Improve new line after { detection in TSMappedType

changelog_unreleased/typescript/14659.md

@@ -0,0 +1,24 @@
+#### Improve new line detection in mapped type (#14659 by @fisker)
+
+<!-- prettier-ignore -->
+```ts
+// Input
+type A1 = { [A in B]:
+T}
+type A2 = {
+  [A in B]:T}
+
+// Prettier stable
+type A1 = {
+  [A in B]: T;
+};
+type A2 = {
+  [A in B]: T;
+};
+
+// Prettier main
+type A1 = { [A in B]: T };
+type A2 = {
+  [A in B]: T;
+};
+```

src/language-js/print/mapped-type.js

@@ -1,6 +1,6 @@
 import { printDanglingComments } from "../../main/comments/print.js";
 import hasNewlineInRange from "../../utils/has-newline-in-range.js";
-import { locStart, locEnd } from "../loc.js";
+import { locStart } from "../loc.js";
 import {
   group,
   softline,
@@ -54,23 +54,27 @@ function printTypeScriptMappedTypeModifier(tokenNode, keyword) {
 
 function printTypescriptMappedType(path, options, print) {
   const { node } = path;
+  // Break after `{` like `printObject`
   const shouldBreak = hasNewlineInRange(
     options.originalText,
     locStart(node),
-    locEnd(node)
+    // Ideally, this should be the next token after `{`, but there is no node starts with it.
+    locStart(node.typeParameter)
   );
 
   return group(
     [
       "{",
       indent([
         options.bracketSpacing ? line : softline,
-        print("typeParameter"),
-        node.optional
-          ? printTypeScriptMappedTypeModifier(node.optional, "?")
-          : "",
-        node.typeAnnotation ? ": " : "",
-        print("typeAnnotation"),
+        group([
+          print("typeParameter"),
+          node.optional
+            ? printTypeScriptMappedTypeModifier(node.optional, "?")
+            : "",
+          node.typeAnnotation ? ": " : "",
+          print("typeAnnotation"),
+        ]),
         options.semi ? ifBreak(";") : "",
       ]),
       printDanglingComments(path, options),

tests/format/typescript/mapped-type/break-mode/__snapshots__/jsfmt.spec.js.snap

@@ -0,0 +1,39 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`break-mode.ts format 1`] = `
+====================================options=====================================
+parsers: ["typescript"]
+printWidth: 80
+                                                                                | printWidth
+=====================================input======================================
+type A1 = { readonly [A in B]: T}
+type A2 = {
+readonly [A in B]: T}
+type A3 = { readonly
+ [A in B]: T}
+type A4 = { readonly [
+A in B]: T}
+type A5 = { readonly [A in B]
+: T}
+type A6 = { readonly [A in B]:
+T}
+type A7 = { readonly [A in B]: T
+}
+
+=====================================output=====================================
+type A1 = { readonly [A in B]: T };
+type A2 = {
+  readonly [A in B]: T;
+};
+type A3 = {
+  readonly [A in B]: T;
+};
+type A4 = {
+  readonly [A in B]: T;
+};
+type A5 = { readonly [A in B]: T };
+type A6 = { readonly [A in B]: T };
+type A7 = { readonly [A in B]: T };
+
+================================================================================
+`;

tests/format/typescript/mapped-type/break-mode/break-mode.ts

@@ -0,0 +1,13 @@
+type A1 = { readonly [A in B]: T}
+type A2 = {
+readonly [A in B]: T}
+type A3 = { readonly
+ [A in B]: T}
+type A4 = { readonly [
+A in B]: T}
+type A5 = { readonly [A in B]
+: T}
+type A6 = { readonly [A in B]:
+T}
+type A7 = { readonly [A in B]: T
+}

tests/format/typescript/mapped-type/break-mode/jsfmt.spec.js

@@ -0,0 +1 @@
+run_spec(import.meta, ["typescript"]);