Allow higher priority dictionaries to delete entries from others (#1160)

Author: user202729

news.d/feature/1160.core.md

@@ -0,0 +1 @@
+Allow higher priority dictionaries to delete entries from others. 

plover/steno_dictionary.py

@@ -183,7 +183,13 @@ def longest_key(self):
     def set_dicts(self, dicts):
         self.dicts = dicts[:]
 
-    def _lookup(self, key, dicts=None, filters=()):
+    def _lookup_keep_deleted(self, key, dicts=None, filters=()):
+        """
+        Lookup a key in the given dicts.
+        If key appears in none of the dicts, return None.
+        If key appears in some dicts but with "{plover:deleted}" as value,
+        return "{plover:deleted}".
+        """
         if dicts is None:
             dicts = self.dicts
         key_len = len(key)
@@ -195,14 +201,26 @@ def _lookup(self, key, dicts=None, filters=()):
             if key_len > d.longest_key:
                 continue
             value = d.get(key)
-            if value:
+            if value is not None:
                 if not any(f(key, value) for f in filters):
                     return value
 
+    def _lookup(self, key, dicts=None, filters=()):
+        """
+        Same as _lookup_keep_deleted, but if key appears in some dicts
+        but with "{plover:deleted}" as value (case-insensitive),
+        return None instead.
+        """
+        result = self._lookup_keep_deleted(key, dicts, filters)
+        if result is None or result.lower() == "{plover:deleted}":
+            return None
+        return result
+
     def _lookup_from_all(self, key, dicts=None, filters=()):
         """Key lookup from all dictionaries
 
-        Returns list of (value, dictionary) tuples
+        Returns list of (value, dictionary) tuples.
+        Entries with value "{plover:deleted}" are kept.
         """
         if dicts is None:
             dicts = self.dicts
@@ -248,7 +266,7 @@ def reverse_lookup(self, value):
             keys.update(
                 k
                 for k in d.reverse_lookup(value)
-                if self._lookup(k, dicts=self.dicts[:n]) is None
+                if self._lookup_keep_deleted(k, dicts=self.dicts[:n]) is None
             )
         return keys
 

test/test_steno_dictionary.py

@@ -14,18 +14,26 @@ def test_dictionary_collection():
     d1 = StenoDictionary()
     d1[("S",)] = "a"
     d1[("T",)] = "b"
+    d1[("H",)] = "{PLOVER:deleted}"
+    d1[("R",)] = "e"
     d1.path = "d1"
     d2 = StenoDictionary()
     d2[("S",)] = "c"
     d2[("W",)] = "d"
+    d2[("H",)] = "f"
+    d2[("R",)] = "{plover:deleted}"
     d2.path = "d2"
     dc = StenoDictionaryCollection([d2, d1])
     assert dc.lookup(("S",)) == "c"
     assert dc.lookup(("W",)) == "d"
     assert dc.lookup(("T",)) == "b"
+    assert dc.lookup(("H",)) == "f"
+    assert dc.lookup(("R",)) == None
     assert dc.lookup_from_all(("S",)) == [("c", d2), ("a", d1)]
     assert dc.lookup_from_all(("W",)) == [("d", d2)]
     assert dc.lookup_from_all(("T",)) == [("b", d1)]
+    assert dc.lookup_from_all(("H",)) == [("f", d2), ("{PLOVER:deleted}", d1)]
+    assert dc.lookup_from_all(("R",)) == [("{plover:deleted}", d2), ("e", d1)]
     f = lambda k, v: v == "c"
     dc.add_filter(f)
     assert dc.lookup(("S",)) == "a"
@@ -50,9 +58,13 @@ def test_dictionary_collection():
     assert dc.lookup(("S",)) == "c"
     assert dc.lookup(("W",)) == "d"
     assert dc.lookup(("T",)) == "b"
+    assert dc.lookup(("H",)) == "f"
+    assert dc.lookup(("R",)) == None
     assert dc.lookup_from_all(("S",)) == [("c", d2), ("a", d1)]
     assert dc.lookup_from_all(("W",)) == [("d", d2)]
     assert dc.lookup_from_all(("T",)) == [("b", d1)]
+    assert dc.lookup_from_all(("H",)) == [("f", d2), ("{PLOVER:deleted}", d1)]
+    assert dc.lookup_from_all(("R",)) == [("{plover:deleted}", d2), ("e", d1)]
 
     assert dc.reverse_lookup("c") == {("S",)}