Fix make_lines excludes fields with empty strings (#655)

influxdb/line_protocol.py

@@ -91,9 +91,11 @@ def _is_float(value):
 
 
 def _escape_value(value):
-    value = _get_unicode(value)
+    if value is None:
+        return ''
 
-    if isinstance(value, text_type) and value != '':
+    value = _get_unicode(value)
+    if isinstance(value, text_type):
         return quote_ident(value)
     elif isinstance(value, integer_types) and not isinstance(value, bool):
         return str(value) + 'i'

influxdb/tests/test_line_protocol.py

@@ -115,6 +115,24 @@ def test_make_lines_unicode(self):
             'test,unicode_tag=\'Привет!\' unicode_val="Привет!"\n'
         )
 
+    def test_make_lines_empty_field_string(self):
+        """Test make lines with an empty string field."""
+        data = {
+            "points": [
+                {
+                    "measurement": "test",
+                    "fields": {
+                        "string": "",
+                    }
+                }
+            ]
+        }
+
+        self.assertEqual(
+            line_protocol.make_lines(data),
+            'test string=""\n'
+        )
+
     def test_tag_value_newline(self):
         """Test make lines with tag value contains newline."""
         data = {