Use a separate values index for booleans

Connects to #96

This prevents collisions between boolean and integer values. In python:
1 == True and 0 == False. But, we don't want these to point to the same
value in the index table.

mapbox_vector_tile/encoder.py

@@ -66,6 +66,7 @@ def addFeatures(self, features, layer_name='',
         self.val_idx = 0
         self.seen_keys_idx = {}
         self.seen_values_idx = {}
+        self.seen_values_bool_idx = {}
 
         for feature in features:
 
@@ -284,8 +285,13 @@ def _handle_attr(self, layer, feature, props):
 
                 feature.tags.append(self.seen_keys_idx[k])
 
-                if v not in self.seen_values_idx:
-                    self.seen_values_idx[v] = self.val_idx
+                if isinstance(v, bool):
+                    values_idx = self.seen_values_bool_idx
+                else:
+                    values_idx = self.seen_values_idx
+
+                if v not in values_idx:
+                    values_idx[v] = self.val_idx
                     self.val_idx += 1
 
                     val = layer.values.add()
@@ -303,4 +309,4 @@ def _handle_attr(self, layer, feature, props):
                     elif isinstance(v, float):
                         val.double_value = v
 
-                feature.tags.append(self.seen_values_idx[v])
+                feature.tags.append(values_idx[v])

tests/test_encoder.py

@@ -490,6 +490,29 @@ def test_too_small_linestring(self):
         features = result['foo']['features']
         self.assertEqual(0, len(features))
 
+    def test_encode_1_True_values(self):
+        geometry = 'POINT(0 0)'
+        properties = {
+            'foo': True,
+            'bar': 1,
+        }
+        source = [{
+            'name': 'layer',
+            'features': [{
+                'geometry': geometry,
+                'properties': properties
+            }]
+        }]
+        encoded = encode(source)
+        decoded = decode(encoded)
+        layer = decoded['layer']
+        features = layer['features']
+        act_props = features[0]['properties']
+        self.assertEquals(act_props['foo'], True)
+        self.assertEquals(act_props['bar'], 1)
+        self.assertTrue(isinstance(act_props['foo'], bool))
+        self.assertFalse(isinstance(act_props['bar'], bool))
+
 
 class TestDictGeometries(BaseTestCase):