fix: file truth models by each platform's target

Lakka builds an image named switch while RetroArch files switch as
nintendo-switch. One canonical name taken across the registry put
Lakka's model under RetroArch's target. generate_truth now writes each
platform under its own target name, and diff_truth --target reads it.

scripts/common.py

@@ -494,8 +494,9 @@ def truth_target_dir(
 
     Slugged from the name the target is filed under: `nx`, `switch` and
     `nintendo-switch` wrote three copies of one model, and a run under one
-    alias left the others stale beside it. generate_truth writes here and
-    the pipeline's diff reads here, so both call this.
+    alias left the others stale beside it. Called per platform, since two
+    platforms can file one name differently (Lakka builds an image named
+    switch). generate_truth writes here and diff_truth reads here.
     """
     named = canonical_target_name(platforms, target, platforms_dir)
     slug = re.sub(r"[^a-z0-9]+", "-", named.strip().lower()).strip("-")

scripts/diff_truth.py

@@ -21,6 +21,7 @@ from common import (
     load_platform_config,
     native_layer,
     require_yaml,
+    truth_target_dir,
     yaml_load,
 )
 from truth import diff_platform_truth
@@ -174,6 +175,11 @@ def main() -> None:
     )
     parser.add_argument("--truth-dir", default="dist/truth")
     parser.add_argument("--platforms-dir", default="platforms")
+    parser.add_argument(
+        "--target",
+        help="read the models generate_truth --target wrote, each under the "
+        "target as its platform files it",
+    )
     args = parser.parse_args()
 
     if args.all:
@@ -188,9 +194,13 @@ def main() -> None:
     compared = 0
 
     for platform in platforms:
-        truth = _load_truth(args.truth_dir, platform)
+        truth_dir = (
+            truth_target_dir(args.truth_dir, [platform], args.target, args.platforms_dir)
+            if args.target else args.truth_dir
+        )
+        truth = _load_truth(truth_dir, platform)
         if truth is None:
-            print(f"skip {platform}: no truth YAML in {args.truth_dir}/", file=sys.stderr)
+            print(f"skip {platform}: no truth YAML in {truth_dir}/", file=sys.stderr)
             continue
 
         try:

scripts/generate_truth.py

@@ -92,15 +92,16 @@ def main(argv: list[str] | None = None) -> None:
 
     # A target-narrowed model is a different artifact: written under the
     # platform's own name it overwrote the full one, and diff_truth then
-    # compared a narrowed model against the whole scrape.
-    output_dir = args.output_dir
-    if args.target:
-        output_dir = truth_target_dir(
-            output_dir, platforms, args.target, args.platforms_dir
-        )
-    os.makedirs(output_dir, exist_ok=True)
-
+    # compared a narrowed model against the whole scrape. Its directory is
+    # the target as this platform files it, as the packs are named: Lakka's
+    # switch is its own image, RetroArch's is nintendo-switch.
     for name in platforms:
+        output_dir = args.output_dir
+        if args.target:
+            output_dir = truth_target_dir(
+                output_dir, [name], args.target, args.platforms_dir
+            )
+        os.makedirs(output_dir, exist_ok=True)
         # Resolve target cores
         target_cores: set[str] | None = None
         if args.target:

scripts/pipeline.py

@@ -45,9 +45,7 @@ from common import (
     ArtifactLockBusy,
     artifact_lock,
     hold_artifact_lock,
-    list_registered_platforms,
     load_data_dir_registry,
-    truth_target_dir,
 )
 from refresh_data_dirs import hold_data_dirs
 
@@ -256,17 +254,9 @@ def _truth_steps(args: argparse.Namespace, results: dict) -> bool:
     """Steps 2c to 2e: truth model, its diff, the native export."""
     all_ok = True
     # Step 2c: Generate truth YAMLs
-    # A targeted run writes its model in a subdirectory of its own, and the
-    # diff has to read the same one or it compares a narrowed model against
-    # the whole scrape.
+    # A targeted run writes each platform's model under the target as that
+    # platform files it; the diff is told the target and reads the same place.
     truth_dir = Path(args.output_dir) / "truth"
-    if args.target:
-        # generate_truth --all writes every registered platform's model.
-        truth_dir = Path(truth_target_dir(
-            str(truth_dir),
-            list_registered_platforms("platforms", include_archived=True),
-            args.target,
-        ))
 
     if args.with_truth or args.with_export:
         truth_cmd = [
@@ -293,6 +283,8 @@ def _truth_steps(args: argparse.Namespace, results: dict) -> bool:
     if args.with_truth or args.with_export:
         diff_cmd = [sys.executable, "scripts/diff_truth.py", "--all"]
         diff_cmd.extend(["--truth-dir", str(truth_dir)])
+        if args.target:
+            diff_cmd.extend(["--target", args.target])
         ok, _ = run(diff_cmd, "2d diff truth")
         results["diff_truth"] = ok
         all_ok = all_ok and ok

tests/test_target_names.py

@@ -113,23 +113,28 @@ class OneTruthModelPerTarget(unittest.TestCase):
     rebuilt the same slug by hand to find it."""
 
     def test_aliases_share_a_directory(self):
-        from common import list_registered_platforms, truth_target_dir  # noqa: PLC0415
+        from common import truth_target_dir  # noqa: PLC0415
 
-        platforms = list_registered_platforms(
-            str(REPO_ROOT / "platforms"), include_archived=True
-        )
+        platforms = str(REPO_ROOT / "platforms")
         dirs = {
-            truth_target_dir("truth", platforms, alias, str(REPO_ROOT / "platforms"))
+            truth_target_dir("truth", ["retroarch"], alias, platforms)
             for alias in ("nx", "switch", "nintendo-switch")
         }
         self.assertEqual(dirs, {str(Path("truth") / "nintendo-switch")})
+        # Lakka builds an image named switch: its own target, its own model.
+        self.assertEqual(
+            truth_target_dir("truth", ["lakka"], "switch", platforms),
+            str(Path("truth") / "switch"),
+        )
 
     def test_writer_and_reader_call_one_function(self):
-        for module in ("generate_truth.py", "pipeline.py"):
+        for module in ("generate_truth.py", "diff_truth.py"):
             source = (REPO_ROOT / "scripts" / module).read_text()
             with self.subTest(module=module):
                 self.assertIn("truth_target_dir(", source)
                 self.assertNotIn('re.sub(\n            r"[^a-z0-9]+"', source)
+        pipeline = (REPO_ROOT / "scripts" / "pipeline.py").read_text()
+        self.assertIn('diff_cmd.extend(["--target", args.target])', pipeline)
 
 
 class TheListingCountsWhatTheFilterUses(unittest.TestCase):