wrong-type-argument integerp when calling ivy-bibtex-display-transformer

[peschkaj]

With a single entry bibtex file:

@misc{norvigLetterFrequencyCounts,
  title = {English Letter Frequency Counts: Mayzner Revisited},
  author = {Norvig, Peter},
  year = {2012},
  howpublished = {\url{http://norvig.com/mayzner.html}},
  note = {Accessed: 2018-05-23}
}

ivy-bibtex errors with "Wrong type argument: integerp, nil"

toggle-debug-on-error output available at https://gist.github.com/peschkaj/2849631261c6ffa7a69bbf5f567834fa

Configuration info:

• emacs version: 26.1 (installed via homebrew using brew install emacs-mac --with-imagemagick --with-modern-icon --with-natural-title-bar)

emacs configuration:

(setq papers-dir   (expand-file-name "~/Documents/reading/")
      papers-pdfs  (concat papers-dir "lib/")
      papers-notes (concat papers-dir "index.org")
      papers-refs  (concat papers-dir "index.bib"))

(use-package ivy-bibtex
    :after ivy
    :config (setq bibtex-completion-bibliography (list papers-refs)
                  bibtex-completion-library-path papers-pdfs
                  bibtex-completion-notes-path   papers-notes
                  bibtex-completion-pdf-field    "file"
                  bibtex-completion-display-formats
                  '((article       . "${=has-pdf=:1}${=has-note=:1} ${=type=:3} ${year:4} ${author:36} ${title:*} ${journal:40}")
                    (inbook        . "${=has-pdf=:1}${=has-note=:1} ${=type=:3} ${year:4} ${author:36} ${title:*} Chapter ${chapter:32}")
                    (incollection  . "${=has-pdf=:1}${=has-note=:1} ${=type=:3} ${year:4} ${author:36} ${title:*} ${booktitle:40}")
                    (inproceedings . "${=has-pdf=:1}${=has-note=:1} ${=type=:3} ${year:4} ${author:36} ${title:*} ${booktitle:40}")
                    (t             . "${=has-pdf=:1}${=has-note=:1} ${=type=:3} ${year:4} ${author:36} ${title:*}"))
                  bibtex-completion-additional-search-fields '(keywords)))
  ;; ivy-bibtex requires ivy's `ivy--regex-ignore-order` regex builder, which
  ;; ignores the order of regexp tokens when searching for matching candidates.
  (setq ivy-re-builders-alist
      '((ivy-bibtex . ivy--regex-ignore-order)
        (t . ivy--regex-plus)))

[tmalsburg]

Hi, thanks for the report. I will try to reproduce this on my system (I'm using helm-bibtex). One question: Are you using org-ref? In the past there were cases where org-ref interfered with plain ivy/helm-bibtex.