Inconsistency with APA style when missing volume number

[LaoLittle]

Description

There is an inconsistency with APA style when handling journal articles that are missing a volume number.

Expected Behavior

According to APA guidelines, the issue number should appear in parentheses when the volume number is missing.

See: https://apastyle.apa.org/style-grammar-guidelines/references/examples/journal-article-references

Steps to reproduce

Create a .bib file using the following Biblatex code

@article{test,
 number    = "13",
}

Compile with the following Typst code:

#bibliography("refs.bib", full: true, style: "american-psychological-association")

Environment

• Typst Web Application
• Deployed on: 2025-09-09T16:28:36.482Z
• Typst Compiler Version: 8ace67d942a4b8c6b9d95b73b3a39f5d0259c7b2
• Google Chrome Version 140.0.7339.133 (Official Build) (arm64)
• macOS 15.6.1

[PgBiel]

I'll note that we take our styles from https://github.com/citation-style-language/styles/, so it's possible it's an issue with the APA style provided there.

With that said, I've done some local tests and this doesn't happen if you use the hayagriva YAML format directly:

wold:
  type: article
  issue: 23
  title: b
  author: c

This produces:

I believe (part of) the reason your example doesn't work is that hayagriva automatically assigns a periodical parent for the article. We can add it manually to the hayagriva YAML and see what happens:

wold:
  type: article
  issue: 23
  title: b
  author: c
  parent:
    type: periodical
    title: d

This produces a similar result to what you're seeing, with the 23 in italics as part of the periodical:

It could be a bug with the official APA style, to be raised upstream at the linked repository, if this is wrong behavior. Alternatively, it's possible the automatic BibLaTeX translation that adds a periodical parent might not be the best option. But not sure.