stats compat API: return "id" lowercase

We use the same endpoint for libpod and docker compat API. However as
reported docker returns "id" lowercase. Because we cannot break the
libpod API right now keep the output for the libpod endpoint and only
change the docker one.

To do so simply use two types that we can cast with different JSON tags.

Fixes #17869

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

pkg/api/handlers/compat/containers_stats.go

@@ -202,7 +202,14 @@ streamLabel: // A label to flatten the scope
 			Networks: net,
 		}
 
-		if err := coder.Encode(s); err != nil {
+		var jsonOut interface{}
+		if utils.IsLibpodRequest(r) {
+			jsonOut = s
+		} else {
+			jsonOut = DockerStatsJSON(s)
+		}
+
+		if err := coder.Encode(jsonOut); err != nil {
 			logrus.Errorf("Unable to encode stats: %v", err)
 			return
 		}

pkg/api/handlers/compat/types.go

@@ -53,3 +53,16 @@ type StatsJSON struct {
 	// Networks request version >=1.21
 	Networks map[string]docker.NetworkStats `json:"networks,omitempty"`
 }
+
+// DockerStatsJSON is the same as StatsJSON except for the lowercase
+// "id" in the JSON tag. This is needed for docker compat but we should
+// not change the libpod API output for backwards compat reasons.
+type DockerStatsJSON struct {
+	Stats
+
+	Name string `json:"name,omitempty"`
+	ID   string `json:"id,omitempty"`
+
+	// Networks request version >=1.21
+	Networks map[string]docker.NetworkStats `json:"networks,omitempty"`
+}

test/apiv2/20-containers.at

@@ -113,7 +113,13 @@ if root; then
     podman run --name $CTRNAME -d -m 512m -v /tmp:/tmp $IMAGE top
 
     t GET libpod/containers/$CTRNAME/stats?stream=false 200 \
-    .memory_stats.limit=536870912
+    .memory_stats.limit=536870912 \
+    .Id~[0-9a-f]\\{64\\}
+
+    # Make sure docker compat endpoint shows "id" lowercase
+    t GET containers/$CTRNAME/stats?stream=false 200 \
+    .memory_stats.limit=536870912 \
+    .id~[0-9a-f]\\{64\\}
 
     podman rm -f $CTRNAME
 fi