into_config() muts a copy of the previous config

crates/nu-protocol/src/config.rs

@@ -191,11 +191,13 @@ pub struct ExploreConfig {
 }
 
 impl Value {
- pub fn into_config(self) -> Result<Config, ShellError> {
+ pub fn into_config(self, config: &Config) -> Result<Config, ShellError> {
  let v = self.as_record();
 
- let mut config = Config::default();
-
+ // Use the passed-in config as a basis for the changes.
+ // This means, among other things, that putting in various invalid values won't
+ // blow away existing changes for those config keys.
+ let mut config = config.clone();
  let mut legacy_options_used = false;
 
  if let Ok(v) = v {

crates/nu-protocol/src/engine/engine_state.rs

@@ -243,7 +243,7 @@ impl EngineState {
  // NOTE: currently (Dec 2022) the subrecords of config.menus, config.keybindings and config.hooks
  // are NOT reconstructed by config_to_nu_record(), but restored from self.config as-is.
  // As such, invalid values may persist on them (as into_config() doesn't remove them.
- if let Ok(config) = v.clone().into_config() {
+ if let Ok(config) = v.clone().into_config(&self.config) {
  // Don't replace self.config unless into_config() succeeds.
  // Note that into_config() produces Err in only very dire circumstances.
  self.config = config;