playground: check file/dir name conflicts in txtar

txtar.go

@@ -9,6 +9,7 @@ import (
 	"errors"
 	"fmt"
 	"path"
+	"path/filepath"
 	"strings"
 
 	"golang.org/x/tools/txtar"
@@ -89,6 +90,7 @@ func splitFiles(src []byte) (*fileSet, error) {
 	if numFiles > limitNumFiles {
 		return nil, fmt.Errorf("too many files in txtar archive (%v exceeds limit of %v)", numFiles, limitNumFiles)
 	}
+	dirFileNameMap := map[string]string{} // holds which filename the dirname is part of
 	for _, f := range a.Files {
 		if len(f.Name) > 200 { // arbitrary limit
 			return nil, errors.New("file name too long")
@@ -111,6 +113,16 @@ func splitFiles(src []byte) (*fileSet, error) {
 		if fs.Contains(f.Name) {
 			return nil, fmt.Errorf("duplicate file name %q", f.Name)
 		}
+		for i := 1; i < len(parts); i++ {
+			dirname := filepath.Join(parts[:i]...)
+			if fs.Contains(dirname) {
+				return nil, fmt.Errorf("conflict file/dir name %q and %q", dirname, f.Name)
+			}
+			dirFileNameMap[dirname] = f.Name
+		}
+		if filename, ok := dirFileNameMap[f.Name]; ok {
+			return nil, fmt.Errorf("conflict dir/file name %q and %q", filename, f.Name)
+		}
 		fs.AddFile(f.Name, f.Data)
 	}
 	return fs, nil

txtar_test.go

@@ -117,6 +117,16 @@ func TestSplitFiles(t *testing.T) {
 			in:      strings.Repeat("-- x.go --\n", 50),
 			wantErr: `too many files in txtar archive (50 exceeds limit of 20)`,
 		},
+		{
+			name:    "reject file overwritten by dir",
+			in:      "-- a --\n-- a/b --\n",
+			wantErr: `conflict file/dir name "a" and "a/b"`,
+		},
+		{
+			name:    "reject dir overwritten by file",
+			in:      "-- a/b --\n-- a --\n",
+			wantErr: `conflict dir/file name "a/b" and "a"`,
+		},
 	} {
 		got, err := splitFiles([]byte(tt.in))
 		var gotErr string