Scala Coding Practices

Scala Coding Practices

Application skill for Scala style learning (from the archived awesome-guidelines style capsules). For Spark/Akka/ZIO stack patterns, load stack capsules under skills/*-foundation.

Core Principle

Scala readability is official layout/naming plus functional safety, immutable data, explicit public types, expression-oriented control, documented API.

When to Use / NOT

• Scala application/library source, Scalafmt/Scalafix/wartremover CI.
• Reviewing naming, types, case classes, control flow, Scaladoc.

NOT when:

• Non-Scala code.
• Generated boilerplate, validate generators instead.
• Spark-internal perf micro-optimizations, use the Databricks guide in stack capsules under skills/*-foundation.

Workflow

1. Format & layout, 2-space, wraps, control spacing (scala-style-formatting-layout.md).
2. Naming, packages, accessors, parentheses (scala-style-naming-packages.md).
3. Types, inference rules, immutability, Option (scala-style-types-immutability.md).
4. Control & docs, return, for, Scaladoc, errors (scala-style-control-api.md).
5. Verify, Scalafmt/Scalafix + sbt test / sbt compile on changed modules.

Red Flags

• Tabs or 4-space indent
• Java getter/setter names in Scala API
• Side-effect nullary method without ()
• Symbolic operators in domain API
• var in case class
• Missing override
• Public method without return type
• Option.get / null
• return in closures
• Public API without Scaladoc

Verification

• Scalafmt/Scalafix on changed files
• Compile + tests for touched projects
• Capsule checklist on public API review

References

• awesome-guidelines/references/scala-style-learning-note.md
• awesome-guidelines/references/scala-style-formatting-layout.md
• awesome-guidelines/references/scala-style-naming-packages.md
• awesome-guidelines/references/scala-style-types-immutability.md
• awesome-guidelines/references/scala-style-control-api.md