Fix typos and other code review suggestions

Co-authored-by: Markus Scheidgen <markus1978@users.noreply.github.com>
Co-authored-by: Johan Bergsma <JPBergsma@users.noreply.github.com>

optimade/filtertransformers/base_transformer.py

@@ -31,7 +31,7 @@ class Quantity:
 
     Attributes:
         name: The name of the quantity as used in the filter expressions.
-        backend_field: The name of the field for this quanity in elastic search, will be
+        backend_field: The name of the field for this quantity in the backend database, will be
             `name` by default.
         length_quantity: Another (typically integer) [`Quantity`][optimade.filtertransformers.base_transformer.Quantity]
             that can be queried as the length of this quantity, e.g. `elements` and `nelements`. Backends
@@ -67,7 +67,7 @@ class BaseTransformer(abc.ABC, Transformer):
         "=": None,
     }
 
-    # map from operators to their syntactic (NOT logical) inverse to handle
+    # map from operators to their syntactic (as opposed to logical) inverse to handle
     # equivalence between cases like "A > 3" and "3 < A".
     _reversed_operator_map = {
         ">": "<",
@@ -292,7 +292,7 @@ def expression(self, arg):
     def expression_clause(self, arg):
         """expression_clause: expression_phrase ( AND expression_phrase )*"""
 
-    def expression_phrase(self, args):
+    def expression_phrase(self, arg):
         """expression_phrase: [ NOT ] ( comparison | "(" expression ")" )"""
 
     def property_first_comparison(self, arg):

optimade/filtertransformers/elasticsearch.py

@@ -151,7 +151,7 @@ def _query_op(
             return Q(query_type, **{field: value})
 
         if op == "!=":
-            # != queries must also include an existence/v check
+            # != queries must also include an existence check
             # Note that for MongoDB, `$exists` will include null-valued fields,
             # where as in ES `exists` excludes them.
             # pylint: disable=invalid-unary-operand-type

optimade/filtertransformers/mongo.py

@@ -503,5 +503,3 @@ def replacement(d, prop, expr):
         return _cached_filter
 
     return filter_
-
-    return filter_

tests/filtertransformers/test_mongo.py

@@ -505,7 +505,11 @@ def test_aliased_length_operator(self, mapper):
         from optimade.filtertransformers.mongo import MongoTransformer
 
         class MyMapper(mapper("StructureMapper")):
-            ALIASES = (("elements", "my_elements"), ("nelements", "nelem"))
+            ALIASES = (
+                ("elements", "my_elements"),
+                ("nelements", "nelem"),
+                ("elements_ratios", "ratios"),
+            )
             LENGTH_ALIASES = (
                 ("chemsys", "nelements"),
                 ("cartesian_site_positions", "nsites"),
@@ -529,6 +533,11 @@ class MyMapper(mapper("StructureMapper")):
         assert transformer.transform(
             parser.parse("cartesian_site_positions LENGTH 3")
         ) == {"nsites": 3}
+
+        assert transformer.transform(parser.parse("elements_ratios LENGTH 3")) == {
+            "ratios": {"$size": 3, "$exists": True}
+        }
+
         assert transformer.transform(
             parser.parse("cartesian_site_positions LENGTH >= 10")
         ) == {"nsites": {"$gte": 10}}