play kube: fix args/command handling

when neither yaml.Args nor yaml.Command are specified, we should use the entrypoint and cmd from the image.

update the tests to cover this and another case (both args and command are specified).
use the registry image instead of redis, as it has both an entrypoint and command specified.
update the documentation around this handling to hopefully prevent regressions and confusion.

Signed-off-by: Peter Hunt <pehunt@redhat.com>

pkg/specgen/generate/kube/kube.go

@@ -112,11 +112,18 @@ func ToSpecGen(ctx context.Context, containerYAML v1.Container, iid string, newI
 		return nil, err
 	}
 	s.WorkDir = "/"
+	// We will use "Docker field name" internally here to avoid confusion
+	// and reference the "Kubernetes field name" when referencing the YAML
+	// ref: https://kubernetes.io/docs/tasks/inject-data-application/define-command-argument-container/#notes
+	entrypoint := []string{}
+	cmd := []string{}
 	if imageData != nil && imageData.Config != nil {
 		if imageData.Config.WorkingDir != "" {
 			s.WorkDir = imageData.Config.WorkingDir
 		}
-		s.Command = imageData.Config.Entrypoint
+		// Pull entrypoint and cmd from image
+		entrypoint = imageData.Config.Entrypoint
+		cmd = imageData.Config.Cmd
 		s.Labels = imageData.Config.Labels
 		if len(imageData.Config.StopSignal) > 0 {
 			stopSignal, err := util.ParseSignal(imageData.Config.StopSignal)
@@ -126,13 +133,18 @@ func ToSpecGen(ctx context.Context, containerYAML v1.Container, iid string, newI
 			s.StopSignal = &stopSignal
 		}
 	}
+	// If only the yaml.Command is specified, set it as the entrypoint and drop the image Cmd
 	if len(containerYAML.Command) != 0 {
-		s.Command = containerYAML.Command
+		entrypoint = containerYAML.Command
+		cmd = []string{}
 	}
-	// doc https://kubernetes.io/docs/tasks/inject-data-application/define-command-argument-container/#notes
+	// Only override the cmd field if yaml.Args is specified
+	// Keep the image entrypoint, or the yaml.command if specified
 	if len(containerYAML.Args) != 0 {
-		s.Command = append(s.Command, containerYAML.Args...)
+		cmd = containerYAML.Args
 	}
+
+	s.Command = append(entrypoint, cmd...)
 	// FIXME,
 	// we are currently ignoring imageData.Config.ExposedPorts
 	if containerYAML.WorkingDir != "" {

test/e2e/play_kube_test.go

@@ -820,8 +820,28 @@ var _ = Describe("Podman play kube", func() {
 		Expect(inspect.OutputToString()).To(ContainSubstring(correctCmd))
 	})
 
+	// If you do not supply command or args for a Container, the defaults defined in the Docker image are used.
+	It("podman play kube test correct args and cmd when not specified", func() {
+		pod := getPod(withCtr(getCtr(withImage(registry), withCmd(nil), withArg(nil))))
+		err := generateKubeYaml("pod", pod, kubeYaml)
+		Expect(err).To(BeNil())
+
+		kube := podmanTest.Podman([]string{"play", "kube", kubeYaml})
+		kube.WaitWithDefaultTimeout()
+		Expect(kube.ExitCode()).To(Equal(0))
+
+		inspect := podmanTest.Podman([]string{"inspect", getCtrNameInPod(pod), "--format", "'{{ .Config.Cmd }}'"})
+		inspect.WaitWithDefaultTimeout()
+		Expect(inspect.ExitCode()).To(Equal(0))
+
+		// this image's ENTRYPOINT is `/entrypoint.sh` and it's COMMAND is `/etc/docker/registry/config.yml`
+		Expect(inspect.OutputToString()).To(ContainSubstring(`[/entrypoint.sh /etc/docker/registry/config.yml]`))
+	})
+
+	// If you supply a command but no args for a Container, only the supplied command is used.
+	// The default EntryPoint and the default Cmd defined in the Docker image are ignored.
 	It("podman play kube test correct command with only set command in yaml file", func() {
-		pod := getPod(withCtr(getCtr(withCmd([]string{"echo", "hello"}), withArg(nil))))
+		pod := getPod(withCtr(getCtr(withImage(registry), withCmd([]string{"echo", "hello"}), withArg(nil))))
 		err := generateKubeYaml("pod", pod, kubeYaml)
 		Expect(err).To(BeNil())
 
@@ -837,8 +857,9 @@ var _ = Describe("Podman play kube", func() {
 		Expect(inspect.OutputToString()).To(ContainSubstring(`[echo hello]`))
 	})
 
+	// If you supply only args for a Container, the default Entrypoint defined in the Docker image is run with the args that you supplied.
 	It("podman play kube test correct command with only set args in yaml file", func() {
-		pod := getPod(withCtr(getCtr(withImage(redis), withCmd(nil), withArg([]string{"echo", "hello"}))))
+		pod := getPod(withCtr(getCtr(withImage(registry), withCmd(nil), withArg([]string{"echo", "hello"}))))
 		err := generateKubeYaml("pod", pod, kubeYaml)
 		Expect(err).To(BeNil())
 
@@ -849,9 +870,27 @@ var _ = Describe("Podman play kube", func() {
 		inspect := podmanTest.Podman([]string{"inspect", getCtrNameInPod(pod), "--format", "'{{ .Config.Cmd }}'"})
 		inspect.WaitWithDefaultTimeout()
 		Expect(inspect.ExitCode()).To(Equal(0))
-		// this image's ENTRYPOINT is called `docker-entrypoint.sh`
-		// so result should be `docker-entrypoint.sh + withArg(...)`
-		Expect(inspect.OutputToString()).To(ContainSubstring(`[docker-entrypoint.sh echo hello]`))
+		// this image's ENTRYPOINT is `/entrypoint.sh`
+		// so result should be `/entrypoint.sh + withArg(...)`
+		Expect(inspect.OutputToString()).To(ContainSubstring(`[/entrypoint.sh echo hello]`))
+	})
+
+	// If you supply a command and args,
+	// the default Entrypoint and the default Cmd defined in the Docker image are ignored.
+	// Your command is run with your args.
+	It("podman play kube test correct command with both set args and cmd in yaml file", func() {
+		pod := getPod(withCtr(getCtr(withImage(registry), withCmd([]string{"echo"}), withArg([]string{"hello"}))))
+		err := generateKubeYaml("pod", pod, kubeYaml)
+		Expect(err).To(BeNil())
+
+		kube := podmanTest.Podman([]string{"play", "kube", kubeYaml})
+		kube.WaitWithDefaultTimeout()
+		Expect(kube.ExitCode()).To(Equal(0))
+
+		inspect := podmanTest.Podman([]string{"inspect", getCtrNameInPod(pod), "--format", "'{{ .Config.Cmd }}'"})
+		inspect.WaitWithDefaultTimeout()
+		Expect(inspect.ExitCode()).To(Equal(0))
+		Expect(inspect.OutputToString()).To(ContainSubstring(`[echo hello]`))
 	})
 
 	It("podman play kube test correct output", func() {