bdd: reorganise field comparisons

Move comparision on Field values from assert_field() into a
comparator class. Replace BadRowValueAssert with a simpler
check_row() function.

test/bdd/steps/check_functions.py

@@ -2,12 +2,14 @@
 #
 # This file is part of Nominatim. (https://nominatim.org)
 #
-# Copyright (C) 2022 by the Nominatim developer community.
+# Copyright (C) 2023 by the Nominatim developer community.
 # For a full list of authors see the git log.
 """
 Collection of assertion functions used for the steps.
 """
 import json
+import math
+import re
 
 class Almost:
     """ Compares a float value with a certain jitter.
@@ -19,6 +21,51 @@ class Almost:
     def __eq__(self, other):
         return abs(other - self.value) < self.offset
 
+
+OSM_TYPE = {'N' : 'node', 'W' : 'way', 'R' : 'relation',
+            'n' : 'node', 'w' : 'way', 'r' : 'relation',
+            'node' : 'n', 'way' : 'w', 'relation' : 'r'}
+
+
+class OsmType:
+    """ Compares an OSM type, accepting both N/R/W and node/way/relation.
+    """
+
+    def __init__(self, value):
+        self.value = value
+
+
+    def __eq__(self, other):
+        return other == self.value or other == OSM_TYPE[self.value]
+
+
+    def __str__(self):
+        return f"{self.value} or {OSM_TYPE[self.value]}"
+
+
+class Field:
+    """ Generic comparator for fields, which looks at the type of the
+        value compared.
+    """
+    def __init__(self, value):
+        self.value = value
+
+    def __eq__(self, other):
+        if isinstance(self.value, float):
+            return math.isclose(self.value, float(other))
+
+        if self.value.startswith('^'):
+            return re.fullmatch(self.value, other)
+
+        if isinstance(other, dict):
+            return other == eval('{' + self.value + '}')
+
+        return str(self.value) == str(other)
+
+    def __str__(self):
+        return str(self.value)
+
+
 class Bbox:
     """ Comparator for bounding boxes.
     """