fix(unit): preserve detailed state on files rescan

Instead of returning STATE_FUZZY in `get_unit_state`, return the more specific
substate if unit has one assigned to it in Weblate.

Author: amCap1712

weblate/trans/models/unit.py

@@ -858,6 +858,11 @@ def get_unit_state(
         # support saving it
         is_existing_fuzzy_state = self.fuzzy or disk_unit_state in FUZZY_STATES
         if unit.is_fuzzy(is_existing_fuzzy_state and not string_changed):
+            # Preserve specific fuzzy sub-state when possible
+            if self.state in FUZZY_STATES:
+                return self.state
+            if disk_unit_state in FUZZY_STATES:
+                return disk_unit_state
             return STATE_FUZZY
 
         if not unit.is_translated():

weblate/trans/tests/test_models.py

@@ -47,6 +47,7 @@
     STATE_APPROVED,
     STATE_FUZZY,
     STATE_NEEDS_CHECKING,
+    STATE_NEEDS_REWRITING,
     STATE_READONLY,
     STATE_TRANSLATED,
 )
@@ -1161,3 +1162,39 @@ def test_xliff_file_sync_gets_automatically_translated_from_file(self) -> None:
 
         car_unit = translation.unit_set.get(source="Car")
         self.assertTrue(car_unit.automatically_translated)
+
+
+class FuzzySubstatePreservationTest(RepoTestCase):
+    """Test that fuzzy sub-states are preserved across file syncs."""
+
+    def setUp(self) -> None:
+        super().setUp()
+        self.user = create_test_user()
+
+    def _test_fuzzy_substate_preserved_after_sync(self, substate) -> None:
+        component = self.create_component()
+        translation = component.translation_set.get(language_code="cs")
+        unit = translation.unit_set.get(source="Hello, world!\n")
+
+        unit.translate(self.user, "Ahoj světe!\n", substate)
+        self.assertEqual(unit.state, substate)
+
+        translation.commit_pending("test", None)
+
+        unit.refresh_from_db()
+        self.assertEqual(unit.state, substate)
+        self.assertNotIn("disk_state", unit.details)
+
+        # Trigger check_sync to simulate repository parsing due to another change
+        translation = component.translation_set.get(language_code="cs")
+        translation.check_sync(force=True)
+
+        # The fuzzy sub-state should be preserved, not changed to STATE_FUZZY
+        unit.refresh_from_db()
+        self.assertEqual(unit.state, substate)
+
+    def test_needs_rewriting_preserved_after_sync(self) -> None:
+        self._test_fuzzy_substate_preserved_after_sync(STATE_NEEDS_REWRITING)
+
+    def test_needs_checking_preserved_after_sync(self) -> None:
+        self._test_fuzzy_substate_preserved_after_sync(STATE_NEEDS_CHECKING)