Render Markdown into email

Render either Plain Markdown or R Markdown directly into the body of an email.

If input is a file then it will be interpreted as R Markdown it its extension is either "Rmd" or "Rmarkdown". Otherwise it will be processed as Plain Markdown.

Usage

render(
  msg,
  input,
  params = NULL,
  squish = TRUE,
  css_files = c(),
  include_css = c("rmd", "bootstrap"),
  language = FALSE,
  interpolate = TRUE,
  .open = "{{",
  .close = "}}",
  .envir = NULL
)

Arguments

msg: A message object.
input: The input Markdown file to be rendered or a character vector of Markdown text.
params: A list of named parameters that override custom parameters specified in the YAML front-matter.
squish: Whether to clean up whitespace in rendered document.
css_files: Extra CSS files.
include_css: Whether to include rendered CSS from various sources ("rmd" — native R Markdown CSS; "bootstrap" — Bootstrap CSS).
language: Language of content. If FALSE then will not include language field. If TRUE then will attempt to auto-detect language. Otherwise will use the specified language.
interpolate: Whether or not to interpolate into input using glue.
.open: The opening delimiter.
.close: The closing delimiter.
.envir: Environment used for glue interpolation. Defaults to parent.frame().

Value

A message object.

Plain Markdown

Plain Markdown is processed with commonmark::markdown_html().

R Markdown

R Markdown is processed with rmarkdown::render().

Regardless of what output type is specified in the input file, render() will always use the "html_document" output format.

Rending an R Markdown document can result in a lot of CSS. When all of the CSS is included in the HTML <head> and sent to GMail it can result in a message which is not correctly displayed inline in the Gmail web client. To get around this you can specify include_css = FALSE. This will mean that some styling will not be present in the resulting message, but that the message content will be correctly rendered inline.

Examples


# Plain Markdown

markdown <- "[This](https://www.google.com) is a link."
filename <- "message.md"

# Render from Markdown in character vector.
msg <- envelope() %>% render(markdown)

# Create a file containing Markdown
cat(markdown, file = filename)

# Render from Markdown in file.
msg <- envelope() %>% render(filename)

# Cleanup.
file.remove(filename)
#> [1] TRUE

# R Markdown

filename <- "gh-doc.Rmd"

# Create an Rmd document from template.
rmarkdown::draft(
  filename,
  template = "github_document",
  package = "rmarkdown",
  edit = FALSE
)

# Check for suitable version of Pandoc (https://pandoc.org/).
#
# Need to have version 2.0 or greater to support required --quiet option.
#
pandoc <- rmarkdown::find_pandoc()
suitable_pandoc <- !is.null(pandoc$dir) && grepl("^2", pandoc$version)

# Render from Rmd file.
if (suitable_pandoc) {
  msg <- envelope() %>%
    render(filename, include_css = c("rmd", "bootstrap"))
}

# Cleanup.
file.remove(filename)
#> [1] TRUE