chore: add empty list check in the get_common_purl_from_artifact_purls function

Signed-off-by: Nathan Nguyen <[email protected]>

Author: nathanwn

src/macaron/vsa/vsa.py

@@ -156,6 +156,9 @@ def get_common_purl_from_artifact_purls(purl_strs: Iterable[str]) -> str | None:
     except ValueError:
         return None
 
+    if len(purls) == 0:
+        return None
+
     purl_type = purls[0].type
     namespace = purls[0].namespace
     name = purls[0].name

tests/vsa/test_vsa.py

@@ -6,7 +6,7 @@
 
 import pytest
 
-from macaron.vsa.vsa import get_components_passing_policy
+from macaron.vsa.vsa import get_common_purl_from_artifact_purls, get_components_passing_policy
 
 
 @pytest.mark.parametrize(
@@ -192,3 +192,39 @@ def test_invalid_subject_verification_result(
 ) -> None:
     """Test the ``get_components_passing_policy`` in cases where the result should be ``None``."""
     assert get_components_passing_policy(policy_result) is None
+
+
+@pytest.mark.parametrize(
+    ("purl_strs", "expected_purl"),
+    [
+        pytest.param(
+            [
+                "pkg:maven/com.fasterxml.jackson/[email protected]?type=jar",
+                "pkg:maven/com.fasterxml.jackson/[email protected]?type=javadoc",
+                "pkg:maven/com.fasterxml.jackson/[email protected]?type=java-source",
+                "pkg:maven/com.fasterxml.jackson/[email protected]?type=pom",
+            ],
+            "pkg:maven/com.fasterxml.jackson/[email protected]",
+            id="Common PURL exists",
+        ),
+        pytest.param(
+            [
+                "pkg:maven/com.fasterxml.jackson/[email protected]?type=jar",
+                "pkg:maven/com.fasterxml.jackson/[email protected]?type=jar",
+            ],
+            None,
+            id="Common PURL does not exist",
+        ),
+        pytest.param(
+            [],
+            None,
+            id="Common PURL does not exist",
+        ),
+    ],
+)
+def test_get_common_purl_from_artifact_purl(
+    purl_strs: list[str],
+    expected_purl: str | None,
+) -> None:
+    """Test the ``get_common_purl_from_artifact_purls`` function."""
+    assert get_common_purl_from_artifact_purls(purl_strs) == expected_purl