Remove spaces in for statement heads (#19188)

Co-authored-by: fisker Cheung <lionkay@gmail.com>

changelog_unreleased/javascript/19188.md

@@ -0,0 +1,16 @@
+#### Remove space in `for` statement without "update" expression (#19188 by @Poliklot)
+
+<!-- prettier-ignore -->
+```jsx
+// Input
+for (initialize;;) {}
+for (; condition;) {}
+
+// Prettier stable
+for (initialize; ; ) {}
+for (; condition; ) {}
+
+// Prettier main
+for (initialize; ;) {}
+for (; condition;) {}
+```

src/language-js/print/for-statement.js

@@ -1,10 +1,4 @@
-import {
-  group,
-  ifBreak,
-  indent,
-  line,
-  softline,
-} from "../../document/index.js";
+import { group, indent, line, softline } from "../../document/index.js";
 import { printDanglingComments } from "../../main/comments/print.js";
 import { printForXStatementBody } from "./clause.js";
 
@@ -34,7 +28,7 @@ function printForStatement(path, options, print) {
           line,
           print("test"),
           ";",
-          node.update ? [line, print("update")] : ifBreak("", line),
+          node.update ? [line, print("update")] : "",
         ]),
         softline,
       ]),

tests/format/flow/flow-repo/binding/__snapshots__/format.test.js.snap

@@ -677,12 +677,12 @@ function try_scope() {
 
 function for_scope_let() {
   let a: number = 0;
-  for (let a = "" /* ok: local to init */; ; ) {}
+  for (let a = "" /* ok: local to init */; ;) {}
 }
 
 function for_scope_var() {
   var a: number = 0;
-  for (var a = "" /* error: string ~> number */; ; ) {}
+  for (var a = "" /* error: string ~> number */; ;) {}
 }
 
 function for_in_scope_let(o: Object) {

tests/format/flow/flow-repo/init/__snapshots__/format.test.js.snap

@@ -577,7 +577,7 @@ function do_while_post_init(b) {
 
 // local use of annotated var in for is ok
 function for_scoped_init(b) {
-  for (; b; ) {
+  for (; b;) {
     var x: number = 0;
     var y: number = x;
   }
@@ -586,14 +586,14 @@ function for_scoped_init(b) {
 // ...but use before for gives undefined
 function for_pre_init(b) {
   var y: number = x; // error
-  for (; b; ) {
+  for (; b;) {
     var x: number = 0;
   }
 }
 
 // ...and after
 function for_post_init(b) {
-  for (; b; ) {
+  for (; b;) {
     var x: number = 0;
   }
   var y: number = x; // error

tests/format/flow/flow-repo/locals/__snapshots__/format.test.js.snap

@@ -98,7 +98,7 @@ function try_scope_finally() {
 function for_scope() {
   let a = "";
   let b = "";
-  for (let a; ; ) {
+  for (let a; ;) {
     a = 0; // doesn't add lower bound to outer a
     b = 0;
   }

tests/format/flow/flow-repo/refinements/__snapshots__/format.test.js.snap

@@ -744,7 +744,7 @@ function def_assign_within_try(b: boolean, obj: Obj) {
 }
 
 function def_assign_within_for(b: boolean, obj: Obj) {
-  for (; b; ) {
+  for (; b;) {
     obj.p = 10; // (obj.p : number)
     var x: number = obj.p; // ok by def assign
   }

tests/format/js/explicit-resource-management/__snapshots__/format.test.js.snap

@@ -170,7 +170,7 @@ for(using /* 1 */ foo of bar());
     /* 2 */ b = foo();
 }
 
-for (using /* 1 */ a = foo(), /* 2 */ b = foo(); ; );
+for (using /* 1 */ a = foo(), /* 2 */ b = foo(); ;);
 
 for (using /* 1 */ foo of bar());
 
@@ -638,7 +638,7 @@ async function f() {
 
 =====================================output=====================================
 async function f() {
-  for (await using basic = reader(); ; );
+  for (await using basic = reader(); ;);
 }
 
 ================================================================================
@@ -964,7 +964,7 @@ for (
   reader = getReader(););
 
 =====================================output=====================================
-for (using; (reader = getReader()); );
+for (using; (reader = getReader()););
 
 ================================================================================
 `;

tests/format/js/for/__snapshots__/format.test.js.snap

@@ -833,6 +833,8 @@ parsers: ["babel", "flow", "typescript"]
                                                       printWidth: 80 (default) |
 =====================================input======================================
 for (;;) {}
+for (initialize;;) {}
+for (; condition;) {}
 for (var i = 0; i < 10; ++i) {}
 
 for (;;) 0;
@@ -840,6 +842,8 @@ for (var i = 0; i < 10; ++i) 0;
 
 =====================================output=====================================
 for (;;) {}
+for (initialize; ;) {}
+for (; condition;) {}
 for (var i = 0; i < 10; ++i) {}
 
 for (;;) 0;
@@ -931,16 +935,16 @@ async function f() {
 for (a in b) 0;
 
 =====================================output=====================================
-for ((x in a); ; ) {}
-for (a = (a in b); ; ) {}
-for (let a = (b in c); ; );
-for (a && (b in c); ; );
-for ((a) => (b in c); ; );
+for ((x in a); ;) {}
+for (a = (a in b); ;) {}
+for (let a = (b in c); ;);
+for (a && (b in c); ;);
+for ((a) => (b in c); ;);
 function* g() {
-  for (yield (a in b); ; );
+  for (yield (a in b); ;);
 }
 async function f() {
-  for (await (a in b); ; );
+  for (await (a in b); ;);
 }
 for (a in b) 0;
 
@@ -1009,22 +1013,22 @@ for (;a = function (x = b in c) {};);
 =====================================output=====================================
 // https://github.com/babel/babel/blob/HEAD/packages/babel-generator/test/fixtures/parentheses/in-inside-for/input.js
 
-for (var a = (b in c); ; );
-for (var a = 1 || (b in c); ; );
-for (var a = 1 + (2 || (b in c)); ; );
-for (var a = () => (b in c); ; );
-for (var a = 1 || (() => (b in c)); ; );
+for (var a = (b in c); ;);
+for (var a = 1 || (b in c); ;);
+for (var a = 1 + (2 || (b in c)); ;);
+for (var a = () => (b in c); ;);
+for (var a = 1 || (() => (b in c)); ;);
 for (
   var a = () => {
     (b in c);
   };
   ;
 );
-for (var a = [(b in c)]; ; );
-for (var a = { b: (b in c) }; ; );
-for (var a = (x = (b in c)) => {}; ; );
-for (var a = class extends (b in c) {}; ; );
-for (var a = function (x = (b in c)) {}; ; );
+for (var a = [(b in c)]; ;);
+for (var a = { b: (b in c) }; ;);
+for (var a = (x = (b in c)) => {}; ;);
+for (var a = class extends (b in c) {}; ;);
+for (var a = function (x = (b in c)) {}; ;);
 
 for (var a in b in c);
 for (var a in 1 || b in c);
@@ -1040,22 +1044,22 @@ for (var a in (x = b in c) => {});
 for (var a in class extends (b in c) {});
 for (var a in function (x = b in c) {});
 
-for (; (a = b in c); );
-for (; (a = 1 || b in c); );
-for (; (a = 1 + (2 || b in c)); );
-for (; (a = () => b in c); );
-for (; (a = 1 || (() => b in c)); );
+for (; (a = b in c););
+for (; (a = 1 || b in c););
+for (; (a = 1 + (2 || b in c)););
+for (; (a = () => b in c););
+for (; (a = 1 || (() => b in c)););
 for (
   ;
   (a = () => {
     b in c;
   });
 );
-for (; (a = [b in c]); );
-for (; (a = { b: b in c }); );
-for (; (a = (x = b in c) => {}); );
-for (; (a = class extends (b in c) {}); );
-for (; (a = function (x = b in c) {}); );
+for (; (a = [b in c]););
+for (; (a = { b: b in c }););
+for (; (a = (x = b in c) => {}););
+for (; (a = class extends (b in c) {}););
+for (; (a = function (x = b in c) {}););
 
 ================================================================================
 `;

tests/format/js/for/for.js

@@ -1,4 +1,6 @@
 for (;;) {}
+for (initialize;;) {}
+for (; condition;) {}
 for (var i = 0; i < 10; ++i) {}
 
 for (;;) 0;

tests/format/js/identifier/parentheses/__snapshots__/format.test.js.snap

@@ -226,7 +226,7 @@ throw (let[0] = 1)
 
 ;[(let[0] = 1)]
 
-for ((let)[0] = 1; ; );
+for ((let)[0] = 1; ;);
 for ((let)[0] in {});
 for ((let)[0] of []);
 
@@ -450,7 +450,7 @@ throw (let[0] = 1);
 
 [(let[0] = 1)];
 
-for ((let)[0] = 1; ; );
+for ((let)[0] = 1; ;);
 for ((let)[0] in {});
 for ((let)[0] of []);