From 77a2bbb1c0df2536638e5a9030cda05d6524513e Mon Sep 17 00:00:00 2001
From: Valentin Rothberg <rothberg@redhat.com>
Date: Wed, 16 Oct 2019 10:30:57 +0200
Subject: stats: list all running containers unless specified otherwise

Unless specified otherwise by --all, --latest or via arguments, list all
running containers.  This matches the behaviour of Docker and is also
illustrated in the man pages where containers and options are marked to
be optional.

Fixes: #4274
Signed-off-by: Valentin Rothberg <rothberg@redhat.com>
---
 cmd/podman/stats.go       |  7 +------
 test/e2e/stats_test.go    | 11 +++++++++++
 test/system/015-help.bats |  8 +++++---
 3 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/cmd/podman/stats.go b/cmd/podman/stats.go
index 25514ec75..f8c476386 100644
--- a/cmd/podman/stats.go
+++ b/cmd/podman/stats.go
@@ -35,7 +35,7 @@ var (
 
 	statsDescription = "Display percentage of CPU, memory, network I/O, block I/O and PIDs for one or more containers."
 	_statsCommand    = &cobra.Command{
-		Use:   "stats [flags] CONTAINER [CONTAINER...]",
+		Use:   "stats [flags] [CONTAINER...]",
 		Short: "Display a live stream of container resource usage statistics",
 		Long:  statsDescription,
 		RunE: func(cmd *cobra.Command, args []string) error {
@@ -44,9 +44,6 @@ var (
 			statsCommand.Remote = remoteclient
 			return statsCmd(&statsCommand)
 		},
-		Args: func(cmd *cobra.Command, args []string) error {
-			return checkAllAndLatest(cmd, args, false)
-		},
 		Example: `podman stats --all --no-stream
   podman stats ctrID
   podman stats --no-stream --format "table {{.ID}} {{.Name}} {{.MemUsage}}" ctrID`,
@@ -92,8 +89,6 @@ func statsCmd(c *cliconfig.StatsValues) error {
 
 	if ctr > 1 {
 		return errors.Errorf("--all, --latest and containers cannot be used together")
-	} else if ctr == 0 {
-		return errors.Errorf("you must specify --all, --latest, or at least one container")
 	}
 
 	runtime, err := libpodruntime.GetRuntime(getContext(), &c.PodmanCommand)
diff --git a/test/e2e/stats_test.go b/test/e2e/stats_test.go
index 4000ab33a..fbf7c9920 100644
--- a/test/e2e/stats_test.go
+++ b/test/e2e/stats_test.go
@@ -11,6 +11,8 @@ import (
 	. "github.com/onsi/gomega"
 )
 
+// TODO: we need to check the output. Currently, we only check the exit codes
+// which is not enough.
 var _ = Describe("Podman stats", func() {
 	var (
 		tempdir    string
@@ -61,6 +63,15 @@ var _ = Describe("Podman stats", func() {
 		Expect(session.ExitCode()).To(Equal(0))
 	})
 
+	It("podman stats on all running containers", func() {
+		session := podmanTest.RunTopContainer("")
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		session = podmanTest.Podman([]string{"stats", "--no-stream"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+	})
+
 	It("podman stats only output cids", func() {
 		session := podmanTest.RunTopContainer("")
 		session.WaitWithDefaultTimeout()
diff --git a/test/system/015-help.bats b/test/system/015-help.bats
index a987f04bc..fd4be87b2 100644
--- a/test/system/015-help.bats
+++ b/test/system/015-help.bats
@@ -55,9 +55,11 @@ function check_help() {
 
         # If usage has required arguments, try running without them
         if expr "$usage" : '.*\[flags\] [A-Z]' >/dev/null; then
-            dprint "podman $@ $cmd (without required args)"
-            run_podman 125 "$@" $cmd
-            is "$output" "Error:"
+            if [ "$cmd" != "stats"]; then
+                dprint "podman $@ $cmd (without required args)"
+                run_podman 125 "$@" $cmd
+                is "$output" "Error:"
+            fi
         fi
 
         count=$(expr $count + 1)
-- 
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