Support $toLong operator (#705)

Co-authored-by: Daniel Londoño <dlondono@azimutenergia.co>
Co-authored-by: Pascal Corpet <pascal@bayesimpact.org>

Missing_Features.rst

@@ -33,7 +33,7 @@ If I miss to include a feature in the below list, Please feel free to add to the
   * Projection operator $map
   * Array operators ($isArray, $indexOfArray, …)
   * `$mergeObjects <https://docs.mongodb.com/manual/reference/operator/aggregation/mergeObjects/>`_
-  * Some type conversion operators ($convert, $toLong, …)
+  * Some type conversion operators ($convert, …)
 * Operators within the query language (find):
   * `$jsonSchema <https://docs.mongodb.com/manual/reference/operator/query/jsonSchema/>`_
   * `$text <https://docs.mongodb.com/manual/reference/operator/query/text/>`_ search

mongomock/aggregate.py

@@ -693,6 +693,19 @@ def _handle_type_convertion_operator(self, operator, values):
                 'You need to import the pymongo library to support decimal128 type.'
             )
 
+        if operator == '$toLong':
+            try:
+                parsed = self.parse(values)
+            except KeyError:
+                return None
+            if decimal_support:
+                if isinstance(parsed, decimal128.Decimal128):
+                    return helpers.to_long(parsed.to_decimal())
+                return helpers.to_long(parsed)
+            raise NotImplementedError(
+                'You need to import the pymongo library to support decimal128 type.'
+            )
+
         # Document: https://docs.mongodb.com/manual/reference/operator/aggregation/toDecimal/
         if operator == '$toDecimal':
             if not decimal_support:

mongomock/helpers.py

@@ -3,7 +3,7 @@
 from mongomock import InvalidURI
 import re
 from six.moves.urllib_parse import unquote_plus
-from six import iteritems, raise_from, string_types
+from six import PY3, iteritems, raise_from, string_types
 import time
 import warnings
 
@@ -418,3 +418,11 @@ def mongodb_to_bool(value):
     """Converts any value to bool the way MongoDB does it"""
 
     return value not in [False, None, 0]
+
+
+def to_long(value):
+    """Backwards compatible `long` function. It tries to convert input to a long integer."""
+    if PY3:
+        global long  # pylint: disable=global-variable-undefined
+        long = int
+    return long(value)

tests/test__collection_api.py

@@ -4455,11 +4455,6 @@ def test__aggregate_not_implemented(self):
                 {'$project': {'a': {'$setIntersection': [[2], [1, 2, 3]]}}},
             ])
 
-        with self.assertRaises(NotImplementedError):
-            self.db.collection.aggregate([
-                {'$project': {'a': {'$toLong': '$scores'}}},
-            ])
-
     def test__aggregate_project_let(self):
         self.db.collection.insert_one({'_id': 1, 'a': 5, 'b': 2, 'c': 3})
         actual = self.db.collection.aggregate([{'$project': {
@@ -6100,6 +6095,68 @@ def test__aggregate_to_int(self):
         }]
         self.assertEqual(expect, list(actual))
 
+    @skipIf(not _HAVE_PYMONGO, 'pymongo not installed')
+    def test__aggregate_to_long(self):
+        collection = self.db.collection
+        collection.insert_one({
+            'boolean_true': True,
+            'boolean_false': False,
+            'integer': 100,
+            'double': 1.999,
+            'decimal': decimal128.Decimal128('5.5000')
+        })
+        actual = collection.aggregate(
+            [
+                {
+                    '$addFields': {
+                        'boolean_true': {'$toLong': '$boolean_true'},
+                        'boolean_false': {'$toLong': '$boolean_false'},
+                        'integer': {'$toLong': '$integer'},
+                        'double': {'$toLong': '$double'},
+                        'decimal': {'$toLong': '$decimal'},
+                        'not_exist': {'$toLong': '$not_exist'},
+                    }
+                },
+                {
+                    '$project': {
+                        '_id': 0
+                    }
+                }
+            ]
+        )
+        expect = [{
+            'boolean_true': 1,
+            'boolean_false': 0,
+            'integer': 100,
+            'double': 1,
+            'decimal': 5,
+            'not_exist': None,
+        }]
+        self.assertEqual(expect, list(actual))
+
+    @skipIf(_HAVE_PYMONGO, 'pymongo installed')
+    def test__aggregate_to_long_no_pymongo(self):
+        collection = self.db.collection
+        collection.drop()
+        collection.insert_one({
+            'double': 1.999,
+        })
+        with self.assertRaises(NotImplementedError):
+            list(collection.aggregate(
+                [
+                    {
+                        '$addFields': {
+                            'double': {'$toLong': '$double'},
+                        }
+                    },
+                    {
+                        '$project': {
+                            '_id': 0
+                        }
+                    }
+                ]
+            ))
+
     @skipIf(not _HAVE_PYMONGO, 'pymongo not installed')
     def test__aggregate_date_to_string(self):
         collection = self.db.collection

tests/test__mongomock.py

@@ -3431,6 +3431,34 @@ def test_aggregate_to_int(self):
         ]
         self.cmp.compare.aggregate(pipeline)
 
+    def test_aggregate_to_long(self):
+        self.cmp.do.drop()
+        self.cmp.do.insert_one({
+            'boolean_true': True,
+            'boolean_false': False,
+            'integer': 100,
+            'double': 1.999,
+            'decimal': decimal128.Decimal128('5.5000')
+        })
+        pipeline = [
+            {
+                '$addFields': {
+                    'boolean_true': {'$toLong': '$boolean_true'},
+                    'boolean_false': {'$toLong': '$boolean_false'},
+                    'integer': {'$toLong': '$integer'},
+                    'double': {'$toLong': '$double'},
+                    'decimal': {'$toLong': '$decimal'},
+                    'not_exist': {'$toLong': '$not_exist'},
+                }
+            },
+            {
+                '$project': {
+                    '_id': 0
+                }
+            }
+        ]
+        self.cmp.compare.aggregate(pipeline)
+
     def test_aggregate_date_to_string(self):
         self.cmp.do.drop()
         self.cmp.do.insert_one({