Scala Development

Build runner

devtool is the default and detects the project itself. Drop to the underlying tool only when it is absent: use bloop if a .bloop directory exists (faster incremental), otherwise sbt. For non-modular projects the module name is root.

bloop compile <module-name>
bloop test <module-name> -o "*<filename>*"

sbt compile
sbt "testOnly *SpecName*"

Design opinions

These are Channing's preferred style and differ from the default choice:

• Encapsulation over transparency: prefer class with private val (or opaque types) over case class when a type has internal structure that shouldn't be part of its public API (e.g. a Map tracking counts, a buffer, an index). Reserve case class for value types where every field is meaningful to callers (e.g. Book(title, author), Config(host, port)). Reaching for case class by default produces types that leak implementation details.

• Typelevel ecosystem: prefer cats, cats-effect and fs2 over the alternatives (ZIO, Akka). This is a codebase consistency choice, not a judgement on the alternatives — mixing effect systems creates friction.

Red flag

A deliberate semantic divergence with no discriminating test. When behaviour intentionally differs from the mirrored precedent or the happy path — scale-insensitive BigDecimal equality, instant-based ZonedDateTime, extension-stack resolution in a repeating row — write the test that fails if the divergence regresses. The reviewer caught these every time; the implementer did not write them first.