exporter: add tests for a directory with an idmap error

this test demonstrates the bug called out in
tonistiigi/fsutil#203

Currently, if a directory's UID can't be mapped to the host,
buildkit will export an invalid tarball.

Signed-off-by: Nick Santos <nick.santos@docker.com>

Author: nicks

exporter/local/fs_test.go

@@ -0,0 +1,169 @@
+package local
+
+import (
+	"context"
+	iofs "io/fs"
+	"os"
+	"path/filepath"
+	"runtime"
+	"testing"
+	"time"
+
+	"github.com/containerd/containerd/content/local"
+	"github.com/containerd/containerd/diff/apply"
+	"github.com/containerd/containerd/diff/walking"
+	ctdmetadata "github.com/containerd/containerd/metadata"
+	"github.com/containerd/containerd/namespaces"
+	"github.com/containerd/containerd/snapshots"
+	"github.com/containerd/containerd/snapshots/native"
+	"github.com/docker/docker/pkg/idtools"
+	"github.com/moby/buildkit/cache"
+	"github.com/moby/buildkit/cache/metadata"
+	"github.com/moby/buildkit/snapshot"
+	containerdsnapshot "github.com/moby/buildkit/snapshot/containerd"
+	"github.com/moby/buildkit/util/leaseutil"
+	"github.com/moby/buildkit/util/winlayers"
+	"github.com/pkg/errors"
+	"github.com/stretchr/testify/require"
+	bolt "go.etcd.io/bbolt"
+)
+
+func TestCreateFS_DirMissingFromIDMap(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		// The chown doesn't work quite the same on Windows, so skip this test.
+		t.Skip("Skipping test on Windows")
+	}
+
+	idmap := &idtools.IdentityMapping{
+		UIDMaps: []idtools.IDMap{
+			{ContainerID: 0, HostID: 0, Size: 1},
+		},
+		GIDMaps: []idtools.IDMap{
+			{ContainerID: 0, HostID: 0, Size: 1},
+		},
+	}
+
+	ctx := namespaces.WithNamespace(context.Background(), "buildkit-test")
+	cm, err := newCacheManager(ctx, t, idmap)
+	require.NoError(t, err)
+	sessionID := "sessionID"
+
+	active, err := cm.New(ctx, nil, nil, cache.CachePolicyRetain)
+	require.NoError(t, err)
+
+	m, err := active.Mount(ctx, false, nil)
+	require.NoError(t, err)
+
+	lm := snapshot.LocalMounter(m)
+	target, err := lm.Mount()
+	require.NoError(t, err)
+
+	_ = os.MkdirAll(filepath.Join(target, "dir"), 0755)
+
+	f, err := os.Create(filepath.Join(target, "dir", "test.txt"))
+	require.NoError(t, err)
+	_ = f.Close()
+
+	_ = os.MkdirAll(filepath.Join(target, "unmapped-dir"), 0755)
+	os.Chown(filepath.Join(target, "unmapped-dir"), 1001, 1001)
+
+	f, err = os.Create(filepath.Join(target, "unmapped-dir", "test.txt"))
+	require.NoError(t, err)
+	_ = f.Close()
+
+	lm.Unmount()
+
+	snap, err := active.Commit(ctx)
+	require.NoError(t, err)
+
+	activeRef, err := cm.Get(ctx, snap.ID(), nil)
+	require.NoError(t, err)
+
+	fs, _, err := CreateFS(ctx, sessionID, "k???", activeRef, nil, time.Now(), CreateFSOpts{})
+	require.NoError(t, err)
+	require.NotNil(t, fs)
+
+	p := []string{}
+	err = fs.Walk(context.Background(), ".", iofs.WalkDirFunc(func(path string, info iofs.DirEntry, err error) error {
+		p = append(p, path)
+		return nil
+	}))
+	require.NoError(t, err)
+	require.Equal(t, []string{
+		"dir",
+		filepath.Join("dir", "test.txt"),
+		// TODO(nicks): "unmapped-dir" should be included in the walk. It is not
+		// because of an upstream bug in fsutil. See:
+		// https://github.com/tonistiigi/fsutil/pull/203
+		//
+		// "unmapped-dir",
+		filepath.Join("unmapped-dir", "test.txt"),
+	}, p)
+}
+
+func newCacheManager(ctx context.Context, t *testing.T, idmap *idtools.IdentityMapping) (cm cache.Manager, err error) {
+	ns, ok := namespaces.Namespace(ctx)
+	if !ok {
+		return nil, errors.Errorf("namespace required for test")
+	}
+
+	tmpdir := t.TempDir()
+
+	snapshotter, err := native.NewSnapshotter(filepath.Join(tmpdir, "snapshots"))
+	if err != nil {
+		return nil, err
+	}
+
+	store, err := local.NewStore(tmpdir)
+	if err != nil {
+		return nil, err
+	}
+
+	db, err := bolt.Open(filepath.Join(tmpdir, "containerdmeta.db"), 0644, nil)
+	if err != nil {
+		return nil, err
+	}
+	t.Cleanup(func() {
+		require.NoError(t, db.Close())
+	})
+
+	sn := "native-snapshotter"
+	mdb := ctdmetadata.NewDB(db, store, map[string]snapshots.Snapshotter{
+		sn: snapshotter,
+	})
+	if err := mdb.Init(context.TODO()); err != nil {
+		return nil, err
+	}
+
+	lm := leaseutil.WithNamespace(ctdmetadata.NewLeaseManager(mdb), ns)
+	c := mdb.ContentStore()
+	applier := winlayers.NewFileSystemApplierWithWindows(c, apply.NewFileSystemApplier(c))
+	differ := winlayers.NewWalkingDiffWithWindows(c, walking.NewWalkingDiff(c))
+
+	md, err := metadata.NewStore(filepath.Join(tmpdir, "metadata.db"))
+	if err != nil {
+		return nil, err
+	}
+	t.Cleanup(func() {
+		require.NoError(t, md.Close())
+	})
+
+	cm, err = cache.NewManager(cache.ManagerOpt{
+		Snapshotter:    snapshot.FromContainerdSnapshotter(sn, containerdsnapshot.NSSnapshotter(ns, mdb.Snapshotter(sn)), idmap),
+		MetadataStore:  md,
+		ContentStore:   c,
+		Applier:        applier,
+		Differ:         differ,
+		LeaseManager:   lm,
+		GarbageCollect: mdb.GarbageCollect,
+		MountPoolRoot:  filepath.Join(tmpdir, "cachemounts"),
+	})
+	if err != nil {
+		return nil, err
+	}
+	t.Cleanup(func() {
+		require.NoError(t, cm.Close())
+	})
+
+	return cm, nil
+}