list: fix IsSet check for global root flag

list.go

@@ -114,7 +114,7 @@ func getContainers(context *cli.Context) ([]containerState, error) {
 	root := context.GlobalString("root")
 	list, err := os.ReadDir(root)
 	if err != nil {
-		if errors.Is(err, os.ErrNotExist) && context.IsSet("root") {
+		if errors.Is(err, os.ErrNotExist) && !context.GlobalIsSet("root") {
 			// Ignore non-existing default root directory
 			// (no containers created yet).
 			return nil, nil

tests/integration/list.bats

@@ -2,13 +2,22 @@
 
 load helpers
 
+# Default root directory for runc (as defined in main.go).
+RUNC_DEFAULT_ROOT="/run/runc"
+
 function setup() {
 	setup_busybox
 	ALT_ROOT="$ROOT/alt"
 	mkdir -p "$ALT_ROOT/state"
 }
 
 function teardown() {
+	# Restore default root if it was backed up by the
+	# "non-existent default root" test.
+	if [ -d "${RUNC_DEFAULT_ROOT}.bak" ]; then
+		rm -rf "$RUNC_DEFAULT_ROOT"
+		mv "${RUNC_DEFAULT_ROOT}.bak" "$RUNC_DEFAULT_ROOT"
+	fi
 	ROOT="$ALT_ROOT" teardown_bundle
 	unset ALT_ROOT
 	teardown_bundle
@@ -51,3 +60,48 @@ function teardown() {
 	[[ "${lines[0]}" == *[,][\{]"\"ociVersion\""[:]"\""*[0-9][\.]*[0-9][\.]*[0-9]*"\""[,]"\"id\""[:]"\"test_box2\""[,]"\"pid\""[:]*[0-9][,]"\"status\""[:]*"\"running\""[,]"\"bundle\""[:]*$bundle*[,]"\"rootfs\""[:]"\""*"\""[,]"\"created\""[:]*[0-9]*[\}]* ]]
 	[[ "${lines[0]}" == *[,][\{]"\"ociVersion\""[:]"\""*[0-9][\.]*[0-9][\.]*[0-9]*"\""[,]"\"id\""[:]"\"test_box3\""[,]"\"pid\""[:]*[0-9][,]"\"status\""[:]*"\"running\""[,]"\"bundle\""[:]*$bundle*[,]"\"rootfs\""[:]"\""*"\""[,]"\"created\""[:]*[0-9]*[\}][\]] ]]
 }
+
+@test "list with non-existent default root succeeds" {
+	# The default root /run/runc is only used when running as real
+	# root; rootless uses $XDG_RUNTIME_DIR/runc instead.
+	requires root unsafe # Modifies /run/runc.
+
+	# Back up and remove the default root to guarantee it
+	# doesn't exist. Restored in teardown.
+	[ -d "$RUNC_DEFAULT_ROOT" ] && mv "$RUNC_DEFAULT_ROOT" "${RUNC_DEFAULT_ROOT}.bak"
+
+	# Use ROOT="" so the runc wrapper doesn't pass --root,
+	# letting runc use its default root.
+	ROOT="" runc list
+	[ "$status" -eq 0 ]
+
+	ROOT="" runc list --format json
+	[ "$status" -eq 0 ]
+	[ "$output" = "null" ]
+
+	ROOT="" runc list -q
+	[ "$status" -eq 0 ]
+	[ "$output" = "" ]
+}
+
+@test "list with empty default root succeeds" {
+	# The default root /run/runc is only used when running as real
+	# root; rootless uses $XDG_RUNTIME_DIR/runc instead.
+	requires root unsafe # Modifies /run/runc.
+
+	# Ensure the default root exists but is empty.
+	mkdir -p "$RUNC_DEFAULT_ROOT"
+
+	# Use ROOT="" so the runc wrapper doesn't pass --root,
+	# letting runc use its default root.
+	ROOT="" runc list
+	[ "$status" -eq 0 ]
+
+	ROOT="" runc list --format json
+	[ "$status" -eq 0 ]
+	[ "$output" = "null" ]
+
+	ROOT="" runc list -q
+	[ "$status" -eq 0 ]
+	[ "$output" = "" ]
+}