artifact mount: improve single blob behavior

If the artifact has a single blob then use the dst path directly as
mount in case it does not exist.

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

docs/source/markdown/options/mount.md

@@ -34,15 +34,20 @@ Options specific to type=**artifact**:
 
 The *src* argument contains the name of the artifact, which must already exist locally.
 The *dst* argument contains the target path, if the path in the container is a
-directory or does not exist the blob title (`org.opencontainers.image.title`
-annotation) will be used as filename and joined to the path. If the annotation
-does not exist the digest will be used as filename instead. This results in all blobs
-of the artifact mounted into the container at the given path.
+directory the blob title (`org.opencontainers.image.title` annotation) will be used as
+filename and joined to the path. If the annotation does not exist the digest will be
+used as filename instead. This results in all blobs of the artifact mounted into the
+container at the given path.
 
 However, if the *dst* path is an existing file in the container, then the blob will be
 mounted directly on it. This only works when the artifact contains a single blob
 or when either *digest* or *title* are specified.
 
+If the *dst* path does not already exist in the container then if the artifact contains
+a single blob it behaves like existing file case and mounts directly to that path.
+If the artifact has more than one blob it works like the existing directory case and
+mounts each blob as file within the *dst* path.
+
 Options specific to type=**volume**:
 
 - *ro*, *readonly*: *true* or *false* (default if unspecified: *false*).

libpod/container_internal_common.go

@@ -554,9 +554,12 @@ func (c *Container) generateSpec(ctx context.Context) (s *spec.Spec, cleanupFunc
 				return nil, nil, err
 			}
 
-			// Ignore the error, destIsFile will return false with errors so if the file does not exist
-			// we treat it as dir, the oci runtime will always create the target bind mount path.
-			destIsFile, _ := containerPathIsFile(c.state.Mountpoint, artifactMount.Dest)
+			destIsFile, err := containerPathIsFile(c.state.Mountpoint, artifactMount.Dest)
+			// When the file does not exists and the artifact has only a single blob to mount
+			// assume it is a file so we use the dest path as direct mount.
+			if err != nil && len(paths) == 1 && errors.Is(err, fs.ErrNotExist) {
+				destIsFile = true
+			}
 			if destIsFile && len(paths) > 1 {
 				return nil, nil, fmt.Errorf("artifact %q contains more than one blob and container path %q is a file", artifactMount.Source, artifactMount.Dest)
 			}

test/e2e/artifact_mount_test.go

@@ -29,7 +29,7 @@ var _ = Describe("Podman artifact mount", func() {
 			{
 				name:          "single artifact mount",
 				mountOpts:     "dst=/test",
-				containerFile: "/test/testfile",
+				containerFile: "/test",
 			},
 			{
 				name:          "single artifact mount on existing file",
@@ -44,7 +44,7 @@ var _ = Describe("Podman artifact mount", func() {
 			{
 				name:          "single artifact mount with digest",
 				mountOpts:     "dst=/data,digest=sha256:e9510923578af3632946ecf5ae479c1b5f08b47464e707b5cbab9819272a9752",
-				containerFile: "/data/sha256-e9510923578af3632946ecf5ae479c1b5f08b47464e707b5cbab9819272a9752",
+				containerFile: "/data",
 			},
 		}
 
@@ -104,21 +104,31 @@ var _ = Describe("Podman artifact mount", func() {
 				},
 			},
 			{
-				name:      "multi blob filter by title",
+				name:      "multi blob filter by title on non existing file",
 				mountOpts: "src=" + ARTIFACT_MULTI + ",dst=/test,title=test2",
 				containerFiles: []expectedFiles{
 					{
-						file:    "/test/test2",
+						file:    "/test",
+						content: artifactContent2,
+					},
+				},
+			},
+			{
+				name:      "multi blob filter by title on existing file",
+				mountOpts: "src=" + ARTIFACT_MULTI + ",dst=/tmp,title=test2",
+				containerFiles: []expectedFiles{
+					{
+						file:    "/tmp/test2",
 						content: artifactContent2,
 					},
 				},
 			},
 			{
 				name:      "multi blob filter by digest",
-				mountOpts: "src=" + ARTIFACT_MULTI + ",dst=/test,digest=sha256:8257bba28b9d19ac353c4b713b470860278857767935ef7e139afd596cb1bb2d",
+				mountOpts: "src=" + ARTIFACT_MULTI + ",dst=/tmp,digest=sha256:8257bba28b9d19ac353c4b713b470860278857767935ef7e139afd596cb1bb2d",
 				containerFiles: []expectedFiles{
 					{
-						file:    "/test/sha256-8257bba28b9d19ac353c4b713b470860278857767935ef7e139afd596cb1bb2d",
+						file:    "/tmp/sha256-8257bba28b9d19ac353c4b713b470860278857767935ef7e139afd596cb1bb2d",
 						content: artifactContent1,
 					},
 				},
@@ -152,12 +162,12 @@ var _ = Describe("Podman artifact mount", func() {
 		podmanTest.PodmanExitCleanly("artifact", "add", artifactName, artifactFile)
 
 		// FIXME: we need https://github.com/containers/container-selinux/pull/360 to fix the selinux access problem, until then disable it.
-		podmanTest.PodmanExitCleanly("run", "--security-opt=label=disable", "--name", ctrName, "-d", "--mount", "type=artifact,src="+artifactName+",dst=/test", ALPINE, "sleep", "100")
+		podmanTest.PodmanExitCleanly("run", "--security-opt=label=disable", "--name", ctrName, "-d", "--mount", "type=artifact,src="+artifactName+",dst=/tmp", ALPINE, "sleep", "100")
 
 		podmanTest.PodmanExitCleanly("artifact", "rm", artifactName)
 
 		// file must sill be readable after artifact removal
-		session := podmanTest.PodmanExitCleanly("exec", ctrName, "cat", "/test/"+artifactFileName)
+		session := podmanTest.PodmanExitCleanly("exec", ctrName, "cat", "/tmp/"+artifactFileName)
 		Expect(session.OutputToString()).To(Equal("hello world"))
 
 		// restart will fail if artifact does not exist
@@ -174,7 +184,7 @@ var _ = Describe("Podman artifact mount", func() {
 		podmanTest.PodmanExitCleanly("artifact", "add", artifactName, artifactFile, artifactFile2)
 		podmanTest.PodmanExitCleanly("start", ctrName)
 
-		session = podmanTest.PodmanExitCleanly("exec", ctrName, "cat", "/test/"+artifactFileName, "/test/"+artifactFile2Name)
+		session = podmanTest.PodmanExitCleanly("exec", ctrName, "cat", "/tmp/"+artifactFileName, "/tmp/"+artifactFile2Name)
 		Expect(session.OutputToString()).To(Equal("hello world second file"))
 	})