations
 
+import sys
+from pathlib import Path
+
+import pytest
+
+sys.path.insert(0, str(Path(__file__).resolve().parent))
+from _repo_layout import engine_dir, find_repo_root  # noqa: E402
+
+ENGINE_DIR = engine_dir(Path(__file__))
+REPO_ROOT = find_repo_root(ENGINE_DIR)
+
+# Whether a `.git` marker was actually found. With none, `find_repo_root` falls
+# back to `start.parent`, which is right for a flat layout and short by one or
+# more levels for a nested one — and nothing here can tell those apart, because
+# the only signal that would is exactly what is missing.
+#
+# THREE ATTEMPTS TO BE CLEVER ABOUT THIS WERE WITHDRAWN, one per review round,
+# and the next one should not be made here:
+#
+#   round 1 — disable skipping entirely when no `.git` was found. Broke the FLAT
+#             sized-down tarball case, which had been skipping correctly: an
+#             accurate skip became a raw FileNotFoundError, #134's own harm class.
+#   round 2 — search both `REPO_ROOT` and its parent. Still wrong at nesting
+#             depth > 1 (`tools/internal/devkit/`), where it emitted a confident
+#             `not vendored` about a file present at the true root; and in the
+#             flat case the second candidate sits OUTSIDE the tree, so a
+#             same-named file above it suppressed a skip that should have fired.
+#   round 3 — this. No guess at all.
+#
+# The root is unknowable without `.git`, so the skip no longer pretends
+# otherwise: it searches the one resolved root and SAYS the root was a guess.
+# That is not a false claim — it states exactly what was checked — and it keeps
+# the clean run a sized-down adopter is owed. #233 holds the resolution.
+_ROOT_FOUND = any((c / ".git").exists() for c in (ENGINE_DIR, *ENGINE_DIR.parents))
+_UNRESOLVED = (
+    "" if _ROOT_FOUND else f" (repo root unresolved — no .git above {ENGINE_DIR}; see #233)"
+)
+
+
+def require_kit_paths(*paths: str) -> None:
+    """Skip the current test unless every path is present, from inside a fixture.
+
+    The fixture-time counterpart of the `kit_repo_only` marker, and the same
+    predicate. It exists because a dependency introduced by a FIXTURE cannot be
+    declared on the tests that use it without repeating a marker on every one of
+    them — and a marker repeated 38 times goes stale the first time someone adds
+    a 39th test. Expressed at the fixture, a new user of that fixture inherits
+    it. `test_kit_repo_only.py` scans for both spellings.
+    """
+    _skip_if_missing(paths, "a fixture this test uses needs")
+
+
+def _skip_if_missing(paths, prefix: str) -> None:
+    if not paths:
+        return
+    missing = [rel for rel in paths if not (REPO_ROOT / rel).exists()]
+    if missing:
+        pytest.skip(f"{prefix}: not vendored in this tree: {', '.join(missing)}{_UNRESOLVED}")
+
 
 def pytest_configure(config) -> None:
-    """Register `driftcheck` so `-m 'not driftcheck'` is a supported invocation.
+    """Register the marks, so `-m` expressions naming them are supported.
 
     Unregistered marks still *match* under `-m`, so the exclusion would work
     without this — it would just warn (`PytestUnknownMarkWarning`) on every run.
@@ -41,3 +100,52 @@ def pytest_configure(config) -> None:
         "(`-m 'not driftcheck'`) because ANY mutation fails it, which reads "
         "as a kill while nothing behavioural caught anything (#33/#112).",
     )
+    config.addinivalue_line(
+        "markers",
+        "kit_repo_only(*paths): asserts against files the kit ships but an "
+        "adopter need not vendor. Skipped when any named path is absent, so a "
+        "sized-down adoption gets a clean run instead of inapplicable failures "
+        "(#134 cause 2).",
+    )
+
+
+def pytest_runtest_setup(item) -> None:
+    """Skip a `kit_repo_only` test whose required paths this tree does not have.
+
+    **Why a skip and not a fix.** These tests are not path-portable-with-effort;
+    they are *inapplicable*. `test_init_sh.py` asserts on `init.sh`'s behaviour,
+    and an adopter who vendored engines and config has no `init.sh` to assert
+    about. Repairing the paths would only convert a `FileNotFoundError` into a
+    differently-worded failure — #134 says exactly that, and the repair of
+    cause 1 in PR #202 demonstrated it: it turned a collection abort into 90
+    legible failures rather than into a clean run.
+
+    **Why the marker takes paths rather than probing for "the kit's own repo".**
+    A test declares what it needs, and the answer is then a fact about the tree
+    rather than a judgement about which repo this is. Any such judgement would
+    be a bound the author sets — the shape `fallback-review-panel.md` records as
+    having opened a hole three times — and no marker file distinguishes the
+    kit's checkout from a full-vendor adoption anyway. A full vendor that keeps
+    `scripts/` runs these tests, correctly, because it genuinely has the files.
+
+    **The limit this leaves, corrected from a claim that was wrong.** An earlier
+    version of this docstring said a deleted kit file would "go quiet rather
+    than red". It does not: `test_kit_repo_only.py`'s positive control asserts
+    every marked path exists in a complete kit tree, and it fires on a deletion
+    exactly as readily as on a typo — measured by deleting each marked path in
+    turn. Deleting `scripts/kit_doctor.py` is louder still, since
+    `test_kit_doctor.py` imports it at module scope and collection aborts.
+
+    What the control genuinely cannot do is tell a deletion from a typo, and it
+    is scoped to trees that hold every file `kit-manifest.json` lists — so a
+    marker naming `init.sh`, which the manifest does not track, is the one path
+    whose typo could go unnoticed in a tree that is otherwise incomplete.
+    """
+    # `iter_markers`, not `get_closest_marker`: a function-level marker must ADD
+    # to a module-level one rather than replace it. `test_init_sh.py`'s six
+    # seeding tests, which need `docs/templates` on top of the module's
+    # `init.sh`, are exactly that case, and
+    # with `get_closest_marker` the function marker silently dropped the
+    # module's `init.sh` requirement. Correctness lens, PR #232 round 1.
+    paths = sorted({rel for m in item.iter_markers("kit_repo_only") for rel in m.args})
+    _skip_if_missing(paths, "needs")