From 29959103a9db4fe486dd99e93803ec5e3fdc97be Mon Sep 17 00:00:00 2001
From: Sosuke Suzuki <aosukeke@gmail.com>
Date: Mon, 15 Jun 2020 20:08:43 +0900
Subject: [PATCH] TypeScript: Prefer leading comment when there is a comment on
 after "?" in conditional types (#8557)

* Fix #8555

* Add changelog
---
 changelog_unreleased/javascript/pr-8557.md    | 22 +++++++++++++++++++
 src/language-js/comments.js                   |  3 ++-
 .../__snapshots__/jsfmt.spec.js.snap          | 20 +++++++++++++++++
 .../typescript/conditional-types/comments.ts  |  4 ++++
 4 files changed, 48 insertions(+), 1 deletion(-)
 create mode 100644 changelog_unreleased/javascript/pr-8557.md
 create mode 100644 tests/typescript/conditional-types/comments.ts

diff --git a/changelog_unreleased/javascript/pr-8557.md b/changelog_unreleased/javascript/pr-8557.md
new file mode 100644
index 000000000..c6c9dcbb4
--- /dev/null
+++ b/changelog_unreleased/javascript/pr-8557.md
@@ -0,0 +1,22 @@
+#### Prefer leading comment when there is a comment on after "?" in conditional types ([#8557](https://github.com/prettier/prettier/pull/8557) by [@sosukesuzuki](https://github.com/sosukesuzuki))
+
+<!-- prettier-ignore -->
+```ts
+// Input
+type A = B extends T
+  ? // comment
+    foo
+  : bar;
+
+// Prettier stable
+type A = B extends T // comment
+  ? foo
+  : bar;
+
+// Prettier master
+type A = B extends T
+  ? // comment
+    foo
+  : bar;
+
+```
diff --git a/src/language-js/comments.js b/src/language-js/comments.js
index 1968ad646..99224c58c 100644
--- a/src/language-js/comments.js
+++ b/src/language-js/comments.js
@@ -407,7 +407,8 @@ function handleConditionalExpressionComments(
   if (
     (!precedingNode || !isSameLineAsPrecedingNode) &&
     enclosingNode &&
-    enclosingNode.type === "ConditionalExpression" &&
+    (enclosingNode.type === "ConditionalExpression" ||
+      enclosingNode.type === "TSConditionalType") &&
     followingNode
   ) {
     addLeadingComment(followingNode, comment);
diff --git a/tests/typescript/conditional-types/__snapshots__/jsfmt.spec.js.snap b/tests/typescript/conditional-types/__snapshots__/jsfmt.spec.js.snap
index 73ab426ab..6326bf563 100644
--- a/tests/typescript/conditional-types/__snapshots__/jsfmt.spec.js.snap
+++ b/tests/typescript/conditional-types/__snapshots__/jsfmt.spec.js.snap
@@ -1,5 +1,25 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
+exports[`comments.ts format 1`] = `
+====================================options=====================================
+parsers: ["typescript"]
+printWidth: 80
+                                                                                | printWidth
+=====================================input======================================
+type A = B extends T
+  ? // comment
+    foo
+  : bar;
+
+=====================================output=====================================
+type A = B extends T
+  ? // comment
+    foo
+  : bar;
+
+================================================================================
+`;
+
 exports[`conditonal-types.ts format 1`] = `
 ====================================options=====================================
 parsers: ["typescript"]
diff --git a/tests/typescript/conditional-types/comments.ts b/tests/typescript/conditional-types/comments.ts
new file mode 100644
index 000000000..b6920fec3
--- /dev/null
+++ b/tests/typescript/conditional-types/comments.ts
@@ -0,0 +1,4 @@
+type A = B extends T
+  ? // comment
+    foo
+  : bar;