Fix for zero-sized layers

Moved a defer up to a better spot.

Fixed TestUntarPathWithInvalidDest to actually fail for the right reason

Closes #18170

Signed-off-by: Doug Davis <dug@us.ibm.com>
Upstream-commit: 7bb9fc415ac50abf5f754005264bfe152eeca7d6
Component: engine

components/engine/pkg/archive/archive.go

@@ -128,7 +128,13 @@ func DecompressStream(archive io.Reader) (io.ReadCloser, error) {
 	p := pools.BufioReader32KPool
 	buf := p.Get(archive)
 	bs, err := buf.Peek(10)
-	if err != nil {
+	if err != nil && err != io.EOF {
+		// Note: we'll ignore any io.EOF error because there are some odd
+		// cases where the layer.tar file will be empty (zero bytes) and
+		// that results in an io.EOF from the Peek() call. So, in those
+		// cases we'll just treat it as a non-compressed stream and
+		// that means just create an empty layer.
+		// See Issue 18170
 		return nil, err
 	}
 

components/engine/pkg/archive/archive_test.go

@@ -216,11 +216,16 @@ func TestUntarPathWithInvalidDest(t *testing.T) {
 	invalidDestFolder := path.Join(tempFolder, "invalidDest")
 	// Create a src file
 	srcFile := path.Join(tempFolder, "src")
-	_, err = os.Create(srcFile)
+	tarFile := path.Join(tempFolder, "src.tar")
+	os.Create(srcFile)
+	os.Create(invalidDestFolder) // being a file (not dir) should cause an error
+	cmd := exec.Command("/bin/sh", "-c", "tar cf "+tarFile+" "+srcFile)
+	_, err = cmd.CombinedOutput()
 	if err != nil {
-		t.Fatalf("Fail to create the source file")
+		t.Fatal(err)
 	}
-	err = UntarPath(srcFile, invalidDestFolder)
+
+	err = UntarPath(tarFile, invalidDestFolder)
 	if err == nil {
 		t.Fatalf("UntarPath with invalid destination path should throw an error.")
 	}