playground: check file/dir name conflicts in txtar

txtar.go

@@ -29,6 +29,9 @@ func (fs *fileSet) Data(filename string) []byte { return fs.m[filename] }
 // Num returns the number of files in the set.
 func (fs *fileSet) Num() int { return len(fs.m) }
 
+// Files returns the filenames in user-provided order.
+func (fs *fileSet) Files() []string { return fs.files }
+
 // Contains reports whether fs contains the given filename.
 func (fs *fileSet) Contains(filename string) bool {
 	_, ok := fs.m[filename]
@@ -113,6 +116,15 @@ func splitFiles(src []byte) (*fileSet, error) {
 		}
 		fs.AddFile(f.Name, f.Data)
 	}
+	for _, filename := range fs.Files() {
+		parts := strings.Split(filename, "/")
+		for i := 1; i < len(parts); i++ {
+			dirname := path.Join(parts[:i]...)
+			if fs.Contains(dirname) {
+				return nil, fmt.Errorf("conflict file/dir name %q and %q", dirname, filename)
+			}
+		}
+	}
 	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 file/dir name "a" and "a/b"`,
+		},
 	} {
 		got, err := splitFiles([]byte(tt.in))
 		var gotErr string