Add checks in create_purl_map

Signed-off-by: Jono Yang <jyang@nexb.com>

Author: JonoYang

src/purl_validator/__init__.py

@@ -35,11 +35,25 @@
 
 
 def create_purl_map(purls):
-    # purls must be sorted and converted to bytes before going into the Map
-    prepared_purls = [(bytes(purl, "utf-8"), 1) for purl in sorted(purls)]
+    # Ensure elements of `purls` are strings:
+    purl_strs = []
+    for purl in purls:
+        if not isinstance(purl, (PackageURL, str)):
+            raise ValueError(f"invalid purl in `purls`: {purl}")
+        if isinstance(purl, PackageURL):
+            purl_str = purl.to_string()
+        else:
+            purl_str = purl
+        purl_strs.append(purl_str)
+
+    # purl strs must be sorted and converted to bytes before going into the Map
+    prepared_purl_strs = [(bytes(purl_str, "utf-8"), 1) for purl_str in sorted(purl_strs)]
+
+    # create map
     temp_dir = fileutils.get_temp_dir()
     map_loc = Path(temp_dir) / "purls.map"
-    ducer.Map.build(map_loc, prepared_purls)
+    ducer.Map.build(map_loc, prepared_purl_strs)
+
     return map_loc