r-package-development

name	r-package-development
description	R package dev with devtools, testthat, and roxygen2.
user-invocable	true
allowed-tools	["Read","Edit","Write","Bash"]
metadata	{"author":"Simon P. Couch (@simonpcouch)","version":"1.2"}

R package development

Key commands

# Run code in the package
Rscript -e "devtools::load_all(); code"

# Run all tests
Rscript -e "devtools::test()"

# Run all tests for files starting with {name}
Rscript -e "devtools::test(filter = '^{name}')"

# Run all tests for R/{name}.R
Rscript -e "devtools::test_active_file('R/{name}.R')"

# Run a single test "blah" for R/{name}.R
Rscript -e "devtools::test_active_file('R/{name}.R', desc = 'blah')"

# Redocument the package
Rscript -e "devtools::document()"

# Check pkgdown documentation
Rscript -e "pkgdown::check_pkgdown()"

# Check the package with R CMD check
Rscript -e "devtools::check()"

# Format code
air format .

Coding

• Always run air format . after generating code.
• Use the base pipe operator (|>) not the magrittr pipe (%>%).
• Use \() ... for single-line anonymous functions. For all other cases, use function() {...}.

Testing

For the full testthat API (fixtures, mocking, snapshots, BDD-style tests), see testing-r-packages. Match the package's existing expect_error()/expect_warning() or snapshot-testing style where precedent exists. On a fresh package with no precedent, follow testing-r-packages' preference for snapshot-based error/warning tests.

• Tests for R/{name}.R go in tests/testthat/test-{name}.R.
• All new code should have an accompanying test.
• If there are existing tests, place new tests next to similar existing tests.
• Strive to keep tests minimal with few comments.
• Avoid expect_true() and expect_false() in favour of a specific expectation which will give a better failure message.
• When testing errors and warnings, match the package's existing precedent where one exists (see above). On a fresh package with no precedent, use expect_snapshot(error = TRUE) for errors and expect_snapshot() for warnings, not expect_error() or expect_warning(). A snapshot lets the user review the full text of the output.

Documentation

• Every user-facing function should be exported and have roxygen2 documentation.
• Wrap roxygen comments at 80 characters.
• Internal functions should not have roxygen documentation.
• Whenever you add a new (non-internal) documentation topic, also add the topic to _pkgdown.yml.
• Always re-document the package after changing a roxygen2 comment.
• Use pkgdown::check_pkgdown() to check that all topics are included in the reference index.

NEWS.md

This is the tidyverse-style default. When the package already has an established NEWS.md style, match that existing style instead --- see r-pkg-news, whose whole job is reading a package's precedent before drafting a new entry.

• Every user-facing change should be given a bullet in NEWS.md. Do not add bullets for small documentation changes or internal refactorings.
• Each bullet should briefly describe the change to the end user.
• If the change is related to a function, put the name of the function early in the bullet.
• If the bullet is related to a GitHub issue or pull request, reference it by number in parentheses before the final period: (#123)..
• Order bullets alphabetically by function name. Put all bullets that don't mention function names at the beginning.

Relationship to other skills

This skill is a day-to-day dev-loop reference (load, test, document, format) with this author's own conventions. It does not replace, and does not cover:

• r-pkg-check --- running and triaging devtools::check() output.
• r-pkg-cran-checklist --- the CRAN release mechanics (win-builder, revdep checks, devtools::release()).
• cran-extrachecks --- the ad-hoc/stylistic CRAN checklist (Title case, @return tags, URL hygiene) that devtools::check() doesn't catch on its own.
• r-pkg-news --- matching a package's existing NEWS.md style, which overrides this skill's own default above.
• testing-r-packages --- the full testthat API (fixtures, mocking, snapshots, BDD-style tests). Match the package's existing expect_error()/expect_warning() or snapshot-testing style where precedent exists. On a fresh package with no precedent, follow testing-r-packages' preference for snapshot-based error/warning tests, which agrees with this skill's own default above.