fix: autofmt duplicate whitespace on attributes, flickering of vscode autoformat (#5159)

* wip: failing test

* edit harness a bit

* wip, not fixed entirely

* fix comment accumulation and whitespace

* fix: autofmt syncrhonize edits with vscode waitUntil edit pipeline

* fix optimization collapsing away whitespace

* comment out test case for now

packages/autofmt/src/writer.rs

@@ -312,8 +312,10 @@ impl<'a> Writer<'a> {
         let mut opt_level = ShortOptimization::NoOpt;
 
         // check if we have a lot of attributes
-        let attr_len = self.is_short_attrs(attributes, spreads);
-        let is_short_attr_list = (attr_len + self.out.indent_level * 4) < 80;
+        let attr_len = self.is_short_attrs(brace, attributes, spreads);
+        let has_postbrace_comments = self.brace_has_trailing_comments(brace);
+        let is_short_attr_list =
+            ((attr_len + self.out.indent_level * 4) < 80) && !has_postbrace_comments;
         let children_len = self
             .is_short_children(children)
             .map_err(|_| std::fmt::Error)?;
@@ -331,6 +333,7 @@ impl<'a> Writer<'a> {
             && attributes.len() <= 1
             && spreads.is_empty()
             && !has_trailing_comments
+            && !has_postbrace_comments
         {
             if children.is_empty() {
                 opt_level = ShortOptimization::Oneliner;
@@ -595,6 +598,15 @@ impl<'a> Writer<'a> {
         let attr_line = attr_span.start().line;
 
         if brace_line != attr_line {
+            // Get the raw line of the attribute
+            let line = self.src.get(attr_line - 1).unwrap_or(&"");
+
+            // Only write comments if the line is empty before the attribute start
+            let row_start = line.get(..attr_span.start().column - 1).unwrap_or("");
+            if !row_start.trim().is_empty() {
+                return Ok(());
+            }
+
             self.write_comments(attr_span.start())?;
         }
 
@@ -648,16 +660,35 @@ impl<'a> Writer<'a> {
             return comments;
         };
 
+        // We go backwards to collect comments and empty lines. We only want to keep one empty line,
+        // the rest should be `//` comments
+        let mut last_line_was_empty = false;
         for (id, line) in lines.iter().enumerate().rev() {
-            if line.trim().starts_with("//") || line.is_empty() && id != 0 {
-                if id != 0 {
+            let trimmed = line.trim();
+            if trimmed.starts_with("//") {
+                comments.push_front(id);
+                last_line_was_empty = false;
+            } else if trimmed.is_empty() {
+                if !last_line_was_empty {
                     comments.push_front(id);
+                    last_line_was_empty = true;
                 }
+
+                continue;
             } else {
                 break;
             }
         }
 
+        // If there is more than 1 comment, make sure the first comment is not an empty line
+        if comments.len() > 1 {
+            if let Some(&first) = comments.back() {
+                if self.src[first].trim().is_empty() {
+                    comments.pop_back();
+                }
+            }
+        }
+
         comments
     }
 
@@ -725,7 +756,12 @@ impl<'a> Writer<'a> {
         }
     }
 
-    fn is_short_attrs(&mut self, attributes: &[Attribute], spreads: &[Spread]) -> usize {
+    fn is_short_attrs(
+        &mut self,
+        _brace: &Brace,
+        attributes: &[Attribute],
+        spreads: &[Spread],
+    ) -> usize {
         let mut total = 0;
 
         // No more than 3 attributes before breaking the line
@@ -746,7 +782,7 @@ impl<'a> Writer<'a> {
                 };
             }
 
-            let name_len = match &attr.name {
+            total += match &attr.name {
                 AttributeName::BuiltIn(name) => {
                     let name = name.to_string();
                     name.len()
@@ -754,7 +790,6 @@ impl<'a> Writer<'a> {
                 AttributeName::Custom(name) => name.value().len() + 2,
                 AttributeName::Spread(_) => unreachable!(),
             };
-            total += name_len;
 
             if attr.can_be_shorthand() {
                 total += 2;
@@ -1090,6 +1125,13 @@ impl<'a> Writer<'a> {
         }
     }
 
+    fn brace_has_trailing_comments(&self, brace: &Brace) -> bool {
+        let span = brace.span.span();
+        let line = self.src.get(span.start().line - 1).unwrap_or(&"");
+        let after_brace = line.get(span.start().column + 1..).unwrap_or("").trim();
+        after_brace.starts_with("//")
+    }
+
     fn has_trailing_comments(&self, children: &[BodyNode], brace: &Brace) -> bool {
         let brace_span = brace.span.span();