Return empty purl fields in purl_to_lookups

    * Add new test

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

src/packageurl/contrib/django/utils.py

@@ -28,7 +28,7 @@
 from packageurl import PackageURL
 
 
-def purl_to_lookups(purl_str, encode=True):
+def purl_to_lookups(purl_str, encode=True, with_empty_values=False, empty=None):
     """
     Return a lookups dict built from the provided `purl` string.
     Those lookups can be used as QuerySet filters.
@@ -41,8 +41,15 @@ def purl_to_lookups(purl_str, encode=True):
     except ValueError:
         return  # Not a valid PackageURL
 
-    package_url_dict = package_url.to_dict(encode=encode)
-    return without_empty_values(package_url_dict)
+    package_url_dict = package_url.to_dict(
+        encode=encode,
+        empty=empty
+    )
+
+    if with_empty_values:
+        return package_url_dict
+    else:
+        return without_empty_values(package_url_dict)
 
 
 def without_empty_values(input_dict):
@@ -54,4 +61,6 @@ def without_empty_values(input_dict):
     """
     empty_values = ([], (), {}, "", None)
 
-    return {key: value for key, value in input_dict.items() if value not in empty_values}
+    return {
+        key: value for key, value in input_dict.items() if value not in empty_values
+    }

tests/contrib/test_utils.py

@@ -53,3 +53,34 @@ def test_purl_to_lookups_with_encode():
         "version": "0",
         "qualifiers": "arch=aarch64&distroversion=edge&reponame=main",
     }
+
+
+def test_purl_to_lookups_with_empty_values():
+    assert purl_to_lookups(
+        purl_str="pkg:alpine/openssl",
+        encode=True,
+        with_empty_values=True
+    ) == {
+        "type": "alpine",
+        "namespace": None,
+        "name": "openssl",
+        "version": None,
+        "qualifiers": None,
+        "subpath": None,
+    }
+
+
+def test_purl_to_lookups_with_empty_values_replaced():
+    assert purl_to_lookups(
+        purl_str="pkg:alpine/openssl",
+        encode=True,
+        with_empty_values=True,
+        empty=""
+    ) == {
+        "type": "alpine",
+        "namespace": "",
+        "name": "openssl",
+        "version": "",
+        "qualifiers": "",
+        "subpath": "",
+    }