ADD nullSafe transformation

README.md

@@ -104,6 +104,7 @@ Result:
 
 - `typeOf`: returns type representation of the data (e.g. `str`, `int`, `float`, etc.)
 - `strToLocation`: given a string with a comma separated list of decimal numbers, returns an array of such numbers. Example: `"value1, value2"|strToLocation`. Example: `"value1, value2"|strToLocation` returns `[value1, value2]`. It's name (maybe not very good :) is due to it can be useful to generate a [GeoJSON](https://geojson.org/) representing a point which coordinates are provided in a string, eg: `{coordinates:(point|strToLocation),type: "Point"}`
+- `nullSafe`: return the input value, if not `None`, or a failsafe value. Example: `a|safeNull(23)` return the value of `a` if `a` is not None or `23` if `a` is None. 
 
 ## Packaging
 
@@ -137,6 +138,8 @@ upload process you will be prompted to provide your user and password.
 
 ## Changelog
 
+- Add: nullSafe transformation ([#11](https://github.com/telefonicasc/tcjexl/issues/11))
+
 0.2.0 (March 11th, 2024)
 
 - Add: allow to use context for transformations arguments (using a patched version of pyjexl)

tcjexl/jexl.py

@@ -75,3 +75,6 @@ def __init__(self, context=None, now=datetime.datetime.now(timezone.utc)):
         # Tested by test_transforms_misc.py
         super().add_transform("typeOf", lambda x: f'{type(x)}'[8:-2])
         super().add_transform("strToLocation", lambda str: [float(x) for x in str.split(",")])
+
+        # Tested by test_null.py
+        super().add_transform("nullSafe", lambda x, y: x if x is not None else y)

tests/test_null.py

@@ -0,0 +1,67 @@
+# Copyright 2024 Telefónica Soluciones de Informática y Comunicaciones de España, S.A.U.
+#
+# This file is part of tcjexl
+#
+# tcjexl is free software: you can redistribute it and/or
+# modify it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 of the
+# License, or (at your option) any later version.
+#
+# tcjexl is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero
+# General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with IoT orchestrator. If not, see http://www.gnu.org/licenses/.
+
+
+import unittest
+from tcjexl import JEXL
+
+
+class TestNull(unittest.TestCase):
+
+    def setUp(self) -> None:
+        self.jexl = JEXL()
+
+    def test_null_fail(self):
+        context = {"a": None}
+
+        self.assertRaises(TypeError, self.jexl.evaluate, 'a*10', context)
+
+    def test_nullsafe_number(self):
+        expr = 'a|nullSafe(0)*10'
+        context1 = {"a": None}
+        context2 = {"a": 23}
+        result1 = self.jexl.evaluate(expr, context1)
+        result2 = self.jexl.evaluate(expr, context2)
+        self.assertEqual(result1, 0)
+        self.assertEqual(result2, 230)
+
+    def test_nullsafe_string(self):
+        expr = "a|nullSafe('foo')+'bar'"
+        context1 = {"a": None}
+        context2 = {"a": 'zzz'}
+        result1 = self.jexl.evaluate(expr, context1)
+        result2 = self.jexl.evaluate(expr, context2)
+        self.assertEqual(result1, 'foobar')
+        self.assertEqual(result2, 'zzzbar')
+
+    def test_nullsafe_boolean(self):
+        expr = "a|nullSafe(false)"
+        context1 = {"a": None}
+        context2 = {"a": True}
+        result1 = self.jexl.evaluate(expr, context1)
+        result2 = self.jexl.evaluate(expr, context2)
+        self.assertEqual(result1, False)
+        self.assertEqual(result2, True)
+
+    def test_nullsafe_variable(self):
+        expr = "a|nullSafe(b)"
+        context1 = {"a": None, "b": 32}
+        context2 = {"a": 4, "b": 32}
+        result1 = self.jexl.evaluate(expr, context1)
+        result2 = self.jexl.evaluate(expr, context2)
+        self.assertEqual(result1, 32)
+        self.assertEqual(result2, 4)