# Julia Coding Practices

> Use when authoring or reviewing Julia, BlueStyle/JuliaFormatter 4-space/92-col layout, explicit using/exports, typed methods with return, kwargs semicolon, docstrings, and formatter/test in CI.

- Skill: `ryan-brosas/julia-coding-practices` (Agent Skill)
- Install (CLI): `npx skillmds@latest add ryan-brosas/julia-coding-practices`
- Raw SKILL.md: https://api.skillmd.com/api/skills/ryan-brosas/julia-coding-practices/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: ryan-brosas (https://skillmd.com/u/ryan-brosas)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/ryan-brosas/julia-coding-practices

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# Julia Coding Practices

Application skill for Julia BlueStyle learning (from the archived `awesome-guidelines` style capsules). When project sets SciMLStyle or custom `.JuliaFormatter.toml`, follow that formatter config first.

## Core Principle

Julia package quality is **formatter-enforced consistency + explicit module APIs**, typed exported methods, qualified extensions, documented surface.

## When to Use / NOT

- Julia packages, libraries, and `.jl` application code (General/Grades).
- Setting up JuliaFormatter, Pkg.test, Documenter in CI.

**NOT when:**

- Generated Julia code, validate generators.
- One-off scripts with no package boundary, apply layout/docs lightly.

## Workflow

1. **Layout**, JuliaFormatter blue, 92 cols (`julia-style-formatting-layout.md`).
2. **Modules**, using, exports (`julia-style-modules-imports.md`).
3. **Methods**, return, kwargs, types (`julia-style-functions-methods.md`).
4. **Docs/tests**, docstrings, testset (`julia-style-docs-tests.md`).
5. **Verify**, `JuliaFormatter.format`, `Pkg.test()`, docstring audit on exports.

## Red Flags

- Tabs or trailing whitespace
- `using A, B` combined import
- Bare `import` extension without qualification
- Code outside module block in module files
- Undocumented exported functions
- Long functions without explicit `return`
- `f(x, y=3)` missing semicolon before kwargs
- Type baked into function name (`process_dataframe`)
- Over-concrete public signatures (`Array{Int}` vs `AbstractArray`)
- Mutable non-const globals
- Missing trailing comma in multiline literals
- Padded `f( x )` brackets
- Chained ternary operators
- `for i = 1:n` instead of `in`
- Internal API without `_` prefix
- `@test x == 0.0` visual noise
- Caret-only Project.toml compat (`^0.17`)

## Verification

- `JuliaFormatter.format(".")` with `style = "blue"`
- `julia --project -e 'using Pkg; Pkg.test()'`
- Exported names have docstrings (manual or tool-assisted)
- Capsule checklist on main module exports


## References

- `awesome-guidelines/references/julia-style-learning-note.md`
- `awesome-guidelines/references/julia-style-formatting-layout.md`
- `awesome-guidelines/references/julia-style-modules-imports.md`
- `awesome-guidelines/references/julia-style-functions-methods.md`
- `awesome-guidelines/references/julia-style-docs-tests.md`