internal/pkg: expand single directory tarball

This enables much cleaner use of their output without giving up any meaningful data.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/pkg/dir_test.go

@@ -202,6 +202,7 @@ func TestFlatten(t *testing.T) {
 			"identifier": {Mode: fs.ModeDir | 0700},
 			"identifier/-P_1iw6yVq_letMHncqcExSE0bYcDhYI5OdY6b1wKASf-Corufvj__XTBUq2Qd2a": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/yJlSb2A3jxaMLuKqwp1GwHOguAHddS9MjygF9ICEeegKfRvgLPdPmNh8mva47f8o")},
 
+			"temp": {Mode: fs.ModeDir | 0700},
 			"work": {Mode: fs.ModeDir | 0700},
 		}, []pkg.FlatEntry{
 			{Mode: fs.ModeDir | 0700, Path: "."},
@@ -222,8 +223,45 @@ func TestFlatten(t *testing.T) {
 			{Mode: fs.ModeDir | 0700, Path: "identifier"},
 			{Mode: fs.ModeSymlink | 0777, Path: "identifier/-P_1iw6yVq_letMHncqcExSE0bYcDhYI5OdY6b1wKASf-Corufvj__XTBUq2Qd2a", Data: []byte("../checksum/yJlSb2A3jxaMLuKqwp1GwHOguAHddS9MjygF9ICEeegKfRvgLPdPmNh8mva47f8o")},
 
+			{Mode: fs.ModeDir | 0700, Path: "temp"},
 			{Mode: fs.ModeDir | 0700, Path: "work"},
-		}, pkg.MustDecode("lmVlYEGNFkwGVpzzS8KYjGBVB6FCyPtk9ViX88zen0GgTKLgGqO6eFxb4dpcP6bR")},
+		}, pkg.MustDecode("d14kfTvK8uyYIrMq-NUPGGIGmYKcFytmrsvEu5oXibVfmxhu7Y_dAt3rXpsHVSPM")},
+
+		{"sample tar expand step unpack", fstest.MapFS{
+			".": {Mode: fs.ModeDir | 0700},
+
+			"libedac.so": {Mode: fs.ModeSymlink | 0777, Data: []byte("/proc/nonexistent/libedac.so")},
+		}, []pkg.FlatEntry{
+			{Mode: fs.ModeDir | 0700, Path: "."},
+
+			{Mode: fs.ModeSymlink | 0777, Path: "libedac.so", Data: []byte("/proc/nonexistent/libedac.so")},
+		}, pkg.MustDecode("rY9_cYWgGWgGI2efznu9RP6bPnjM6I5CHFY2nGysnlbPDdOx_iIaiGKYesmMARwC")},
+
+		{"sample tar expand", fstest.MapFS{
+			".": {Mode: fs.ModeDir | 0700},
+
+			"checksum": {Mode: fs.ModeDir | 0700},
+			"checksum/rY9_cYWgGWgGI2efznu9RP6bPnjM6I5CHFY2nGysnlbPDdOx_iIaiGKYesmMARwC":            {Mode: fs.ModeDir | 0500},
+			"checksum/rY9_cYWgGWgGI2efznu9RP6bPnjM6I5CHFY2nGysnlbPDdOx_iIaiGKYesmMARwC/libedac.so": {Mode: fs.ModeSymlink | 0777, Data: []byte("/proc/nonexistent/libedac.so")},
+
+			"identifier": {Mode: fs.ModeDir | 0700},
+			"identifier/-P_1iw6yVq_letMHncqcExSE0bYcDhYI5OdY6b1wKASf-Corufvj__XTBUq2Qd2a": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/rY9_cYWgGWgGI2efznu9RP6bPnjM6I5CHFY2nGysnlbPDdOx_iIaiGKYesmMARwC")},
+
+			"temp": {Mode: fs.ModeDir | 0700},
+			"work": {Mode: fs.ModeDir | 0700},
+		}, []pkg.FlatEntry{
+			{Mode: fs.ModeDir | 0700, Path: "."},
+
+			{Mode: fs.ModeDir | 0700, Path: "checksum"},
+			{Mode: fs.ModeDir | 0500, Path: "checksum/rY9_cYWgGWgGI2efznu9RP6bPnjM6I5CHFY2nGysnlbPDdOx_iIaiGKYesmMARwC"},
+			{Mode: fs.ModeSymlink | 0777, Path: "checksum/rY9_cYWgGWgGI2efznu9RP6bPnjM6I5CHFY2nGysnlbPDdOx_iIaiGKYesmMARwC/libedac.so", Data: []byte("/proc/nonexistent/libedac.so")},
+
+			{Mode: fs.ModeDir | 0700, Path: "identifier"},
+			{Mode: fs.ModeSymlink | 0777, Path: "identifier/-P_1iw6yVq_letMHncqcExSE0bYcDhYI5OdY6b1wKASf-Corufvj__XTBUq2Qd2a", Data: []byte("../checksum/rY9_cYWgGWgGI2efznu9RP6bPnjM6I5CHFY2nGysnlbPDdOx_iIaiGKYesmMARwC")},
+
+			{Mode: fs.ModeDir | 0700, Path: "temp"},
+			{Mode: fs.ModeDir | 0700, Path: "work"},
+		}, pkg.MustDecode("tqrqx8Ig_l9jjDywovatvg3btS-6hf182Ofzpjcrj2148NhobE_Xb7wrYptZoXFD")},
 	}
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {

internal/pkg/tar.go

@@ -108,6 +108,10 @@ func (a *tarArtifact) Cure(work, temp *check.Absolute, loadData CacheDataFunc) (
 	}
 	var madeDirectories []dirTargetPerm
 
+	if err = os.MkdirAll(temp.String(), 0700); err != nil {
+		return
+	}
+
 	var header *tar.Header
 	r := tar.NewReader(tr)
 	for header, err = r.Next(); err == nil; header, err = r.Next() {
@@ -125,7 +129,7 @@ func (a *tarArtifact) Cure(work, temp *check.Absolute, loadData CacheDataFunc) (
 			case tar.TypeReg:
 				var f *os.File
 				if f, err = os.OpenFile(
-					work.Append(header.Name).String(),
+					temp.Append(header.Name).String(),
 					os.O_CREATE|os.O_EXCL|os.O_WRONLY,
 					header.FileInfo().Mode()&0400,
 				); err != nil {
@@ -142,7 +146,7 @@ func (a *tarArtifact) Cure(work, temp *check.Absolute, loadData CacheDataFunc) (
 			case tar.TypeLink:
 				if err = os.Link(
 					header.Linkname,
-					work.Append(header.Name).String(),
+					temp.Append(header.Name).String(),
 				); err != nil {
 					return
 				}
@@ -151,14 +155,14 @@ func (a *tarArtifact) Cure(work, temp *check.Absolute, loadData CacheDataFunc) (
 			case tar.TypeSymlink:
 				if err = os.Symlink(
 					header.Linkname,
-					work.Append(header.Name).String(),
+					temp.Append(header.Name).String(),
 				); err != nil {
 					return
 				}
 				break
 
 			case tar.TypeDir:
-				pathname := work.Append(header.Name)
+				pathname := temp.Append(header.Name)
 				madeDirectories = append(madeDirectories, dirTargetPerm{
 					path: pathname,
 					mode: header.FileInfo().Mode(),
@@ -185,14 +189,29 @@ func (a *tarArtifact) Cure(work, temp *check.Absolute, loadData CacheDataFunc) (
 	if errors.Is(err, io.EOF) {
 		err = nil
 	}
-
 	if err == nil {
 		for _, e := range madeDirectories {
 			if err = os.Chmod(e.path.String(), e.mode&0500); err != nil {
 				return
 			}
 		}
-		err = os.Chmod(work.String(), 0500)
+	} else {
+		return
+	}
+
+	var entries []os.DirEntry
+	if entries, err = os.ReadDir(temp.String()); err != nil {
+		return
+	}
+
+	if len(entries) == 1 && entries[0].IsDir() {
+		p := temp.Append(entries[0].Name())
+		if err = os.Chmod(p.String(), 0700); err != nil {
+			return
+		}
+		err = os.Rename(p.String(), work.String())
+	} else {
+		err = os.Rename(temp.String(), work.String())
 	}
 	return
 }

internal/pkg/tar_test.go

@@ -17,7 +17,9 @@ import (
 func TestTar(t *testing.T) {
 	t.Parallel()
 
-	testdataFsys := fstest.MapFS{
+	checkWithCache(t, []cacheTestCase{
+		{"http", nil, func(t *testing.T, base *check.Absolute, c *pkg.Cache) {
+			checkTarHTTP(t, base, c, fstest.MapFS{
 				".": {Mode: fs.ModeDir | 0700},
 
 				"checksum": {Mode: fs.ModeDir | 0700},
@@ -25,15 +27,38 @@ func TestTar(t *testing.T) {
 				"checksum/1TL00Qb8dcqayX7wTO8WNaraHvY6b-KCsctLDTrb64QBCmxj_-byK1HdIUwMaFEP/check":          {Mode: 0400, Data: []byte{0, 0}},
 				"checksum/1TL00Qb8dcqayX7wTO8WNaraHvY6b-KCsctLDTrb64QBCmxj_-byK1HdIUwMaFEP/lib":            {Mode: fs.ModeDir | 0700},
 				"checksum/1TL00Qb8dcqayX7wTO8WNaraHvY6b-KCsctLDTrb64QBCmxj_-byK1HdIUwMaFEP/lib/pkgconfig":  {Mode: fs.ModeDir | 0700},
-		"checksum/1TL00Qb8dcqayX7wTO8WNaraHvY6b-KCsctLDTrb64QBCmxj_-byK1HdIUwMaFEP/lib/libedac.so": {Mode: 01000000777, Data: []byte("/proc/nonexistent/libedac.so")},
+				"checksum/1TL00Qb8dcqayX7wTO8WNaraHvY6b-KCsctLDTrb64QBCmxj_-byK1HdIUwMaFEP/lib/libedac.so": {Mode: fs.ModeSymlink | 0777, Data: []byte("/proc/nonexistent/libedac.so")},
 
 				"identifier": {Mode: fs.ModeDir | 0700},
-		"identifier/HnySzeLQvSBZuTUcvfmLEX_OmH4yJWWH788NxuLuv7kVn8_uPM6Ks4rqFWM2NZJY": {Mode: 01000000777, Data: []byte("../checksum/1TL00Qb8dcqayX7wTO8WNaraHvY6b-KCsctLDTrb64QBCmxj_-byK1HdIUwMaFEP")},
-		"identifier/Zx5ZG9BAwegNT3zQwCySuI2ktCXxNgxirkGLFjW4FW06PtojYVaCdtEw8yuntPLa": {Mode: 01000000777, Data: []byte("../checksum/1TL00Qb8dcqayX7wTO8WNaraHvY6b-KCsctLDTrb64QBCmxj_-byK1HdIUwMaFEP")},
+				"identifier/HnySzeLQvSBZuTUcvfmLEX_OmH4yJWWH788NxuLuv7kVn8_uPM6Ks4rqFWM2NZJY": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/1TL00Qb8dcqayX7wTO8WNaraHvY6b-KCsctLDTrb64QBCmxj_-byK1HdIUwMaFEP")},
+				"identifier/Zx5ZG9BAwegNT3zQwCySuI2ktCXxNgxirkGLFjW4FW06PtojYVaCdtEw8yuntPLa": {Mode: fs.ModeSymlink | 0777, Data: []byte("../checksum/1TL00Qb8dcqayX7wTO8WNaraHvY6b-KCsctLDTrb64QBCmxj_-byK1HdIUwMaFEP")},
 
 				"work": {Mode: fs.ModeDir | 0700},
-	}
+			}, pkg.MustDecode(
+				"yJlSb2A3jxaMLuKqwp1GwHOguAHddS9MjygF9ICEeegKfRvgLPdPmNh8mva47f8o",
+			))
+		}, pkg.MustDecode("d14kfTvK8uyYIrMq-NUPGGIGmYKcFytmrsvEu5oXibVfmxhu7Y_dAt3rXpsHVSPM")},
 
+		{"http expand", nil, func(t *testing.T, base *check.Absolute, c *pkg.Cache) {
+			checkTarHTTP(t, base, c, fstest.MapFS{
+				".": {Mode: fs.ModeDir | 0700},
+
+				"lib":            {Mode: fs.ModeDir | 0700},
+				"lib/libedac.so": {Mode: fs.ModeSymlink | 0777, Data: []byte("/proc/nonexistent/libedac.so")},
+			}, pkg.MustDecode(
+				"rY9_cYWgGWgGI2efznu9RP6bPnjM6I5CHFY2nGysnlbPDdOx_iIaiGKYesmMARwC",
+			))
+		}, pkg.MustDecode("tqrqx8Ig_l9jjDywovatvg3btS-6hf182Ofzpjcrj2148NhobE_Xb7wrYptZoXFD")},
+	})
+}
+
+func checkTarHTTP(
+	t *testing.T,
+	base *check.Absolute,
+	c *pkg.Cache,
+	testdataFsys fs.FS,
+	wantChecksum pkg.Checksum,
+) {
 	var testdata string
 	{
 		var buf bytes.Buffer
@@ -68,8 +93,6 @@ func TestTar(t *testing.T) {
 		"testdata": {Data: []byte(testdata), Mode: 0400},
 	}))
 
-	checkWithCache(t, []cacheTestCase{
-		{"http", nil, func(t *testing.T, base *check.Absolute, c *pkg.Cache) {
 	wantIdent := func() pkg.ID {
 		h := sha512.New384()
 		h.Write([]byte{byte(pkg.KindTar), 0, 0, 0, 0, 0, 0, 0})
@@ -96,9 +119,6 @@ func TestTar(t *testing.T) {
 		"identifier",
 		pkg.Encode(wantIdent),
 	)
-			wantChecksum := pkg.MustDecode(
-				"yJlSb2A3jxaMLuKqwp1GwHOguAHddS9MjygF9ICEeegKfRvgLPdPmNh8mva47f8o",
-			)
 	if pathname, checksum, err := c.Cure(a); err != nil {
 		t.Fatalf("Cure: error = %v", err)
 	} else if !pathname.Is(wantPathname) {
@@ -109,6 +129,4 @@ func TestTar(t *testing.T) {
 			Want: wantChecksum,
 		})
 	}
-		}, pkg.MustDecode("lmVlYEGNFkwGVpzzS8KYjGBVB6FCyPtk9ViX88zen0GgTKLgGqO6eFxb4dpcP6bR")},
-	})
 }