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Closure Compiler is a JavaScript optimizing compiler. It parses your
JavaScript, analyzes it, removes dead code and rewrites and minimizes
what's left. It also checks syntax, variable references, and types, and
warns about common JavaScript pitfalls. It is used in many of Google's
JavaScript apps, including Gmail, Google Web Search, Google Maps, and
Google Docs.
/*
* Copyright 2008 The Closure Compiler Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.javascript.jscomp;
import com.google.common.base.Preconditions;
import com.google.common.collect.HashMultimap;
import com.google.common.collect.Maps;
import com.google.common.collect.Multimap;
import com.google.javascript.jscomp.ControlFlowGraph.Branch;
import com.google.javascript.jscomp.NodeTraversal.Callback;
import com.google.javascript.jscomp.graph.DiGraph.DiGraphNode;
import com.google.javascript.rhino.Node;
import com.google.javascript.rhino.Token;
import java.util.ArrayDeque;
import java.util.Comparator;
import java.util.Deque;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.PriorityQueue;
/**
* This is a compiler pass that computes a control flow graph.
*
*/
final class ControlFlowAnalysis implements Callback, CompilerPass {
/**
* Based roughly on the first few pages of
*
* "Declarative Intraprocedural Flow Analysis of Java Source Code by
* Nilsson-Nyman, Hedin, Magnusson & Ekman",
*
* this pass computes the control flow graph from the AST. However, a full
* attribute grammar is not necessary. We will compute the flow edges with a
* single post order traversal. The "follow()" of a given node will be
* computed recursively in a demand driven fashion.
*
* As of this moment, we are not performing any inter-procedural analysis
* within our framework.
*/
private final AbstractCompiler compiler;
private ControlFlowGraph cfg;
private Map astPosition;
// TODO(nicksantos): should these be node annotations?
private Map, Integer> nodePriorities;
// We order CFG nodes by by looking at the AST positions.
// CFG nodes that come first lexically should be visited first, because
// they will often be executed first in the source program.
private final Comparator> priorityComparator =
new Comparator>() {
@Override
public int compare(
DiGraphNode a, DiGraphNode b) {
return astPosition.get(a.getValue()) - astPosition.get(b.getValue());
}
};
private int astPositionCounter;
private int priorityCounter;
private final boolean shouldTraverseFunctions;
private final boolean edgeAnnotations;
// We need to store where we started, in case we aren't doing a flow analysis
// for the whole scope. This happens, for example, when running type inference
// on only the externs.
private Node root;
/*
* This stack captures the structure of nested TRY blocks. The top of the
* stack is the inner most TRY block. A FUNCTION node in this stack implies
* that the handler is determined by the caller of the function at runtime.
*/
private final Deque exceptionHandler = new ArrayDeque();
/*
* This map is used to handle the follow of FINALLY. For example:
*
* while(x) {
* try {
* try {
* break;
* } catch (a) {
* } finally {
* foo();
* }
* fooFollow();
* } catch (b) {
* } finally {
* bar();
* }
* barFollow();
* }
* END();
*
* In this case finallyMap will contain a map from:
* first FINALLY -> bar()
* second FINALLY -> END()
*
* When we are connecting foo() and bar() to to their respective follow, we
* must also look up this map and connect:
* foo() -> bar()
* bar() -> END
*/
private final Multimap finallyMap = HashMultimap.create();
/**
* Constructor.
*
* @param compiler Compiler instance.
* @param shouldTraverseFunctions Whether functions should be traversed (true
* by default).
* @param edgeAnnotations Whether to allow edge annotations. By default,
* only node annotations are allowed.
*/
ControlFlowAnalysis(AbstractCompiler compiler,
boolean shouldTraverseFunctions, boolean edgeAnnotations) {
this.compiler = compiler;
this.shouldTraverseFunctions = shouldTraverseFunctions;
this.edgeAnnotations = edgeAnnotations;
}
ControlFlowGraph getCfg() {
return cfg;
}
@Override
public void process(Node externs, Node root) {
this.root = root;
astPositionCounter = 0;
astPosition = Maps.newHashMap();
nodePriorities = Maps.newHashMap();
cfg = new AstControlFlowGraph(computeFallThrough(root), nodePriorities,
edgeAnnotations);
NodeTraversal.traverse(compiler, root, this);
astPosition.put(null, ++astPositionCounter); // the implicit return is last.
// Now, generate the priority of nodes by doing a depth-first
// search on the CFG.
priorityCounter = 0;
DiGraphNode entry = cfg.getEntry();
prioritizeFromEntryNode(entry);
if (shouldTraverseFunctions) {
// If we're traversing inner functions, we need to rank the
// priority of them too.
for (DiGraphNode candidate : cfg.getDirectedGraphNodes()) {
Node value = candidate.getValue();
if (value != null && value.getType() == Token.FUNCTION) {
Preconditions.checkState(
!nodePriorities.containsKey(candidate) || candidate == entry);
prioritizeFromEntryNode(candidate);
}
}
}
// At this point, all reachable nodes have been given a priority, but
// unreachable nodes have not been given a priority. Put them last.
// Presumably, it doesn't really matter what priority they get, since
// this shouldn't happen in real code.
for (DiGraphNode candidate : cfg.getDirectedGraphNodes()) {
if (!nodePriorities.containsKey(candidate)) {
nodePriorities.put(candidate, ++priorityCounter);
}
}
// Again, the implicit return node is always last.
nodePriorities.put(cfg.getImplicitReturn(), ++priorityCounter);
}
/**
* Given an entry node, find all the nodes reachable from that node
* and prioritize them.
*/
private void prioritizeFromEntryNode(DiGraphNode entry) {
PriorityQueue> worklist =
new PriorityQueue>(10, priorityComparator);
worklist.add(entry);
while (!worklist.isEmpty()) {
DiGraphNode current = worklist.remove();
if (nodePriorities.containsKey(current)) {
continue;
}
nodePriorities.put(current, ++priorityCounter);
List> successors =
cfg.getDirectedSuccNodes(current);
for (DiGraphNode candidate : successors) {
worklist.add(candidate);
}
}
}
@Override
public boolean shouldTraverse(
NodeTraversal nodeTraversal, Node n, Node parent) {
astPosition.put(n, astPositionCounter++);
switch (n.getType()) {
case Token.FUNCTION:
if (shouldTraverseFunctions || n == cfg.getEntry().getValue()) {
exceptionHandler.push(n);
return true;
}
return false;
case Token.TRY:
exceptionHandler.push(n);
return true;
}
/*
* We are going to stop the traversal depending on what the node's parent
* is.
*
* We are only interested in adding edges between nodes that change control
* flow. The most obvious ones are loops and IF-ELSE's. A statement
* transfers control to its next sibling.
*
* In case of an expression tree, there is no control flow within the tree
* even when there are short circuited operators and conditionals. When we
* are doing data flow analysis, we will simply synthesize lattices up the
* expression tree by finding the meet at each expression node.
*
* For example: within a Token.SWITCH, the expression in question does not
* change the control flow and need not to be considered.
*/
if (parent != null) {
switch (parent.getType()) {
case Token.FOR:
// Only traverse the body of the for loop.
return n == parent.getLastChild();
// Skip the conditions.
case Token.IF:
case Token.WHILE:
case Token.WITH:
return n != parent.getFirstChild();
case Token.DO:
return n != parent.getFirstChild().getNext();
// Only traverse the body of the cases
case Token.SWITCH:
case Token.CASE:
case Token.CATCH:
case Token.LABEL:
return n != parent.getFirstChild();
case Token.FUNCTION:
return n == parent.getFirstChild().getNext().getNext();
case Token.CONTINUE:
case Token.BREAK:
case Token.EXPR_RESULT:
case Token.VAR:
case Token.RETURN:
case Token.THROW:
return false;
case Token.TRY:
/* Just before we are about to visit the second child of the TRY node,
* we know that we will be visiting either the CATCH or the FINALLY.
* In other words, we know that the post order traversal of the TRY
* block has been finished, no more exceptions can be caught by the
* handler at this TRY block and should be taken out of the stack.
*/
if (n == parent.getFirstChild().getNext()) {
Preconditions.checkState(exceptionHandler.peek() == parent);
exceptionHandler.pop();
}
}
}
return true;
}
@Override
public void visit(NodeTraversal t, Node n, Node parent) {
switch (n.getType()) {
case Token.IF:
handleIf(n);
return;
case Token.WHILE:
handleWhile(n);
return;
case Token.DO:
handleDo(n);
return;
case Token.FOR:
handleFor(n);
return;
case Token.SWITCH:
handleSwitch(n);
return;
case Token.CASE:
handleCase(n);
return;
case Token.DEFAULT:
handleDefault(n);
return;
case Token.BLOCK:
case Token.SCRIPT:
handleStmtList(n);
return;
case Token.FUNCTION:
handleFunction(n);
return;
case Token.EXPR_RESULT:
handleExpr(n);
return;
case Token.THROW:
handleThrow(n);
return;
case Token.TRY:
handleTry(n);
return;
case Token.CATCH:
handleCatch(n);
return;
case Token.BREAK:
handleBreak(n);
return;
case Token.CONTINUE:
handleContinue(n);
return;
case Token.RETURN:
handleReturn(n);
return;
case Token.WITH:
handleWith(n);
return;
case Token.LABEL:
return;
default:
handleStmt(n);
return;
}
}
private void handleIf(Node node) {
Node thenBlock = node.getFirstChild().getNext();
Node elseBlock = thenBlock.getNext();
createEdge(node, Branch.ON_TRUE, computeFallThrough(thenBlock));
if (elseBlock == null) {
createEdge(node, Branch.ON_FALSE,
computeFollowNode(node, this)); // not taken branch
} else {
createEdge(node, Branch.ON_FALSE, computeFallThrough(elseBlock));
}
connectToPossibleExceptionHandler(
node, NodeUtil.getConditionExpression(node));
}
private void handleWhile(Node node) {
// Control goes to the first statement if the condition evaluates to true.
createEdge(node, Branch.ON_TRUE,
computeFallThrough(node.getFirstChild().getNext()));
// Control goes to the follow() if the condition evaluates to false.
createEdge(node, Branch.ON_FALSE,
computeFollowNode(node, this));
connectToPossibleExceptionHandler(
node, NodeUtil.getConditionExpression(node));
}
private void handleDo(Node node) {
// The first edge can be the initial iteration as well as the iterations
// after.
createEdge(node, Branch.ON_TRUE, computeFallThrough(node.getFirstChild()));
// The edge that leaves the do loop if the condition fails.
createEdge(node, Branch.ON_FALSE,
computeFollowNode(node, this));
connectToPossibleExceptionHandler(
node, NodeUtil.getConditionExpression(node));
}
private void handleFor(Node forNode) {
if (forNode.getChildCount() == 4) {
// We have for (init; cond; iter) { body }
Node init = forNode.getFirstChild();
Node cond = init.getNext();
Node iter = cond.getNext();
Node body = iter.getNext();
// After initialization, we transfer to the FOR which is in charge of
// checking the condition (for the first time).
createEdge(init, Branch.UNCOND, forNode);
// The edge that transfer control to the beginning of the loop body.
createEdge(forNode, Branch.ON_TRUE, computeFallThrough(body));
// The edge to end of the loop.
createEdge(forNode, Branch.ON_FALSE,
computeFollowNode(forNode, this));
// The end of the body will have a unconditional branch to our iter
// (handled by calling computeFollowNode of the last instruction of the
// body. Our iter will jump to the forNode again to another condition
// check.
createEdge(iter, Branch.UNCOND, forNode);
connectToPossibleExceptionHandler(init, init);
connectToPossibleExceptionHandler(forNode, cond);
connectToPossibleExceptionHandler(iter, iter);
} else {
// We have for (item in collection) { body }
Node item = forNode.getFirstChild();
Node collection = item.getNext();
Node body = collection.getNext();
// The edge that transfer control to the beginning of the loop body.
createEdge(forNode, Branch.ON_TRUE, computeFallThrough(body));
// The edge to end of the loop.
createEdge(forNode, Branch.ON_FALSE,
computeFollowNode(forNode, this));
connectToPossibleExceptionHandler(forNode, collection);
}
}
private void handleSwitch(Node node) {
// Transfer to the first non-DEFAULT CASE. if there are none, transfer
// to the DEFAULT or the EMPTY node.
Node next = getNextSiblingOfType(
node.getFirstChild().getNext(), Token.CASE, Token.EMPTY);
if (next != null) { // Has at least one CASE or EMPTY
createEdge(node, Branch.UNCOND, next);
} else { // Has no CASE but possibly a DEFAULT
if (node.getFirstChild().getNext() != null) {
createEdge(node, Branch.UNCOND, node.getFirstChild().getNext());
} else { // No CASE, no DEFAULT
createEdge(node, Branch.UNCOND, computeFollowNode(node, this));
}
}
connectToPossibleExceptionHandler(node, node.getFirstChild());
}
private void handleCase(Node node) {
// Case is a bit tricky....First it goes into the body if condition is true.
createEdge(node, Branch.ON_TRUE,
node.getFirstChild().getNext());
// Look for the next CASE, skipping over DEFAULT.
Node next = getNextSiblingOfType(node.getNext(), Token.CASE);
if (next != null) { // Found a CASE
Preconditions.checkState(next.getType() == Token.CASE);
createEdge(node, Branch.ON_FALSE, next);
} else { // No more CASE found, go back and search for a DEFAULT.
Node parent = node.getParent();
Node deflt = getNextSiblingOfType(
parent.getFirstChild().getNext(), Token.DEFAULT);
if (deflt != null) { // Has a DEFAULT
createEdge(node, Branch.ON_FALSE, deflt);
} else { // No DEFAULT found, go to the follow of the SWITCH.
createEdge(node, Branch.ON_FALSE, computeFollowNode(node, this));
}
}
connectToPossibleExceptionHandler(node, node.getFirstChild());
}
private void handleDefault(Node node) {
// Directly goes to the body. It should not transfer to the next case.
createEdge(node, Branch.UNCOND, node.getFirstChild());
}
private void handleWith(Node node) {
// Directly goes to the body. It should not transfer to the next case.
createEdge(node, Branch.UNCOND, node.getLastChild());
connectToPossibleExceptionHandler(node, node.getFirstChild());
}
private void handleStmtList(Node node) {
Node parent = node.getParent();
// Special case, don't add a block of empty CATCH block to the graph.
if (node.getType() == Token.BLOCK && parent != null &&
parent.getType() == Token.TRY &&
NodeUtil.getCatchBlock(parent) == node &&
!NodeUtil.hasCatchHandler(node)) {
return;
}
// A block transfer control to its first child if it is not empty.
Node child = node.getFirstChild();
// Function declarations are skipped since control doesn't go into that
// function (unless it is called)
while (child != null && child.getType() == Token.FUNCTION) {
child = child.getNext();
}
if (child != null) {
createEdge(node, Branch.UNCOND, computeFallThrough(child));
} else {
createEdge(node, Branch.UNCOND, computeFollowNode(node, this));
}
// Synthetic blocks
if (parent != null) {
switch (parent.getType()) {
case Token.DEFAULT:
case Token.CASE:
case Token.TRY:
break;
default:
if (node.getType() == Token.BLOCK && node.isSyntheticBlock()) {
createEdge(node, Branch.SYN_BLOCK, computeFollowNode(node, this));
}
break;
}
}
}
private void handleFunction(Node node) {
// A block transfer control to its first child if it is not empty.
Preconditions.checkState(node.getChildCount() >= 3);
createEdge(node, Branch.UNCOND,
computeFallThrough(node.getFirstChild().getNext().getNext()));
Preconditions.checkState(exceptionHandler.peek() == node);
exceptionHandler.pop();
}
private void handleExpr(Node node) {
createEdge(node, Branch.UNCOND, computeFollowNode(node, this));
connectToPossibleExceptionHandler(node, node);
}
private void handleThrow(Node node) {
connectToPossibleExceptionHandler(node, node);
}
private void handleTry(Node node) {
createEdge(node, Branch.UNCOND, node.getFirstChild());
}
private void handleCatch(Node node) {
createEdge(node, Branch.UNCOND, node.getLastChild());
}
private void handleBreak(Node node) {
String label = null;
// See if it is a break with label.
if (node.hasChildren()) {
label = node.getFirstChild().getString();
}
Node cur;
Node lastJump;
Node parent = node.getParent();
/*
* Continuously look up the ancestor tree for the BREAK target or the target
* with the corresponding label and connect to it. If along the path we
* discover a FINALLY, we will connect the BREAK to that FINALLY. From then
* on, we will just record the control flow changes in the finallyMap. This
* is due to the fact that we need to connect any node that leaves its own
* FINALLY block to the outer FINALLY or the BREAK's target but those nodes
* are not known yet due to the way we traverse the nodes.
*/
for (cur = node, lastJump = node;
!isBreakTarget(cur, label);
cur = parent, parent = parent.getParent()) {
if (cur.getType() == Token.TRY && NodeUtil.hasFinally(cur)) {
if (lastJump == node) {
createEdge(lastJump, Branch.UNCOND, computeFallThrough(
cur.getLastChild()));
} else {
finallyMap.put(lastJump, computeFallThrough(cur.getLastChild()));
}
lastJump = cur;
}
Preconditions.checkState(parent != null, "Cannot find break target.");
}
if (lastJump == node) {
createEdge(lastJump, Branch.UNCOND, computeFollowNode(cur, this));
} else {
finallyMap.put(lastJump, computeFollowNode(cur, this));
}
}
private void handleContinue(Node node) {
String label = null;
if (node.hasChildren()) {
label = node.getFirstChild().getString();
}
Node cur;
Node lastJump;
// Similar to handBreak's logic with a few minor variation.
Node parent = node.getParent();
for (cur = node, lastJump = node;
!isContinueTarget(cur, parent, label);
cur = parent, parent = parent.getParent()) {
if (cur.getType() == Token.TRY && NodeUtil.hasFinally(cur)) {
if (lastJump == node) {
createEdge(lastJump, Branch.UNCOND, cur.getLastChild());
} else {
finallyMap.put(lastJump, computeFallThrough(cur.getLastChild()));
}
lastJump = cur;
}
Preconditions.checkState(parent != null, "Cannot find continue target.");
}
Node iter = cur;
if (cur.getChildCount() == 4) {
iter = cur.getFirstChild().getNext().getNext();
}
if (lastJump == node) {
createEdge(node, Branch.UNCOND, iter);
} else {
finallyMap.put(lastJump, iter);
}
}
private void handleReturn(Node node) {
Node lastJump = null;
for (Iterator iter = exceptionHandler.iterator(); iter.hasNext();) {
Node curHandler = iter.next();
if (NodeUtil.isFunction(curHandler)) {
break;
}
if (NodeUtil.hasFinally(curHandler)) {
if (lastJump == null) {
createEdge(node, Branch.UNCOND, curHandler.getLastChild());
} else {
finallyMap.put(lastJump,
computeFallThrough(curHandler.getLastChild()));
}
lastJump = curHandler;
}
}
if (node.hasChildren()) {
connectToPossibleExceptionHandler(node, node.getFirstChild());
}
if (lastJump == null) {
createEdge(node, Branch.UNCOND, null);
} else {
finallyMap.put(lastJump, null);
}
}
private void handleStmt(Node node) {
// Simply transfer to the next line.
createEdge(node, Branch.UNCOND, computeFollowNode(node, this));
connectToPossibleExceptionHandler(node, node);
}
static Node computeFollowNode(Node node, ControlFlowAnalysis cfa) {
return computeFollowNode(node, node, cfa);
}
static Node computeFollowNode(Node node) {
return computeFollowNode(node, node, null);
}
/**
* Computes the follow() node of a given node and its parent. There is a side
* effect when calling this function. If this function computed an edge that
* exists a FINALLY, it'll attempt to connect the fromNode to the outer
* FINALLY according to the finallyMap.
*
* @param fromNode The original source node since {@code node} is changed
* during recursion.
* @param node The node that follow() should compute.
*/
private static Node computeFollowNode(
Node fromNode, Node node, ControlFlowAnalysis cfa) {
/*
* This is the case where:
*
* 1. Parent is null implies that we are transferring control to the end of
* the script.
*
* 2. Parent is a function implies that we are transferring control back to
* the caller of the function.
*
* 3. If the node is a return statement, we should also transfer control
* back to the caller of the function.
*
* 4. If the node is root then we have reached the end of what we have been
* asked to traverse.
*
* In all cases we should transfer control to a "symbolic return" node.
* This will make life easier for DFAs.
*/
Node parent = node.getParent();
if (parent == null || parent.getType() == Token.FUNCTION ||
(cfa != null && node == cfa.root)) {
return null;
}
// If we are just before a IF/WHILE/DO/FOR:
switch (parent.getType()) {
// The follow() of any of the path from IF would be what follows IF.
case Token.IF:
return computeFollowNode(fromNode, parent, cfa);
case Token.CASE:
case Token.DEFAULT:
// After the body of a CASE, the control goes to the body of the next
// case, without having to go to the case condition.
if (parent.getNext() != null) {
if (parent.getNext().getType() == Token.CASE) {
return parent.getNext().getFirstChild().getNext();
} else if (parent.getNext().getType() == Token.DEFAULT) {
return parent.getNext().getFirstChild();
} else {
Preconditions.checkState(false, "Not reachable");
}
} else {
return computeFollowNode(fromNode, parent, cfa);
}
break;
case Token.FOR:
if (NodeUtil.isForIn(parent)) {
return parent;
} else {
return parent.getFirstChild().getNext().getNext();
}
case Token.WHILE:
case Token.DO:
return parent;
case Token.TRY:
// If we are coming out of the TRY block...
if (parent.getFirstChild() == node) {
if (NodeUtil.hasFinally(parent)) { // and have FINALLY block.
return computeFallThrough(parent.getLastChild());
} else { // and have no FINALLY.
return computeFollowNode(fromNode, parent, cfa);
}
// CATCH block.
} else if (NodeUtil.getCatchBlock(parent) == node){
if (NodeUtil.hasFinally(parent)) { // and have FINALLY block.
return computeFallThrough(node.getNext());
} else {
return computeFollowNode(fromNode, parent, cfa);
}
// If we are coming out of the FINALLY block...
} else if (parent.getLastChild() == node){
if (cfa != null) {
for (Node finallyNode : cfa.finallyMap.get(parent)) {
cfa.createEdge(fromNode, Branch.UNCOND, finallyNode);
}
}
return computeFollowNode(fromNode, parent, cfa);
}
}
// Now that we are done with the special cases follow should be its
// immediate sibling, unless its sibling is a function
Node nextSibling = node.getNext();
// Skip function declarations because control doesn't get pass into it.
while (nextSibling != null && nextSibling.getType() == Token.FUNCTION) {
nextSibling = nextSibling.getNext();
}
if (nextSibling != null) {
return computeFallThrough(nextSibling);
} else {
// If there are no more siblings, control is transfered up the AST.
return computeFollowNode(fromNode, parent, cfa);
}
}
/**
* Computes the destination node of n when we want to fallthough into the
* subtree of n. We don't always create a CFG edge into n itself because of
* DOs and FORs.
*/
static Node computeFallThrough(Node n) {
switch (n.getType()) {
case Token.DO:
return computeFallThrough(n.getFirstChild());
case Token.FOR:
if (NodeUtil.isForIn(n)) {
return n;
}
return computeFallThrough(n.getFirstChild());
case Token.LABEL:
return computeFallThrough(n.getLastChild());
default:
return n;
}
}
/**
* Connects the two nodes in the control flow graph.
*
* @param fromNode Source.
* @param toNode Destination.
*/
private void createEdge(Node fromNode, ControlFlowGraph.Branch branch,
Node toNode) {
cfg.createNode(fromNode);
cfg.createNode(toNode);
cfg.connectIfNotFound(fromNode, branch, toNode);
}
/**
* Connects cfgNode to the proper CATCH block if target subtree might throw
* an exception. If there are FINALLY blocks reached before a CATCH, it will
* make the corresponding entry in finallyMap.
*/
private void connectToPossibleExceptionHandler(Node cfgNode, Node target) {
if (mayThrowException(target) && !exceptionHandler.isEmpty()) {
Node lastJump = cfgNode;
for (Node handler : exceptionHandler) {
if (NodeUtil.isFunction(handler)) {
return;
}
Preconditions.checkState(handler.getType() == Token.TRY);
Node catchBlock = NodeUtil.getCatchBlock(handler);
if (!NodeUtil.hasCatchHandler(catchBlock)) { // No catch but a FINALLY.
if (lastJump == cfgNode) {
createEdge(cfgNode, Branch.ON_EX, handler.getLastChild());
} else {
finallyMap.put(lastJump, handler.getLastChild());
}
} else { // Has a catch.
if (lastJump == cfgNode) {
createEdge(cfgNode, Branch.ON_EX, catchBlock);
return;
} else {
finallyMap.put(lastJump, catchBlock);
}
}
lastJump = handler;
}
}
}
/**
* Get the next sibling (including itself) of one of the given types.
*/
private static Node getNextSiblingOfType(Node first, int ... types) {
for (Node c = first; c != null; c = c.getNext()) {
for (int type : types) {
if (c.getType() == type) {
return c;
}
}
}
return null;
}
/**
* Checks if target is actually the break target of labeled continue. The
* label can be null if it is an unlabeled break.
*/
public static boolean isBreakTarget(Node target, String label) {
return isBreakStructure(target, label != null) &&
matchLabel(target.getParent(), label);
}
/**
* Checks if target is actually the continue target of labeled continue. The
* label can be null if it is an unlabeled continue.
*/
private static boolean isContinueTarget(
Node target, Node parent, String label) {
return isContinueStructure(target) && matchLabel(parent, label);
}
/**
* Check if label is actually referencing the target control structure. If
* label is null, it always returns true.
*/
private static boolean matchLabel(Node target, String label) {
if (label == null) {
return true;
}
while (target.getType() == Token.LABEL) {
if (target.getFirstChild().getString().equals(label)) {
return true;
}
target = target.getParent();
}
return false;
}
/**
* Determines if the subtree might throw an exception.
*/
public static boolean mayThrowException(Node n) {
switch (n.getType()) {
case Token.CALL:
case Token.GETPROP:
case Token.GETELEM:
case Token.THROW:
case Token.NEW:
case Token.ASSIGN:
case Token.INC:
case Token.DEC:
case Token.INSTANCEOF:
return true;
case Token.FUNCTION:
return false;
}
for (Node c = n.getFirstChild(); c != null; c = c.getNext()) {
if (!ControlFlowGraph.isEnteringNewCfgNode(c) && mayThrowException(c)) {
return true;
}
}
return false;
}
/**
* Determines whether the given node can be terminated with a BREAK node.
*/
static boolean isBreakStructure(Node n, boolean labeled) {
switch (n.getType()) {
case Token.FOR:
case Token.DO:
case Token.WHILE:
case Token.SWITCH:
return true;
case Token.BLOCK:
case Token.IF:
case Token.TRY:
return labeled;
default:
return false;
}
}
/**
* Determines whether the given node can be advanced with a CONTINUE node.
*/
static boolean isContinueStructure(Node n) {
switch (n.getType()) {
case Token.FOR:
case Token.DO:
case Token.WHILE:
return true;
default:
return false;
}
}
/**
* Get the TRY block with a CATCH that would be run if n throws an exception.
* @return The CATCH node or null if it there isn't a CATCH before the
* the function terminates.
*/
static Node getExceptionHandler(Node n) {
for (Node cur = n;
cur.getType() != Token.SCRIPT && cur.getType() != Token.FUNCTION;
cur = cur.getParent()) {
Node catchNode = getCatchHandlerForBlock(cur);
if (catchNode != null) {
return catchNode;
}
}
return null;
}
/**
* Locate the catch BLOCK given the first block in a TRY.
* @return The CATCH node or null there is no catch handler.
*/
static Node getCatchHandlerForBlock(Node block) {
if (block.getType() == Token.BLOCK &&
block.getParent().getType() == Token.TRY &&
block.getParent().getFirstChild() == block) {
for (Node s = block.getNext(); s != null; s = s.getNext()) {
if (NodeUtil.hasCatchHandler(s)) {
return s.getFirstChild();
}
}
}
return null;
}
/**
* A {@link ControlFlowGraph} which provides a node comparator based on the
* pre-order traversal of the AST.
*/
private static class AstControlFlowGraph extends ControlFlowGraph {
private final Map, Integer> priorities;
/**
* Constructor.
* @param entry The entry node.
* @param priorities The map from nodes to position in the AST (to be
* filled by the {@link ControlFlowAnalysis#shouldTraverse}).
*/
private AstControlFlowGraph(Node entry,
Map, Integer> priorities,
boolean edgeAnnotations) {
super(entry,
true /* node annotations */, edgeAnnotations);
this.priorities = priorities;
}
@Override
/**
* Returns a node comparator based on the pre-order traversal of the AST.
* @param isForward x 'before' y in the pre-order traversal implies
* x 'less than' y (if true) and x 'greater than' y (if false).
*/
public Comparator> getOptionalNodeComparator(
boolean isForward) {
if (isForward) {
return new Comparator>() {
@Override
public int compare(
DiGraphNode n1, DiGraphNode n2) {
return getPosition(n1) - getPosition(n2);
}
};
} else {
return new Comparator>() {
@Override
public int compare(
DiGraphNode n1, DiGraphNode n2) {
return getPosition(n2) - getPosition(n1);
}
};
}
}
/**
* Gets the pre-order traversal position of the given node.
* @return An arbitrary counter used for comparing positions.
*/
private int getPosition(DiGraphNode n) {
Integer priority = priorities.get(n);
Preconditions.checkNotNull(priority);
return priority;
}
}
}