Author vs Contributor for R package - which role for small code contribution?

If someone has provided a useful block of code to an R library, what is the appropriate role for them in package documentation?

Why it matters

I have seen contributor role given to such cases, but after reviewing the definitions of author and contributor, I believe author is the appropriate role. But there may be something else more appropriate (or perhaps both author/contributor)

What library of congress says

Author:

A person, family, or organization responsible for creating a work that is primarily textual in content, regardless of media type (e.g., printed text, spoken word, electronic text, tactile text) or genre (e.g., poems, novels, screenplays, blogs). Use also for persons, etc., creating a new work by paraphrasing, rewriting, or adapting works by another creator such that the modification has substantially changed the nature and content of the original or changed the medium of expression

Contributor:

A person, family or organization responsible for making contributions to the resource. This includes those whose work has been contributed to a larger work, such as an anthology, serial publication, or other compilation of individual works. If a more specific role is available, prefer that, e.g. editor, compiler, illustrator

Possible points of confusion

• When a pull request is accepted, github will refer to the creator of the PR as a 'contributor'
• In day-to-day conversation, someone who provides useful input into a project could reasonably be called a 'contributor'

As pointed out in previous answers, the idea was to distinguish how substantial the different code contributions are. The manual page ?person explains:

The new scheme also adds the possibility of specifying roles based on a subset of the MARC Code List for Relators (URL: https://www.loc.gov/marc/relators/relaterm.html). When giving the roles of persons in the context of authoring R packages, the following usage is suggested.

• "aut" (Author) Use for full authors who have made substantial contributions to the package and should show up in the package citation.
• "cre" (Creator) Use for the package maintainer.
• "ctb" (Contributor) Use for authors who have made smaller contributions (such as code patches etc.) but should not show up in the package citation.

Suggestions for the usage of further roles in the context of R packages are also provided there ("com", "cph", "ctr", "dtc", "fnd", "rev", "ths", "trl"). The citation mentioned above is the "default" or "auto" citation that you get from citation("foo") if package "foo" has no dedicated CITATION file. If it has you can still get the default by citation("foo", auto = TRUE). See ?citation for more details.

Coming back to the question of "author" vs. "contributor": When we wrote the documentation above (and the accompanying paper by Hornik et al. in The R Journal) we deliberately just gave rough guidelines because the ultimate decision what is "substantial enough" needs to be made by the package authors themselves. This is not unsimilar to the decision who to include in the author list of a scientific paper vs. mentioning in the acknowledgments - for which the practices also vary a lot across disciplines/communities.

A strategy that is not uncommon is to distinguish three levels of contribution:

• Those who made very small contributions (like small fixes or improvements) are not listed in the DESCRIPTION but acknowledged in the NEWS or Changelog. This applies to many small contributions made through bug/issue trackers or small pull requests on GitHub or similar platforms.
• Those who provided larger patches, small helper functions, additions for specific cases, etc. who should be listed in the DESCRIPTION as "conributors" (ctb). This also applies to the case where code parts are copied from other packages or other sources.
• Those who made larger and/or continuing contributions that are substantial enough to be listed as "authors" (aut) in the DESCRIPTION and the package's default/auto citation.

Reference: Hornik K, Murdoch D, Zeileis A (2012). "Who Did What? The Roles of R Package Authors and How to Refer to Them." The R Journal, 4(1), 64-69. doi:10.32614/RJ-2012-009