feat(embedded): Add prefix-char frontmatter syntax support

This is a follow up to #13241 with another syntax being discussed. This one is a bit more polarizing but we're hoping first-hand experience with it can help people get a feel for how well it works in practice. As the experiment is meant to be short-lived, this is implemented in a hacky way and docs aren't updated.
rust-lang · Jan 3, 2024 · b77ce7f · b77ce7f
1 parent f9946d1
commit b77ce7f
Showing 1 changed file with 58 additions and 8 deletions.
diff --git a/src/cargo/util/toml/embedded.rs b/src/cargo/util/toml/embedded.rs
@@ -185,7 185,7 @@ fn sanitize_name(name: &str) -> String {
 struct Source<'s> {
  shebang: Option<&'s str>,
  info: Option<&'s str>,
- frontmatter: Option<&'s str>,
  frontmatter: Option<String>,
  content: &'s str,
 }
 
@@ -234,11 234,14 @@ fn split_source(input: &str) -> CargoResult<Source<'_>> {
  0 => {
  return Ok(source);
  }
  1 if tick_char == '#' => {
  // Attribute
  return Ok(source);
  }
  2 if tick_char == '#' => {
  return split_prefix_source(source, "##");
  }
  1 | 2 => {
- if tick_char == '#' {
- // Attribute
- return Ok(source);
- }
  anyhow::bail!("found {tick_end} `{tick_char}` in rust frontmatter, expected at least 3")
  }
  _ => source.content.split_at(tick_end),
@@ -252,7 255,7 @@ fn split_source(input: &str) -> CargoResult<Source<'_>> {
  let Some((frontmatter, content)) = source.content.split_once(fence_pattern) else {
  anyhow::bail!("no closing `{fence_pattern}` found for frontmatter");
  };
- source.frontmatter = Some(frontmatter);
  source.frontmatter = Some(frontmatter.to_owned());
  source.content = content;
 
  let (line, content) = source
@@ -268,6 271,22 @@ fn split_source(input: &str) -> CargoResult<Source<'_>> {
  Ok(source)
 }
 
 fn split_prefix_source<'s>(mut source: Source<'s>, prefix: &str) -> CargoResult<Source<'s>> {
  let mut frontmatter = String::new();
  while let Some(rest) = source.content.strip_prefix(prefix) {
  if !rest.is_empty() && !rest.starts_with(' ') {
  anyhow::bail!("frontmatter must have a space between `##` and the content");
  }
  let (line, rest) = rest.split_once('\n').unwrap_or((rest, ""));
  frontmatter.push_str(" ");
  frontmatter.push_str(line);
  frontmatter.push('\n');
  source.content = rest;
  }
  source.frontmatter = Some(frontmatter);
  Ok(source)
 }
 
 #[cfg(test)]
 mod test_expand {
  use super::*;
@@ -375,7 394,7 @@ fn main() {}
  }
 
  #[test]
- fn test_dash() {
  fn test_dash_fence() {
  snapbox::assert_matches(
  r#"[[bin]]
 name = "test-"
@@ -408,7 427,7 @@ fn main() {}
  }
 
  #[test]
- fn test_hash() {
  fn test_hash_fence() {
  snapbox::assert_matches(
  r#"[[bin]]
 name = "test-"
@@ -436,6 455,37 @@ strip = true
 time="0.1.25"
 ###
 fn main() {}
 "#),
  );
  }
 
  #[test]
  fn test_hash_prefix() {
  snapbox::assert_matches(
  r#"[[bin]]
 name = "test-"
 path = [..]
 
 [dependencies]
 time = "0.1.25"
 
 [package]
 autobenches = false
 autobins = false
 autoexamples = false
 autotests = false
 build = false
 edition = "2021"
 name = "test-"
 
 [profile.release]
 strip = true
 
 [workspace]
 "#,
  si!(r#"## [dependencies]
 ## time="0.1.25"
 fn main() {}
 "#),
  );
  }