ActiveSupportCacheStore: race_condition_ttl is a silent no-op (missing assignment)

[plantoeat]

Summary

In Flipper::Adapters::ActiveSupportCacheStore#write_options, the race_condition_ttl option is never actually passed to @cache.fetch / @cache.write because the assignment operator is missing. The option has been silently broken since it was introduced in #932.

Location

lib/flipper/adapters/active_support_cache_store.rb#L78-L83 on main:

def write_options
  write_options = {}
  write_options[:expires_in] = @ttl if @ttl
  write_options[:race_condition_ttl] if @race_condition_ttl   # ← no-op
  write_options
end

The third line reads write_options[:race_condition_ttl] (which returns nil on a freshly-created empty hash with no default) and discards the result. It should be:

write_options[:race_condition_ttl] = @race_condition_ttl if @race_condition_ttl

Impact

Anyone configuring the adapter with race_condition_ttl: gets the option accepted without error and exposed via the race_condition_ttl reader, but it never reaches ActiveSupport::Cache::Store. The thundering-herd protection users expect from race_condition_ttl is not actually in effect.

How it slipped through

#932 added both the feature and the bug in a single commit. The accompanying specs in spec/flipper/adapters/active_support_cache_store_spec.rb only assert that the constructor sets the reader (expect(adapter.race_condition_ttl).to eq(race_condition_ttl)). There's no behavioral test that @cache.fetch / @cache.write actually receives race_condition_ttl in its options hash, so the typo wasn't caught.

Proposed fix

1. Add the missing = @race_condition_ttl in write_options.
2. Add a spec that stubs cache.fetch (or uses a cache double) and asserts the options hash includes race_condition_ttl: <value> when the adapter was constructed with one.

Happy to open a PR for this if it'd be helpful.

How it was found

Caught by Cursor Bugbot during review of a downstream PR that vendors this adapter file. I verified against main that the bug is still present.