Fix active parameter in signature help (#142)

pyls/plugins/signature.py

@@ -26,10 +26,11 @@ def pyls_signature_help(document, position):
             'documentation': ""
         } for p in s.params]
 
+    # We only return a single signature because Python doesn't allow overloading
     sig_info = {'signatures': [sig], 'activeSignature': 0}
 
     if s.index is not None and s.params:
         # Then we know which parameter we're looking at
-        sig['activeParameter'] = s.index
+        sig_info['activeParameter'] = s.index
 
     return sig_info

test/plugins/test_signature.py

@@ -1,4 +1,5 @@
 # Copyright 2017 Palantir Technologies, Inc.
+import pytest
 from pyls import uris
 from pyls.plugins.signature import pyls_signature_help
 from pyls.workspace import Document
@@ -28,7 +29,11 @@ def test_signature():
     sig_position = {'line': 6, 'character': 5}
     doc = Document(DOC_URI, DOC)
 
-    sigs = pyls_signature_help(doc, sig_position)['signatures']
+    sig_info = pyls_signature_help(doc, sig_position)
+
+    sigs = sig_info['signatures']
     assert len(sigs) == 1
     assert sigs[0]['label'] == 'main(param1, param2)'
     assert sigs[0]['parameters'][0]['label'] == 'param1'
+
+    assert sig_info['activeParameter'] == 0