Fix content app not showing file size for 0 byte files

fixes: pulp#5100

CHANGES/5100.bugfix

@@ -0,0 +1 @@
+Fixed content directory listing not showing file size for 0-byte files.

pulpcore/content/handler.py

@@ -421,7 +421,7 @@ def render_html(directory_list, path="", dates=None, sizes=None):
 {% else -%}
 {% set date = "" -%}
 {% endif -%}
-{% if sizes.get(name, "") -%}
+{% if name in sizes -%}
 {% set size | filesizeformat -%}
 {{ sizes.get(name) }}
 {% endset -%}

pulpcore/tests/functional/api/using_plugin/test_content_directory.py

@@ -12,3 +12,33 @@ def test_hidden_distros(file_distribution_factory, pulp_content_url, http_get):
         assert content.count(f'a href="{d.base_path}/"') == 1
     for d in hidden:
         assert content.count(f'a href="{d.base_path}/"') == 0
+
+
+@pytest.mark.parallel
+def test_zero_byte_file_listing(
+    file_bindings,
+    file_distribution_factory,
+    file_repo_with_auto_publish,
+    random_artifact_factory,
+    http_get,
+    monitor_task,
+    pulpcore_bindings,
+):
+    try:
+        zero_file = random_artifact_factory(size=0)
+    except pulpcore_bindings.ApiException:
+        zero_file = pulpcore_bindings.ArtifactsApi.list(
+            sha256="e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+        ).results[0]
+    task = file_bindings.ContentFilesApi.create(
+        relative_path="zero",
+        artifact=zero_file.pulp_href,
+        repository=file_repo_with_auto_publish.pulp_href,
+    ).task
+    monitor_task(task)
+    distribution = file_distribution_factory(repository=file_repo_with_auto_publish.pulp_href)
+
+    response = http_get(distribution.base_url)
+    z_line = [i for i in response.decode("utf-8").split("\n") if i.startswith('<a href="zero">')]
+    assert len(z_line) == 1
+    assert z_line[0].endswith("0 Bytes")