Scala Cheat Sheet

Scala cheat sheet with real commands and snippets for setup, core workflows, debugging, and production-safe automation patterns. If you are working across tools, pair this with the Rust Cheat Sheet and Swift Cheat Sheet.

Setup and Tooling

Goal: Install and verify language toolchain

# Run scala command
scala -version

# Run scalac command
scalac -version

# Run sbt command
sbt --version

Core Workflows

Goal: Run and build source code

# Execute scala workflow
scala Main.scala

# Execute scalac workflow
scalac Main.scala && scala Main

Goal: Use a practical code snippet

object Main extends App {
  val nums = List(1, 2, 3, 4)
  val evens = nums.filter(_ % 2 == 0)
  println(evens)
}

Testing and Formatting

Goal: Run automated tests

# Execute test-related command
sbt test

# Execute test-related command
sbt "testOnly *MySpec"

Goal: Run lint and formatter checks

# Execute quality command
sbt scalafmtAll

# Execute quality command
sbt scalafixAll

Automation and CI

Goal: Create a repeatable CI shell step

# Run strict shell mode for CI step
set -euo pipefail

# Install dependencies deterministically
npm ci || pip install -r requirements.txt || true

# Run tests and fail fast on errors
sbt test

Debugging and Troubleshooting

Goal: Trace runtime issues

# Print runtime and package manager versions
node --version || python --version || true

# Search stack traces and TODO markers
rg "Traceback|Exception|TODO" .

# Re-run tests with verbose output
sbt test -v || sbt test --verbose || true

Common Gotchas

• Pin Scala language/runtime versions in local and CI environments.
• Keep formatting and linting automated to avoid noisy diffs in code review.
• Prefer explicit dependency lock files for reproducible builds.
• Write small, deterministic tests that can run quickly in pre-commit checks.
• Document compiler/interpreter flags used in production builds.

Related Sheets

• Rust Cheat Sheet — daily Rust commands and production-ready examples.
• Swift Cheat Sheet — daily Swift commands and production-ready examples.
• YAML Cheat Sheet — daily YAML commands and production-ready examples.