Hang at equals token in assignment if expression cannot hang internally (#440)

* Only use hanging assignment if the expression can be hanged

Otherwise, keep hanging at equals token instead

* Add test case

* Update changelog

* Make parentheses an indicator of a hangable expression

* Update snapshots

Author: JohnnyMorganz

CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fixed leading trivia on semicolon lost when semicolon is removed ([#431](https://github.com/JohnnyMorganz/StyLua/issues/431))
 - Fixed shape calculation of the RHS of a binary expression not correctly reset when hanging, causing it to expand unnecessarily ([#432](https://github.com/JohnnyMorganz/StyLua/issues/432))
 - Fixed unstable formatting of tables at column width boundary ([#436](https://github.com/JohnnyMorganz/StyLua/issues/436))
+- Fixed assignments no longer hanging at equals token if a comment is present, but the expression is not hangable at a binop. ([#439](https://github.com/JohnnyMorganz/StyLua/issues/439))
 
 ## [0.13.0] - 2022-03-31
 ### Added

src/formatters/assignment.rs

@@ -239,8 +239,9 @@ fn attempt_assignment_tactics(
 
         // Find the better format out of the hanging shape or the normal formatting
         // If the expression contains comments, we must hang
-        if trivia_util::expression_contains_inline_comments(expression)
-            || hanging_shape.used_width() < formatting_shape.used_width()
+        if trivia_util::can_hang_expression(expression)
+            && (trivia_util::expression_contains_inline_comments(expression)
+                || hanging_shape.used_width() < formatting_shape.used_width())
         {
             // Hanging version is better
             (hanging_expr_list, equal_token)

src/formatters/trivia_util.rs

@@ -58,7 +58,7 @@ pub fn spans_multiple_lines<T: std::fmt::Display>(item: &T) -> bool {
 
 pub fn can_hang_expression(expression: &Expression) -> bool {
     match expression {
-        Expression::Parentheses { expression, .. } => can_hang_expression(expression),
+        Expression::Parentheses { .. } => true, // Can always hang parentheses if necessary
         Expression::UnaryOperator { expression, .. } => can_hang_expression(expression),
         Expression::BinaryOperator { .. } => true, // If a binop is present, then we can hang the expression
         Expression::Value { value, .. } => match &**value {

tests/inputs-luau/assignment-hang-1.lua

@@ -0,0 +1,31 @@
+-- https://github.com/JohnnyMorganz/StyLua/issues/439
+exports.separateDisplayNameAndHOCs =
+	function(displayName: string | nil, type_: ElementType): (string | nil, Array<string> | nil)
+		if displayName == nil then
+			return nil, nil
+		end
+
+		local hocDisplayNames: Array<string>? = nil
+
+		if
+			type_ == ElementTypeClass
+			or type_ == ElementTypeForwardRef
+			or type_ == ElementTypeFunction
+			or type_ == ElementTypeMemo
+		then
+			-- ROBLOX deviation: use match instead of indexOf
+			if (displayName :: string):match("%(") then
+				-- ROBLOX deviation: use gmatch instead of /[^()]+/g
+				local matches = (displayName :: string):gmatch("[^()]+")
+				local nextMatch = matches()
+				if nextMatch then
+					displayName = nextMatch
+					hocDisplayNames = {}
+					while nextMatch :: any ~= nil do
+						nextMatch = matches()
+						table.insert(hocDisplayNames :: Array<string>, nextMatch)
+					end
+				end
+			end
+		end
+	end

tests/snapshots/tests__luau@assignment-hang-1.lua.snap

@@ -0,0 +1,38 @@
+---
+source: tests/tests.rs
+assertion_line: 30
+expression: format(&contents)
+
+---
+-- https://github.com/JohnnyMorganz/StyLua/issues/439
+exports.separateDisplayNameAndHOCs =
+	function(displayName: string | nil, type_: ElementType): (string | nil, Array<string> | nil)
+		if displayName == nil then
+			return nil, nil
+		end
+
+		local hocDisplayNames: Array<string>? = nil
+
+		if
+			type_ == ElementTypeClass
+			or type_ == ElementTypeForwardRef
+			or type_ == ElementTypeFunction
+			or type_ == ElementTypeMemo
+		then
+			-- ROBLOX deviation: use match instead of indexOf
+			if (displayName :: string):match("%(") then
+				-- ROBLOX deviation: use gmatch instead of /[^()]+/g
+				local matches = (displayName :: string):gmatch("[^()]+")
+				local nextMatch = matches()
+				if nextMatch then
+					displayName = nextMatch
+					hocDisplayNames = {}
+					while nextMatch :: any ~= nil do
+						nextMatch = matches()
+						table.insert(hocDisplayNames :: Array<string>, nextMatch)
+					end
+				end
+			end
+		end
+	end
+