Add clarifying comment explaining e.Metadata check

Signed-off-by: Enis Inan <[email protected]>

cmd/docs.go

@@ -65,6 +65,10 @@ func docsMain(cmd *cobra.Command, args []string) exitCode {
 	//
 	// if the entry has any supported attributes. Otherwise, it prints an appropriate
 	// note then prints the attributes/metadata description.
+	//
+	// NOTE: If the entry has attributes but doesn't have any partial metadata, then
+	// entry.Metadata contains all of the attributes so this check still works. See
+	// plugin.PartialMetadata's comments for more details.
 	if len(entry.Metadata) > 0 {
 		addSection(docs, stringifySupportedAttributes(path, entry))
 	}

plugin/methodWrappers.go

@@ -184,7 +184,9 @@ func Size(ctx context.Context, e Entry) (uint64, error) {
 }
 
 // PartialMetadata returns the entry's partial metadata, a subset of the entry's
-// metadata that is typically provided by the plugin API's List endpoint.
+// metadata that is typically provided by the plugin API's List endpoint. If the
+// entry didn't specify any partial metadata, then this returns Attributes(e).ToMap()
+// to enforce the "attributes are a subset of the partial metadata" invariant.
 func PartialMetadata(e Entry) JSONObject {
 	return e.eb().partialMetadata()
 }