update prefix generation function

keep vowels but remove all punctuation characters as per #287

prez/services/curie_functions.py

@@ -1,5 +1,6 @@
 import logging
 import re
+import string
 from urllib.parse import urlparse
 
 from aiocache import caches
@@ -35,10 +36,10 @@ def namespace_registered(namespace):
 def valid_prefix(prefix: str):
     """For turtle serialization, as per https://www.w3.org/TR/turtle/#grammar-production-PN_PREFIX"""
     valid = True
-    PN_CHARS_BASE = r"([A-Z]|[a-z]|[\u00C0-\u00D6]|[\u00D8-\u00F6]|[\u00F8-\u02FF]|[\u0370-\u037D]|[\u037F-\u1FFF]|[\u200C-\u200D]|[\u2070-\u218F]|[\u2C00-\u2FEF]|[\u3001-\uD7FF]|[\uF900-\uFDCF]|[\uFDF0-\uFFFD]|[\U00010000-\U000EFFFF])"
-    PN_CHARS_U = rf"({PN_CHARS_BASE}|_)"
-    PN_CHARS = rf"({PN_CHARS_U}|-|[0-9]|\u00B7|[\u0300-\u036F]|[\u203F-\u2040])"
-    PN_PREFIX = rf"({PN_CHARS_BASE}(({PN_CHARS}|.)*{PN_CHARS})?)"
+    PN_CHARS_BASE = "([A-Z]|[a-z]|[\u00C0-\u00D6]|[\u00D8-\u00F6]|[\u00F8-\u02FF]|[\u0370-\u037D]|[\u037F-\u1FFF]|[\u200C-\u200D]|[\u2070-\u218F]|[\u2C00-\u2FEF]|[\u3001-\uD7FF]|[\uF900-\uFDCF]|[\uFDF0-\uFFFD]|[\U00010000-\U000EFFFF])"
+    PN_CHARS_U = f"({PN_CHARS_BASE}|_)"
+    PN_CHARS = f"({PN_CHARS_U}|-|[0-9]|\u00B7|[\u0300-\u036F]|[\u203F-\u2040])"
+    PN_PREFIX = f"({PN_CHARS_BASE}(({PN_CHARS}|.)*{PN_CHARS})?)"
     matches = re.match(PN_PREFIX, prefix)
     if not matches:
         valid = False
@@ -57,20 +58,17 @@ def generate_new_prefix(uri):
 
     split_prefix_path = ns[:-1].rsplit("/", 1)
     if len(split_prefix_path) > 1:
-        to_generate_prefix_from = split_prefix_path[-1].lower()
-        # attempt to just use the last part of the path prior to the fragment or "identifier"
-        if len(to_generate_prefix_from) <= 6:
-            proposed_prefix = to_generate_prefix_from
-            if not prefix_registered(proposed_prefix):
-                prefix_graph.bind(proposed_prefix, ns)
-                return
-        # otherwise, remove vowels to reduce length
-        proposed_prefix = "".join(
-            [c for c in to_generate_prefix_from if c not in "aeiou!@#$%^&*()_+-=,."]
+        path_part = split_prefix_path[-1]
+        # generate a prefix using the last part of the path prior to the fragment or 'identifier'
+        # converts to lowercase and removes punctuation characters
+        proposed_prefix = (
+            path_part
+            .lower()
+            .translate(str.maketrans("", "", string.punctuation))
         )
         if not valid_prefix(proposed_prefix):
-            # if we still can't get a nice prefix. use an ugly but valid one using a hash of the IRI
-            proposed_prefix = f"ns{hash(to_generate_prefix_from)}"
+            # if the generated prefix is not valid use an ugly but valid one by hashing the last part of the uri
+            proposed_prefix = f"ns{hash(path_part)}"
         if not prefix_registered(proposed_prefix):
             prefix_graph.bind(proposed_prefix, ns)
             return