fix: check targeted packs the way --all builds

scripts/generate_pack.py

@@ -3413,12 +3413,15 @@ 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.
+    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.
     """
     if not target_name:
         return None
     cache, _kept = build_target_cores_cache(
-        [platform_name], target_name, platforms_dir
+        [platform_name], target_name, platforms_dir, is_all=True
     )
     return cache.get(platform_name)
 

tests/test_target_verify.py

@@ -0,0 +1,39 @@
+"""A targeted pack is checked under the target reading it was built with.
+
+`--all --target x86_64` packs a platform that has no target file unnarrowed
+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.
+"""
+
+from __future__ import annotations
+
+import sys
+import tempfile
+import unittest
+from pathlib import Path
+
+REPO_ROOT = Path(__file__).resolve().parent.parent
+sys.path.insert(0, str(REPO_ROOT / "scripts"))
+
+from common import build_target_cores_cache
+from generate_pack import _target_cores_for
+
+
+class CheckReadsTheTargetLikeTheBuild(unittest.TestCase):
+    def test_a_platform_without_a_target_file(self):
+        with tempfile.TemporaryDirectory() as platforms:
+            built, kept = build_target_cores_cache(
+                ["recalbox"], "x86_64", platforms, is_all=True
+            )
+            self.assertEqual((built, kept), ({"recalbox": None}, ["recalbox"]))
+            self.assertIsNone(_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"))
+        self.assertTrue(cores)
+
+
+if __name__ == "__main__":
+    unittest.main()