Keep User Filament Presets on Printers Their Parent Listed in 2.4.2

User presets store only their diff, so they inherit the parent's
compatible_printers. Profile changes since 2.4.2 renamed and narrowed many
system filament presets, so user presets made against them disappear from
printers they were made for and the saved selection silently falls back to
another filament at startup.

orca_profile_tool.py legacy-compat writes, per current system filament
preset, the printers it covered in an older release and no longer lists,
kept only where a preset with the same filament_id still covers the printer
and they share an extruder variant. The loader gives these printers to user
presets that inherit their parent's list, without writing any file; saving
a preset detached, cloned or with its own list drops them.

scripts/tests/test_profile_tool.py

@@ -1258,6 +1258,97 @@ class TestVariantNames(TreeCase):
         self.assertIn('holds the legacy variant "Direct Drive Normal"', out)
 
 
+# ---------------------------------------------------------------------------
+# legacy-compat
+# ---------------------------------------------------------------------------
+
+class TestLegacyCompat(unittest.TestCase):
+    """A base release and the current tree, each with one vendor."""
+
+    def setUp(self):
+        self.base, self.cur = Tree(), Tree()
+        self.addCleanup(self.base.cleanup)
+        self.addCleanup(self.cur.cleanup)
+
+    @staticmethod
+    def printer(tree, name, **extra):
+        tree.write("V", f"machine/{name}.json",
+                   {"type": "machine", "name": name, "instantiation": "true", **extra})
+        tree.index("V", "machine", name, f"machine/{name}.json")
+
+    @staticmethod
+    def filament(tree, name, printers, filament_id="OFpetg01", **extra):
+        tree.write("V", f"filament/{name}.json",
+                   {"type": "filament", "name": name, "instantiation": "true",
+                    "filament_id": filament_id, "compatible_printers": printers, **extra})
+        tree.index("V", "filament", name, f"filament/{name}.json")
+
+    def generate(self):
+        return apt.legacy_compatible_printers(self.base.profiles, self.cur.profiles)
+
+    def test_renamed_and_narrowed_preset_keeps_printers_a_same_id_sibling_covers(self):
+        for tree in (self.base, self.cur):
+            for p in ("A 0.4", "A 0.6", "B 0.4"):
+                self.printer(tree, p)
+        self.filament(self.base, "PETG @A-all", ["A 0.4", "A 0.6", "B 0.4"])
+        self.filament(self.cur, "PETG @V A-all", ["A 0.6"], renamed_from="PETG @A-all;PETG A-all")
+        self.filament(self.cur, "PETG @A 0.4", ["A 0.4"])
+        self.assertEqual(self.generate(), {"PETG @V A-all": ["A 0.4"]})
+
+    def test_printer_without_a_successor_is_left_out(self):
+        for tree in (self.base, self.cur):
+            for p in ("A 0.4", "A 0.6"):
+                self.printer(tree, p)
+        self.filament(self.base, "PETG @A", ["A 0.4", "A 0.6"])
+        self.filament(self.cur, "PETG @A", ["A 0.6"])
+        self.filament(self.cur, "Other @A", ["A 0.4"], filament_id="OFother1")
+        self.assertEqual(self.generate(), {})
+
+    def test_printer_names_follow_printer_renames(self):
+        self.printer(self.base, "Old 0.4")
+        self.printer(self.base, "A 0.6")
+        self.printer(self.cur, "New 0.4", renamed_from="Old 0.4")
+        self.printer(self.cur, "A 0.6")
+        self.filament(self.base, "PETG @A", ["Old 0.4", "A 0.6"])
+        self.filament(self.cur, "PETG @A", ["A 0.6"])
+        self.filament(self.cur, "PETG @New", ["New 0.4"])
+        self.assertEqual(self.generate(), {"PETG @A": ["New 0.4"]})
+
+    def test_printer_without_a_shared_extruder_variant_is_left_out(self):
+        for tree in (self.base, self.cur):
+            self.printer(tree, "Direct 0.4", printer_extruder_variant=["Direct Drive Standard"])
+            self.printer(tree, "Bowden 0.4", printer_extruder_variant=["Bowden Standard"])
+        self.filament(self.base, "PETG @all", ["Direct 0.4", "Bowden 0.4"])
+        self.filament(self.cur, "PETG @all", ["Direct 0.4"],
+                      filament_extruder_variant=["Direct Drive Standard"])
+        self.filament(self.cur, "PETG @Bowden", ["Bowden 0.4"])
+        self.assertEqual(self.generate(), {})
+
+    def test_preset_now_listing_no_printer_is_skipped(self):
+        for tree in (self.base, self.cur):
+            self.printer(tree, "A 0.4")
+        self.filament(self.base, "PETG @A", ["A 0.4"])
+        self.filament(self.cur, "PETG @A", [])
+        self.assertEqual(self.generate(), {})
+
+    def test_check_passes_on_a_current_map_and_fails_on_a_stale_one(self):
+        for tree in (self.base, self.cur):
+            for p in ("A 0.4", "A 0.6"):
+                self.printer(tree, p)
+        self.filament(self.base, "PETG @A", ["A 0.4", "A 0.6"])
+        self.filament(self.cur, "PETG @A", ["A 0.6"])
+        self.filament(self.cur, "PETG @A 0.4", ["A 0.4"])
+        output = os.path.join(self.cur.dir, "map.json")
+        argv = ["legacy-compat", "--base", self.base.profiles, "--profiles", self.cur.profiles,
+                "--output", output]
+        with contextlib.redirect_stdout(io.StringIO()):
+            self.assertEqual(apt.main(argv), 0)
+            self.assertEqual(apt.main(argv + ["--check"]), 0)
+            with open(output, "w", encoding="utf-8") as f:
+                json.dump({"presets": {}}, f)
+            self.assertEqual(apt.main(argv + ["--check"]), 1)
+
+
 class TestDispatch(TreeCase):
     def test_each_command_reaches_its_own_writer(self):
         self.t.write("V", "filament/A.json", {"type": "filament", "name": "A"})