fix(cost_map): fail the guard when the pins file is missing

ci_cd/cost_map_guard.py

@@ -3,7 +3,8 @@
 Every pull request whose diff against its merge base touches one of the three cost map files or the pins file gets
 the file checks: the files parse, the backup copy matches the root file, the JSON schema is in sync and validates the
 map, and every capability pinned in ci_cd/cost_map_pins.json (a value verified against a live provider call where the
-provider's model listing says otherwise) still holds in the map. A pull request that leaves all of them untouched
+provider's model listing says otherwise) still holds in the map, so a pull request that deletes the pins file fails
+too. A pull request that leaves all of them untouched
 skips the checks, since merging it keeps the base branch's copies and its head tree only carries whatever state the
 branch was cut from. Pull requests from the cost map sync bot (branches named litellm_cost_map_sync_*) always get the
 file checks and additionally may only touch the three cost map files and may only add or update models, so a sync
@@ -132,7 +133,7 @@ def _pin_violations(parsed: CostMap, entries: dict[str, dict[str, object]]) -> I
 
 def pin_failures(pins_text: str, head_map: CostMap) -> tuple[str, ...]:
     if not pins_text:
-        return ()
+        return (f"{PINS_PATH} is missing; restore it, its pins were verified against live provider calls",)
     parsed: Final = _parse_object(pins_text, PINS_PATH)
     if isinstance(parsed, str):
         return (parsed,)

tests/unit/test_cost_map_guard.py

@@ -51,8 +51,11 @@ def _serialize(cost_map: dict[str, object]) -> str:
     return json.dumps(cost_map, indent=4, ensure_ascii=False) + "\n"
 
 
+NO_PINS: Final = "{}\n"
+
+
 def _snapshot(
-    cost_map: dict[str, object], backup: str | None = None, schema: str | None = None, pins: str = ""
+    cost_map: dict[str, object], backup: str | None = None, schema: str | None = None, pins: str = NO_PINS
 ) -> object:
     text = _serialize(cost_map)
     rendered = schema_module.render(schema_module.build_schema(cost_map))
@@ -114,7 +117,7 @@ def test_schema_validation_errors_are_reported() -> None:
 
 def test_unclassified_entry_key_is_reported() -> None:
     text = _serialize({**BASE_MAP, "openrouter/c": _entry(weird_thing=1)})
-    head = guard.Snapshot(cost_map=text, backup=text, schema=BASE.schema)
+    head = guard.Snapshot(cost_map=text, backup=text, schema=BASE.schema, pins=NO_PINS)
     (failure,) = _failures(head, bot=False)
     assert "Unclassified keys" in failure and "weird_thing" in failure
 
@@ -229,6 +232,13 @@ def test_malformed_pins_are_reported(pins: str, expected: str) -> None:
     assert _failures(_snapshot(BASE_MAP, pins=pins), bot=False) == (expected,)
 
 
+@pytest.mark.parametrize("bot", [False, True])
+def test_a_missing_pins_file_fails(bot: bool) -> None:
+    assert _failures(_snapshot(BASE_MAP, pins=""), bot=bot) == (
+        f"{guard.PINS_PATH} is missing; restore it, its pins were verified against live provider calls",
+    )
+
+
 def test_bot_may_not_touch_the_pins_file() -> None:
     head = _snapshot(BASE_MAP, pins=PINS)
     changed = (*guard.GUARDED_PATHS, guard.PINS_PATH)
@@ -247,9 +257,10 @@ def test_checked_in_pins_hold_in_the_checked_in_cost_map() -> None:
 
 def _commit(repo: Path, cost_map: dict[str, object], message: str, pins: str | None = None) -> str:
     text = _serialize(cost_map)
-    if pins is not None:
-        (repo / guard.PINS_PATH).parent.mkdir(exist_ok=True)
-        (repo / guard.PINS_PATH).write_text(pins)
+    pins_file = repo / guard.PINS_PATH
+    if pins is not None or not pins_file.exists():
+        pins_file.parent.mkdir(exist_ok=True)
+        pins_file.write_text(NO_PINS if pins is None else pins)
     (repo / guard.COST_MAP_PATH).write_text(text)
     (repo / guard.BACKUP_PATH).parent.mkdir(exist_ok=True)
     (repo / guard.BACKUP_PATH).write_text(text)
@@ -357,6 +368,17 @@ def test_main_reads_the_pins_from_the_head_revision(tmp_path: Path, head_ref: st
     assert [line for line in result.stdout.splitlines() if line.startswith(pin_line)]
 
 
+def test_main_fails_a_pr_that_deletes_the_pins_file(tmp_path: Path) -> None:
+    subprocess.run(("git", "init", "-q", str(tmp_path)), check=True)
+    base: Final = _commit(tmp_path, BASE_MAP, "base", pins=PINS)
+    subprocess.run(("git", "rm", "-q", guard.PINS_PATH), cwd=tmp_path, check=True)
+    head: Final = _git_commit(tmp_path, "delete the pins")
+    result: Final = _run_guard(tmp_path, base, head, "litellm_fix_pricing")
+    assert result.returncode == 1, result.stdout + result.stderr
+    missing: Final = f"- {guard.PINS_PATH} is missing; restore it, its pins were verified against live provider calls"
+    assert missing in result.stdout.splitlines()
+
+
 def test_main_checks_a_pins_only_pr_against_the_head_map(tmp_path: Path) -> None:
     subprocess.run(("git", "init", "-q", str(tmp_path)), check=True)
     base: Final = _commit(tmp_path, {**BASE_MAP, "openrouter/a": _entry(supports_vision=False)}, "base")