Exclude states with no matching gold annotations from parsing

spacy/syntax/arc_eager.pyx

@@ -350,7 +350,9 @@ cdef class ArcEager(TransitionSystem):
         def __get__(self):
             return (SHIFT, REDUCE, LEFT, RIGHT, BREAK)
 
-    cdef int preprocess_gold(self, GoldParse gold) except -1:
+    def preprocess_gold(self, GoldParse gold):
+        if all([h is None for h in gold.heads]):
+            return None
         for i in range(gold.length):
             if gold.heads[i] is None: # Missing values
                 gold.c.heads[i] = i
@@ -361,6 +363,7 @@ cdef class ArcEager(TransitionSystem):
                     label = 'ROOT'
                 gold.c.heads[i] = gold.heads[i]
                 gold.c.labels[i] = self.strings[label]
+        return gold
 
     cdef Transition lookup_transition(self, object name) except *:
         if '-' in name:

spacy/syntax/ner.pyx

@@ -95,9 +95,12 @@ cdef class BiluoPushDown(TransitionSystem):
         else:
             return MOVE_NAMES[move] + '-' + self.strings[label]
 
-    cdef int preprocess_gold(self, GoldParse gold) except -1:
+    def preprocess_gold(self, GoldParse gold):
+        if all([tag == '-' for tag in gold.ner]):
+            return None
         for i in range(gold.length):
             gold.c.ner[i] = self.lookup_transition(gold.ner[i])
+        return gold
 
     cdef Transition lookup_transition(self, object name) except *:
         if name == '-' or name == None:

spacy/syntax/nn_parser.pyx

@@ -318,15 +318,14 @@ cdef class Parser:
             golds = [golds]
 
         cuda_stream = get_cuda_stream()
-        for gold in golds:
-            self.moves.preprocess_gold(gold)
+        golds = [self.moves.preprocess_gold(g) for g in golds]
 
         states = self.moves.init_batch(docs)
         state2vec, vec2scores = self.get_batch_model(len(states), tokvecs, cuda_stream,
                                                       drop)
 
         todo = [(s, g) for (s, g) in zip(states, golds)
-                if not s.is_final()]
+                if not s.is_final() and g is not None]
 
         backprops = []
         cdef float loss = 0.

spacy/syntax/transition_system.pxd

@@ -43,8 +43,6 @@ cdef class TransitionSystem:
     cdef int initialize_state(self, StateC* state) nogil
     cdef int finalize_state(self, StateC* state) nogil
 
-    cdef int preprocess_gold(self, GoldParse gold) except -1
-
     cdef Transition lookup_transition(self, object name) except *
 
     cdef Transition init_transition(self, int clas, int move, int label) except *

spacy/syntax/transition_system.pyx

@@ -70,7 +70,7 @@ cdef class TransitionSystem:
     def finalize_doc(self, doc):
         pass
 
-    cdef int preprocess_gold(self, GoldParse gold) except -1:
+    def preprocess_gold(self, GoldParse gold):
         raise NotImplementedError
 
     cdef Transition lookup_transition(self, object name) except *: