protect_unescaped: Protect unescaped square brackets from being escaped

In tinkr: Cast '(R)Markdown' Files to 'XML' and Back Again

Protect unescaped square brackets from being escaped

Description

Commonmark allows both ⁠[unescaped]⁠ and ⁠\[escaped\]⁠ square brackets, but in the XML representation, it makes no note of which square brackets were originally escaped and thus will escape both in the output. This function protects brackets that were unescaped in the source document from being escaped.

Usage

protect_unescaped(body, txt, ns = md_ns())

Arguments

body	an XML body
txt	the text of a source file
ns	an the namespace that resolves the Markdown namespace (defaults to md_ns())

Details

This is an internal function that is run by default via to_xml() and yarn$new(). It uses the original document, parsed as text, to find and protect unescaped square brackets from being escaped in the output.

Example: child documents and footnotes

For example, let's say you have two R Markdown documents, one references the other as a child, which has a reference-style link:

index.Rmd:

## Title

Without protection reference style links (e.g. \[text\]\[link\]) like this
[outside link][reflink] would be accidentally escaped.
This is a footnote [^1].

[^1]: footnotes are not recognised by commonmark

```{r, child="child.Rmd"}
```

child.Rmd:

...
[reflink]: https://example.com

Without protection, the roundtripped index.Rmd document would look like this:

## Title

Without protection reference style links (e.g. \[text\]\[link\]) like this
\[outside link\]\[reflink\] would be accidentally escaped.
This is a footnote \[^1\]

\[^1\]: footnotes are not recognised by commonmark

```{r, child="child.Rmd"}
```

This function provides the protection that allows these unescaped brackets to remain unescaped during roundtrip.

Note

Because the This body to be an XML document with sourcepos attributes on the nodes, which is achieved by using sourcepos = TRUE with to_xml() or yarn.

Examples

f <- system.file("extdata", "link-test.md", package = "tinkr")
md <- yarn$new(f, sourcepos = TRUE, unescaped = FALSE)
md$show()
if (requireNamespace("withr")) {
lines <- readLines(f)[-length(md$yaml)]
lnks <- withr::with_namespace("tinkr", 
  protect_unescaped(body = md$body, txt = lines))
md$body <- lnks
md$show()
}

tinkr documentation built on March 31, 2023, 8:12 p.m.