fix: refuse a target --verify-packs cannot honour

An unknown target, or one the platform does not publish, was dropped and
the full pack verified under it with rc 0 (finding 34).

scripts/generate_pack.py

@@ -2652,6 +2652,19 @@ def _run_verify_packs(args: argparse.Namespace) -> None:
     else:
         raise ValueError("--verify-packs requires --platform or --all")
 
+    # The target is checked as the build checks it: a mistyped one, or one
+    # the platform does not publish, was dropped and the full pack verified
+    # under it, `all OK` for a pack no build had made.
+    target_cores_cache: dict[str, set[str] | None] = {}
+    if args.target:
+        try:
+            target_cores_cache, platforms = build_target_cores_cache(
+                platforms, args.target, args.platforms_dir, is_all=args.all
+            )
+        except (FileNotFoundError, ValueError) as e:
+            print(f"ERROR: {e}", file=sys.stderr)
+            sys.exit(1)
+
     all_ok = True
     verify_regions = getattr(args, "regions", None)
     verify_profiles = load_emulator_profiles(args.emulators_dir)
@@ -2689,7 +2702,7 @@ def _run_verify_packs(args: argparse.Namespace) -> None:
             else:
                 print(f"  {platform_name}: SKIP (no pack in {args.output_dir})")
             continue
-        tc = _target_cores_for(platform_name, args.target, args.platforms_dir)
+        tc = target_cores_cache.get(platform_name)
         # A group pack and a pack built for the platform alone can both be
         # present, and each one is a pack of this platform.
         for pack_name in found:
@@ -4877,17 +4890,12 @@ def _target_cores_for(
 ) -> set[str] | None:
     """Cores a target leaves available, or None when no target was asked for.
 
-    None means no narrowing, which is what an unfiltered pack expects. Read
-    the way --all builds: a platform without a target file was packed
-    unnarrowed under the target's name, and checking that pack must not
-    raise where building it did not.
+    Called on a platform the build already packed under the target, so the
+    target is known to it: a platform without one is left out of the run.
     """
     if not target_name:
         return None
-    try:
-        return load_target_config(platform_name, target_name, platforms_dir)
-    except (FileNotFoundError, ValueError):
-        return None
+    return load_target_config(platform_name, target_name, platforms_dir)
 
 
 def _expected_pack_names(

tests/test_target_verify.py

@@ -4,7 +4,8 @@
 under the target's name (Recalbox, Lakka, BizHawk, MiSTer, ROCKNIX). The
 conformance check read the same target without the --all tolerance, raised
 FileNotFoundError on the first of those packs and stopped the run in a
-traceback after every pack had been written.
+traceback after every pack had been written. Such a platform is now left
+out of a targeted --all run, and the check refuses it as the build does.
 """
 
 from __future__ import annotations
@@ -31,7 +32,10 @@ class CheckReadsTheTargetLikeTheBuild(unittest.TestCase):
                 contextlib.redirect_stdout(io.StringIO()):
             with self.assertRaises(ValueError):
                 build_target_cores_cache(["recalbox"], "x86_64", platforms, is_all=True)
-            self.assertIsNone(_target_cores_for("recalbox", "x86_64", platforms))
+        # The build never packs such a platform under the target, so the
+        # check refuses it too instead of reading the full pack.
+        with self.assertRaises(FileNotFoundError):
+            _target_cores_for("recalbox", "x86_64", platforms)
 
     def test_a_platform_with_a_target_file_is_narrowed(self):
         cores = _target_cores_for("retroarch", "switch", str(REPO_ROOT / "platforms"))

tests/test_verify_pack_choice.py

@@ -116,6 +116,24 @@ class VerifyPackChoice(unittest.TestCase):
             dict(zip((name for _p, name in checked), self.variants)), names
         )
 
+    def test_a_target_the_platform_lacks_is_refused(self):
+        """`--platform bizhawk --target rpi4typo --verify-packs` verified the
+        full pack and said `all OK`, where the build refused the target."""
+        import contextlib
+        import io
+
+        bizhawk = self.gp._platform_pack_stem(["bizhawk"], "bizhawk", "platforms")
+        self._touch(f"{bizhawk}_BIOS_Pack.zip")
+        self._touch(f"{self.stem}_BIOS_Pack.zip")
+        for platform, target in (("bizhawk", "rpi4typo"), ("retroarch", "swich")):
+            with self.subTest(platform=platform), \
+                    contextlib.redirect_stdout(io.StringIO()), \
+                    contextlib.redirect_stderr(io.StringIO()), \
+                    self.assertRaises(SystemExit) as ctx:
+                self._run(self._args(platform=platform, target=target))
+            self.assertEqual(ctx.exception.code, 1)
+            self.assertEqual(self.variants, [])
+
     def test_the_run_ends_on_a_summary(self):
         """A failing pack was named only above its own error lines, and the
         log ended on the last platform's OK line."""