proton-mail-android/docs/0001-declare-constants-at-the-top-of-the-file.md

Constants are created by file as a top level declaration

• Status: Accepted
• Deciders: Marino, Zorica, Stefanija, Davide, Tomasz, Maciej
• Date: 17/09/2021

Context and Problem Statement

This is a minor code-style decision regarding where constants should be placed.

Considered Options

1. Declare constants at the top of the file (right after imports)

import ...

const val PUBLIC_CONSTANT="value"
private const val CONSTANT="value"

class { ... }

2. Declare constants at a file's level but at the bottom
3. Declare constants in a companion object, at the bottom of the file

Decision Outcome

Accepting the risks of name clashes that might turn out from making some private constants public when they are declared outside of companion objects (as evaluated low probability-low impact), we decided to go for Option #1. Such decison was based on the fact that we didn't see major differencies between the listed approaches and approach #1 is already the one with the wider usage in the codebase.