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Copy pathstmtlist.go
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379 lines (368 loc) · 14 KB
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package js
import (
"github.com/tdewolff/parse/v2/js"
)
func optimizeStmt(i js.IStmt) js.IStmt {
// convert if/else into expression statement, and optimize blocks
if ifStmt, ok := i.(*js.IfStmt); ok {
if truthy, ok := isTruthy(ifStmt.Cond); ok && truthy {
if hasSideEffects(ifStmt.Cond) {
ifStmt.Else = nil
return i // TODO: remove if and return StmtList(Cond, Body)
}
return optimizeStmt(ifStmt.Body)
} else if ok {
// falsy
if isEmptyStmt(ifStmt.Else) {
if hasSideEffects(ifStmt.Cond) {
return &js.ExprStmt{Value: ifStmt.Cond}
}
return &js.EmptyStmt{}
} else if hasSideEffects(ifStmt.Cond) {
if unaryExpr, ok := ifStmt.Cond.(*js.UnaryExpr); ok && unaryExpr.Op == js.NotToken {
ifStmt.Cond = unaryExpr.X
} else {
ifStmt.Cond = &js.UnaryExpr{js.NotToken, ifStmt.Cond}
}
ifStmt.Body, ifStmt.Else = ifStmt.Else, nil
return i // TODO: remove if and return StmtList(Cond, Body)
}
return optimizeStmt(ifStmt.Else)
}
ifStmt.Body = optimizeStmt(ifStmt.Body)
if ifStmt.Else != nil {
ifStmt.Else = optimizeStmt(ifStmt.Else)
}
hasIf := !isEmptyStmt(ifStmt.Body)
hasElse := !isEmptyStmt(ifStmt.Else)
if unaryExpr, ok := ifStmt.Cond.(*js.UnaryExpr); ok && unaryExpr.Op == js.NotToken && hasElse {
ifStmt.Cond = unaryExpr.X
ifStmt.Body, ifStmt.Else = ifStmt.Else, ifStmt.Body
hasIf, hasElse = hasElse, hasIf
}
if !hasIf && !hasElse {
if hasSideEffects(ifStmt.Cond) {
return &js.ExprStmt{Value: ifStmt.Cond}
}
return &js.EmptyStmt{}
} else if hasIf && !hasElse {
if X, isExprBody := ifStmt.Body.(*js.ExprStmt); isExprBody {
if unaryExpr, ok := ifStmt.Cond.(*js.UnaryExpr); ok && unaryExpr.Op == js.NotToken {
left := groupExpr(unaryExpr.X, binaryLeftPrecMap[js.OrToken])
right := groupExpr(X.Value, binaryRightPrecMap[js.OrToken])
return &js.ExprStmt{&js.BinaryExpr{js.OrToken, left, right}}
}
left := groupExpr(ifStmt.Cond, binaryLeftPrecMap[js.AndToken])
right := groupExpr(X.Value, binaryRightPrecMap[js.AndToken])
return &js.ExprStmt{&js.BinaryExpr{js.AndToken, left, right}}
} else if X, isIfStmt := ifStmt.Body.(*js.IfStmt); isIfStmt && isEmptyStmt(X.Else) {
left := groupExpr(ifStmt.Cond, binaryLeftPrecMap[js.AndToken])
right := groupExpr(X.Cond, binaryRightPrecMap[js.AndToken])
ifStmt.Cond = &js.BinaryExpr{js.AndToken, left, right}
ifStmt.Body = X.Body
return ifStmt
}
} else if !hasIf && hasElse {
if X, isExprElse := ifStmt.Else.(*js.ExprStmt); isExprElse {
left := groupExpr(ifStmt.Cond, binaryLeftPrecMap[js.OrToken])
right := groupExpr(X.Value, binaryRightPrecMap[js.OrToken])
return &js.ExprStmt{&js.BinaryExpr{js.OrToken, left, right}}
}
} else if hasIf && hasElse {
XExpr, isExprBody := ifStmt.Body.(*js.ExprStmt)
YExpr, isExprElse := ifStmt.Else.(*js.ExprStmt)
if isExprBody && isExprElse {
return &js.ExprStmt{condExpr(ifStmt.Cond, XExpr.Value, YExpr.Value)}
}
XReturn, isReturnBody := ifStmt.Body.(*js.ReturnStmt)
YReturn, isReturnElse := ifStmt.Else.(*js.ReturnStmt)
if isReturnBody && isReturnElse {
if XReturn.Value == nil && YReturn.Value == nil {
return &js.ReturnStmt{commaExpr(ifStmt.Cond, &js.UnaryExpr{
Op: js.VoidToken,
X: &js.LiteralExpr{js.NumericToken, zeroBytes},
})}
} else if XReturn.Value != nil && YReturn.Value != nil {
return &js.ReturnStmt{condExpr(ifStmt.Cond, XReturn.Value, YReturn.Value)}
}
return ifStmt
}
XThrow, isThrowBody := ifStmt.Body.(*js.ThrowStmt)
YThrow, isThrowElse := ifStmt.Else.(*js.ThrowStmt)
if isThrowBody && isThrowElse {
return &js.ThrowStmt{condExpr(ifStmt.Cond, XThrow.Value, YThrow.Value)}
}
}
} else if decl, ok := i.(*js.VarDecl); ok {
// TODO: remove function name in var name=function name(){}
//for _, item := range decl.List {
// if v, ok := item.Binding.(*js.Var); ok && item.Default != nil {
// if fun, ok := item.Default.(*js.FuncDecl); ok && fun.Name != nil && bytes.Equal(v.Data, fun.Name.Data) {
// scope := fun.Body.Scope
// for i, vorig := range scope.Declared {
// if fun.Name == vorig {
// scope.Declared = append(scope.Declared[:i], scope.Declared[i+1:]...)
// }
// }
// scope.AddUndeclared(v)
// v.Uses += fun.Name.Uses - 1
// fun.Name.Link = v
// fun.Name = nil
// }
// }
//}
if decl.TokenType == js.ErrorToken {
// convert hoisted var declaration to expression or empty (if there are no defines) statement
for _, item := range decl.List {
if item.Default != nil {
return &js.ExprStmt{Value: decl}
}
}
return &js.EmptyStmt{}
}
// TODO: remove unused declarations
//for i := 0; i < len(decl.List); i++ {
// if v, ok := decl.List[i].Binding.(*js.Var); ok && v.Uses < 2 {
// decl.List = append(decl.List[:i], decl.List[i+1:]...)
// i--
// }
//}
//if len(decl.List) == 0 {
// return &js.EmptyStmt{}
//}
return decl
} else if blockStmt, ok := i.(*js.BlockStmt); ok {
// merge body and remove braces if it is not a lexical declaration
blockStmt.List = optimizeStmtList(blockStmt.List, defaultBlock)
if len(blockStmt.List) == 1 {
if _, ok := blockStmt.List[0].(*js.ClassDecl); ok {
return &js.EmptyStmt{}
} else if varDecl, ok := blockStmt.List[0].(*js.VarDecl); ok && varDecl.TokenType != js.VarToken {
// remove let or const declaration in otherwise empty scope, but keep assignments
exprs := []js.IExpr{}
for _, item := range varDecl.List {
if bindingUsed(item.Binding) {
return blockStmt
} else if item.Default != nil && hasSideEffects(item.Default) {
exprs = append(exprs, item.Default)
}
}
if len(exprs) == 0 {
return &js.EmptyStmt{}
} else if len(exprs) == 1 {
return &js.ExprStmt{exprs[0]}
}
return &js.ExprStmt{&js.CommaExpr{exprs}}
}
return optimizeStmt(blockStmt.List[0])
} else if len(blockStmt.List) == 0 {
return &js.EmptyStmt{}
}
return blockStmt
}
return i
}
func optimizeStmtList(list []js.IStmt, blockType blockType) []js.IStmt {
// merge expression statements as well as if/else statements followed by flow control statements
if len(list) == 0 {
return list
}
j := 0 // write index
for i := 0; i < len(list); i++ { // read index
if ifStmt, ok := list[i].(*js.IfStmt); ok && !isEmptyStmt(ifStmt.Else) {
// if(a)return b;else c => if(a)b; c
if unary, ok := ifStmt.Cond.(*js.UnaryExpr); ok && unary.Op == js.NotToken && isFlowStmt(lastStmt(ifStmt.Else)) {
ifStmt.Cond = unary.X
ifStmt.Body, ifStmt.Else = ifStmt.Else, ifStmt.Body
}
if isFlowStmt(lastStmt(ifStmt.Body)) {
// if body ends in flow statement (return, throw, break, continue), we can remove the else statement and put its body in the current scope
if blockStmt, ok := ifStmt.Else.(*js.BlockStmt); ok {
blockStmt.Scope.Unscope()
list = append(list[:i+1], append(blockStmt.List, list[i+1:]...)...)
} else {
list = append(list[:i+1], append([]js.IStmt{ifStmt.Else}, list[i+1:]...)...)
}
ifStmt.Else = nil
}
}
list[i] = optimizeStmt(list[i])
if _, ok := list[i].(*js.EmptyStmt); ok {
k := i + 1
for ; k < len(list); k++ {
if _, ok := list[k].(*js.EmptyStmt); !ok {
break
}
}
list = append(list[:i], list[k:]...)
i--
continue
}
if 0 < i {
// merge expression statements with expression, return, and throw statements
if left, ok := list[i-1].(*js.ExprStmt); ok {
if right, ok := list[i].(*js.ExprStmt); ok {
right.Value = commaExpr(left.Value, right.Value)
j--
} else if returnStmt, ok := list[i].(*js.ReturnStmt); ok && returnStmt.Value != nil {
returnStmt.Value = commaExpr(left.Value, returnStmt.Value)
j--
} else if throwStmt, ok := list[i].(*js.ThrowStmt); ok {
throwStmt.Value = commaExpr(left.Value, throwStmt.Value)
j--
} else if forStmt, ok := list[i].(*js.ForStmt); ok {
// TODO: only merge lhs expression that don't have 'in' or 'of' keywords (slow to check?)
if forStmt.Init == nil {
forStmt.Init = left.Value
j--
} else if decl, ok := forStmt.Init.(*js.VarDecl); ok && len(decl.List) == 0 {
forStmt.Init = left.Value
j--
} else if ok && (decl.TokenType == js.VarToken || decl.TokenType == js.ErrorToken) {
// this is the second VarDecl, so we are hoisting var declarations, which means the forInit variables are already in 'left'
if merge := mergeVarDeclExprStmt(decl, left, true); merge {
j--
}
}
} else if whileStmt, ok := list[i].(*js.WhileStmt); ok {
// TODO: only merge lhs expression that don't have 'in' or 'of' keywords (slow to check?)
var body *js.BlockStmt
if blockStmt, ok := whileStmt.Body.(*js.BlockStmt); ok {
body = blockStmt
} else {
body = &js.BlockStmt{}
body.List = []js.IStmt{whileStmt.Body}
}
list[i] = &js.ForStmt{Init: left.Value, Cond: whileStmt.Cond, Post: nil, Body: body}
j--
} else if switchStmt, ok := list[i].(*js.SwitchStmt); ok {
switchStmt.Init = commaExpr(left.Value, switchStmt.Init)
j--
} else if withStmt, ok := list[i].(*js.WithStmt); ok {
withStmt.Cond = commaExpr(left.Value, withStmt.Cond)
j--
} else if ifStmt, ok := list[i].(*js.IfStmt); ok {
ifStmt.Cond = commaExpr(left.Value, ifStmt.Cond)
j--
} else if varDecl, ok := list[i].(*js.VarDecl); ok && varDecl.TokenType == js.VarToken {
if merge := mergeVarDeclExprStmt(varDecl, left, true); merge {
j--
}
}
} else if left, ok := list[i-1].(*js.VarDecl); ok {
if right, ok := list[i].(*js.VarDecl); ok && left.TokenType == right.TokenType {
// merge const and let declarations, or non-hoisted var declarations
right.List = append(left.List, right.List...)
j--
// remove from vardecls list of scope
scope := left.Scope.Func
for i, decl := range scope.VarDecls {
if left == decl {
scope.VarDecls = append(scope.VarDecls[:i], scope.VarDecls[i+1:]...)
break
}
}
} else if left.TokenType == js.VarToken {
if exprStmt, ok := list[i].(*js.ExprStmt); ok {
// pull in assignments to variables into the declaration, e.g. var a;a=5 => var a=5
if merge := mergeVarDeclExprStmt(left, exprStmt, false); merge {
list[i] = list[i-1]
j--
}
} else if forStmt, ok := list[i].(*js.ForStmt); ok {
// TODO: only merge lhs expression that don't have 'in' or 'of' keywords (slow to check?)
if forStmt.Init == nil {
forStmt.Init = left
j--
} else if decl, ok := forStmt.Init.(*js.VarDecl); ok && decl.TokenType == js.ErrorToken && !hasDefines(decl) {
forStmt.Init = left
j--
} else if ok && (decl.TokenType == js.VarToken || decl.TokenType == js.ErrorToken) {
// this is the second VarDecl, so we are hoisting var declarations, which means the forInit variables are already in 'left'
mergeVarDecls(left, decl, false)
decl.TokenType = js.VarToken
forStmt.Init = left
j--
}
} else if whileStmt, ok := list[i].(*js.WhileStmt); ok {
// TODO: only merge lhs expression that don't have 'in' or 'of' keywords (slow to check?)
var body *js.BlockStmt
if blockStmt, ok := whileStmt.Body.(*js.BlockStmt); ok {
body = blockStmt
} else {
body = &js.BlockStmt{}
body.List = []js.IStmt{whileStmt.Body}
}
list[i] = &js.ForStmt{Init: left, Cond: whileStmt.Cond, Post: nil, Body: body}
j--
}
}
}
}
list[j] = list[i]
// merge if/else with return/throw when followed by return/throw
MergeIfReturnThrow:
if 0 < j {
// separate from expression merging in case of: if(a)return b;b=c;return d
if ifStmt, ok := list[j-1].(*js.IfStmt); ok && isEmptyStmt(ifStmt.Body) != isEmptyStmt(ifStmt.Else) {
// either the if body is empty or the else body is empty. In case where both bodies have return/throw, we already rewrote that if statement to an return/throw statement
if returnStmt, ok := list[j].(*js.ReturnStmt); ok {
if returnStmt.Value == nil {
if left, ok := ifStmt.Body.(*js.ReturnStmt); ok && left.Value == nil {
list[j-1] = &js.ExprStmt{Value: ifStmt.Cond}
} else if left, ok := ifStmt.Else.(*js.ReturnStmt); ok && left.Value == nil {
list[j-1] = &js.ExprStmt{Value: ifStmt.Cond}
}
} else {
if left, ok := ifStmt.Body.(*js.ReturnStmt); ok && left.Value != nil {
returnStmt.Value = condExpr(ifStmt.Cond, left.Value, returnStmt.Value)
list[j-1] = returnStmt
j--
goto MergeIfReturnThrow
} else if left, ok := ifStmt.Else.(*js.ReturnStmt); ok && left.Value != nil {
returnStmt.Value = condExpr(ifStmt.Cond, returnStmt.Value, left.Value)
list[j-1] = returnStmt
j--
goto MergeIfReturnThrow
}
}
} else if throwStmt, ok := list[j].(*js.ThrowStmt); ok {
if left, ok := ifStmt.Body.(*js.ThrowStmt); ok {
throwStmt.Value = condExpr(ifStmt.Cond, left.Value, throwStmt.Value)
list[j-1] = throwStmt
j--
goto MergeIfReturnThrow
} else if left, ok := ifStmt.Else.(*js.ThrowStmt); ok {
throwStmt.Value = condExpr(ifStmt.Cond, throwStmt.Value, left.Value)
list[j-1] = throwStmt
j--
goto MergeIfReturnThrow
}
}
}
}
j++
}
// remove superfluous return or continue
if 0 < j {
if blockType == functionBlock {
if returnStmt, ok := list[j-1].(*js.ReturnStmt); ok {
if returnStmt.Value == nil || isUndefined(returnStmt.Value) {
j--
} else if commaExpr, ok := returnStmt.Value.(*js.CommaExpr); ok && isUndefined(commaExpr.List[len(commaExpr.List)-1]) {
// rewrite function f(){return a,void 0} => function f(){a}
if len(commaExpr.List) == 2 {
list[j-1] = &js.ExprStmt{Value: commaExpr.List[0]}
} else {
commaExpr.List = commaExpr.List[:len(commaExpr.List)-1]
}
}
}
} else if blockType == iterationBlock {
if branchStmt, ok := list[j-1].(*js.BranchStmt); ok && branchStmt.Type == js.ContinueToken && branchStmt.Label == nil {
j--
}
}
}
return list[:j]
}