JS: merge more cases of var decl and for stmt

Author: tdewolff

js/js_test.go

@@ -275,9 +275,9 @@ func TestJS(t *testing.T) {
 		{`var a;var b=6;a=7`, `var b=6,a=7`}, // swap declaration order to maintain definition order
 		{`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;;);`},
-		//{`while(b);var a=4;var b=5;`, `for(var a=4,b=5;b;);`},
-		//{`for(var c;b;){let a=8};var a`, `for(var c,a;b;)let a=8`},
+		{`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`},
 
 		// function and method declarations
 		{`function g(){return}`, `function g(){}`},
@@ -536,7 +536,11 @@ func TestJS(t *testing.T) {
 		{`a={b(c){d}}`, `a={b(c){d}}`},
 		{`a(b,...c)`, `a(b,...c)`},
 		//{`'a b c'.split(' ')`, `['a','b','c']`}, // TODO?
-		//{`!function(){var a}`, `!function(){}`}, // TODO? remove unused variables
+		//{`!function(){var a}`, `!function(){}`}, // TODO: remove unused variables
+		//{`const a=6;f(a)`, `f(6)`},             // TODO: inline single-use variables that are literals
+		//{`let a="string";f(a)`, `f("string")`}, // TODO: inline single-use variables that are literals
+		{`let a="string"`, `let a="string"`},
+		//{`{let a="string"}`, ``}, // TODO: remove unused variables that are not in global scope
 
 		// merge expressions
 		{`b=5;return a+b`, `return b=5,a+b`},
@@ -555,6 +559,7 @@ func TestJS(t *testing.T) {
 		{`var a=b in c;for(;b;)c()`, `for(var a=(b in c);b;)c()`},
 		{`var a=5;while(b)c()`, `for(var a=5;b;)c()`},
 		{`let a=5;while(b)c()`, `let a=5;while(b)c()`},
+		//{`var a;for(a=5;b;)c()`, `for(var a=5;b;)c()`}, // TODO
 		{`a=5;for(var b=4;b;)c()`, `a=5;for(var b=4;b;)c()`},
 		{`a=5;switch(b=4){}`, `switch(a=5,b=4){}`},
 		{`a=5;with(b=4){}`, `with(a=5,b=4);`},

js/stmtlist.go

@@ -146,14 +146,18 @@ func (m *jsMinifier) optimizeStmtList(list []js.IStmt, blockType blockType) []js
 					j--
 				}
 			} else if left, ok := list[i-1].(*js.VarDecl); ok {
-				if right, ok := list[i].(*js.VarDecl); ok && left.TokenType != js.VarToken && left.TokenType == right.TokenType {
-					// merge const, let declarations
+				if right, ok := list[i].(*js.VarDecl); ok && left.TokenType == right.TokenType {
+					// merge const and let declarations
 					right.List = append(left.List, right.List...)
 					j--
-				} else if forStmt, ok := list[i].(*js.ForStmt); ok && left.TokenType == js.VarToken && forStmt.Init == nil {
+				} else if forStmt, ok := list[i].(*js.ForStmt); ok && left.TokenType == js.VarToken {
 					// TODO: only merge statements that don't have 'in' or 'of' keywords (slow to check?)
-					forStmt.Init = left
-					j--
+					if forStmt.Init == nil {
+						forStmt.Init = left
+						j--
+					} else {
+						// TODO: merge with expressions if they define the declarations
+					}
 				} else if whileStmt, ok := list[i].(*js.WhileStmt); ok && left.TokenType == js.VarToken {
 					// TODO: only merge statements that don't have 'in' or 'of' keywords (slow to check?)
 					var body js.BlockStmt

js/vars.go

@@ -146,19 +146,24 @@ func (m *jsMinifier) hoistVars(body *js.BlockStmt) *js.VarDecl {
 		var decl *js.VarDecl
 		if varDecl, ok := body.List[0].(*js.VarDecl); ok && varDecl.TokenType == js.VarToken {
 			decl = varDecl
-			//} else if forStmt, ok := body.List[0].(*js.ForStmt); ok && forStmt.Init != nil {
-			//	if varDecl, ok := forStmt.Init.(*js.VarDecl); ok && varDecl.TokenType == js.VarToken {
-			//		decl = varDecl
-			//	}
-			//} else if whileStmt, ok := body.List[0].(*js.WhileStmt); ok {
-			//	decl = &js.VarDecl{js.VarToken, nil}
-			//	var forBody js.BlockStmt
-			//	if blockStmt, ok := whileStmt.Body.(*js.BlockStmt); ok {
-			//		forBody = *blockStmt
-			//	} else {
-			//		forBody.List = []js.IStmt{whileStmt.Body}
-			//	}
-			//	body.List[0] = &js.ForStmt{decl, whileStmt.Cond, nil, forBody}
+		} else if forStmt, ok := body.List[0].(*js.ForStmt); ok {
+			// TODO: only merge statements that don't have 'in' or 'of' keywords (slow to check?)
+			if forStmt.Init == nil {
+				decl = &js.VarDecl{js.VarToken, nil}
+				forStmt.Init = decl
+			} else if varDecl, ok := forStmt.Init.(*js.VarDecl); ok && varDecl.TokenType == js.VarToken {
+				decl = varDecl
+			}
+		} else if whileStmt, ok := body.List[0].(*js.WhileStmt); ok {
+			// TODO: only merge statements that don't have 'in' or 'of' keywords (slow to check?)
+			decl = &js.VarDecl{js.VarToken, nil}
+			var forBody js.BlockStmt
+			if blockStmt, ok := whileStmt.Body.(*js.BlockStmt); ok {
+				forBody = *blockStmt
+			} else {
+				forBody.List = []js.IStmt{whileStmt.Body}
+			}
+			body.List[0] = &js.ForStmt{decl, whileStmt.Cond, nil, forBody}
 		}
 		if decl != nil {
 			// original declarations