What is the difference between a linter and a formatter, and how should they be used in CI?

• A. They are two names for the same tool and should run only locally.
• B. A linter formats code while a formatter checks correctness.
• C. A linter enforces correctness and anti-patterns; a formatter enforces style, and both should run in CI.
• D. A linter compiles code and a formatter debugs it.

Answer: (C)

The main idea is that a linter analyzes code for correctness and potential issues, while a formatter strictly enforces a consistent style. A linter looks for bugs, bad patterns, unused variables, potential security issues, and other quality problems that could affect readability or reliability. A formatter, on the other hand, rewrites code to match a shared style—consistent indentation, spacing, line lengths, and other formatting rules—so the codebase looks uniform regardless of who wrote it.

In CI, running both is helpful because it catches problems early and keeps the project consistent. The linter can fail the build when it detects issues that could lead to bugs or drift from agreed conventions, prompting fixes before code merges. The formatter ensures style consistency; it can either automatically fix formatting or require that the code already adheres to the style, depending on your workflow. Running both together provides ongoing quality checks and reduces arguments about formatting and code quality.