fix: write one truth model per target, not alias

generate_truth named a narrowed model's directory after the target
as typed, so three aliases of one target wrote three copies, and
the pipeline rebuilt the slug by hand to diff it. One function now
names the directory from the canonical target for both.

scripts/common.py

@@ -487,6 +487,21 @@ def canonical_target_name(
     return found.pop() if len(found) == 1 else target
 
 
+def truth_target_dir(
+    output_dir: str, platforms: list[str], target: str, platforms_dir: str = "platforms"
+) -> str:
+    """Where a target-narrowed truth model is written and read.
+
+    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.
+    """
+    named = canonical_target_name(platforms, target, platforms_dir)
+    slug = re.sub(r"[^a-z0-9]+", "-", named.strip().lower()).strip("-")
+    return os.path.join(output_dir, slug or "target")
+
+
 def load_target_config(
     platform_name: str,
     target: str,

scripts/generate_truth.py

@@ -10,7 +10,6 @@ from __future__ import annotations
 
 import argparse
 import os
-import re
 import sys
 
 sys.path.insert(0, os.path.dirname(__file__))
@@ -21,6 +20,7 @@ from common import (
     load_platform_config,
     load_target_config,
     require_yaml,
+    truth_target_dir,
     write_text_atomic,
     yaml_load,
 )
@@ -94,8 +94,9 @@ def main(argv: list[str] | None = None) -> None:
     # compared a narrowed model against the whole scrape.
     output_dir = args.output_dir
     if args.target:
-        slug = re.sub(r"[^a-z0-9]+", "-", args.target.strip().lower()).strip("-")
-        output_dir = os.path.join(output_dir, slug or "target")
+        output_dir = truth_target_dir(
+            output_dir, platforms, args.target, args.platforms_dir
+        )
     os.makedirs(output_dir, exist_ok=True)
 
     for name in platforms:

scripts/pipeline.py

@@ -41,7 +41,13 @@ if sys.version_info < (3, 12):
     sys.exit(f"pipeline.py needs Python 3.12 or newer, this is {sys.version.split()[0]}")
 
 sys.path.insert(0, str(Path(__file__).parent))
-from common import ArtifactLockBusy, artifact_lock, hold_artifact_lock
+from common import (
+    ArtifactLockBusy,
+    artifact_lock,
+    hold_artifact_lock,
+    list_registered_platforms,
+    truth_target_dir,
+)
 
 
 def run(cmd: list[str], label: str) -> tuple[bool, str]:
@@ -253,9 +259,12 @@ def _truth_steps(args: argparse.Namespace, results: dict) -> bool:
     # the whole scrape.
     truth_dir = Path(args.output_dir) / "truth"
     if args.target:
-        truth_dir = truth_dir / re.sub(
-            r"[^a-z0-9]+", "-", args.target.strip().lower()
-        ).strip("-")
+        # 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 = [

tests/test_target_names.py

@@ -107,6 +107,31 @@ class EachPlatformNamesTheTargetItsOwnWay(unittest.TestCase):
         self.assertNotIn("args.target = canonical_target_name(", source)
 
 
+class OneTruthModelPerTarget(unittest.TestCase):
+    """generate_truth slugged the typed name: --target nx, switch and
+    nintendo-switch wrote three copies of one model, and the pipeline's diff
+    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
+
+        platforms = list_registered_platforms(
+            str(REPO_ROOT / "platforms"), include_archived=True
+        )
+        dirs = {
+            truth_target_dir("truth", platforms, alias, str(REPO_ROOT / "platforms"))
+            for alias in ("nx", "switch", "nintendo-switch")
+        }
+        self.assertEqual(dirs, {str(Path("truth") / "nintendo-switch")})
+
+    def test_writer_and_reader_call_one_function(self):
+        for module in ("generate_truth.py", "pipeline.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)
+
+
 class TheListingCountsWhatTheFilterUses(unittest.TestCase):
     """--list-targets showed Batocera x86_64 with 198 cores; --target x86_64
     filters on 187 once _overrides.yml removes machine variants and launchers."""