Feature: query string API endpoint (#3513)

* exposed API endpoint to get querystring for a slice

* Added unit tests for endpoint

* fixed test case for python3

* moved get querystring logic into its own func

* renamed query string endpoint

tests/utils_tests.py

@@ -1,7 +1,16 @@
 from datetime import datetime, date, timedelta, time
 from decimal import Decimal
 from superset.utils import (
-    json_int_dttm_ser, json_iso_dttm_ser, base_json_conv, parse_human_timedelta, zlib_compress, zlib_decompress_to_string
+    json_int_dttm_ser,
+    json_iso_dttm_ser,
+    base_json_conv,
+    parse_human_timedelta,
+    zlib_compress,
+    zlib_decompress_to_string,
+    datetime_f,
+    JSONEncodedDict,
+    validate_json,
+    SupersetException,
 )
 import unittest
 import uuid
@@ -52,3 +61,25 @@ class UtilsTestCase(unittest.TestCase):
         got_str = zlib_decompress_to_string(blob)
         self.assertEquals(json_str, got_str)
 
+    def test_datetime_f(self):
+        self.assertEquals(datetime_f(datetime(1990, 9, 21, 19, 11, 19, 626096)),
+            '<nobr>1990-09-21T19:11:19.626096</nobr>')
+        self.assertEquals(len(datetime_f(datetime.now())), 28)
+        self.assertEquals(datetime_f(None), '<nobr>None</nobr>')
+        iso = datetime.now().isoformat()[:10].split('-')
+        [a, b, c] = [int(v) for v in iso]
+        self.assertEquals(datetime_f(datetime(a, b, c)), '<nobr>00:00:00</nobr>')
+
+    def test_json_encoded_obj(self):
+        obj = {'a': 5, 'b': ['a', 'g', 5]}
+        val = '{"a": 5, "b": ["a", "g", 5]}'
+        jsonObj = JSONEncodedDict()
+        resp = jsonObj.process_bind_param(obj, 'dialect')
+        self.assertIn('"a": 5', resp)
+        self.assertIn('"b": ["a", "g", 5]', resp)
+        self.assertEquals(jsonObj.process_result_value(val, 'dialect'), obj)
+
+    def test_validate_json(self):
+        invalid = '{"a": 5, "b": [1, 5, ["g", "h]]}'
+        with self.assertRaises(SupersetException):
+            validate_json(invalid)