Add test for tar2ext layer expansion

tar2ext layer expansion had a bug where during a tar expansion if a file showed up before
its parent directory then the expansion would fail with path not found error. This was
fixed in microsoft#972. This commit just a adds a test for that fix.

Signed-off-by: Amit Barve <ambarve@microsoft.com>

ext4/tar2ext4/tar2ext4_test.go

@@ -0,0 +1,90 @@
+package tar2ext4
+
+import (
+	"path/filepath"
+	"testing"
+
+	"archive/tar"
+	"os"
+	"strings"
+	"time"
+)
+
+// Test_UnorderedTarExpansion tests that we are correctly able to expand a layer tar file
+// which has one or many files in an unordered fashion. By unordered we mean that the
+// entry of a file shows up during an expansion before the entry of one of the parent
+// directories of that file.  In such cases we create that parent directory with same
+// permissions as its parent and then later on fix the permissions when we actually see
+// the entry of that parent directory.
+func Test_UnorderedTarExpansion(t *testing.T) {
+	tmpTarFilePath := filepath.Join(os.TempDir(), "test-layer.tar")
+	layerTar, err := os.Create(tmpTarFilePath)
+	if err != nil {
+		t.Fatalf("failed to create output file: %s", err)
+	}
+	defer os.Remove(tmpTarFilePath)
+
+	tw := tar.NewWriter(layerTar)
+	var files = []struct {
+		path, body string
+	}{
+		{"data/", ""},
+		{"root.txt", "inside root.txt"},
+		{"foo/bar.txt", "inside bar.txt"},
+		{"foo/", ""},
+		{"A/B/b.txt", "inside b.txt"},
+		{"A/a.txt", "inside a.txt"},
+		{"A/", ""},
+		{"A/B/", ""},
+	}
+	for _, file := range files {
+		var hdr *tar.Header
+		if strings.HasSuffix(file.path, "/") {
+			hdr = &tar.Header{
+				Name:       file.path,
+				Mode:       0777,
+				Size:       0,
+				ModTime:    time.Now(),
+				AccessTime: time.Now(),
+				ChangeTime: time.Now(),
+			}
+		} else {
+			hdr = &tar.Header{
+				Name:       file.path,
+				Mode:       0777,
+				Size:       int64(len(file.body)),
+				ModTime:    time.Now(),
+				AccessTime: time.Now(),
+				ChangeTime: time.Now(),
+			}
+		}
+		if err := tw.WriteHeader(hdr); err != nil {
+			t.Fatal(err)
+		}
+		if !strings.HasSuffix(file.path, "/") {
+			if _, err := tw.Write([]byte(file.body)); err != nil {
+				t.Fatal(err)
+			}
+		}
+	}
+	if err := tw.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	// Now try to import this tar and verify that there is no failure.
+	if _, err := layerTar.Seek(0, 0); err != nil {
+		t.Fatalf("failed to seek file: %s", err)
+	}
+
+	opts := []Option{AppendVhdFooter, ConvertWhiteout}
+	tmpVhdPath := filepath.Join(os.TempDir(), "test-vhd.vhdx")
+	layerVhd, err := os.Create(tmpVhdPath)
+	if err != nil {
+		t.Fatalf("failed to create output VHD: %s", err)
+	}
+	defer os.Remove(tmpVhdPath)
+
+	if err := Convert(layerTar, layerVhd, opts...); err != nil {
+		t.Fatalf("failed to convert tar to layer vhd: %s", err)
+	}
+}