nix develop: Filter some bash magic variables

src/nix/develop.cc

@@ -72,7 +72,7 @@ struct BuildEnvironment
     void toBash(std::ostream & out, const std::set<std::string> & ignoreVars) const
     {
         for (auto & [name, value] : vars) {
-            if (!ignoreVars.count(name) && !hasPrefix(name, "BASH_")) {
+            if (!ignoreVars.count(name)) {
                 if (auto str = std::get_if<String>(&value)) {
                     out << fmt("%s=%s\n", name, shellEscape(str->value));
                     if (str->exported)
@@ -191,17 +191,13 @@ struct Common : InstallableCommand, MixProfile
 {
     std::set<std::string> ignoreVars{
         "BASHOPTS",
-        "EUID",
         "HOME", // FIXME: don't ignore in pure mode?
-        "HOSTNAME",
         "NIX_BUILD_TOP",
         "NIX_ENFORCE_PURITY",
         "NIX_LOG_FD",
         "NIX_REMOTE",
         "PPID",
-        "PWD",
         "SHELLOPTS",
-        "SHLVL",
         "SSL_CERT_FILE", // FIXME: only want to ignore /no-cert-file.crt
         "TEMP",
         "TEMPDIR",

src/nix/get-env.sh

@@ -42,6 +42,20 @@ __dumpEnv() {
         local type="${BASH_REMATCH[1]}"
         local __var_name="${BASH_REMATCH[2]}"
 
+        if [[ $__var_name =~ ^BASH_ || \
+              $__var_name = _ || \
+              $__var_name = DIRSTACK || \
+              $__var_name = EUID || \
+              $__var_name = FUNCNAME || \
+              $__var_name = HISTCMD || \
+              $__var_name = HOSTNAME || \
+              $__var_name = PIPESTATUS || \
+              $__var_name = PWD || \
+              $__var_name = RANDOM || \
+              $__var_name = SHLVL || \
+              $__var_name = SECONDS \
+            ]]; then continue; fi
+
         if [[ -z $__first ]]; then printf ',\n'; else __first=; fi
 
         printf "    "