err on invalid feature flag (#4263)

* err on invalid feature flag

* print all invalid flags and improve error message

src/config.rs

@@ -778,12 +778,15 @@ fn validate_config(cfg: &ConfigItems) -> Result<(), Error> {
  }
  }
 
+ // TODO: deal with deprecated flags so they can be removed from this list, cf. #4263
  const KNOWN_FLAGS: &[&str] =
  &["autofill-overlay", "autofill-v2", "browser-fileless-import", "fido2-vault-credentials"];
- for flag in parse_experimental_client_feature_flags(&cfg.experimental_client_feature_flags).keys() {
- if !KNOWN_FLAGS.contains(&flag.as_str()) {
- warn!("The experimental client feature flag {flag:?} is unrecognized. Please ensure the feature flag is spelled correctly and that it is supported in this version.");
- }
+ let configured_flags = parse_experimental_client_feature_flags(&cfg.experimental_client_feature_flags);
+ let invalid_flags: Vec<_> = configured_flags.keys().filter(|flag| !KNOWN_FLAGS.contains(&flag.as_str())).collect();
+ if !invalid_flags.is_empty() {
+ err!(format!("Unrecognized experimental client feature flags: {invalid_flags:?}.\n\n\
+ Please ensure all feature flags are spelled correctly and that they are supported in this version.\n\
+ Supported flags: {KNOWN_FLAGS:?}"));
  }
 
  const MAX_FILESIZE_KB: i64 = i64::MAX >> 10;