Best practices

Best Practices

This list is a community-maintained guide for some "best practice" suggestions. Written in the TLDR style, suggestions are in no particular order, should be beneficial to users with any level of Nim proficiency.

• Use 2-spaces indentation.
• Use func where possible.
• Use auto instead of any.
• Use self instead of this for specifying the main object argument in routines.
• Use const and let where possible.
• Put your types near the top of the file.
• Use import for public code instead of include.
• Use include for unittesting private code instead of import.
• Use runnableExamples for code examples in the documentation.
• Use tuple to return multiple values of different types.
• Standard library imports should be prefixed with std/, like std/os, std/[strutils, sequtils], etc.
• Use when isMainModule: to specify code that'll only run if the source file is the main one.
• Design your code to work in-place, then use sugar.dup if you need to call it out-of-place.
• Prefer in-place functions, for example, sort instead of sorted where appropriate.
• Use options for optional types and optional returns.
• Use Natural or Positive as an argument or input type for non-negative integers.
• Use char to operate on single characters, for example "foo" & '\n' instead of "foo" & "\n".
• Annotating routines with {.deprecated.} will make the compiler print out all places where that routine is called.
• Procedures like echo, repr, astToStr, assert, expandMacros and the compiler switch --expandArc can be useful for debugging.
• In macros prefer to operate on the AST instead of using parseStmt and string operations.
• For designing new macros write the desired result manually and then use dumpAstGen to get macro code that will generate the same code.
• Use string to represent strings of any kind (Nim strings are not encoded in any way) - NOT for binary blobs.
• Use seq[byte] to represent raw binary blobs.
• Prefer to use func and/or proc even for OOP, use interface-like libraries (for example iface instead of method unless there's no way around it.
• Use nimble init or a "repo template" like nimtemplate to start a new project.
• Try to use FIXME, NOTE, OPTIMIZE, TODO in relevant code comments so that editors and GitHub Actions can read them.
• For documentation it is generally preferred to use descriptive third person present tense with proper punctuation.
• For documentation the first paragraph of a doc comment must be a summary, it should concisely define the purpose and functionality of the module/library.
• Do NOT use distinct tuple.
• Do NOT use float for things that need to be precise (like money), instead consider using decimal.
• Do NOT use discard on a Future.
• Do NOT add label names to the block statement if you don't use them.
• Do NOT write error messages in ALL_CAPS.
• Do NOT use exclamation marks in error messages.
• Do NOT name your variables in ALL_CAPS unless it's required for FFI purposes.
• Do NOT use Natural or Positive as a return type for integers, use int or uint instead.
• Do NOT use try blocks with a lot of except branches, use explicit control flow instead.
• Do NOT repeat & too much for string concatenation, use add instead.
• Do NOT repeat & too much to string formatting, use std/strformat instead.
• Do NOT call randomize() in your libraries that use std/random, users should call it themselves.

See also:

• https://nim-lang.github.io/Nim/nep1.html
• https://status-im.github.io/nim-style-guide
• https://community.kde.org/Policies/Commit_Policy#Guidelines
• Naming things cheatsheet, language agnostic