kubectl diff: Print error when something goes wrong

pkg/kubectl/cmd/diff/diff.go

@@ -122,8 +122,7 @@ func (d *DiffProgram) getCommand(args ...string) exec.Cmd {
 
 // Run runs the detected diff program. `from` and `to` are the directory to diff.
 func (d *DiffProgram) Run(from, to string) error {
-	d.getCommand(from, to).Run() // Ignore diff return code
-	return nil
+	return d.getCommand(from, to).Run()
 }
 
 // Printer is used to print an object.
@@ -396,8 +395,5 @@ func RunDiff(f cmdutil.Factory, diff *DiffProgram, options *DiffOptions) error {
 		return err
 	}
 
-	// Error ignore on purpose. diff(1) for example, returns an error if there is any diff.
-	_ = differ.Run(diff)
-
-	return nil
+	return differ.Run(diff)
 }

test/cmd/diff.sh

@@ -27,12 +27,12 @@ run_kubectl_diff_tests() {
     kube::log::status "Testing kubectl diff"
 
     # Test that it works when the live object doesn't exist
-    output_message=$(kubectl diff -f hack/testdata/pod.yaml)
+    output_message=$(! kubectl diff -f hack/testdata/pod.yaml)
     kube::test::if_has_string "${output_message}" 'test-pod'
 
     kubectl apply -f hack/testdata/pod.yaml
 
-    output_message=$(kubectl diff -f hack/testdata/pod-changed.yaml)
+    output_message=$(! kubectl diff -f hack/testdata/pod-changed.yaml)
     kube::test::if_has_string "${output_message}" 'k8s.gcr.io/pause:3.0'
 
     kubectl delete -f  hack/testdata/pod.yaml