JS: don't remove braces when there are lexical declarations, fixes #326

go.mod

@@ -2,6 +2,8 @@ module github.com/tdewolff/minify/v2
 
 go 1.13
 
+replace github.com/tdewolff/parse/v2 => ../parse
+
 require (
 	github.com/cheekybits/is v0.0.0-20150225183255-68e9c0620927 // indirect
 	github.com/dustin/go-humanize v1.0.0

js/js.go

@@ -391,7 +391,14 @@ func (m *jsMinifier) minifyBlockAsStmt(blockStmt *js.BlockStmt, blockType blockT
 	// minify block when statement is expected, i.e. semicolon if empty or remove braces for single statement
 	// assume we already renamed the scope
 	blockStmt.List = m.optimizeStmtList(blockStmt.List, blockType)
-	if 1 < len(blockStmt.List) {
+	hasLexicalVars := false
+	for _, v := range blockStmt.Scope.Declared[blockStmt.Scope.NumForInit:] {
+		if v.Decl == js.LexicalDecl {
+			hasLexicalVars = true
+			break
+		}
+	}
+	if 1 < len(blockStmt.List) || hasLexicalVars {
 		m.minifyBlockStmt(*blockStmt)
 	} else if len(blockStmt.List) == 1 {
 		m.minifyStmt(blockStmt.List[0])
@@ -407,6 +414,7 @@ func (m *jsMinifier) minifyStmtOrBlock(i js.IStmt, blockType blockType) {
 		m.renamer.renameScope(blockStmt.Scope)
 		m.minifyBlockAsStmt(blockStmt, blockType)
 	} else {
+		// optimizeStmtList can in some cases expand one stmt to two shorter stmts
 		list := m.optimizeStmtList([]js.IStmt{i}, blockType)
 		if len(list) == 1 {
 			m.minifyStmt(list[0])

js/js_test.go

@@ -104,6 +104,7 @@ func TestJS(t *testing.T) {
 		{`for (a in b){a}`, `for(a in b)a`},
 		{`for (var a of b){a}`, `for(var a of b)a`},
 		{`for (a of b){a}`, `for(a of b)a`},
+		{`for (;;){let a}`, `for(;;){let a}`},
 		{`while(a < 10){a}`, `while(a<10)a`},
 		{`while(a < 10){a;b}`, `while(a<10)a,b`},
 		{`while(a < 10){while(b);c}`, `while(a<10){while(b);c}`},
@@ -276,8 +277,8 @@ func TestJS(t *testing.T) {
 		{`var a=5;var b=6;a=7`, `var a=5,b=6;a=7`},
 		{`var a;var b=6;z=7`, `var b=6,a;z=7`},
 		{`for(var a=6,b=7;;);var c=8`, `for(var a=6,b=7,c=8;;);`},
-		{`for(var c;b;){let a=8};var a`, `for(var c,a;b;)let a=8`},
-		{`for(;b;){let a=8};var a;var b`, `for(var a,b;b;)let a=8`},
+		{`for(var c;b;){let a=8};var a`, `for(var c,a;b;){let a=8}`},
+		{`for(;b;){let a=8};var a;var b`, `for(var a,b;b;){let a=8}`},
 
 		// function and method declarations
 		{`function g(){return}`, `function g(){}`},