path/filepath: EvalSymlinks ignores link type on Windows #71165
Description
Windows makes a distinction between symlinks to a file and to a directory. A file link pointing to a directory cannot be traversed, nor can a directory link pointing to a file.
filepath.EvalSymlinks doesn't pay any attention to the type of links, however, and will resolve links that Windows will not. It probably should behave consistently with the rest of the OS.
Possible testcases (currently failing):
func TestWindowsEvalSymlinksDirectoryLinkToFile(t *testing.T) {
dir := tempDirCanonical(t)
if err := os.WriteFile(dir+"/target", nil, 0666); err != nil {
t.Fatal(err)
}
mustExec(t, "cmd", "/c", "mklink", "/D", dir+`\symlink`, dir+`\target`)
if _, err := filepath.EvalSymlinks(dir + `\symlink`); err == nil {
t.Errorf("EvalSymlinks(symlink) succeeded; want error (directory link to file target)")
}
if _, err := os.ReadFile(dir + `\symlink`); err == nil {
t.Errorf("ReadFile(symlink) succeeded; want error (directory link to file target)")
}
}
func TestWindowsEvalSymlinksFileLinkToDirectory(t *testing.T) {
dir := tempDirCanonical(t)
if err := os.Mkdir(dir+"/target", 0777); err != nil {
t.Fatal(err)
}
mustExec(t, "cmd", "/c", "mklink", dir+`\symlink`, dir+`\target`)
if _, err := filepath.EvalSymlinks(dir + `\symlink`); err == nil {
t.Errorf("EvalSymlinks(filelink) succeeded; want error (file link to directory target)")
}
if _, err := os.ReadDir(dir + `\symlink`); err == nil {
t.Errorf("ReadDir(symlink) succeeded; want error (file link to directory target)")
}
}
func mustExec(t *testing.T, cmd string, args ...string) {
output, err := exec.Command(cmd, args...).CombinedOutput()
if err != nil {
t.Fatalf("command failed: %q\n%v", cmd, string(output))
}
}