From f603ca4688b499a8ba8336502b07833d6cdb46ee Mon Sep 17 00:00:00 2001
From: Christopher Chedeau <vjeuxx@gmail.com>
Date: Mon, 16 Jan 2017 09:54:39 -0800
Subject: [PATCH] Make sure empty for loops generate valid code (#224)

```js
for (;;);
function f() {}
```

The `;` was dropped meaning that the line right after was executed within the for loop which is not correct.

I tried to return `;` but it looks like

```js
for (;;)
  ;
```

which looks super weird so I ended up printing `{}` which looks like

```js
for (;;) {}
```
---
 src/printer.js                                |  8 +++++--
 .../__snapshots__/jsfmt.spec.js.snap          | 21 +++++++++++++++++++
 tests/empty_statement/body.js                 |  7 +++++++
 tests/empty_statement/jsfmt.spec.js           |  1 +
 4 files changed, 35 insertions(+), 2 deletions(-)
 create mode 100644 tests/empty_statement/__snapshots__/jsfmt.spec.js.snap
 create mode 100644 tests/empty_statement/body.js
 create mode 100644 tests/empty_statement/jsfmt.spec.js

diff --git a/src/printer.js b/src/printer.js
index 62b5d7df..0bdd19e9 100644
--- a/src/printer.js
+++ b/src/printer.js
@@ -799,8 +799,8 @@ function genericPrintNoParens(path, options, print) {
       return concat([
         "with (",
         path.call(print, "object"),
-        ") ",
-        path.call(print, "body")
+        ")",
+        adjustClause(path.call(print, "body"), options)
       ]);
     case "IfStatement":
       const con = adjustClause(path.call(print, "consequent"), options);
@@ -2111,6 +2111,10 @@ function printJSXElement(path, options, print) {
 }
 
 function adjustClause(clause, options, forceSpace) {
+  if (clause === "") {
+    return ";";
+  }
+
   if (isCurlyBracket(clause) || forceSpace) {
     return concat([ " ", clause ]);
   }
diff --git a/tests/empty_statement/__snapshots__/jsfmt.spec.js.snap b/tests/empty_statement/__snapshots__/jsfmt.spec.js.snap
new file mode 100644
index 00000000..db47c9da
--- /dev/null
+++ b/tests/empty_statement/__snapshots__/jsfmt.spec.js.snap
@@ -0,0 +1,21 @@
+exports[`test body.js 1`] = `
+"with (a);
+if (1); else if (2); else;
+for (;;);
+while (1);
+for (var i in o);
+for (var i of o);
+do; while(1);
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+with (a);
+if (1);
+else if (2);
+else;
+for (;;);
+while (1);
+for (var i in o);
+for (var i of o);
+do;
+while (1);
+"
+`;
diff --git a/tests/empty_statement/body.js b/tests/empty_statement/body.js
new file mode 100644
index 00000000..85c9f5b7
--- /dev/null
+++ b/tests/empty_statement/body.js
@@ -0,0 +1,7 @@
+with (a);
+if (1); else if (2); else;
+for (;;);
+while (1);
+for (var i in o);
+for (var i of o);
+do; while(1);
diff --git a/tests/empty_statement/jsfmt.spec.js b/tests/empty_statement/jsfmt.spec.js
new file mode 100644
index 00000000..989047bc
--- /dev/null
+++ b/tests/empty_statement/jsfmt.spec.js
@@ -0,0 +1 @@
+run_spec(__dirname);