Fix space issue in mapped type formatting (#21712)

* Add the test for mapped type formatting issue

* Fix inconsistent number of spaces within braces when formatting mapped types

src/services/formatting/rules.ts

@@ -469,7 +469,9 @@ namespace ts.formatting {
     }
 
     function isBraceWrappedContext(context: FormattingContext): boolean {
-        return context.contextNode.kind === SyntaxKind.ObjectBindingPattern || isSingleLineBlockContext(context);
+        return context.contextNode.kind === SyntaxKind.ObjectBindingPattern ||
+            context.contextNode.kind === SyntaxKind.MappedType ||
+            isSingleLineBlockContext(context);
     }
 
     // This check is done before an open brace in a control construct, a function, or a typescript block declaration

tests/cases/fourslash/formattingMultipleMappedType.ts

@@ -0,0 +1,36 @@
+/// <reference path='fourslash.ts' />
+
+/////*x1*/type x1<T> = {[K in keyof T]: number}
+/////*x2*/type x2<T> = { [K in keyof T]: number }
+/////*x3*/type x3<T> = { [K in keyof T]: number}
+/////*x4*/type x4<T> = {[K in keyof T]: number }
+/////*x5*/type x5<T> = {    [K in keyof T]: number}
+/////*x6*/type x6<T> = {[K in keyof T]: number    }
+/////*x7*/type x7<T> = {    [K in keyof T]: number     }
+/////*x8*/type x8<T> = {    [K in keyof T]: number     };
+////
+/////*y1*/type y1 = {foo: number}
+/////*y2*/type y2 = { foo: number }
+/////*y3*/type y3 = { foo: number}
+/////*y4*/type y4 = {foo: number }
+/////*y5*/type y5 = {    foo: number}
+/////*y6*/type y6 = {foo: number   }
+/////*y7*/type y7 = {   foo: number   }
+/////*y8*/type y8 = {   foo: number   };
+
+format.document();
+for (let index = 1; index < 8; index++) {
+    goTo.marker(`x${index}`);
+    verify.currentLineContentIs(`type x${index}<T> = { [K in keyof T]: number }`);   
+}
+
+goTo.marker(`x8`);
+verify.currentLineContentIs(`type x8<T> = { [K in keyof T]: number };`);   
+
+for (let index = 1; index < 8; index++) {
+    goTo.marker(`y${index}`);
+    verify.currentLineContentIs(`type y${index} = { foo: number }`);   
+}
+
+goTo.marker(`y8`);
+verify.currentLineContentIs(`type y8 = { foo: number };`);