initial subrecord filter

saucebrush/filters.py

@@ -122,6 +122,29 @@ class ValidationError(Exception):
         super(ValidationError, self).__init__(repr(record))
         self.record = record
 
+def _dotted_get(d, path):
+    if path:
+        key_pieces = path.split('.', 1)
+        piece = d[key_pieces[0]]
+        if isinstance(piece, (tuple, list)):
+            return [_dotted_get(i, '.'.join(key_pieces[1:])) for i in piece]
+        elif isinstance(piece, (dict)):
+            return _dotted_get(piece, '.'.join(key_pieces[1:]))
+    else:
+        return d
+
+class SubrecordFilter(Filter):
+
+    def __init__(self, field_path, filter_):
+        self.field_path = field_path
+        self.filter = filter_
+
+    def process_record(self, record):
+        subrecord = _dotted_get(record, self.field_path)
+        for p in subrecord:
+            p = self.filter.process_record(p)
+        return record
+
 #####################
 ## Generic Filters ##
 #####################

saucebrush/tests/filters.py

@@ -2,6 +2,7 @@ import unittest
 import operator
 import types
 from saucebrush.filters import (Filter, YieldFilter, FieldFilter,
+                                SubrecordFilter,
                                 ConditionalFilter, FieldModifier,
                                 FieldRemover, FieldMerger, FieldAdder,
                                 FieldCopier, FieldRenamer, Unique)
@@ -99,6 +100,24 @@ class FilterTestCase(unittest.TestCase):
         # ensure only even numbers remain
         self.assertEquals(list(result), [0,2,4,6,8])
 
+    ### FILTERS FOR Subrecord
+
+    def test_subrecord_filter(self):
+        data = [{'a': [{'b': 2}, {'b': 4}]},
+                {'a': [{'b': 5}]},
+                {'a': [{'b': 8}, {'b':2}, {'b':1}]}]
+
+
+        expected = [{'a': [{'b': 4}, {'b': 8}]},
+                {'a': [{'b': 10}]},
+                {'a': [{'b': 16}, {'b':4}, {'b':2}]}]
+
+        sf = SubrecordFilter('a', FieldDoubler('b'))
+        result = sf.attach(data)
+
+        self.assertEquals(list(result), expected)
+
+
     def test_field_modifier(self):
         # another version of FieldDoubler
         fm = FieldModifier(['a', 'c'], lambda x: x*2)