From 5db7366ad03905e9e4c60fd11f345d843ff36f2c Mon Sep 17 00:00:00 2001
From: Victorien Elvinger <victorien@elvinger.fr>
Date: Tue, 21 Feb 2023 23:56:50 +0100
Subject: [PATCH] fix(rome_js_formatter): mapped type formatting

---
 .../src/ts/types/mapped_type.rs               | 10 +++--
 .../tests/specs/ts/type/mapped_type.ts        |  1 +
 .../tests/specs/ts/type/mapped_type.ts.snap   | 39 +++++++++++++++++++
 3 files changed, 46 insertions(+), 4 deletions(-)
 create mode 100644 crates/rome_js_formatter/tests/specs/ts/type/mapped_type.ts
 create mode 100644 crates/rome_js_formatter/tests/specs/ts/type/mapped_type.ts.snap

diff --git a/crates/rome_js_formatter/src/ts/types/mapped_type.rs b/crates/rome_js_formatter/src/ts/types/mapped_type.rs
index f6811912b53..678961e3d37 100644
--- a/crates/rome_js_formatter/src/ts/types/mapped_type.rs
+++ b/crates/rome_js_formatter/src/ts/types/mapped_type.rs
@@ -28,9 +28,14 @@ impl FormatNodeRule<TsMappedType> for FormatTsMappedType {
 
         let property_name = property_name?;
 
+        // Check if the user introduced a new line inside the node.
         let should_expand = node
             .syntax()
             .tokens()
+            // Skip the first token to avoid formatter instability. See #4165.
+            // This also makes sense since leading trivia of the first token
+            // are not part of the interior of the node.
+            .skip(1)
             .flat_map(|token| {
                 token
                     .leading_trivia()
@@ -47,8 +52,6 @@ impl FormatNodeRule<TsMappedType> for FormatTsMappedType {
             });
 
         let format_inner = format_with(|f| {
-            write!(f, [soft_line_break_or_space()])?;
-
             if let Some(readonly_modifier) = &readonly_modifier {
                 write!(f, [readonly_modifier.format(), space()])?;
             }
@@ -81,8 +84,7 @@ impl FormatNodeRule<TsMappedType> for FormatTsMappedType {
             f,
             [
                 &l_curly_token.format(),
-                group(&indent(&format_inner)).should_expand(should_expand),
-                soft_line_break_or_space(),
+                group(&soft_space_or_block_indent(&format_inner)).should_expand(should_expand),
                 r_curly_token.format(),
             ]
         )
diff --git a/crates/rome_js_formatter/tests/specs/ts/type/mapped_type.ts b/crates/rome_js_formatter/tests/specs/ts/type/mapped_type.ts
new file mode 100644
index 00000000000..b9fedaa846c
--- /dev/null
+++ b/crates/rome_js_formatter/tests/specs/ts/type/mapped_type.ts
@@ -0,0 +1 @@
+type LongNameHereToCauseLineBreak_aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa ={ [K in "foo"]: string };
\ No newline at end of file
diff --git a/crates/rome_js_formatter/tests/specs/ts/type/mapped_type.ts.snap b/crates/rome_js_formatter/tests/specs/ts/type/mapped_type.ts.snap
new file mode 100644
index 00000000000..0dbf9013446
--- /dev/null
+++ b/crates/rome_js_formatter/tests/specs/ts/type/mapped_type.ts.snap
@@ -0,0 +1,39 @@
+---
+source: crates/rome_formatter_test/src/snapshot_builder.rs
+assertion_line: 212
+info: ts/type/mapped_type.ts
+---
+
+# Input
+
+```ts
+type LongNameHereToCauseLineBreak_aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa ={ [K in "foo"]: string };
+```
+
+
+=============================
+
+# Outputs
+
+## Output 1
+
+-----
+Indent style: Tab
+Line width: 80
+Quote style: Double Quotes
+Quote properties: As needed
+Trailing comma: All
+Semicolons: Always
+-----
+
+```ts
+type LongNameHereToCauseLineBreak_aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa =
+	{ [K in "foo"]: string };
+```
+
+# Lines exceeding max width of 80 characters
+```
+    1: type LongNameHereToCauseLineBreak_aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa =
+```
+
+