Auto-linking

Within a package

pkgdown will automatically link to documentation and articles wherever it’s possible to do unambiguously. This includes:

• Bare function calls, like build_site().
• Calls to ?, like ?build_site or package?pkgdown.
• Calls to help(), like help("pkgdown").
• Calls to vignette(), like vignette("pkgdown").

Across packages

Linking to documentation in another package is straightforward. Just adapt the call in the usual way:

• purrr::map(), MASS::addterm().
• ?purrr::map, ?MASS::addterm.
• vignette("other-langs", package = "purrr"), vignette("longintro", package = "rpart")

If pkgdown can find a pkgdown site for the remote package, it will link to it; otherwise it will link to http://rdrr.io/ for documentation, and CRAN for vignettes. In order for a pkgdown site to be findable, it needs to be listed in two places:

• In the URL field in the DESCRIPTION, as in dplyr:

  URL: http://dplyr.tidyverse.org, https://github.com/tidyverse/dplyr

• In the url field in _pkgdown.yml, as in dplyr

  url: https://dplyr.tidyverse.org

  When this field is defined, pkgdown generate a public facing pkgdown.yml file that provides metadata about the site:

  pandoc: '2.2'
  pkgdown: 1.3.0
  pkgdown_sha: ~
  articles:
    compatibility: compatibility.html
    dplyr: dplyr.html
    dplyr_0.8.0: future/dplyr_0.8.0.html
    dplyr_0.8.0_new_hybrid: future/dplyr_0.8.0_new_hybrid.html
    programming: programming.html
    two-table: two-table.html
    window-functions: window-functions.html
  urls:
    reference: https://dplyr.tidyverse.org/reference
    article: https://dplyr.tidyverse.org/articles

Now, when you build a pkgdown site for a package that links to the dplyr documentation (e.g., dplyr::mutate()), pkgdown looks first in dplyr’s DESCRIPTION to find its website, then it looks for pkgdown.yml, and uses the metadata to generate the correct links.