Fix nested directory listing for archives without explicit directory …

…names.

.gitignore

@@ -1 +1,2 @@
 _gitignore
+__debug_bin

archiver.go

@@ -148,6 +148,9 @@ func nameOnDiskToNameInArchive(nameOnDisk, rootOnDisk, rootInArchive string) str
 //
 // For example, "a/b/c" => "b/c".
 func trimTopDir(dir string) string {
+	if len(dir) > 0 && dir[0] == '/' {
+		dir = dir[1:]
+	}
 	if pos := strings.Index(dir, "/"); pos >= 0 {
 		return dir[pos+1:]
 	}
@@ -159,6 +162,9 @@ func trimTopDir(dir string) string {
 //
 // For example, "a/b/c" => "a".
 func topDir(dir string) string {
+	if len(dir) > 0 && dir[0] == '/' {
+		dir = dir[1:]
+	}
 	if pos := strings.Index(dir, "/"); pos >= 0 {
 		return dir[:pos]
 	}

archiver_test.go

@@ -7,6 +7,46 @@ import (
 	"testing"
 )
 
+func TestTrimTopDir(t *testing.T) {
+	for _, tc := range []struct {
+		input string
+		want  string
+	}{
+		{input: "a/b/c", want: "b/c"},
+		{input: "a", want: "a"},
+		{input: "abc/def", want: "def"},
+		{input: "/abc/def", want: "def"},
+	} {
+		tc := tc
+		t.Run(tc.input, func(t *testing.T) {
+			got := trimTopDir(tc.input)
+			if got != tc.want {
+				t.Errorf("want: '%s', got: '%s')", tc.want, got)
+			}
+		})
+	}
+}
+
+func TestTopDir(t *testing.T) {
+	for _, tc := range []struct {
+		input string
+		want  string
+	}{
+		{input: "a/b/c", want: "a"},
+		{input: "a", want: "a"},
+		{input: "abc/def", want: "abc"},
+		{input: "/abc/def", want: "abc"},
+	} {
+		tc := tc
+		t.Run(tc.input, func(t *testing.T) {
+			got := topDir(tc.input)
+			if got != tc.want {
+				t.Errorf("want: '%s', got: '%s')", tc.want, got)
+			}
+		})
+	}
+}
+
 func TestFileIsIncluded(t *testing.T) {
 	for i, tc := range []struct {
 		included  []string

fs.go

@@ -458,13 +458,17 @@ func (f ArchiveFS) ReadDir(name string) ([]fs.DirEntry, error) {
 			// leaving them to be inferred from the names of files instead (issue #330)
 			// so as we traverse deeper, we need to implicitly find subfolders within
 			// this current directory and add fake entries to the output
-			remainingPath := strings.TrimPrefix(file.NameInArchive, name)
+			remainingPath := file.NameInArchive
+
+			if name != "." {
+				remainingPath = strings.TrimPrefix(file.NameInArchive, name)
+			}
 			nextDir := topDir(remainingPath)        // if name in archive is "a/b/c" and root is "a", this becomes "b" (the implied folder to add)
 			implicitDir := path.Join(name, nextDir) // the full path of the implied directory
 
 			// create fake entry only if no entry currently exists (don't overwrite a real entry)
 			if _, ok := entries[implicitDir]; !ok {
-				entries[implicitDir] = implicitDirEntry{implicitDir}
+				entries[implicitDir] = implicitDirEntry{nextDir}
 			}
 
 			return fs.SkipDir

fs_test.go

@@ -9,7 +9,10 @@ import (
 	"log"
 	"net/http"
 	"path"
+	"sort"
 	"testing"
+
+	"github.com/google/go-cmp/cmp"
 )
 
 func TestPathWithoutTopDir(t *testing.T) {
@@ -40,9 +43,14 @@ func TestPathWithoutTopDir(t *testing.T) {
 }
 
 //go:generate zip testdata/test.zip go.mod
+//go:generate zip -qr9 testdata/nodir.zip archiver.go go.mod cmd/arc/main.go .github/ISSUE_TEMPLATE/bug_report.md .github/FUNDING.yml README.md .github/workflows/ubuntu-latest.yml
 
-//go:embed testdata/test.zip
-var testZIP []byte
+var (
+	//go:embed testdata/test.zip
+	testZIP []byte
+	//go:embed testdata/nodir.zip
+	nodirZIP []byte
+)
 
 func ExampleArchiveFS_Stream() {
 	fsys := ArchiveFS{
@@ -70,3 +78,42 @@ func ExampleArchiveFS_Stream() {
 	// go.mod
 	// true
 }
+
+func TestArchiveFS_Stream_Nodir(t *testing.T) {
+	fsys := ArchiveFS{
+		Stream: io.NewSectionReader(bytes.NewReader(nodirZIP), 0, int64(len(nodirZIP))),
+		Format: Zip{},
+	}
+
+	if err := verifyDirList(fsys, ".", []string{".github", "README.md", "archiver.go", "cmd", "go.mod"}); err != nil {
+		t.Error(err)
+	}
+
+	if err := verifyDirList(fsys, ".github", []string{"FUNDING.yml", "ISSUE_TEMPLATE", "workflows"}); err != nil {
+		t.Error(err)
+	}
+
+	if err := verifyDirList(fsys, "cmd", []string{"arc"}); err != nil {
+		t.Error(err)
+	}
+}
+
+func verifyDirList(fsys ArchiveFS, dir string, want []string) error {
+	dis, err := fsys.ReadDir(dir)
+	if err != nil {
+		return err
+	}
+
+	dirs := []string{}
+	for _, di := range dis {
+		dirs = append(dirs, di.Name())
+	}
+
+	// Stabilize the sort order
+	sort.Strings(dirs)
+
+	if diff := cmp.Diff(want, dirs); diff != "" {
+		return fmt.Errorf("ReadDir() mismatch (-want +got):\n%s", diff)
+	}
+	return nil
+}

go.mod

@@ -14,6 +14,7 @@ require (
 
 require (
 	github.com/golang/snappy v0.0.4
+	github.com/google/go-cmp v0.5.8
 	github.com/pierrec/lz4/v4 v4.1.14
 	golang.org/x/text v0.3.7
 )

go.sum

@@ -5,6 +5,8 @@ github.com/dsnet/compress v0.0.1/go.mod h1:Aw8dCMJ7RioblQeTqt88akK31OvO8Dhf5Jflh
 github.com/dsnet/golib v0.0.0-20171103203638-1ea166775780/go.mod h1:Lj+Z9rebOhdfkVLjJ8T6VcRQv3SXugXy999NBtR9aFY=
 github.com/golang/snappy v0.0.4 h1:yAGX7huGHXlcLOEtBnF4w7FQwA26wojNCwOYAEhLjQM=
 github.com/golang/snappy v0.0.4/go.mod h1:/XxbfmMg8lxefKM7IXC3fBNl/7bRcc72aCRzEWrmP2Q=
+github.com/google/go-cmp v0.5.8 h1:e6P7q2lk1O+qJJb4BtCQXlK8vWEO8V1ZeuEdJNOqZyg=
+github.com/google/go-cmp v0.5.8/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/klauspost/compress v1.4.1/go.mod h1:RyIbtBH6LamlWaDj8nUwkbUhJ87Yi3uG0guNDohfE1A=
 github.com/klauspost/compress v1.15.5 h1:qyCLMz2JCrKADihKOh9FxnW3houKeNsp2h5OEz0QSEA=
 github.com/klauspost/compress v1.15.5/go.mod h1:PhcZ0MbTNciWF3rruxRgKxI5NkcHHrHUDtV4Yw2GlzU=