fix(35179): formatter incorrectly remove spaces

src/services/formatting/rules.ts

@@ -70,8 +70,8 @@ namespace ts.formatting {
             rule("NoSpaceAfterUnaryPrefixOperator", unaryPrefixOperators, unaryPrefixExpressions, [isNonJsxSameLineTokenContext, isNotBinaryOpContext], RuleAction.DeleteSpace),
             rule("NoSpaceAfterUnaryPreincrementOperator", SyntaxKind.PlusPlusToken, unaryPreincrementExpressions, [isNonJsxSameLineTokenContext], RuleAction.DeleteSpace),
             rule("NoSpaceAfterUnaryPredecrementOperator", SyntaxKind.MinusMinusToken, unaryPredecrementExpressions, [isNonJsxSameLineTokenContext], RuleAction.DeleteSpace),
-            rule("NoSpaceBeforeUnaryPostincrementOperator", unaryPostincrementExpressions, SyntaxKind.PlusPlusToken, [isNonJsxSameLineTokenContext], RuleAction.DeleteSpace),
-            rule("NoSpaceBeforeUnaryPostdecrementOperator", unaryPostdecrementExpressions, SyntaxKind.MinusMinusToken, [isNonJsxSameLineTokenContext], RuleAction.DeleteSpace),
+            rule("NoSpaceBeforeUnaryPostincrementOperator", unaryPostincrementExpressions, SyntaxKind.PlusPlusToken, [isNonJsxSameLineTokenContext, isNotStatementConditionContext], RuleAction.DeleteSpace),
+            rule("NoSpaceBeforeUnaryPostdecrementOperator", unaryPostdecrementExpressions, SyntaxKind.MinusMinusToken, [isNonJsxSameLineTokenContext, isNotStatementConditionContext], RuleAction.DeleteSpace),
 
             // More unary operator special-casing.
             // DevDiv 181814: Be careful when removing leading whitespace
@@ -790,6 +790,25 @@ namespace ts.formatting {
         return context.contextNode.kind === SyntaxKind.NonNullExpression;
     }
 
+    function isNotStatementConditionContext(context: FormattingContext): boolean {
+        return !isStatementConditionContext(context);
+    }
+
+    function isStatementConditionContext(context: FormattingContext): boolean {
+        switch (context.contextNode.kind) {
+            case SyntaxKind.IfStatement:
+            case SyntaxKind.ForStatement:
+            case SyntaxKind.ForInStatement:
+            case SyntaxKind.ForOfStatement:
+            case SyntaxKind.DoStatement:
+            case SyntaxKind.WhileStatement:
+                return true;
+
+            default:
+                return false;
+        }
+    }
+
     function isSemicolonDeletionContext(context: FormattingContext): boolean {
         let nextTokenKind = context.nextTokenSpan.kind;
         let nextTokenStart = context.nextTokenSpan.pos;

tests/cases/fourslash/spaceAfterStatementConditions.ts

@@ -0,0 +1,49 @@
+/// <reference path="fourslash.ts"/>
+
+////let i = 0;
+////
+////if(i<0) ++i;
+////if(i<0) --i;
+////
+////while(i<0) ++i;
+////while(i<0) --i;
+////
+////do ++i;
+////while(i<0)
+////do --i;
+////while(i<0)
+////
+////for(let prop in { foo: 1 }) ++i;
+////for(let prop in { foo: 1 }) --i;
+////
+////for(let foo of [1, 2]) ++i;
+////for(let foo of [1, 2]) --i;
+////
+////for(let j = 0; j < 10; j++) ++i;
+////for(let j = 0; j < 10; j++) --i;
+////
+
+format.document();
+verify.currentFileContentIs(
+`let i = 0;
+
+if (i < 0) ++i;
+if (i < 0) --i;
+
+while (i < 0) ++i;
+while (i < 0) --i;
+
+do ++i;
+while (i < 0)
+do --i;
+while (i < 0)
+
+for (let prop in { foo: 1 }) ++i;
+for (let prop in { foo: 1 }) --i;
+
+for (let foo of [1, 2]) ++i;
+for (let foo of [1, 2]) --i;
+
+for (let j = 0; j < 10; j++) ++i;
+for (let j = 0; j < 10; j++) --i;
+`);