1 files changed, 106 insertions, 0 deletions
diff --git a/cli/ast/comments.rs b/cli/ast/comments.rs
new file mode 100644
index 000000000..dfe7f99a9
--- /dev/null
+++ b/cli/ast/comments.rs
@@ -0,0 +1,106 @@
+// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
+
+use std::cell::RefCell;
+use std::rc::Rc;
+use std::sync::Arc;
+use swc_common::comments::Comment;
+use swc_common::comments::Comments;
+use swc_common::comments::SingleThreadedComments;
+use swc_common::comments::SingleThreadedCommentsMapInner;
+use swc_common::BytePos;
+
+/// An implementation of swc's `Comments` that implements `Sync`
+/// to support being used in multi-threaded code. This implementation
+/// is immutable and should you need mutability you may create a copy
+/// by converting it to an swc `SingleThreadedComments`.
+#[derive(Clone, Debug)]
+pub struct MultiThreadedComments {
+  leading: Arc<SingleThreadedCommentsMapInner>,
+  trailing: Arc<SingleThreadedCommentsMapInner>,
+}
+
+impl MultiThreadedComments {
+  pub fn from_single_threaded(comments: SingleThreadedComments) -> Self {
+    let (leading, trailing) = comments.take_all();
+    let leading = Arc::new(Rc::try_unwrap(leading).unwrap().into_inner());
+    let trailing = Arc::new(Rc::try_unwrap(trailing).unwrap().into_inner());
+    MultiThreadedComments { leading, trailing }
+  }
+
+  pub fn as_single_threaded(&self) -> SingleThreadedComments {
+    let leading = Rc::new(RefCell::new((*self.leading).to_owned()));
+    let trailing = Rc::new(RefCell::new((*self.trailing).to_owned()));
+    SingleThreadedComments::from_leading_and_trailing(leading, trailing)
+  }
+
+  /// Gets a vector of all the comments sorted by position.
+  pub fn get_vec(&self) -> Vec<Comment> {
+    let mut comments = self
+      .leading
+      .values()
+      .chain(self.trailing.values())
+      .flatten()
+      .cloned()
+      .collect::<Vec<_>>();
+    comments.sort_by_key(|comment| comment.span.lo);
+    comments
+  }
+}
+
+impl Comments for MultiThreadedComments {
+  fn has_leading(&self, pos: BytePos) -> bool {
+    self.leading.contains_key(&pos)
+  }
+
+  fn get_leading(&self, pos: BytePos) -> Option<Vec<Comment>> {
+    self.leading.get(&pos).cloned()
+  }
+
+  fn has_trailing(&self, pos: BytePos) -> bool {
+    self.trailing.contains_key(&pos)
+  }
+
+  fn get_trailing(&self, pos: BytePos) -> Option<Vec<Comment>> {
+    self.trailing.get(&pos).cloned()
+  }
+
+  fn add_leading(&self, _pos: BytePos, _cmt: Comment) {
+    panic_readonly();
+  }
+
+  fn add_leading_comments(&self, _pos: BytePos, _comments: Vec<Comment>) {
+    panic_readonly();
+  }
+
+  fn move_leading(&self, _from: BytePos, _to: BytePos) {
+    panic_readonly();
+  }
+
+  fn take_leading(&self, _pos: BytePos) -> Option<Vec<Comment>> {
+    panic_readonly();
+  }
+
+  fn add_trailing(&self, _pos: BytePos, _cmt: Comment) {
+    panic_readonly();
+  }
+
+  fn add_trailing_comments(&self, _pos: BytePos, _comments: Vec<Comment>) {
+    panic_readonly();
+  }
+
+  fn move_trailing(&self, _from: BytePos, _to: BytePos) {
+    panic_readonly();
+  }
+
+  fn take_trailing(&self, _pos: BytePos) -> Option<Vec<Comment>> {
+    panic_readonly();
+  }
+
+  fn add_pure_comment(&self, _pos: BytePos) {
+    panic_readonly();
+  }
+}
+
+fn panic_readonly() -> ! {
+  panic!("MultiThreadedComments do not support write operations")
+}