Fix ArtifactFileField.pre_save spurious rejection when MEDIA_ROOT is empty

CHANGES/8041.bugfix

@@ -0,0 +1 @@
+Fixed ``ArtifactFileField.pre_save`` spuriously rejecting artifact uploads whose filenames start with ``artifact`` when ``MEDIA_ROOT`` is empty (S3/Azure object-storage backends). The ``startswith`` guard now short-circuits when ``MEDIA_ROOT`` is empty, preventing false detection of fresh uploads as already-stored artifacts.

pulpcore/app/models/fields.py

@@ -70,7 +70,12 @@ def pre_save(self, model_instance, add):
             artifact_storage_path,
             os.path.join(settings.MEDIA_ROOT, artifact_storage_path),
         ]
-        is_in_artifact_storage = file.name.startswith(os.path.join(settings.MEDIA_ROOT, "artifact"))
+        # Guard against empty MEDIA_ROOT (object-storage backends such as S3/Azure set it to ""),
+        # where os.path.join("", "artifact") == "artifact" and any filename starting with
+        # "artifact" would be falsely detected as already residing in artifact storage.
+        is_in_artifact_storage = bool(settings.MEDIA_ROOT) and file.name.startswith(
+            os.path.join(settings.MEDIA_ROOT, "artifact")
+        )
 
         if not already_in_place and is_in_artifact_storage:
             raise ValueError(

pulpcore/tests/functional/api/test_artifact_presave_gh8041.py

@@ -0,0 +1,40 @@
+"""
+Regression test for https://github.com/pulp/pulpcore/issues/8041
+
+``ArtifactFileField.pre_save`` used a raw ``startswith`` against ``settings.MEDIA_ROOT``
+to detect files already in artifact storage. When ``MEDIA_ROOT`` is ``""``
+(S3/Azure object-storage backends), ``os.path.join("", "artifact") == "artifact"``,
+so any upload whose filename started with ``"artifact"`` was falsely detected as
+already-stored and raised ``ValueError`` → HTTP 500.
+"""
+
+import os
+
+import pytest
+
+
+@pytest.mark.parametrize(
+    "filename",
+    [
+        "artifact-foo-1.0-1.noarch.rpm",
+        "artifact-bar.tar.gz",
+    ],
+)
+def test_artifact_upload_artifact_prefix_filename_when_media_root_empty(
+    pulpcore_bindings, tmp_path, pulp_settings, filename
+):
+    """Upload a file whose name starts with ``artifact`` — must succeed on object-storage backends.
+
+    This test only applies when ``MEDIA_ROOT`` is empty (object-storage backends such
+    as S3 and Azure). On filesystem backends the bug does not occur, so the test is
+    skipped to avoid false positives.
+    """
+    if pulp_settings.MEDIA_ROOT:
+        pytest.skip("Bug GH-8041 only affects backends where MEDIA_ROOT is empty (S3/Azure).")
+
+    temp_file = tmp_path / filename
+    temp_file.write_bytes(os.urandom(32))
+
+    # Before the fix this raised HTTP 500 (ValueError in ArtifactFileField.pre_save).
+    artifact = pulpcore_bindings.ArtifactsApi.create(str(temp_file))
+    assert artifact.pulp_href is not None