From b5a276ea6476232f4b625c9b9aaf6a9ce41e64e7 Mon Sep 17 00:00:00 2001
From: Nalin Dahyabhai <nalin@redhat.com>
Date: Tue, 24 Sep 2019 16:39:30 -0400
Subject: [PATCH] ImageSize: don't get tripped up by images with no layers

Images don't have to have layers, so they don't have to have top layers,
and we shouldn't return an error when attempting to determine the size
of such an image.

Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>
---
 cmd/containers-storage/create.go |  7 +++++--
 store.go                         |  6 ++++--
 tests/image.bats                 | 26 ++++++++++++++++++++++++++
 3 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/cmd/containers-storage/create.go b/cmd/containers-storage/create.go
index 8414e18aa..197824512 100644
--- a/cmd/containers-storage/create.go
+++ b/cmd/containers-storage/create.go
@@ -148,7 +148,10 @@ func createImage(flags *mflag.FlagSet, action string, m storage.Store, args []st
 		}
 		paramMetadata = string(b)
 	}
-	layer := args[0]
+	layer := ""
+	if len(args) > 0 {
+		layer = args[0]
+	}
 	imageOptions := &storage.ImageOptions{
 		Digest: digest.Digest(paramDigest),
 	}
@@ -251,7 +254,7 @@ func init() {
 		names:       []string{"create-image", "createimage"},
 		optionsHelp: "[options [...]] topLayerNameOrID",
 		usage:       "Create a new image using layers",
-		minArgs:     1,
+		minArgs:     0,
 		maxArgs:     1,
 		action:      createImage,
 		addFlags: func(flags *mflag.FlagSet, cmd *command) {
diff --git a/store.go b/store.go
index dd3405212..54400a4f1 100644
--- a/store.go
+++ b/store.go
@@ -1587,10 +1587,12 @@ func (s *store) ImageSize(id string) (int64, error) {
 		return -1, errors.Wrapf(ErrImageUnknown, "error locating image with ID %q", id)
 	}
 
-	// Start with a list of the image's top layers.
+	// Start with a list of the image's top layers, if it has any.
 	queue := make(map[string]struct{})
 	for _, layerID := range append([]string{image.TopLayer}, image.MappedTopLayers...) {
-		queue[layerID] = struct{}{}
+		if layerID != "" {
+			queue[layerID] = struct{}{}
+		}
 	}
 	visited := make(map[string]struct{})
 	// Walk all of the layers.
diff --git a/tests/image.bats b/tests/image.bats
index 5eec5c191..d38607f0c 100644
--- a/tests/image.bats
+++ b/tests/image.bats
@@ -28,3 +28,29 @@ load helpers
 	[[ "$output" =~ "Data: random1" ]]
 	[[ "$output" =~ "Data: random2" ]]
 }
+
+@test "layerless-image" {
+	# Add an image with no specified layers.
+	name=wonderful-image
+	run storage --debug=false create-image --name $name
+	[ "$status" -eq 0 ]
+	[ "$output" != "" ]
+	image=${lines[0]}
+
+	# Add a couple of big data items.
+	createrandom ${TESTDIR}/random1
+	createrandom ${TESTDIR}/random2
+	storage set-image-data -f ${TESTDIR}/random1 $image random1
+	storage set-image-data -f ${TESTDIR}/random2 $image random2
+
+	# Get information about the image, and make sure the ID, name, and data names were preserved,
+	# and that we can properly report its disk usage.
+	run storage image $image
+	echo "$output"
+	[ "$status" -eq 0 ]
+	[[ "$output" =~ "ID: $image" ]]
+	[[ "$output" =~ "Name: $name" ]]
+	[[ "$output" =~ "Data: random1" ]]
+	[[ "$output" =~ "Data: random2" ]]
+	[[ "$output" =~ "Size: 512" ]]
+}