Fix collapsing when varexpr prefix has trailing comments (#511)

* Add test case

* Check for trailing comments on varexpr prefix for hang

* Update snapshot

* Update changelog

CHANGELOG.md

@@ -6,6 +6,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+- Fixed var expression with trailing comments on initial prefix being collapsed leading to malformed formatting ([#509](https://github.com/JohnnyMorganz/StyLua/issues/509))
+
 ## [0.14.1] - 2022-07-21
 ### Changed
 - Chained var expression formatting will now follow the exact same steps as chained function call formatting

src/formatters/functions.rs

@@ -917,7 +917,10 @@ pub fn format_function_call(
     let num_suffixes = function_call.suffixes().count();
 
     // If there are comments within the chain, then we must hang the chain otherwise it can lead to an issue
-    let must_hang = {
+    let must_hang = trivia_util::trivia_contains_comments(
+        trivia_util::prefix_trailing_trivia(function_call.prefix()).iter(),
+        trivia_util::CommentSearch::Single,
+    ) || {
         let mut peekable_suffixes = function_call.suffixes().peekable();
         let mut must_hang = false;
         while let Some(suffix) = peekable_suffixes.next() {

src/formatters/trivia_util.rs

@@ -122,6 +122,14 @@ fn function_args_trailing_trivia(function_args: &FunctionArgs) -> Vec<Token> {
     }
 }
 
+pub fn prefix_trailing_trivia(prefix: &Prefix) -> Vec<Token> {
+    match prefix {
+        Prefix::Name(name) => name.trailing_trivia().cloned().collect(),
+        Prefix::Expression(expression) => get_expression_trailing_trivia(expression),
+        other => panic!("unknown node {:?}", other),
+    }
+}
+
 pub fn suffix_leading_trivia(suffix: &Suffix) -> impl Iterator<Item = &Token> {
     match suffix {
         Suffix::Index(index) => match index {

tests/inputs/var-expression-comments-2.lua

@@ -0,0 +1,3 @@
+-- https://github.com/JohnnyMorganz/StyLua/issues/509
+local foo = bar -- comment after bar
+        .fizz -- comment after fizz

tests/snapshots/tests__standard@var-expression-comments-2.lua.snap

@@ -0,0 +1,8 @@
+---
+source: tests/tests.rs
+expression: format(&contents)
+---
+-- https://github.com/JohnnyMorganz/StyLua/issues/509
+local foo = bar -- comment after bar
+	.fizz -- comment after fizz
+