write-rbs

RBS signatures live in sig/ mirroring lib/, one .rbs file per .rb file. Check for an existing signature first, generate a prototype with bundle exec rake "rbs:prototype[lib/<path>.rb]", then clean up over-emitted untyped and leading :: namespaces against the project conventions.

Run bundle exec steep check lib/datadog/<path>.rb to scope the check to the edited file's Ruby source, since a sig/ path silently passes even on broken signatures. Always run the full bundle exec steep check before considering types done, as scoped checks miss breaks in referencing signatures.

Use an interface when a parameter or return is duck-typed and you depend on methods rather than a concrete class. Name it with a leading underscore, list only the domain methods you actually call, and never pad it with predicates like nil? just to satisfy the checker.

No, never write a vendored signature from how calling code uses the gem, since inference from usage can be wrong. Always read the gem's real source first, and use untyped rather than any for genuinely open values in vendored stubs.

Use any only when every possible type is intentionally valid and the code does not depend on the concrete type. Use untyped when the type is merely not-yet-modeled, and never use untyped when the type is inferable from the code.

Scoping steep check to a sig/ path silently passes even on broken signatures, and checking one Ruby file will not catch breaks in other signatures that reference it. Always run the full bundle exec steep check before treating types as done.