empty lists cause error about missing metadata

[docwhat]

When a kind: List is empty (items contains no objects) then kubeval incorrectly complains about a missing metadata key.

❯ cat empty-list.yaml
---
apiVersion: v1
kind: List
items: []
❯ cat empty-list.yaml | kubeval
ERR  - stdin: Missing 'metadata' key
❯ kubeval --version
Version: 0.15.0
Commit: df50ea7fd4fd202458002a40a6a39ffbb3125bad
Date: 2020-04-14T09:32:50Z

[docwhat]

Here's a quick patch to add a test:

diff --git a/fixtures/list_empty_valid.yaml b/fixtures/list_empty_valid.yaml
new file mode 100644
index 0000000..2276fbb
--- /dev/null
+++ b/fixtures/list_empty_valid.yaml
@@ -0,0 +1,4 @@
+---
+apiVersion: v1
+kind: List
+items: []
\ No newline at end of file
diff --git a/kubeval/kubeval_test.go b/kubeval/kubeval_test.go
index d8132d7..b9c9be1 100644
--- a/kubeval/kubeval_test.go
+++ b/kubeval/kubeval_test.go
@@ -34,6 +34,7 @@ func TestValidateValidInputs(t *testing.T) {
 		"extra_property.yaml",
 		"full_domain_group.yaml",
 		"unconventional_keys.yaml",
+		"list_empty_valid.yaml",
 		"list_valid.yaml",
 		"same-object-different-namespace.yaml",
 		"same-object-different-namespace-default.yaml",

[yannh]

@docwhat This page seems to say that the metadata field is mandatory? https://kubernetes.io/docs/concepts/overview/working-with-objects/kubernetes-objects/#required-fields

[docwhat]

Unfortunately, this isn't clearly documented. My thinking is thus:

Based on kubernetes/kubectl#837, kind: List is just union of all the kind: *List types. In 1.19 all the kind: *List docs have metadata as type ObjectMeta. The docs for ObjectMeta says:

ObjectMeta is metadata that all persisted resources must have, which includes all objects users must create.

All the Lists are not persisted; there is no List object stored in the cluster.

[pgold30]

@docwhat hitting this issue now , you know if your fix is going to be merged ?

[docwhat]

You'd have to ask the Authors. I'm just a external user like yourself. 😜