Increase robustness for predicates missing a POS

Resolves #129

delphin/mrs/components.py

@@ -456,7 +456,9 @@ def string_or_grammar_pred(predstr):
     @classmethod
     def realpred(cls, lemma, pos, sense=None):
         """Return a Pred from its components."""
-        string_tokens = [lemma, pos]
+        string_tokens = [lemma]
+        if pos is not None:
+            string_tokens.append(pos)
         if sense is not None:
             sense = str(sense)
             string_tokens.append(sense)

tests/mrs_components_test.py

@@ -396,6 +396,14 @@ def testSpred(self):
         assert p.pos == 'n'
         assert p.sense == '1'
         assert p.short_form() == '_dog_n_1'
+        # see https://github.com/delph-in/pydelphin/issues/129
+        p = spred('_te_adjunct_rel')
+        assert p.type == Pred.STRINGPRED
+        assert p.string == '_te_adjunct_rel'
+        assert p.lemma == 'te'
+        assert p.pos == None
+        assert p.sense == 'adjunct'
+        assert p.short_form() == '_te_adjunct'
         #TODO: the following shouldn't throw warnings.. the code should
         # be more robust, but there should be some Warning or logging
         #with pytest.raises(ValueError): spred('_dog_rel')
@@ -433,6 +441,15 @@ def testRealPred(self):
         assert p.pos == 'n'
         assert p.sense == '1'
         assert p.short_form() == '_dog_n_1'
+        # see https://github.com/delph-in/pydelphin/issues/129
+        p = Pred.realpred('te', None, 'adjunct')
+        assert p.type == Pred.REALPRED
+        assert p.string == '_te_adjunct_rel'
+        assert p.lemma == 'te'
+        assert p.pos == None
+        assert p.sense == 'adjunct'
+        assert p.short_form() == '_te_adjunct'
+
         with pytest.raises(TypeError): Pred.realpred(lemma='dog')
         with pytest.raises(TypeError): Pred.realpred(pos='n')
         repr(p)  # no error

tests/mrs_dmrx_test.md

@@ -89,6 +89,21 @@ convenient:
 
 ```
 
+See https://github.com/delph-in/pydelphin/issues/129
+
+```python
+>>> m3 = next(dmrx.loads('''<dmrs-list>
+... <dmrs cfrom="-1" cto="-1">
+... <node nodeid="10000"><realpred lemma="te" sense="adjunct" /><sortinfo /></node>
+... </dmrs></dmrs-list>'''))
+>>> nodes(m3)[0].pred  # doctest: +ELLIPSIS
+<Pred object _te_adjunct_rel ...>
+>>> nodes(m3)[0].pred.pos is None
+True
+
+```
+
+
 ## Serialization
 
 The default prints everything on one line.
@@ -126,3 +141,11 @@ Using the `pretty_print` parameter adds newlines.
 </dmrs-list>
 
 ```
+
+See https://github.com/delph-in/pydelphin/issues/129
+
+```python
+>>> print(dmrx.dumps([m3]))
+<dmrs-list><dmrs cfrom="-1" cto="-1"><node cfrom="-1" cto="-1" nodeid="10000"><realpred lemma="te" sense="adjunct" /><sortinfo cvarsort="u" /></node></dmrs></dmrs-list>
+
+```