use std::fmt::{Display, Formatter}; /// Markdown text.#[derive(Debug)]pub struct MarkdownString(pub String); impl Display for MarkdownString { fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result { write!(f, "{}", self.0) }} impl MarkdownString { /// Escapes markdown special characters. /// /// Also escapes the following markdown extensions: /// /// * `^` for superscripts /// * `$` for inline math /// * `~` for strikethrough /// /// Escape of some character is unnecessary because while they are involved in markdown syntax, /// the other characters involved are escaped: /// /// * `!`, `]`, `(`, and `)` are used in link syntax, but `[` is escaped so these are parsed as /// plaintext. /// /// * `;` is used in HTML entity syntax, but `&` is escaped, so they are parsed as plaintext. /// /// TODO: There is one escape this doesn't do currently. Period after numbers at the start of the /// line (`[0-9]*\.`) should also be escaped to avoid it being interpreted as a list item. pub fn escape(text: &str) -> Self { let mut chunks = Vec::new(); let mut start_of_unescaped = None; for (ix, c) in text.char_indices() { match c { // Always escaped. '\\' | '`' | '*' | '_' | '[' | '^' | '$' | '~' | '&' | // TODO: these only need to be escaped when they are the first non-whitespace // character of the line of a block. There should probably be both an `escape_block` // which does this and an `escape_inline` method which does not escape these. '#' | '+' | '=' | '-' => { match start_of_unescaped { None => {} Some(start_of_unescaped) => { chunks.push(&text[start_of_unescaped..ix]); } } chunks.push("\\"); // Can include this char in the "unescaped" text since a // backslash was just emitted. start_of_unescaped = Some(ix); } // Escaped since `<` is used in opening HTML tags. `<` is used since Markdown // supports HTML entities, and this allows the text to be used directly in HTML. '<' => { match start_of_unescaped { None => {} Some(start_of_unescaped) => { chunks.push(&text[start_of_unescaped..ix]); } } chunks.push("<"); start_of_unescaped = None; } // Escaped since `>` is used for blockquotes. `>` is used since Markdown supports // HTML entities, and this allows the text to be used directly in HTML. '>' => { match start_of_unescaped { None => {} Some(start_of_unescaped) => { chunks.push(&text[start_of_unescaped..ix]); } } chunks.push("gt;"); start_of_unescaped = None; } _ => { if start_of_unescaped.is_none() { start_of_unescaped = Some(ix); } } } } if let Some(start_of_unescaped) = start_of_unescaped { chunks.push(&text[start_of_unescaped..]) } Self(chunks.concat()) } /// Returns markdown for inline code (wrapped in backticks), handling code that contains backticks /// and spaces. All whitespace is treated as a single space character. For text that does not /// contain whitespace other than ' ', this escaping roundtrips through pulldown-cmark. /// /// When used in tables, `|` should be escaped like `\|` in the text provided to this function. pub fn inline_code(text: &str) -> Self { // Apache License 2.0, same as this crate. // // Copied from `pulldown-cmark-to-cmark-20.0.0` with modifications: // // * Handling of all whitespace. pulldown-cmark-to-cmark is anticipating // `Code` events parsed by pulldown-cmark. // // * Direct return of string. // // https://github.com/Byron/pulldown-cmark-to-cmark/blob/3c850de2d3d1d79f19ca5f375e1089a653cf3ff7/src/lib.rs#L290 let mut all_whitespace = true; let text = text .chars() .map(|c| { if c.is_whitespace() { ' ' } else { all_whitespace = false; c } }) .collect::<String>(); // When inline code has leading and trailing ' ' characters, additional space is needed // to escape it, unless all characters are space. if all_whitespace { Self(format!("`{text}`")) } else { // More backticks are needed to delimit the inline code than the maximum number of // backticks in a consecutive run. let backticks = "`".repeat(count_max_consecutive_chars(&text, '`') + 1); let space = match text.as_bytes() { &[b'`', ..] | &[.., b'`'] => " ", // Space needed to separate backtick. &[b' ', .., b' '] => " ", // Space needed to escape inner space. _ => "", // No space needed. }; Self(format!("{backticks}{space}{text}{space}{backticks}")) } }} // Copied from `pulldown-cmark-to-cmark-20.0.0` with changed names.// https://github.com/Byron/pulldown-cmark-to-cmark/blob/3c850de2d3d1d79f19ca5f375e1089a653cf3ff7/src/lib.rs#L1063// Apache License 2.0, same as this code.fn count_max_consecutive_chars(text: &str, search: char) -> usize { let mut in_search_chars = false; let mut max_count = 0; let mut cur_count = 0; for ch in text.chars() { if ch == search { cur_count += 1; in_search_chars = true; } else if in_search_chars { max_count = max_count.max(cur_count); cur_count = 0; in_search_chars = false; } } max_count.max(cur_count)} #[cfg(test)]mod tests { use super::*; #[test] fn test_markdown_string_escape() { let input = r#" # Heading Another heading === Another heading variant --- Paragraph with [link](https://example.com) and `code`, *emphasis*, and ~strikethrough~. ``` code block ``` List with varying leaders: - Item 1 * Item 2 + Item 3 Some math: $`\sqrt{3x-1}+(1+x)^2`$ HTML entity: "#; let expected = r#" \# Heading Another heading \=\=\= Another heading variant \-\-\- Paragraph with \[link](https://example.com) and \`code\`, \*emphasis\*, and \~strikethrough\~. \`\`\` code block \`\`\` List with varying leaders: \- Item 1 \* Item 2 \+ Item 3 Some math: \$\`\\sqrt{3x\-1}\+(1\+x)\^2\`\$ HTML entity: \ "#; assert_eq!(MarkdownString::escape(input).0, expected); } #[test] fn test_markdown_string_inline_code() { assert_eq!(MarkdownString::inline_code(" ").0, "` `"); assert_eq!(MarkdownString::inline_code("text").0, "`text`"); assert_eq!(MarkdownString::inline_code("text ").0, "`text `"); assert_eq!(MarkdownString::inline_code(" text ").0, "` text `"); assert_eq!(MarkdownString::inline_code("`").0, "`` ` ``"); assert_eq!(MarkdownString::inline_code("``").0, "``` `` ```"); assert_eq!(MarkdownString::inline_code("`text`").0, "`` `text` ``"); assert_eq!( MarkdownString::inline_code("some `text` no leading or trailing backticks").0, "``some `text` no leading or trailing backticks``" ); } #[test] fn test_count_max_consecutive_chars() { assert_eq!( count_max_consecutive_chars("``a```b``", '`'), 3, "the highest seen consecutive segment of backticks counts" ); assert_eq!( count_max_consecutive_chars("```a``b`", '`'), 3, "it can't be downgraded later" ); }}
use std::fmt::{Display, Formatter};
/// Markdown text.
#[derive(Debug)]
pub struct MarkdownString(pub String);
impl Display for MarkdownString {
fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
write!(f, "{}", self.0)
}
}
impl MarkdownString {
/// Escapes markdown special characters.
///
/// Also escapes the following markdown extensions:
///
/// * `^` for superscripts
/// * `$` for inline math
/// * `~` for strikethrough
///
/// Escape of some character is unnecessary because while they are involved in markdown syntax,
/// the other characters involved are escaped:
///
/// * `!`, `]`, `(`, and `)` are used in link syntax, but `[` is escaped so these are parsed as
/// plaintext.
///
/// * `;` is used in HTML entity syntax, but `&` is escaped, so they are parsed as plaintext.
///
/// TODO: There is one escape this doesn't do currently. Period after numbers at the start of the
/// line (`[0-9]*\.`) should also be escaped to avoid it being interpreted as a list item.
pub fn escape(text: &str) -> Self {
let mut chunks = Vec::new();
let mut start_of_unescaped = None;
for (ix, c) in text.char_indices() {
match c {
// Always escaped.
'\\' | '`' | '*' | '_' | '[' | '^' | '$' | '~' | '&' |
// TODO: these only need to be escaped when they are the first non-whitespace
// character of the line of a block. There should probably be both an `escape_block`
// which does this and an `escape_inline` method which does not escape these.
'#' | '+' | '=' | '-' => {
match start_of_unescaped {
None => {}
Some(start_of_unescaped) => {
chunks.push(&text[start_of_unescaped..ix]);
}
}
chunks.push("\\");
// Can include this char in the "unescaped" text since a
// backslash was just emitted.
start_of_unescaped = Some(ix);
}
// Escaped since `<` is used in opening HTML tags. `<` is used since Markdown
// supports HTML entities, and this allows the text to be used directly in HTML.
'<' => {
match start_of_unescaped {
None => {}
Some(start_of_unescaped) => {
chunks.push(&text[start_of_unescaped..ix]);
}
}
chunks.push("<");
start_of_unescaped = None;
}
// Escaped since `>` is used for blockquotes. `>` is used since Markdown supports
// HTML entities, and this allows the text to be used directly in HTML.
'>' => {
match start_of_unescaped {
None => {}
Some(start_of_unescaped) => {
chunks.push(&text[start_of_unescaped..ix]);
}
}
chunks.push("gt;");
start_of_unescaped = None;
}
_ => {
if start_of_unescaped.is_none() {
start_of_unescaped = Some(ix);
}
}
}
}
if let Some(start_of_unescaped) = start_of_unescaped {
chunks.push(&text[start_of_unescaped..])
}
Self(chunks.concat())
}
/// Returns markdown for inline code (wrapped in backticks), handling code that contains backticks
/// and spaces. All whitespace is treated as a single space character. For text that does not
/// contain whitespace other than ' ', this escaping roundtrips through pulldown-cmark.
///
/// When used in tables, `|` should be escaped like `\|` in the text provided to this function.
pub fn inline_code(text: &str) -> Self {
// Apache License 2.0, same as this crate.
//
// Copied from `pulldown-cmark-to-cmark-20.0.0` with modifications:
//
// * Handling of all whitespace. pulldown-cmark-to-cmark is anticipating
// `Code` events parsed by pulldown-cmark.
//
// * Direct return of string.
//
// https://github.com/Byron/pulldown-cmark-to-cmark/blob/3c850de2d3d1d79f19ca5f375e1089a653cf3ff7/src/lib.rs#L290
let mut all_whitespace = true;
let text = text
.chars()
.map(|c| {
if c.is_whitespace() {
' '
} else {
all_whitespace = false;
c
}
})
.collect::<String>();
// When inline code has leading and trailing ' ' characters, additional space is needed
// to escape it, unless all characters are space.
if all_whitespace {
Self(format!("`{text}`"))
} else {
// More backticks are needed to delimit the inline code than the maximum number of
// backticks in a consecutive run.
let backticks = "`".repeat(count_max_consecutive_chars(&text, '`') + 1);
let space = match text.as_bytes() {
&[b'`', ..] | &[.., b'`'] => " ", // Space needed to separate backtick.
&[b' ', .., b' '] => " ", // Space needed to escape inner space.
_ => "", // No space needed.
};
Self(format!("{backticks}{space}{text}{space}{backticks}"))
}
}
}
// Copied from `pulldown-cmark-to-cmark-20.0.0` with changed names.
// https://github.com/Byron/pulldown-cmark-to-cmark/blob/3c850de2d3d1d79f19ca5f375e1089a653cf3ff7/src/lib.rs#L1063
// Apache License 2.0, same as this code.
fn count_max_consecutive_chars(text: &str, search: char) -> usize {
let mut in_search_chars = false;
let mut max_count = 0;
let mut cur_count = 0;
for ch in text.chars() {
if ch == search {
cur_count += 1;
in_search_chars = true;
} else if in_search_chars {
max_count = max_count.max(cur_count);
cur_count = 0;
in_search_chars = false;
}
}
max_count.max(cur_count)
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_markdown_string_escape() {
let input = r#"
# Heading
Another heading
===
Another heading variant
---
Paragraph with [link](https://example.com) and `code`, *emphasis*, and ~strikethrough~.
```
code block
```
List with varying leaders:
- Item 1
* Item 2
+ Item 3
Some math: $`\sqrt{3x-1}+(1+x)^2`$
HTML entity:
"#;
let expected = r#"
\# Heading
Another heading
\=\=\=
Another heading variant
\-\-\-
Paragraph with \[link](https://example.com) and \`code\`, \*emphasis\*, and \~strikethrough\~.
\`\`\`
code block
\`\`\`
List with varying leaders:
\- Item 1
\* Item 2
\+ Item 3
Some math: \$\`\\sqrt{3x\-1}\+(1\+x)\^2\`\$
HTML entity: \
"#;
assert_eq!(MarkdownString::escape(input).0, expected);
}
#[test]
fn test_markdown_string_inline_code() {
assert_eq!(MarkdownString::inline_code(" ").0, "` `");
assert_eq!(MarkdownString::inline_code("text").0, "`text`");
assert_eq!(MarkdownString::inline_code("text ").0, "`text `");
assert_eq!(MarkdownString::inline_code(" text ").0, "` text `");
assert_eq!(MarkdownString::inline_code("`").0, "`` ` ``");
assert_eq!(MarkdownString::inline_code("``").0, "``` `` ```");
assert_eq!(MarkdownString::inline_code("`text`").0, "`` `text` ``");
assert_eq!(
MarkdownString::inline_code("some `text` no leading or trailing backticks").0,
"``some `text` no leading or trailing backticks``"
);
}
#[test]
fn test_count_max_consecutive_chars() {
assert_eq!(
count_max_consecutive_chars("``a```b``", '`'),
3,
"the highest seen consecutive segment of backticks counts"
);
assert_eq!(
count_max_consecutive_chars("```a``b`", '`'),
3,
"it can't be downgraded later"
);
}
}