perf: cached source

Author: SyMind

src/cached_source.rs

@@ -74,6 +74,7 @@ self_cell::self_cell!(
  impl { Debug }
 );
 
+/// A wrapper around any [`Source`] that caches expensive computations to improve performance.
 pub struct CachedSource(CachedSourceCell);
 
 impl CachedSource {
@@ -121,14 +122,18 @@ impl Source for CachedSource {
  dependent.cached_colomns_map.get_or_init(|| {
  let map = owner.inner.map(options);
  unsafe { std::mem::transmute::<Option<SourceMap>, Option<SourceMap<'static>>>(map) }
- }).clone()
+ })
+ .as_ref()
+ .map(|m| m.as_borrowed())
  })
  } else {
  self.0.with_dependent(|owner, dependent| {
  dependent.cached_line_only_map.get_or_init(|| {
  let map = owner.inner.map(options);
  unsafe { std::mem::transmute::<Option<SourceMap>, Option<SourceMap<'static>>>(map) }
- }).clone()
+ })
+ .as_ref()
+ .map(|m| m.as_borrowed())
  })
  }
  }
@@ -255,7 +260,7 @@ mod tests {
  value: "\nconsole.log(1);\n".to_string(),
  name: "index.js".to_string(),
  source_map: SourceMap::new(
- ";AACA".into(),
+ ";AACA",
  vec!["index.js".into()],
  vec!["// DELETE IT\nconsole.log(1)".into()],
  vec![],

src/helpers.rs

@@ -63,9 +63,8 @@ pub fn get_map<'a, S: StreamChunks>(
  },
  );
  let mappings = mappings_encoder.drain();
- (!mappings.is_empty()).then(|| {
- SourceMap::new(Cow::Owned(mappings), sources, sources_content, names)
- })
+ (!mappings.is_empty())
+ .then(|| SourceMap::new(mappings, sources, sources_content, names))
 }
 
 /// [StreamChunks] abstraction, see [webpack-sources source.streamChunks](https://github.com/webpack/webpack-sources/blob/9f98066311d53a153fdc7c633422a1d086528027/lib/helpers/streamChunks.js#L13).
@@ -1241,7 +1240,7 @@ pub fn stream_and_get_source_and_map<'a, S: StreamChunks>(
  None
  } else {
  Some(SourceMap::new(
- Cow::Owned(mappings),
+ mappings.to_string(),
  sources,
  sources_content,
  names,