Fix the declared return type of RustCodeOwners.for_file

[dduugg]

• I bumped the gem version (or don't need to) 💎

The bug

RustCodeOwners.for_file returns a serialized copy of the Rust Team struct:

pub struct Team {
    pub team_name: String,
    pub team_config_yml: String,
    pub reasons: Vec<String>,
}

Two places declare that as T::Hash[Symbol, String], which never matched, because reasons is an Array:

• CodeOwnership::Private::TeamFinder.for_file — T.let(RustCodeOwners.for_file(file_path), T.nilable(T::Hash[Symbol, String]))
• CodeOwnership.for_file_verbose — declared returns(T.nilable(T::Hash[Symbol, String]))

It went unnoticed because sorbet-runtime only checks the outer class of a collection type: T::Hash[Symbol, String].valid? is obj.is_a?(Hash), so any Hash passes and the value types are never looked at.

How it surfaced

Enabling recursive runtime typechecking in a host application — pointing each collection type's valid? at its existing recursively_valid?, as Homebrew/brew#20644 does — makes every for_file call raise:

T.let: Expected type T.nilable(T::Hash[Symbol, String]), got type Hash with value
{team_name: "...", team_config_yml: "...", reasons: [...]}

In our monolith that's 238 raises during boot alone, via CodeOwnership.for_class in an observability initializer.

The fix

Declare the actual shape, shared by both call sites:

FileOwnershipDetails = T.type_alias do
  { team_name: String, team_config_yml: String, reasons: T::Array[String] }
end

team_name is a non-optional Rust String, so it can never serialize to nil. That makes the result.nil? || result[:team_name].nil? guard and its paired T.must dead code, and the shape now enforces what the guard was defending against — both are dropped.

Specs

The stubs returned { team_name: 'Bar' }, which the shape correctly rejects; they now return the whole struct. caches nil when team_name is nil covered a state the extension cannot produce and the type no longer admits, so it's removed — caches nil when rust returns nil still covers the nil path.

bundle exec rspec → 91 examples, 0 failures, 1 pending. bundle exec srb tc → clean.