Add EnrichingProxy to run enrichment during !Lookups

emrichen/context.py

@@ -61,3 +61,25 @@ def add_variables(self, *variable_sources, **override_variables) -> None:
                     self.update(yaml_document)
 
         self.update(override_variables)
+
+
+class EnrichingProxy:
+    __slots__ = ('_context', '_target')
+
+    def __init__(self, context, target):
+        self._context = context
+        self._target = target
+
+    def __getitem__(self, key):
+        return EnrichingProxy(
+            context=self._context,
+            target=self._context.enrich(self._target[key]),
+        )
+
+    def __len__(self):
+        return len(self._target)
+
+    @classmethod
+    def unwrap(cls, obj):
+        assert isinstance(obj, cls)
+        return obj._target

emrichen/tags/lookup.py

@@ -3,7 +3,7 @@
 
 import jsonpath_rw
 
-from ..context import Context
+from ..context import Context, EnrichingProxy
 from .base import BaseTag
 
 
@@ -13,7 +13,10 @@ def parse_jsonpath(expr: str):
 
 
 def find_jsonpath_in_context(jsonpath_str: str, context: Context) -> List[jsonpath_rw.DatumInContext]:
-    return parse_jsonpath(jsonpath_str).find(context)
+    result = parse_jsonpath(jsonpath_str).find(EnrichingProxy(context, context))
+    for datum in result:
+        datum.value = EnrichingProxy.unwrap(datum.value)
+    return result
 
 
 class Lookup(BaseTag):

tests/test_lookup.py

@@ -68,7 +68,6 @@ def test_lookup_no_match():
     assert 'no matches for' in str(ei.value)
 
 
-@pytest.mark.xfail
 def test_late_enrich():
     template = Template.parse(
         '''
@@ -103,3 +102,17 @@ def test_lookup_enrich():
 '''
     )
     assert template.enrich({}) == [{'should_contain_5': [5]}]
+
+
+@pytest.mark.xfail
+def test_recursive_data_structure():
+    template = Template.parse('''
+!Defaults
+x:
+    y: 5
+    x: !Var x
+---
+five: !Lookup x.y
+also_five: !Lookup x.x.x.x.x.y
+''')
+    assert template.enrich({}) == [{'five': 5, 'also_five': 5}]