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Skillsjustfile

justfile

Coding & development

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Updated 10-16 03:52

About this skill

Justfile

Author and maintain Just task runners. House style matches this repo's root justfile: minimum-version ≥ 1.55.0, default-list, require(), [default] / [doc] / [group] / [arg], prefer [script] for multi-line bodies. Distill casey/Just principles; never paste third-party skill prose or embed the casey README.

Load reference files on demand from the index below — do not load all at once. Frontmatter is for discovery; references carry deep procedure.

Permission posture

write-scoped — may write justfiles; read-only just inspect by default; ask before destructive recipes, deleting a Makefile, or running side-effecting recipes.

Dispatch

$ARGUMENTS Mode
(empty) / help Empty-args gallery
create [description] Create
edit [path|recipe] Edit
migrate [source] Migrate
check [path] Check
discover [query] Discover
Natural language about justfiles Auto-detect

Auto-detection heuristic

  1. Existing justfile / Justfile + modify/fix/rename → edit
  2. "migrate" / Makefile / package.json scripts → just → migrate
  3. "lint" / "check" / "fmt" / house-style audit → check
  4. "list" / "show" / "what recipes" / dump → discover
  5. New justfile or "add recipe" without existing file → create
  6. Pure shell / CI YAML / Make build semantics / mise / Compose → refuse (see negatives)

Empty args

When $ARGUMENTS is empty, show the mode gallery, posture line, critical rules summary, and reference index. Do not invent a mutating default.

Canonical vocabulary

Use these exactly (canonical terms):

Term Meaning
write-scoped May write justfiles; ask before destructive runs/deletes
house style This repo's justfile conventions (default-list, [doc], [script], …)
discover Read-only inspect via just --list / --show / --dump
migrate Map Makefile/npm task scripts into Just recipes
[script] Multi-line script recipe attribute (never combine with recipe-level @)
opt-in gate Create-mode confirmations before overwrite or side effects

Critical rules

  1. Version-first — run just --version before using mid-2026 attributes; prefer ≥1.55.0.
  2. Quiet vs script — never put @ on a [script] recipe; use @ only for line quieting.
  3. Prefer [script] for multi-line shell; avoid fragile escaped multi-line recipes.
  4. No blind --fmt — inspect with --dump / --check first; apply --fmt only with intent.
  5. Dry-run / inspect before side effects — discover with --list/--show before running recipes that write, delete, or network.
  6. check.py-before-complete — after skill or justfile edits in this repo skill, run uv run python scripts/check.py from skills/justfile/ before declaring done.
  7. No secrets in justfiles — use env / dotenv / user-owned secrets; never hardcode tokens.
  8. Ask before deleting Makefile or other source runners during migrate.

Operator contract

create

  1. Confirm target path; refuse overwrite without explicit approval.
  2. Load references/create.md (includes opt-in gate).
  3. Scaffold house-style settings + [default] list recipe + grouped docs.
  4. Prefer require("tool") for hard deps; document optional tools.

edit

  1. Read the target justfile; run discover inspect if recipes unclear.
  2. Load references/edit.md.
  3. Preserve house settings; migrate Make-flavored ## comment docs to [doc].

migrate

  1. Inventory Makefile / npm scripts; map to recipes (see references/migrate.md).
  2. Keep sources until user approves deletion.
  3. Convert Make ## help to Just [doc] / default-list — never keep Make comment-docs as the Just help system.

check

  1. Load references/check.md.
  2. just --version, then --list / --dump / --check as needed.
  3. Report house-style gaps; do not auto---fmt unless asked.

discover

  1. Load references/discover.md.
  2. Prefer read-only: --list, --show, --dump (--dump-format=json), --groups.
  3. Link casey manual for deep semantics: https://just.systems/man/en/

When NOT to use

  • Shell script generation → shell-scripter
  • Shell convention-only edits → shell-conventions
  • CI/CD workflow YAML → devops-engineer
  • Make file-timestamp / pattern-rule builds (not task recipes)
  • Docker Compose authorship
  • Toolchain version management as the product → mise tooling

See references/when-not-just.md.

Reference index

File Use when
references/discover.md Inspect recipes with just CLI
references/create.md New justfile + opt-in gate
references/edit.md Change existing recipes/settings
references/migrate.md Makefile / npm → just
references/check.md Lint / fmt-check / house-style audit
references/when-not-just.md Scope refusals and redirects
references/pitfalls.md Common Just footguns
references/patterns.md House-style recipe patterns

Validation Contract

Run from this skill directory before declaring changes complete:

uv run python scripts/check.py
uv run python skills/skill-creator/scripts/audit.py skills/justfile/
uv run python skills/skill-creator/scripts/package.py skills/justfile --dry-run

scripts/check.py chains validate_skill.py, validate_evals.py, package dry-run, and audit. Completion criteria:

  1. uv run python scripts/check.py exits 0.
  2. Audit grade A (≥90).
  3. Package --dry-run reports portable with no errors.
  4. No portable-CLI violations remain under this skill directory.

Example Blocks

When $ARGUMENTS is empty, show:

  • /justfile
  • /justfile help
  • /justfile create <description>
  • /justfile edit <path|recipe>
  • /justfile migrate <Makefile|package.json>
  • /justfile check [path]
  • /justfile discover [query]

State the write-scoped boundary (justfile writes OK; ask before destructive recipe runs or Makefile deletion) and the validation command:

uv run python skills/justfile/scripts/check.py