Improve formatting for unions of tables to enforce hanging (#1027)

* Add test case

* Ensure unions of (multiline) tables are always formatted multiline

* Update snapshot

* Update changelog

* fix snapshot

Author: JohnnyMorganz

CHANGELOG.md

@@ -11,6 +11,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Added option `block_newline_gaps` to determine whether newline gaps at the start / end of blocks should be preserved. Defaults to `Never`, which is the original behaviour. ([#857](https://github.com/JohnnyMorganz/StyLua/pull/857))
 
+### Changed
+
+- Luau: Improved union of tables formatting to hang the union type rather than attempt to hug all the tables together ([#958](https://github.com/JohnnyMorganz/StyLua/issues/958))
+
 ### Fixed
 
 - Fixed formatting of index containing brackets string in parentheses ([#992](https://github.com/JohnnyMorganz/StyLua/pull/992))

src/formatters/luau.rs

@@ -51,6 +51,16 @@ fn should_hug_type(type_info: &TypeInfo) -> bool {
     }
 }
 
+fn is_union_of_tables(type_info: &TypeInfo) -> bool {
+    match type_info {
+        TypeInfo::Union(union) => union
+            .types()
+            .iter()
+            .all(|ty| matches!(ty, TypeInfo::Table { .. })),
+        _ => false,
+    }
+}
+
 fn format_hangable_type_info_internal(
     ctx: &Context,
     type_info: &TypeInfo,
@@ -1140,11 +1150,13 @@ fn attempt_assigned_type_tactics(
         // If we can hang the type definition, and its over width, then lets try doing so
         if can_hang_type(type_info)
             && (must_hang
-                || (shape.test_over_budget(&strip_trailing_trivia(&singleline_type_definition))))
+                || shape.test_over_budget(&strip_trailing_trivia(&singleline_type_definition))
+                || spans_multiple_lines(&singleline_type_definition))
         {
             // If we should hug the type, then lets check out the proper definition and see if it fits
             if !must_hang
                 && should_hug_type(type_info)
+                && !is_union_of_tables(type_info)
                 && !shape.test_over_budget(&proper_type_definition)
             {
                 type_definition = proper_type_definition;

tests/inputs-luau/type-union-tables-1.lua

@@ -0,0 +1,20 @@
+-- https://github.com/JohnnyMorganz/StyLua/issues/958
+
+export type AstExprTableItem =
+	| { kind: "list", value: AstExpr, separator: Token<"," | ";">? }
+	| { kind: "record", key: string, equals: Token<"=">, value: AstExpr, separator: Token<"," | ";">? }
+	| { kind: "general", key: string, equals: Token<"=">, value: AstExpr, separator: Token<"," | ";">? }
+
+export type AstExprTableItem = | { kind: "list", value: AstExpr, separator: Token<"," | ";">? } | {
+	kind: "record",
+	key: string,
+	equals: Token<"=">,
+	value: AstExpr,
+	separator: Token<"," | ";">?,
+} | {
+	kind: "general",
+	key: string,
+	equals: Token<"=">,
+	value: AstExpr,
+	separator: Token<"," | ";">?,
+}

tests/snapshots/[email protected]

@@ -0,0 +1,28 @@
+---
+source: tests/tests.rs
+expression: "format(&contents, LuaVersion::Luau)"
+input_file: tests/inputs-luau/type-union-tables-1.lua
+---
+-- https://github.com/JohnnyMorganz/StyLua/issues/958
+
+export type AstExprTableItem =
+	| { kind: "list", value: AstExpr, separator: Token<"," | ";">? }
+	| { kind: "record", key: string, equals: Token<"=">, value: AstExpr, separator: Token<"," | ";">? }
+	| { kind: "general", key: string, equals: Token<"=">, value: AstExpr, separator: Token<"," | ";">? }
+
+export type AstExprTableItem =
+	| { kind: "list", value: AstExpr, separator: Token<"," | ";">? }
+	| {
+		kind: "record",
+		key: string,
+		equals: Token<"=">,
+		value: AstExpr,
+		separator: Token<"," | ";">?,
+	}
+	| {
+		kind: "general",
+		key: string,
+		equals: Token<"=">,
+		value: AstExpr,
+		separator: Token<"," | ";">?,
+	}