1 files changed, 88 insertions, 0 deletions
diff --git a/src/internal/safefilepath/path_test.go b/src/internal/safefilepath/path_test.go
new file mode 100644
index 0000000000..dc662c18b3
--- /dev/null
+++ b/src/internal/safefilepath/path_test.go
@@ -0,0 +1,88 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package safefilepath_test
+
+import (
+	"internal/safefilepath"
+	"os"
+	"path/filepath"
+	"runtime"
+	"testing"
+)
+
+type PathTest struct {
+	path, result string
+}
+
+const invalid = ""
+
+var fspathtests = []PathTest{
+	{".", "."},
+	{"/a/b/c", "/a/b/c"},
+	{"a\x00b", invalid},
+}
+
+var winreservedpathtests = []PathTest{
+	{`a\b`, `a\b`},
+	{`a:b`, `a:b`},
+	{`a/b:c`, `a/b:c`},
+	{`NUL`, `NUL`},
+	{`./com1`, `./com1`},
+	{`a/nul/b`, `a/nul/b`},
+}
+
+// Whether a reserved name with an extension is reserved or not varies by
+// Windows version.
+var winreservedextpathtests = []PathTest{
+	{"nul.txt", "nul.txt"},
+	{"a/nul.txt/b", "a/nul.txt/b"},
+}
+
+var plan9reservedpathtests = []PathTest{
+	{`#c`, `#c`},
+}
+
+func TestFromFS(t *testing.T) {
+	switch runtime.GOOS {
+	case "windows":
+		if canWriteFile(t, "NUL") {
+			t.Errorf("can unexpectedly write a file named NUL on Windows")
+		}
+		if canWriteFile(t, "nul.txt") {
+			fspathtests = append(fspathtests, winreservedextpathtests...)
+		} else {
+			winreservedpathtests = append(winreservedpathtests, winreservedextpathtests...)
+		}
+		for i := range winreservedpathtests {
+			winreservedpathtests[i].result = invalid
+		}
+		for i := range fspathtests {
+			fspathtests[i].result = filepath.FromSlash(fspathtests[i].result)
+		}
+	case "plan9":
+		for i := range plan9reservedpathtests {
+			plan9reservedpathtests[i].result = invalid
+		}
+	}
+	tests := fspathtests
+	tests = append(tests, winreservedpathtests...)
+	tests = append(tests, plan9reservedpathtests...)
+	for _, test := range tests {
+		got, err := safefilepath.FromFS(test.path)
+		if (got == "") != (err != nil) {
+			t.Errorf(`FromFS(%q) = %q, %v; want "" only if err != nil`, test.path, got, err)
+		}
+		if got != test.result {
+			t.Errorf("FromFS(%q) = %q, %v; want %q", test.path, got, err, test.result)
+		}
+	}
+}
+
+func canWriteFile(t *testing.T, name string) bool {
+	path := filepath.Join(t.TempDir(), name)
+	os.WriteFile(path, []byte("ok"), 0666)
+	b, _ := os.ReadFile(path)
+	return string(b) == "ok"
+}