# Julia Package Dev

> Create and develop Julia packages in local environments, including package bootstrapping, multi-package workspaces, package extensions, and Pkg apps. Use when starting a package or managing package environments, dependencies, structure, and related development workflows. Use when this capability is needed.

- Skill: `tomevault-io/julia-package-dev` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tomevault-io/julia-package-dev`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/julia-package-dev/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: tomevault-io (https://skillmd.com/u/tomevault-io)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tomevault-io/julia-package-dev

---


# Julia Package Development

Use this skill for package-oriented Julia work: bootstrapping a package,
local environments, multi-package workspaces, extensions, and Pkg apps.

## Core Workflow

```julia
using Pkg

Pkg.activate("./dev")
Pkg.develop(path="./MyPackage.jl")
using MyPackage
```

Prefer environments over mutating the global default environment.

- Set `ENV["JULIA_PKG_SERVER_REGISTRY_PREFERENCE"] = "eager"` before `Pkg`
  operations in local or CI sessions in this workspace. Use this by default
  when recent registrations may matter; otherwise just-registered packages can
  appear to be missing and create false resolution failures.
- Prefer `Pkg.test(...)` over directly executing `test/runtests.jl` when
  validating a package checkout. Treat direct `test/runtests.jl` execution as
  a runner-debugging path, not the default validation path.
- Never read or edit `Manifest.toml` directly. Treat every manifest as
  generated state owned by `Pkg`.
- If dependency resolution behaves impossibly, run `Pkg.update()` and
  `Pkg.resolve()` in the relevant environment first. If recurrent issues
  remain, delete the relevant `Manifest.toml` file and regenerate it with
  `Pkg.instantiate()`.
- Read `Project.toml` when needed, but change dependencies and compat entries
  only through `Pkg` APIs such as `Pkg.add`, `Pkg.develop`, `Pkg.rm`,
  `Pkg.free`, and `Pkg.compat`.

## Multi-Repo Rule

- In a workspace with sibling repos, if compat or registry resolution blocks
  testing, first `Pkg.develop(path=...)` the local dependency checkouts already
  present, preferably on their current `master`/`main`.
- Do this before chasing registry lag or editing compat blindly.

## Pick a Topic

- Pkg commands and dependency management:
  `references/pkg-commands.md`
- Interactive debugging and exploration:
  `references/debugging.md`
- Multi-package development and release flow:
  `references/multipackage-git-workflow.md`
- Package extension patterns:
  `references/extension-patterns.md`
- Testing and documenting extensions:
  `references/extension-testing.md`
- User-facing extension error hints:
  `references/weakdephelpers.md`
- Pkg app scaffolding and CLI patterns:
  `references/pkg-app-patterns.md`

## Common Tasks

### Shared Workspace

```julia
using Pkg
Pkg.activate("quantum-dev")
Pkg.develop(path="./QuantumInterface.jl")
Pkg.develop(path="./QuantumSavory.jl")
```

## Notes

- Use `julia-tests` for test execution and organization.
- Use `julia-docs` for docs setup and doctests.
- Use `julia-comonicon` when you need a richer CLI than Pkg apps provide.

## Related Skills

- `julia-tests`
- `julia-docs`
- `julia-scratch`

---
> Source: [krastanov/juliallmagentskills](https://github.com/krastanov/juliallmagentskills) — distributed by [TomeVault](https://tomevault.io).
<!-- tomevault:4.0:skill_md:2026-05-29 -->