From 120197e370dde6df9961adc9603344434d93b658 Mon Sep 17 00:00:00 2001
From: divybot <divybot@users.noreply.github.com>
Date: Thu, 28 May 2026 15:26:39 +0000
Subject: [PATCH] fix: surround template literal type expressions with newlines
 on multi-line
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

When a template literal type's `${...}` placeholder contains an expression
that does not fit on a single line (notably a `TsUnionType` or
`TsIntersectionType`), the generator broke on the separator (`|` / `&`)
without adding the surrounding newlines + indent that `BinExpr`,
`CondExpr`, etc. already trigger. This produced output like

    export type SortSelector = `${
      | typeof Descending
      | typeof Ascending}${SortItems}`;

instead of

    export type SortSelector = `${
      typeof Descending | typeof Ascending
    }${SortItems}`;

Adding `TsUnionType` and `TsIntersectionType` to
`get_possible_surround_newlines` reuses the existing
`surround_with_newlines_indented_if_multi_line` codepath, so the union
expression stays on one line whenever it fits inside the indented inner
column and otherwise gets a clean indented block — matching how
`BinExpr` is already handled.

Closes denoland/deno#29868
---
 src/generation/generate.rs                    |  1 +
 .../specs/types/TplLitType/TplLitType_All.txt | 23 +++++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/src/generation/generate.rs b/src/generation/generate.rs
index 7fb3a332..119454db 100644
--- a/src/generation/generate.rs
+++ b/src/generation/generate.rs
@@ -3279,6 +3279,7 @@ fn gen_template_literal<'a>(quasis: Vec<Node<'a>>, exprs: Vec<Node<'a>>, context
       Node::OptChainExpr(expr) => get_possible_surround_newlines(expr.base.as_node()),
       Node::CondExpr(_) => true,
       Node::BinExpr(_) => true,
+      Node::TsUnionType(_) | Node::TsIntersectionType(_) => true,
       Node::MemberExpr(expr) => !keep_member_expr_on_one_line(expr),
       Node::CallExpr(expr) => !keep_call_expr_on_one_line(expr.into()),
       Node::OptCall(expr) => !keep_call_expr_on_one_line(expr.into()),
diff --git a/tests/specs/types/TplLitType/TplLitType_All.txt b/tests/specs/types/TplLitType/TplLitType_All.txt
index 4a9f5632..52145bd3 100644
--- a/tests/specs/types/TplLitType/TplLitType_All.txt
+++ b/tests/specs/types/TplLitType/TplLitType_All.txt
@@ -1,5 +1,28 @@
+~~ lineWidth: 80, indentWidth: 2 ~~
 == should format a template literal type ==
 type Test<T> = `${string    &    keyof    T}Changed`;
 
 [expect]
 type Test<T> = `${string & keyof T}Changed`;
+
+== should keep union template literal type expression on one line when it fits ==
+type Foo = `${typeof X | typeof Y}__${typeof Z | typeof W}`;
+
+[expect]
+type Foo = `${typeof X | typeof Y}__${typeof Z | typeof W}`;
+
+== should surround union template literal type expression with newlines when too long ==
+export type SortSelector = `${typeof Descending | typeof Ascending}${SortItems}`;
+
+[expect]
+export type SortSelector = `${
+  typeof Descending | typeof Ascending
+}${SortItems}`;
+
+== should surround intersection template literal type expression with newlines when too long ==
+export type IntersectionTpl = `${typeof Descending & typeof Ascending}${SortItems}`;
+
+[expect]
+export type IntersectionTpl = `${
+  typeof Descending & typeof Ascending
+}${SortItems}`;