Allow higher priority dictionaries to delete entries from others

news.d/feature/1160.core.md

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

plover/steno_dictionary.py

@@ -178,7 +178,13 @@ 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)
@@ -190,14 +196,26 @@ 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
@@ -241,7 +259,7 @@ def reverse_lookup(self, value):
                 continue
             # Ignore key if it's overridden by a higher priority dictionary.
             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
 
     def casereverse_lookup(self, value):

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'