public override void Visit(JsConditional node)
{
if (node != null)
{
// we have two choices for the conditional. Either:
// 1. we wrap the whole thing in a logical-not operator, which means we also need to
// add parentheses, since conditional is lower-precedence than the logicial not, or
// 2. apply the logical-not to both the true- and false-branches.
// The first is guaranteed 3 additional characters. We have to check the delta for
// each branch and add them together to know how much the second would cost. If it's
// greater than 3, then we just want to not the whole thing.
var notTrue = new JsLogicalNot(node.TrueExpression, m_parser);
var notFalse = new JsLogicalNot(node.FalseExpression, m_parser);
var costNottingBoth = notTrue.Measure() + notFalse.Measure();
if (m_measure)
{
// we're just measuring -- adjust the delta accordingly
// (the lesser of the two options)
m_delta += (costNottingBoth > 3) ? 3 : costNottingBoth;
}
else if (costNottingBoth > 3)
{
// just wrap the whole thing
WrapWithLogicalNot(node);
}
else
{
// less bytes to wrap each branch separately
node.TrueExpression.Accept(this);
node.FalseExpression.Accept(this);
}
}
}
public void Visit(JsConditional node)
{
if (node != null)
{
if (node.Condition != null)
{
node.Condition.Accept(this);
}
var startingIndex = m_orderIndex;
if (node.TrueExpression != null)
{
node.TrueExpression.Accept(this);
}
var trueEndIndex = m_orderIndex;
m_orderIndex = startingIndex;
if (node.FalseExpression != null)
{
node.FalseExpression.Accept(this);
}
m_orderIndex = Math.Max(trueEndIndex, m_orderIndex);
node.Index = NextOrderIndex;
}
}
public void Visit(JsConditional node)
{
// if there's a condition node, recurse into it
if (node != null && node.Condition != null)
{
node.Condition.Accept(this);
}
}
public void Visit(JsConditional node)
{
if (node != null)
{
if (node.Condition != null)
{
node.Condition.Accept(this);
}
var startingIndex = m_orderIndex;
if (node.TrueExpression != null)
{
node.TrueExpression.Accept(this);
}
var trueEndIndex = m_orderIndex;
m_orderIndex = startingIndex;
if (node.FalseExpression != null)
{
node.FalseExpression.Accept(this);
}
m_orderIndex = Math.Max(trueEndIndex, m_orderIndex);
node.Index = NextOrderIndex;
}
}
public void Visit(JsConditional node)
{
// lesser precedence than the new operator; use parens
m_needsParens = true;
}
public void Visit(JsConditional node)
{
// lesser precedence than the new operator; use parens
m_needsParens = true;
}
private JsAstNode ParseExpression(JsAstNode leftHandSide, bool single, bool bCanAssign, JsToken inToken)
{
// new op stack with dummy op
Stack<JsContext> opsStack = new Stack<JsContext>();
opsStack.Push(null);
// term stack, push left-hand side onto it
Stack<JsAstNode> termStack = new Stack<JsAstNode>();
termStack.Push(leftHandSide);
JsAstNode expr = null;
try
{
for (; ; )
{
// if 'binary op' or 'conditional'
// if we are looking for a single expression, then also bail when we hit a comma
// inToken is a special case because of the for..in syntax. When ParseExpression is called from
// for, inToken = JSToken.In which excludes JSToken.In from the list of operators, otherwise
// inToken = JSToken.None which is always true if the first condition is true
if (JsScanner.IsProcessableOperator(m_currentToken.Token)
&& inToken != m_currentToken.Token
&& (!single || m_currentToken.Token != JsToken.Comma))
{
// for the current token, get the operator precedence and whether it's a right-association operator
var prec = JsScanner.GetOperatorPrecedence(m_currentToken);
bool rightAssoc = JsScanner.IsRightAssociativeOperator(m_currentToken.Token);
// while the current operator has lower precedence than the operator at the top of the stack
// or it has the same precedence and it is left associative (that is, no 'assign op' or 'conditional')
var stackPrec = JsScanner.GetOperatorPrecedence(opsStack.Peek());
while (prec < stackPrec || prec == stackPrec && !rightAssoc)
{
// pop the top two elements off the stack along with the current operator,
// combine them, then push the results back onto the term stack
JsAstNode operand2 = termStack.Pop();
JsAstNode operand1 = termStack.Pop();
expr = CreateExpressionNode(opsStack.Pop(), operand1, operand2);
termStack.Push(expr);
// get the precendence of the current item on the top of the op stack
stackPrec = JsScanner.GetOperatorPrecedence(opsStack.Peek());
}
// now the current operator has higher precedence that every scanned operators on the stack, or
// it has the same precedence as the one at the top of the stack and it is right associative
// push operator and next term
// but first: special case conditional '?:'
if (JsToken.ConditionalIf == m_currentToken.Token)
{
// pop term stack
JsAstNode condition = termStack.Pop();
// if this is an assignment, throw a warning in case the developer
// meant to use == instead of =
// but no warning if the condition is wrapped in parens.
var binOp = condition as JsBinaryOperator;
if (binOp != null && binOp.OperatorToken == JsToken.Assign)
{
condition.Context.HandleError(JsError.SuspectAssignment);
}
var questionCtx = m_currentToken.Clone();
GetNextToken();
// get expr1 in logOrExpr ? expr1 : expr2
JsAstNode operand1 = ParseExpression(true);
JsContext colonCtx = null;
if (JsToken.Colon != m_currentToken.Token)
{
ReportError(JsError.NoColon);
}
else
{
colonCtx = m_currentToken.Clone();
}
GetNextToken();
// get expr2 in logOrExpr ? expr1 : expr2
JsAstNode operand2 = ParseExpression(true, inToken);
expr = new JsConditional(condition.Context.CombineWith(operand2.Context), this)
{
Condition = condition,
QuestionContext = questionCtx,
TrueExpression = operand1,
ColonContext = colonCtx,
FalseExpression = operand2
};
termStack.Push(expr);
}
else
{
if (JsScanner.IsAssignmentOperator(m_currentToken.Token))
{
if (!bCanAssign)
{
ReportError(JsError.IllegalAssignment);
SkipTokensAndThrow();
}
}
else
{
// if the operator is a comma, we can get another assign; otherwise we can't
bCanAssign = (m_currentToken.Token == JsToken.Comma);
}
// push the operator onto the operators stack
opsStack.Push(m_currentToken.Clone());
// push new term
GetNextToken();
if (bCanAssign)
{
termStack.Push(ParseUnaryExpression(out bCanAssign, false));
}
else
{
bool dummy;
termStack.Push(ParseUnaryExpression(out dummy, false));
}
}
}
else
{
// done with expression; go and unwind the stack of expressions/operators
break;
}
}
// there are still operators to be processed
while (opsStack.Peek() != null)
{
// pop the top two term and the top operator, combine them into a new term,
// and push the results back onto the term stacck
JsAstNode operand2 = termStack.Pop();
JsAstNode operand1 = termStack.Pop();
expr = CreateExpressionNode(opsStack.Pop(), operand1, operand2);
// push node onto the stack
termStack.Push(expr);
}
Debug.Assert(termStack.Count == 1);
return termStack.Pop();
}
catch (RecoveryTokenException exc)
{
exc._partiallyComputedNode = leftHandSide;
throw;
}
}
public override void Visit(JsBlock node)
{
if (node != null)
{
// if this block has a block scope, then look at the lexically-declared names (if any)
// and throw an error if any are defined as var's within this scope (ES6 rules).
// if this is the body of a function object, use the function scope.
JsActivationObject lexicalScope = node.BlockScope;
if (lexicalScope == null)
{
var functionObject = node.Parent as JsFunctionObject;
if (functionObject != null)
{
lexicalScope = functionObject.FunctionScope;
}
}
if (lexicalScope != null)
{
foreach (var lexDecl in lexicalScope.LexicallyDeclaredNames)
{
var varDecl = lexicalScope.VarDeclaredName(lexDecl.Name);
if (varDecl != null)
{
// collision.
// if the lexical declaration is a let or const declaration (as opposed to a function declaration),
// then force the warning to an error. This is so the function declaration will remain a warning if
// it collides with a var.
varDecl.NameContext.HandleError(JsError.DuplicateLexicalDeclaration, lexDecl is JsLexicalDeclaration);
// mark them both a no-rename to preserve the collision in the output
lexDecl.VariableField.IfNotNull(v => v.CanCrunch = false);
varDecl.VariableField.IfNotNull(v => v.CanCrunch = false);
}
}
}
// we might things differently if these statements are the body collection for a function
// because we can assume the implicit return statement at the end of it
bool isFunctionLevel = (node.Parent is JsFunctionObject);
// if we want to remove debug statements...
if (m_parser.Settings.StripDebugStatements && m_parser.Settings.IsModificationAllowed(JsTreeModifications.StripDebugStatements))
{
// do it now before we try doing other things
StripDebugStatements(node);
}
// analyze all the statements in our block and recurse them
if (node.BlockScope != null)
{
m_scopeStack.Push(node.BlockScope);
}
try
{
// don't call the base class to recurse -- let's walk the block
// backwards in case any of the children opt to delete themselves.
for (var ndx = node.Count - 1; ndx >= 0; --ndx)
{
node[ndx].Accept(this);
}
}
finally
{
if (node.BlockScope != null)
{
m_scopeStack.Pop();
}
}
if (m_parser.Settings.RemoveUnneededCode)
{
// go forward, and check the count each iteration because we might be ADDING statements to the block.
// let's look at all our if-statements. If a true-clause ends in a return, then we don't
// need the else-clause; we can pull its statements out and stick them after the if-statement.
// also, if we encounter a return-, break- or continue-statement, we can axe everything after it
for (var ndx = 0; ndx < node.Count; ++ndx)
{
// see if it's an if-statement with both a true and a false block
var ifNode = node[ndx] as JsIfNode;
if (ifNode != null
&& ifNode.TrueBlock != null
&& ifNode.TrueBlock.Count > 0
&& ifNode.FalseBlock != null)
{
// now check to see if the true block ends in a return statement
if (ifNode.TrueBlock[ifNode.TrueBlock.Count - 1] is JsReturnNode)
{
// transform: if(cond){statements1;return}else{statements2} to if(cond){statements1;return}statements2
// it does. insert all the false-block statements after the if-statement
node.InsertRange(ndx + 1, ifNode.FalseBlock.Children);
// and then remove the false block altogether
ifNode.FalseBlock = null;
}
}
else if (node[ndx] is JsReturnNode
|| node[ndx] is JsBreak
|| node[ndx] is JsContinueNode
|| node[ndx] is JsThrowNode)
{
// we have an exit node -- no statments afterwards will be executed, so clear them out.
// transform: {...;return;...} to {...;return}
// transform: {...;break;...} to {...;break}
// transform: {...;continue;...} to {...;continue}
// transform: {...;throw;...} to {...;throw}
// we've found an exit statement, and it's not the last statement in the function.
// walk the rest of the statements and delete anything that isn't a function declaration
// or a var- or const-statement.
for (var ndxRemove = node.Count - 1; ndxRemove > ndx; --ndxRemove)
{
var funcObject = node[ndxRemove] as JsFunctionObject;
if (funcObject == null || funcObject.FunctionType != JsFunctionType.Declaration)
{
// if it's a const-statement, leave it.
// we COULD check to see if the constant is referenced anywhere and delete
// any that aren't. Maybe later.
// we also don't want to do like the var-statements and remove the initializers.
// Not sure if any browsers would fail a const WITHOUT an initializer.
if (!(node[ndxRemove] is JsConstStatement))
{
var varStatement = node[ndxRemove] as JsVar;
if (varStatement != null)
{
// var statements can't be removed, but any initializers should
// be deleted since they won't get executed.
for (var ndxDecl = 0; ndxDecl < varStatement.Count; ++ndxDecl)
{
if (varStatement[ndxDecl].Initializer != null)
{
varStatement[ndxDecl].Initializer = null;
}
}
}
else
{
// not a function declaration, and not a var statement -- get rid of it
JsDetachReferences.Apply(node[ndxRemove]);
node.RemoveAt(ndxRemove);
}
}
}
}
}
}
}
// now check the last statement -- if it's an if-statement where the true-block is a single return
// and there is no false block, convert this one statement to a conditional. We might back it out later
// if we don't combine the conditional with other stuff.
// but we can only do this if we're at the functional level because of the implied return at the end
// of that block.
if (isFunctionLevel && node.Count > 0
&& m_parser.Settings.IsModificationAllowed(JsTreeModifications.IfConditionReturnToCondition))
{
JsReturnNode returnNode;
var ifNode = FindLastStatement(node) as JsIfNode;
if (ifNode != null && ifNode.FalseBlock == null
&& ifNode.TrueBlock.Count == 1
&& (returnNode = ifNode.TrueBlock[0] as JsReturnNode) != null)
{
// if the return node doesn't have an operand, then we can just replace the if-statement with its conditional
if (returnNode.Operand == null)
{
// if the condition is a constant, then eliminate it altogether
if (ifNode.Condition.IsConstant)
{
// delete the node altogether. Because the condition is a constant,
// there is no else-block, and the if-block only contains a return
// with no expression, we don't have anything to detach.
node.ReplaceChild(ifNode, null);
}
else
{
// transform: {...;if(cond)return;} to {...;cond;}
node.ReplaceChild(ifNode, ifNode.Condition);
}
}
else if (returnNode.Operand.IsExpression)
{
// this is a strategic replacement that might pay off later. And if
// it doesn't, we'll eventually back it out after all the other stuff
// if applied on top of it.
// transform: if(cond)return expr;} to return cond?expr:void 0}
var conditional = new JsConditional(null, m_parser)
{
Condition = ifNode.Condition,
TrueExpression = returnNode.Operand,
FalseExpression = CreateVoidNode()
};
// replace the if-statement with the new return node
node.ReplaceChild(ifNode, new JsReturnNode(ifNode.Context, m_parser)
{
Operand = conditional
});
Optimize(conditional);
}
}
}
// now walk through and combine adjacent expression statements, and adjacent var-for statements
// and adjecent expression-return statements
if (m_parser.Settings.IsModificationAllowed(JsTreeModifications.CombineAdjacentExpressionStatements))
{
CombineExpressions(node);
}
// check to see if we want to combine a preceding var with a for-statement
if (m_parser.Settings.IsModificationAllowed(JsTreeModifications.MoveVarIntoFor))
{
// look at the statements in the block.
// walk BACKWARDS down the list because we'll be removing items when we encounter
// var statements that can be moved inside a for statement's initializer
// we also don't need to check the first one, since there is nothing before it.
for (int ndx = node.Count - 1; ndx > 0; --ndx)
{
// see if the previous statement is a var statement
// (we've already combined adjacent var-statements)
JsForNode forNode;
JsWhileNode whileNode;
var previousVar = node[ndx - 1] as JsVar;
if (previousVar != null && (forNode = node[ndx] as JsForNode) != null)
{
// BUT if the var statement has any initializers containing an in-operator, first check
// to see if we haven't killed that move before we try moving it. Opera 11 seems to have
// an issue with that syntax, even if properly parenthesized.
if (m_parser.Settings.IsModificationAllowed(JsTreeModifications.MoveInExpressionsIntoForStatement)
|| !previousVar.ContainsInOperator)
{
// and see if the forNode's initializer is empty
if (forNode.Initializer != null)
{
// not empty -- see if it is a Var node
JsVar varInitializer = forNode.Initializer as JsVar;
if (varInitializer != null)
{
// transform: var decls1;for(var decls2;...) to for(var decls1,decls2;...)
// we want to PREPEND the initializers in the previous var-statement
// to our for-statement's initializer var-statement list
varInitializer.InsertAt(0, previousVar);
// then remove the previous var statement
node.RemoveAt(ndx - 1);
// this will bump the for node up one position in the list, so the next iteration
// will be right back on this node in case there are other var statements we need
// to combine
}
else
{
// we want to see if the initializer expression is a series of one or more
// simple assignments to variables that are in the previous var statement.
// if all the expressions are assignments to variables that are defined in the
// previous var statement, then we can just move the var statement into the
// for statement.
var binaryOp = forNode.Initializer as JsBinaryOperator;
if (binaryOp != null && AreAssignmentsInVar(binaryOp, previousVar))
{
// transform: var decls;for(expr1;...) to for(var decls,expr1;...)
// WHERE expr1 only consists of assignments to variables that are declared
// in that previous var-statement.
// TODO: we *could* also do it is the expr1 assignments are to lookups that are
// defined in THIS scope (not any outer scopes), because it wouldn't hurt to have
// then in a var statement again.
// create a list and fill it with all the var-decls created from the assignment
// operators in the expression
var varDecls = new List<JsVariableDeclaration>();
ConvertAssignmentsToVarDecls(binaryOp, varDecls, m_parser);
// then go through and append each one to the var statement before us
foreach (var varDecl in varDecls)
{
previousVar.Append(varDecl);
}
// move the previous var-statement into our initializer
forNode.Initializer = previousVar;
// and remove the previous var-statement from the list.
node.RemoveAt(ndx - 1);
// this will bump the for node up one position in the list, so the next iteration
// will be right back on this node, but the initializer will not be null
}
}
}
else
{
// transform: var decls;for(;...) to for(var decls;...)
// if it's empty, then we're free to add the previous var statement
// to this for statement's initializer. remove it from it's current
// position and add it as the initializer
node.RemoveAt(ndx - 1);
forNode.Initializer = previousVar;
// this will bump the for node up one position in the list, so the next iteration
// will be right back on this node, but the initializer will not be null
}
}
}
else if (previousVar != null
&& (whileNode = node[ndx] as JsWhileNode) != null
&& m_parser.Settings.IsModificationAllowed(JsTreeModifications.ChangeWhileToFor))
{
// transform: var ...;while(cond)... => for(var ...;cond;)...
node[ndx] = new JsForNode(null, m_parser)
{
Initializer = previousVar,
Condition = whileNode.Condition,
Body = whileNode.Body
};
node.RemoveAt(ndx - 1);
}
}
}
// see if the last statement is a return statement
JsReturnNode lastReturn;
if ((lastReturn = FindLastStatement(node) as JsReturnNode) != null)
{
// set this flag to true if we end up adding an expression to the block.
// before exiting, we'll go through and combine adjacent expressions again if this
// flag has been set to true.
bool changedStatementToExpression = false;
// get the index of the statement before the last return
// (skip over function decls and importand comments)
var indexPrevious = PreviousStatementIndex(node, lastReturn);
// just out of curiosity, let's see if we fit a common pattern:
// var name=expr;return name;
// or
// const name=expr;return name;
// if so, we can cut out the var and simply return the expression
JsLookup lookup;
if ((lookup = lastReturn.Operand as JsLookup) != null && indexPrevious >= 0)
{
// use the base class for both the var- and const-statements so we will
// pick them both up at the same time
var varStatement = node[indexPrevious] as JsDeclaration;
if (varStatement != null)
{
// if the last vardecl in the var statement matches the return lookup, and no
// other references exist for this field (refcount == 1)...
JsVariableDeclaration varDecl;
if ((varDecl = varStatement[varStatement.Count - 1]).Initializer != null
&& varDecl.IsEquivalentTo(lookup)
&& varDecl.VariableField.RefCount == 1)
{
// clean up the field's references because we're removing both the lookup reference
// in the return statement and the vardecl.
varDecl.VariableField.References.Remove(lookup);
varDecl.VariableField.Declarations.Remove(varDecl);
if (varStatement.Count == 1)
{
// transform: ...;var name=expr;return name} to ...;return expr}
// there's only one vardecl in the var, so get rid of the entire statement
lastReturn.Operand = varDecl.Initializer;
node.RemoveAt(indexPrevious);
}
else
{
// multiple vardecls are in the statement; we only need to get rid of the last one
lastReturn.Operand = varDecl.Initializer;
varStatement[varStatement.Count - 1] = null;
}
}
}
}
// check to see if we can combine the return statement with a previous if-statement
// into a simple return-conditional. The true statement needs to have no false block,
// and only one statement in the true block.
JsConditional conditional;
JsIfNode previousIf;
while (indexPrevious >= 0
&& lastReturn != null
&& (previousIf = node[indexPrevious] as JsIfNode) != null
&& previousIf.TrueBlock != null && previousIf.TrueBlock.Count == 1
&& previousIf.FalseBlock == null)
{
// assume no change is made for this loop
bool somethingChanged = false;
// and that one true-block statement needs to be a return statement
var previousReturn = previousIf.TrueBlock[0] as JsReturnNode;
if (previousReturn != null)
{
if (lastReturn.Operand == null)
{
if (previousReturn.Operand == null)
{
// IF we are at the function level, then the block ends in an implicit return (undefined)
// and we can change this if to just the condition. If we aren't at the function level,
// then we have to leave the return, but we can replace the if with just the condition.
if (!isFunctionLevel)
{
// not at the function level, so the return must stay.
if (previousIf.Condition.IsConstant)
{
// transform: if(cond)return;return} to return}
node.RemoveAt(indexPrevious);
somethingChanged = true;
}
else
{
// transform: if(cond)return;return} to cond;return}
node[indexPrevious] = previousIf.Condition;
}
}
else if (previousIf.Condition.IsConstant)
{
// transform: remove if(cond)return;return} because cond is a constant
node.ReplaceChild(lastReturn, null);
node.RemoveAt(indexPrevious);
somethingChanged = true;
}
else
{
// transform: if(cond)return;return} to cond}
// replace the final return with just the condition, then remove the previous if
if (node.ReplaceChild(lastReturn, previousIf.Condition))
{
node.RemoveAt(indexPrevious);
somethingChanged = true;
}
}
}
else
{
// transform: if(cond)return expr;return} to return cond?expr:void 0
conditional = new JsConditional(null, m_parser)
{
Condition = previousIf.Condition,
TrueExpression = previousReturn.Operand,
FalseExpression = CreateVoidNode()
};
// replace the final return with the new return, then delete the previous if-statement
if (node.ReplaceChild(lastReturn, new JsReturnNode(null, m_parser)
{
Operand = conditional
}))
{
node.RemoveAt(indexPrevious);
Optimize(conditional);
somethingChanged = true;
}
}
}
else
{
if (previousReturn.Operand == null)
{
// transform: if(cond)return;return expr} to return cond?void 0:expr
conditional = new JsConditional(null, m_parser)
{
Condition = previousIf.Condition,
TrueExpression = CreateVoidNode(),
FalseExpression = lastReturn.Operand
};
// replace the final return with the new return, then delete the previous if-statement
if (node.ReplaceChild(lastReturn, new JsReturnNode(null, m_parser)
{
Operand = conditional
}))
{
node.RemoveAt(indexPrevious);
Optimize(conditional);
somethingChanged = true;
}
}
else if (previousReturn.Operand.IsEquivalentTo(lastReturn.Operand))
{
if (previousIf.Condition.IsConstant)
{
// the condition is constant, and the returns return the same thing.
// get rid of the if statement altogether.
// transform: if(cond)return expr;return expr} to return expr}
JsDetachReferences.Apply(previousReturn.Operand);
node.RemoveAt(indexPrevious);
somethingChanged = true;
}
else
{
// transform: if(cond)return expr;return expr} to return cond,expr}
// create a new binary op with the condition and the final-return operand,
// replace the operand on the final-return with the new binary operator,
// and then delete the previous if-statement
JsDetachReferences.Apply(previousReturn.Operand);
lastReturn.Operand = JsCommaOperator.CombineWithComma(null, m_parser, previousIf.Condition, lastReturn.Operand);
node.RemoveAt(indexPrevious);
somethingChanged = true;
}
}
else
{
// transform: if(cond)return expr1;return expr2} to return cond?expr1:expr2}
// create a new conditional with the condition and the return operands,
// replace the operand on the final-return with the new conditional operator,
// and then delete the previous if-statement
// transform: if(cond)return expr1;return expr2} to return cond?expr1:expr2}
conditional = new JsConditional(null, m_parser)
{
Condition = previousIf.Condition,
TrueExpression = previousReturn.Operand,
FalseExpression = lastReturn.Operand
};
// replace the operand on the final-return with the new conditional operator,
// and then delete the previous if-statement
lastReturn.Operand = conditional;
node.RemoveAt(indexPrevious);
Optimize(conditional);
somethingChanged = true;
}
}
}
if (!somethingChanged)
{
// nothing changed -- break out of the loop
break;
}
else
{
// set the flag that indicates something changed in at least one of these loops
changedStatementToExpression = true;
// and since we changed something, we need to bump the index down one
// AFTER we grab the last return node (which has slipped into the same position
// as the previous node)
lastReturn = node[indexPrevious--] as JsReturnNode;
}
}
// if we added any more expressions since we ran our expression-combination logic,
// run it again.
if (changedStatementToExpression
&& m_parser.Settings.IsModificationAllowed(JsTreeModifications.CombineAdjacentExpressionStatements))
{
CombineExpressions(node);
}
// and FINALLY, we want to see if what we did previously didn't pan out and we end
// in something like return cond?expr:void 0, in which case we want to change it
// back to a simple if(condition)return expr; (saves four bytes).
// see if the last statement is a return statement that returns a conditional
if (lastReturn != null
&& (conditional = lastReturn.Operand as JsConditional) != null)
{
var unaryOperator = conditional.FalseExpression as JsUnaryOperator;
if (unaryOperator != null
&& unaryOperator.OperatorToken == JsToken.Void
&& unaryOperator.Operand is JsConstantWrapper)
{
unaryOperator = conditional.TrueExpression as JsUnaryOperator;
if (unaryOperator != null && unaryOperator.OperatorToken == JsToken.Void)
{
if (isFunctionLevel)
{
// transform: ...;return cond?void 0:void 0} to ...;cond}
// function level ends in an implicit "return void 0"
node.ReplaceChild(lastReturn, conditional.Condition);
}
else
{
// transform: ...;return cond?void 0:void 0} to ...;cond;return}
// non-function level doesn't end in an implicit return,
// so we need to break them out into two statements
node.ReplaceChild(lastReturn, conditional.Condition);
node.Append(new JsReturnNode(null, m_parser));
}
}
else if (isFunctionLevel)
{
// transform: ...;return cond?expr:void 0} to ...;if(cond)return expr}
// (only works at the function-level because of the implicit return statement)
var ifNode = new JsIfNode(lastReturn.Context, m_parser)
{
Condition = conditional.Condition,
TrueBlock = JsAstNode.ForceToBlock(new JsReturnNode(null, m_parser)
{
Operand = conditional.TrueExpression
})
};
node.ReplaceChild(lastReturn, ifNode);
}
}
else if (isFunctionLevel)
{
unaryOperator = conditional.TrueExpression as JsUnaryOperator;
if (unaryOperator != null
&& unaryOperator.OperatorToken == JsToken.Void
&& unaryOperator.Operand is JsConstantWrapper)
{
// transform: ...;return cond?void 0;expr} to ...;if(!cond)return expr}
// (only works at the function level because of the implicit return)
// get the logical-not of the conditional
var logicalNot = new JsLogicalNot(conditional.Condition, m_parser);
logicalNot.Apply();
// create a new if-node based on the condition, with the branches swapped
// (true-expression goes to false-branch, false-expression goes to true-branch
var ifNode = new JsIfNode(lastReturn.Context, m_parser)
{
Condition = conditional.Condition,
TrueBlock = JsAstNode.ForceToBlock(new JsReturnNode(null, m_parser)
{
Operand = conditional.FalseExpression
})
};
node.ReplaceChild(lastReturn, ifNode);
}
}
}
}
if (m_parser.Settings.IsModificationAllowed(JsTreeModifications.CombineEquivalentIfReturns))
{
// walk backwards looking for if(cond1)return expr1;if(cond2)return expr2;
// (backwards, because we'll be combining those into one statement, reducing the number of statements.
// don't go all the way to zero, because each loop will compare the statement to the PREVIOUS
// statement, and the first statement (index==0) has no previous statement.
for (var ndx = node.Count - 1; ndx > 0; --ndx)
{
// see if the current statement is an if-statement with no else block, and a true
// block that contains a single return-statement WITH an expression.
JsAstNode currentExpr = null;
JsAstNode condition2;
if (IsIfReturnExpr(node[ndx], out condition2, ref currentExpr) != null)
{
// see if the previous statement is also the same pattern, but with
// the equivalent expression as its return operand
JsAstNode condition1;
var matchedExpression = currentExpr;
var ifNode = IsIfReturnExpr(node[ndx - 1], out condition1, ref matchedExpression);
if (ifNode != null)
{
// it is a match!
// let's combine them -- we'll add the current condition to the
// previous condition with a logical-or and delete the current statement.
// transform: if(cond1)return expr;if(cond2)return expr; to if(cond1||cond2)return expr;
ifNode.Condition = new JsBinaryOperator(null, m_parser)
{
Operand1 = condition1,
Operand2 = condition2,
OperatorToken = JsToken.LogicalOr,
TerminatingContext = ifNode.TerminatingContext ?? node.TerminatingContext
};
JsDetachReferences.Apply(currentExpr);
node.RemoveAt(ndx);
}
}
}
}
if (isFunctionLevel
&& m_parser.Settings.IsModificationAllowed(JsTreeModifications.InvertIfReturn))
{
// walk backwards looking for if (cond) return; whenever we encounter that statement,
// we can change it to if (!cond) and put all subsequent statements in the block inside the
// if's true-block.
for (var ndx = node.Count - 1; ndx >= 0; --ndx)
{
var ifNode = node[ndx] as JsIfNode;
if (ifNode != null
&& ifNode.FalseBlock == null
&& ifNode.TrueBlock != null
&& ifNode.TrueBlock.Count == 1)
{
var returnNode = ifNode.TrueBlock[0] as JsReturnNode;
if (returnNode != null && returnNode.Operand == null)
{
// we have if(cond)return;
// logical-not the condition, remove the return statement,
// and move all subsequent sibling statements inside the if-statement.
JsLogicalNot.Apply(ifNode.Condition, m_parser);
ifNode.TrueBlock.Clear();
var ndxMove = ndx + 1;
if (node.Count == ndxMove + 1)
{
// there's only one statement after our if-node.
// see if it's ALSO an if-node with no else block.
var secondIfNode = node[ndxMove] as JsIfNode;
if (secondIfNode != null && (secondIfNode.FalseBlock == null || secondIfNode.FalseBlock.Count == 0))
{
// it is!
// transform: if(cond1)return;if(cond2){...} => if(!cond1&&cond2){...}
// (the cond1 is already inverted at this point)
// combine cond2 with cond1 via a logical-and,
// move all secondIf statements inside the if-node,
// remove the secondIf node.
node.RemoveAt(ndxMove);
ifNode.Condition = new JsBinaryOperator(null, m_parser)
{
Operand1 = ifNode.Condition,
Operand2 = secondIfNode.Condition,
OperatorToken = JsToken.LogicalAnd
};
ifNode.TrueBlock = secondIfNode.TrueBlock;
}
else if (node[ndxMove].IsExpression
&& m_parser.Settings.IsModificationAllowed(JsTreeModifications.IfConditionCallToConditionAndCall))
{
// now we have if(cond)expr; optimize that!
var expression = node[ndxMove];
node.RemoveAt(ndxMove);
IfConditionExpressionToExpression(ifNode, expression);
}
}
// just move all the following statements inside the if-statement
while (node.Count > ndxMove)
{
var movedNode = node[ndxMove];
node.RemoveAt(ndxMove);
ifNode.TrueBlock.Append(movedNode);
}
}
}
}
}
else
{
var isIteratorBlock = node.Parent is JsForNode
|| node.Parent is JsForIn
|| node.Parent is JsWhileNode
|| node.Parent is JsDoWhile;
if (isIteratorBlock
&& m_parser.Settings.IsModificationAllowed(JsTreeModifications.InvertIfContinue))
{
// walk backwards looking for if (cond) continue; whenever we encounter that statement,
// we can change it to if (!cond) and put all subsequent statements in the block inside the
// if's true-block.
for (var ndx = node.Count - 1; ndx >= 0; --ndx)
{
var ifNode = node[ndx] as JsIfNode;
if (ifNode != null
&& ifNode.FalseBlock == null
&& ifNode.TrueBlock != null
&& ifNode.TrueBlock.Count == 1)
{
var continueNode = ifNode.TrueBlock[0] as JsContinueNode;
// if there's no label, then we're good. Otherwise we can only make this optimization
// if the label refers to the parent iterator node.
if (continueNode != null
&& (string.IsNullOrEmpty(continueNode.Label) || (LabelMatchesParent(continueNode.Label, node.Parent))))
{
// if this is the last statement, then we don't really need the if at all
// and can just replace it with its condition
if (ndx < node.Count - 1)
{
// we have if(cond)continue;st1;...stn;
// logical-not the condition, remove the continue statement,
// and move all subsequent sibling statements inside the if-statement.
JsLogicalNot.Apply(ifNode.Condition, m_parser);
ifNode.TrueBlock.Clear();
// TODO: if we removed a labeled continue, do we need to fix up some label references?
var ndxMove = ndx + 1;
if (node.Count == ndxMove + 1)
{
// there's only one statement after our if-node.
// see if it's ALSO an if-node with no else block.
var secondIfNode = node[ndxMove] as JsIfNode;
if (secondIfNode != null && (secondIfNode.FalseBlock == null || secondIfNode.FalseBlock.Count == 0))
{
// it is!
// transform: if(cond1)continue;if(cond2){...} => if(!cond1&&cond2){...}
// (the cond1 is already inverted at this point)
// combine cond2 with cond1 via a logical-and,
// move all secondIf statements inside the if-node,
// remove the secondIf node.
ifNode.Condition = new JsBinaryOperator(null, m_parser)
{
Operand1 = ifNode.Condition,
Operand2 = secondIfNode.Condition,
OperatorToken = JsToken.LogicalAnd
};
ifNode.TrueBlock = secondIfNode.TrueBlock;
node.RemoveAt(ndxMove);
}
else if (node[ndxMove].IsExpression
&& m_parser.Settings.IsModificationAllowed(JsTreeModifications.IfConditionCallToConditionAndCall))
{
// now we have if(cond)expr; optimize that!
var expression = node[ndxMove];
node.RemoveAt(ndxMove);
IfConditionExpressionToExpression(ifNode, expression);
}
}
// just move all the following statements inside the if-statement
while (node.Count > ndxMove)
{
var movedNode = node[ndxMove];
node.RemoveAt(ndxMove);
ifNode.TrueBlock.Append(movedNode);
}
}
else
{
// we have if(cond)continue} -- nothing after the if.
// the loop is going to continue anyway, so replace the if-statement
// with the condition and be done
if (ifNode.Condition.IsConstant)
{
// consition is constant -- get rid of the if-statement altogether
node.RemoveAt(ndx);
}
else
{
// condition isn't constant
node[ndx] = ifNode.Condition;
}
}
}
}
}
}
}
}
}
private void DoConditional(JsConditional node)
{
if (m_parser.Settings.IsModificationAllowed(JsTreeModifications.EvaluateNumericExpressions))
{
// if the condition is a literal, evaluating the condition doesn't do anything, AND
// we know now whether it's true or not.
JsConstantWrapper literalCondition = node.Condition as JsConstantWrapper;
if (literalCondition != null)
{
try
{
// if the boolean represenation of the literal is true, we can replace the condition operator
// with the true expression; otherwise we can replace it with the false expression
ReplaceNodeCheckParens(node, literalCondition.ToBoolean() ? node.TrueExpression : node.FalseExpression);
}
catch (InvalidCastException)
{
// ignore any invalid cast errors
}
}
}
}
public override void Visit(JsConditional node)
{
if (node != null)
{
// we have two choices for the conditional. Either:
// 1. we wrap the whole thing in a logical-not operator, which means we also need to
// add parentheses, since conditional is lower-precedence than the logicial not, or
// 2. apply the logical-not to both the true- and false-branches.
// The first is guaranteed 3 additional characters. We have to check the delta for
// each branch and add them together to know how much the second would cost. If it's
// greater than 3, then we just want to not the whole thing.
var notTrue = new JsLogicalNot(node.TrueExpression, m_parser);
var notFalse = new JsLogicalNot(node.FalseExpression, m_parser);
var costNottingBoth = notTrue.Measure() + notFalse.Measure();
if (m_measure)
{
// we're just measuring -- adjust the delta accordingly
// (the lesser of the two options)
m_delta += (costNottingBoth > 3) ? 3 : costNottingBoth;
}
else if (costNottingBoth > 3)
{
// just wrap the whole thing
WrapWithLogicalNot(node);
}
else
{
// less bytes to wrap each branch separately
node.TrueExpression.Accept(this);
node.FalseExpression.Accept(this);
}
}
}
public override void Visit(JsConditional node)
{
if (node != null)
{
// depth-first
base.Visit(node);
DoConditional(node);
}
}
private void Optimize(JsConditional node)
{
// now check to see if the condition starts with a not-operator. If so, we can get rid of it
// and swap the true/false children
var unary = node.Condition as JsUnaryOperator;
if (unary != null && unary.OperatorToken == JsToken.LogicalNot
&& !unary.OperatorInConditionalCompilationComment
&& m_parser.Settings.IsModificationAllowed(JsTreeModifications.IfNotTrueFalseToIfFalseTrue))
{
// get rid of the not by replacing it with its operand
// and swap the branches
node.Condition = unary.Operand;
node.SwapBranches();
}
// see if the two branches are both assignment operations to the same variable.
// if so, we can pull the assignment outside the conditional and have the conditional
// be the assignment
var trueAssign = node.TrueExpression as JsBinaryOperator;
if (trueAssign != null && trueAssign.IsAssign)
{
var falseAssign = node.FalseExpression as JsBinaryOperator;
if (falseAssign != null && falseAssign.OperatorToken == trueAssign.OperatorToken)
{
// see if the left-hand-side is equivalent
if (trueAssign.Operand1.IsEquivalentTo(falseAssign.Operand1))
{
// we're going to be getting rid of the left-hand side in the false-block,
// so we need to remove any references it may represent
JsDetachReferences.Apply(falseAssign.Operand1);
// transform: cond?lhs=expr1:lhs=expr2 to lhs=cond?expr1:expr2s
var binaryOp = new JsBinaryOperator(node.Context, m_parser)
{
Operand1 = trueAssign.Operand1,
Operand2 = new JsConditional(node.Context, m_parser)
{
Condition = node.Condition,
QuestionContext = node.QuestionContext,
TrueExpression = trueAssign.Operand2,
ColonContext = node.ColonContext,
FalseExpression = falseAssign.Operand2
},
OperatorContext = trueAssign.OperatorContext,
OperatorToken = trueAssign.OperatorToken,
TerminatingContext = node.TerminatingContext
};
node.Parent.ReplaceChild(node, binaryOp);
}
}
}
}
public override void Visit(JsIfNode node)
{
if (node != null)
{
if (m_parser.Settings.StripDebugStatements
&& m_parser.Settings.IsModificationAllowed(JsTreeModifications.StripDebugStatements))
{
if (node.TrueBlock != null && node.TrueBlock.IsDebuggerStatement)
{
node.TrueBlock = null;
}
if (node.FalseBlock != null && node.FalseBlock.IsDebuggerStatement)
{
node.FalseBlock = null;
}
}
// recurse....
base.Visit(node);
// now check to see if the two branches are now empty.
// if they are, null them out.
if (node.TrueBlock != null && node.TrueBlock.Count == 0)
{
node.TrueBlock = null;
}
if (node.FalseBlock != null && node.FalseBlock.Count == 0)
{
node.FalseBlock = null;
}
if (node.TrueBlock != null && node.FalseBlock != null)
{
// neither true block nor false block is null.
// if they're both expressions, convert them to a condition operator
if (node.TrueBlock.IsExpression && node.FalseBlock.IsExpression
&& m_parser.Settings.IsModificationAllowed(JsTreeModifications.IfExpressionsToExpression))
{
// if this statement has both true and false blocks, and they are both expressions,
// then we can simplify this to a conditional expression.
// because the blocks are expressions, we know they only have ONE statement in them,
// so we can just dereference them directly.
JsConditional conditional;
var logicalNot = new JsLogicalNot(node.Condition, m_parser);
if (logicalNot.Measure() < 0)
{
// applying a logical-not makes the condition smaller -- reverse the branches
logicalNot.Apply();
conditional = new JsConditional(node.Context, m_parser)
{
Condition = node.Condition,
TrueExpression = node.FalseBlock[0],
FalseExpression = node.TrueBlock[0]
};
}
else
{
// regular order
conditional = new JsConditional(node.Context, m_parser)
{
Condition = node.Condition,
TrueExpression = node.TrueBlock[0],
FalseExpression = node.FalseBlock[0]
};
}
node.Parent.ReplaceChild(
node,
conditional);
Optimize(conditional);
}
else
{
// see if logical-notting the condition produces something smaller
var logicalNot = new JsLogicalNot(node.Condition, m_parser);
if (logicalNot.Measure() < 0)
{
// it does -- not the condition and swap the branches
logicalNot.Apply();
node.SwapBranches();
}
// see if the true- and false-branches each contain only a single statement
if (node.TrueBlock.Count == 1 && node.FalseBlock.Count == 1)
{
// they do -- see if the true-branch's statement is a return-statement
var trueReturn = node.TrueBlock[0] as JsReturnNode;
if (trueReturn != null && trueReturn.Operand != null)
{
// it is -- see if the false-branch is also a return statement
var falseReturn = node.FalseBlock[0] as JsReturnNode;
if (falseReturn != null && falseReturn.Operand != null)
{
// transform: if(cond)return expr1;else return expr2 to return cond?expr1:expr2
var conditional = new JsConditional(null, m_parser)
{
Condition = node.Condition,
TrueExpression = trueReturn.Operand,
FalseExpression = falseReturn.Operand
};
// create a new return node from the conditional and replace
// our if-node with it
var returnNode = new JsReturnNode(node.Context, m_parser)
{
Operand = conditional
};
node.Parent.ReplaceChild(
node,
returnNode);
Optimize(conditional);
}
}
}
}
}
else if (node.FalseBlock != null)
{
// true block must be null.
// if there is no true branch but a false branch, then
// put a not on the condition and move the false branch to the true branch.
if (node.FalseBlock.IsExpression
&& m_parser.Settings.IsModificationAllowed(JsTreeModifications.IfConditionCallToConditionAndCall))
{
// if (cond); else expr ==> cond || expr
// but first -- which operator to use? if(a);else b --> a||b, and if(!a);else b --> a&&b
// so determine which one is smaller: a or !a
// assume we'll use the logical-or, since that doesn't require changing the condition
var newOperator = JsToken.LogicalOr;
var logicalNot = new JsLogicalNot(node.Condition, m_parser);
if (logicalNot.Measure() < 0)
{
// !a is smaller, so apply it and use the logical-or operator
logicalNot.Apply();
newOperator = JsToken.LogicalAnd;
}
var binaryOp = new JsBinaryOperator(node.Context, m_parser)
{
Operand1 = node.Condition,
Operand2 = node.FalseBlock[0],
OperatorToken = newOperator,
};
// we don't need to analyse this new node because we've already analyzed
// the pieces parts as part of the if. And this visitor's method for the BinaryOperator
// doesn't really do anything else. Just replace our current node with this
// new node
node.Parent.ReplaceChild(node, binaryOp);
}
else if (m_parser.Settings.IsModificationAllowed(JsTreeModifications.IfConditionFalseToIfNotConditionTrue))
{
// logical-not the condition
// if(cond);else stmt ==> if(!cond)stmt
var logicalNot = new JsLogicalNot(node.Condition, m_parser);
logicalNot.Apply();
// and swap the branches
node.SwapBranches();
}
}
else if (node.TrueBlock != null)
{
// false block must be null
if (node.TrueBlock.IsExpression
&& m_parser.Settings.IsModificationAllowed(JsTreeModifications.IfConditionCallToConditionAndCall))
{
// convert the if-node to an expression
IfConditionExpressionToExpression(node, node.TrueBlock[0]);
}
}
else if (m_parser.Settings.IsModificationAllowed(JsTreeModifications.IfEmptyToExpression))
{
// NEITHER branches have anything now!
// as long as the condition doesn't
// contain calls or assignments, we should be able to completely delete
// the statement altogether rather than changing it to an expression
// statement on the condition.
// but how do we KNOW there are no side-effects?
// if the condition is a constant or operations on constants, delete it.
// or if the condition itself is a debugger statement -- a call, lookup, or member.
var remove = node.Condition.IsConstant || node.Condition.IsDebuggerStatement;
if (remove)
{
// we're pretty sure there are no side-effects; remove it altogether
node.Parent.ReplaceChild(node, null);
}
else
{
// We don't know what it is and what the side-effects may be, so
// just change this statement into an expression statement by replacing us with
// the expression
// no need to analyze -- we already recursed
node.Parent.ReplaceChild(node, node.Condition);
}
}
if (node.FalseBlock == null
&& node.TrueBlock != null
&& node.TrueBlock.Count == 1
&& m_parser.Settings.IsModificationAllowed(JsTreeModifications.CombineNestedIfs))
{
var nestedIf = node.TrueBlock[0] as JsIfNode;
if (nestedIf != null && nestedIf.FalseBlock == null)
{
// we have nested if-blocks.
// transform if(cond1)if(cond2){...} to if(cond1&&cond2){...}
// change the first if-statement's condition to be cond1&&cond2
// move the nested if-statement's true block to the outer if-statement
node.Condition = new JsBinaryOperator(null, m_parser)
{
Operand1 = node.Condition,
Operand2 = nestedIf.Condition,
OperatorToken = JsToken.LogicalAnd
};
node.TrueBlock = nestedIf.TrueBlock;
}
}
}
}
public void Visit(JsConditional node)
{
// invalid! ignore
IsValid = false;
}
public void Visit(JsConditional node)
{
if (node != null)
{
var symbol = StartSymbol(node);
var isNoIn = m_noIn;
if (node.Condition != null)
{
AcceptNodeWithParens(node.Condition, node.Condition.Precedence < JsOperatorPrecedence.LogicalOr);
SetContextOutputPosition(node.Context);
}
if (m_settings.OutputMode == MinifierOutputMode.MultipleLines)
{
OutputPossibleLineBreak(' ');
OutputPossibleLineBreak('?');
MarkSegment(node, null, node.QuestionContext ?? node.Context);
BreakLine(false);
if (!m_onNewLine)
{
OutputPossibleLineBreak(' ');
}
}
else
{
OutputPossibleLineBreak('?');
MarkSegment(node, null, node.QuestionContext ?? node.Context);
}
m_startOfStatement = false;
if (node.TrueExpression != null)
{
m_noIn = isNoIn;
AcceptNodeWithParens(node.TrueExpression, node.TrueExpression.Precedence < JsOperatorPrecedence.Assignment);
}
if (m_settings.OutputMode == MinifierOutputMode.MultipleLines)
{
OutputPossibleLineBreak(' ');
OutputPossibleLineBreak(':');
MarkSegment(node, null, node.ColonContext ?? node.Context);
BreakLine(false);
if (!m_onNewLine)
{
OutputPossibleLineBreak(' ');
}
}
else
{
OutputPossibleLineBreak(':');
MarkSegment(node, null, node.ColonContext ?? node.Context);
}
if (node.FalseExpression != null)
{
m_noIn = isNoIn;
AcceptNodeWithParens(node.FalseExpression, node.FalseExpression.Precedence < JsOperatorPrecedence.Assignment);
}
m_noIn = isNoIn;
EndSymbol(symbol);
}
}
public void Visit(JsConditional node)
{
// not applicable; terminate
}
public void Visit(JsConditional node)
{
// not applicable; terminate
}
public void Visit(JsConditional node)
{
// invalid! ignore
IsValid = false;
}
public override void Visit(JsConditional node)
{
if (node != null)
{
// analye all the children
base.Visit(node);
// and then optimize our node
Optimize(node);
}
}