Do not attempt to use expanded prefix if it is not found in importmap

linkml_runtime/utils/context_utils.py

@@ -66,11 +66,12 @@ def map_import(importmap: Dict[str, str], namespaces: Callable[[None], "Namespac
         # the importmap may contain mappings for prefixes
         prefix, lname = sname.split(':', 1)
         prefix += ':'
-        expanded_prefix = importmap.get(prefix, prefix)
-        if expanded_prefix.startswith("http"):
-            sname = expanded_prefix + lname
-        else:
-            sname = os.path.join(expanded_prefix, lname)
+        expanded_prefix = importmap.get(prefix)
+        if expanded_prefix is not None:
+            if expanded_prefix.startswith("http"):
+                sname = expanded_prefix + lname
+            else:
+                sname = os.path.join(expanded_prefix, lname)
     sname = importmap.get(sname, sname)  # Import map may use CURIE
     sname = str(namespaces().uri_for(sname)) if ':' in sname else sname
     return importmap.get(sname, sname)  # It may also use URI or other forms

tests/test_utils/test_schemaview.py

@@ -545,7 +545,7 @@ def test_non_linkml_remote_import(self):
             prefixes=[
                 Prefix(
                     prefix_prefix="foo",
-                    prefix_reference="https://w3id.org/linkml"
+                    prefix_reference="https://w3id.org/linkml/"
                 )
             ],
             imports=[