kubectl: Fix in-cluster config not loaded on flags

tchap · tchap · commit 58ea7d6c2c2e · 2025-05-27T01:00:17.000+02:00
In-cluster config is now being skipped when certain command line flags
are specified, like --request-timeout. This is now fixed and in-cluster
config is loaded even when such a flag is specified.
diff --git a/staging/src/k8s.io/client-go/tools/clientcmd/merged_client_builder.go b/staging/src/k8s.io/client-go/tools/clientcmd/merged_client_builder.go
@@ -109,9 +109,17 @@ func (config *DeferredLoadingClientConfig) ClientConfig() (*restclient.Config, e
 			return nil, err
 		}
 	case mergedConfig != nil:
-		// the configuration is valid, but if this is equal to the defaults we should try
-		// in-cluster configuration
-		if !config.loader.IsDefaultConfig(mergedConfig) {
+		// The configuration is valid, but we should try in-cluster configuration if the merged config is empty.
+		// You may feel like using config.loader.IsDefaultConfig(mergedConfig), but that does not work.
+		// The loaded config becomes non-default as soon as any override is used, immediately disabling in-cluster.
+		// So for our purpose, the loaded config is default as long as it is empty.
+		c, err := mergedClientConfig.RawConfig()
+		if err != nil {
+			return nil, err
+		}
+
+		// Return the merged config when it's not empty.
+		if len(c.Contexts) != 0 || len(c.Clusters) != 0 || len(c.AuthInfos) != 0 {
 			return mergedConfig, nil
 		}
 	}
