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Highlight and link a code block

Source: R/highlight.R
highlight.Rd

This function:

  • syntax highlights code

  • links function calls to their documentation (where possible)

  • in comments, translates ANSI escapes in to HTML equivalents.

Usage

highlight(text, classes = classes_chroma(), pre_class = NULL, code = FALSE)

classes_pandoc()

classes_chroma()

Arguments

text

String of code to highlight and link.

classes

A mapping between token names and CSS class names. Bundled classes_pandoc() and classes_chroma() provide mappings that (roughly) match Pandoc and chroma (used by hugo) classes so you can use existing themes.

pre_class

Class(es) to give output <pre>.

code

If TRUE, wrap output in a <code> block

Value

If text is valid R code, an HTML <pre> tag. Otherwise, NA.

A string containing syntax highlighted HTML or NA (if text

isn't parseable).

Options

downlit provides a number of options to control the details of the linking. They are particularly important if you want to generate "local" links.

  • downlit.package: name of the current package. Determines when topic_index and article_index

  • downlit.topic_index and downlit.article_index: named character vector that maps from topic/article name to path.

  • downlit.rdname: name of current Rd file being documented (if any); used to avoid self-links.

  • downlit.attached: character vector of currently attached R packages.

  • downlit.local_packages: named character vector providing relative paths (value) to packages (name) that can be reached with relative links from the target HTML document.

  • downlit.topic_path and downlit.article_path: paths to reference topics and articles/vignettes relative to the "current" file.

Examples

cat(highlight("1 + 1"))
#> <span><span class='m'>1</span> <span class='o'>+</span> <span class='m'>1</span></span>
cat(highlight("base::t(1:3)"))
#> <span><span class='nf'>base</span><span class='nf'>::</span><span class='nf'><a href='https://rdrr.io/r/base/t.html'>t</a></span><span class='o'>(</span><span class='m'>1</span><span class='o'>:</span><span class='m'>3</span><span class='o'>)</span></span>

# Unparseable R code returns NA
cat(highlight("base::t("))
#> NA