[processor/k8sattributes] allow metadata extractions to be empty list

.chloggen/k8sattribute-processor-null-metadata.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: processor/k8sattributes
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: allow metadata extractions to be null
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [14452]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

processor/k8sattributesprocessor/options.go

@@ -125,6 +125,9 @@ func enabledAttributes() (attributes []string) {
 // If no fields explicitly provided, the defaults are pulled from metadata.yaml.
 func withExtractMetadata(fields ...string) option {
 	return func(p *kubernetesprocessor) error {
+		if fields == nil {
+			return nil
+		}
 		if len(fields) == 0 {
 			fields = enabledAttributes()
 		}