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/*
* Copyright 2004 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 static com.google.common.base.Strings.nullToEmpty;
import com.google.common.base.Preconditions;
import com.google.javascript.rhino.InputId;
import com.google.javascript.rhino.Node;
import com.google.javascript.rhino.Token;
import java.util.ArrayDeque;
import java.util.Deque;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.Set;
/**
* NodeTraversal allows an iteration through the nodes in the parse tree,
* and facilitates the optimizations on the parse tree.
*
*/
public class NodeTraversal {
private final AbstractCompiler compiler;
private final Callback callback;
/** Contains the current node*/
private Node curNode;
public static final DiagnosticType NODE_TRAVERSAL_ERROR =
DiagnosticType.error("JSC_NODE_TRAVERSAL_ERROR", "{0}");
/**
* Stack containing the Scopes that have been created. The Scope objects
* are lazily created; so the {@code scopeRoots} stack contains the
* Nodes for all Scopes that have not been created yet.
*/
private final Deque scopes = new ArrayDeque<>();
/**
* A stack of scope roots. All scopes that have not been created
* are represented in this Deque.
*/
private final Deque scopeRoots = new ArrayDeque<>();
/**
* A stack of scope roots that are valid cfg roots. All cfg roots that have not been created
* are represented in this Deque.
*/
private final Deque cfgRoots = new ArrayDeque<>();
/**
* Stack of control flow graphs (CFG). There is one CFG per scope. CFGs
* are lazily populated: elements are {@code null} until requested by
* {@link #getControlFlowGraph()}. Note that {@link ArrayDeque} does not allow
* {@code null} elements, so {@link LinkedList} is used instead.
*/
Deque> cfgs = new LinkedList<>();
/** The current source file name */
private String sourceName;
/** The current input */
private InputId inputId;
/** The scope creator */
private final ScopeCreator scopeCreator;
private final boolean useBlockScope;
/** Possible callback for scope entry and exist **/
private ScopedCallback scopeCallback;
/** Callback for passes that iterate over a list of functions */
public interface FunctionCallback {
void enterFunction(AbstractCompiler compiler, Node fnRoot);
}
/**
* Callback for tree-based traversals
*/
public interface Callback {
/**
* Visits a node in pre order (before visiting its children) and decides
* whether this node's children should be traversed. If children are
* traversed, they will be visited by
* {@link #visit(NodeTraversal, Node, Node)} in postorder.
* Implementations can have side effects (e.g. modifying the parse
* tree).
* @return whether the children of this node should be visited
*/
boolean shouldTraverse(NodeTraversal nodeTraversal, Node n, Node parent);
/**
* Visits a node in postorder (after its children have been visited).
* A node is visited only if all its parents should be traversed
* ({@link #shouldTraverse(NodeTraversal, Node, Node)}).
* Implementations can have side effects (e.g. modifying the parse
* tree).
*/
void visit(NodeTraversal t, Node n, Node parent);
}
/**
* Callback that also knows about scope changes
*/
public interface ScopedCallback extends Callback {
/**
* Called immediately after entering a new scope. The new scope can
* be accessed through t.getScope()
*/
void enterScope(NodeTraversal t);
/**
* Called immediately before exiting a scope. The ending scope can
* be accessed through t.getScope()
*/
void exitScope(NodeTraversal t);
}
/**
* Abstract callback to visit all nodes in postorder.
*/
public abstract static class AbstractPostOrderCallback implements Callback {
@Override
public final boolean shouldTraverse(NodeTraversal nodeTraversal, Node n,
Node parent) {
return true;
}
}
/** Abstract callback to visit all nodes in preorder. */
public abstract static class AbstractPreOrderCallback implements Callback {
@Override
public void visit(NodeTraversal t, Node n, Node parent) {}
}
/**
* Abstract scoped callback to visit all nodes in postorder.
*/
public abstract static class AbstractScopedCallback
implements ScopedCallback {
@Override
public final boolean shouldTraverse(NodeTraversal nodeTraversal, Node n,
Node parent) {
return true;
}
@Override
public void enterScope(NodeTraversal t) {}
@Override
public void exitScope(NodeTraversal t) {}
}
/**
* Abstract callback to visit all nodes but not traverse into function
* bodies.
*/
public abstract static class AbstractShallowCallback implements Callback {
@Override
public final boolean shouldTraverse(NodeTraversal nodeTraversal, Node n,
Node parent) {
// We do want to traverse the name of a named function, but we don't
// want to traverse the arguments or body.
return parent == null || !parent.isFunction() ||
n == parent.getFirstChild();
}
}
/**
* Abstract callback to visit all structure and statement nodes but doesn't
* traverse into functions or expressions.
*/
public abstract static class AbstractShallowStatementCallback
implements Callback {
@Override
public final boolean shouldTraverse(NodeTraversal nodeTraversal, Node n,
Node parent) {
return parent == null || NodeUtil.isControlStructure(parent)
|| NodeUtil.isStatementBlock(parent);
}
}
/**
* Abstract callback to visit a pruned set of nodes.
*/
public abstract static class AbstractNodeTypePruningCallback
implements Callback {
private final Set nodeTypes;
private final boolean include;
/**
* Creates an abstract pruned callback.
* @param nodeTypes the nodes to include in the traversal
*/
public AbstractNodeTypePruningCallback(Set nodeTypes) {
this(nodeTypes, true);
}
/**
* Creates an abstract pruned callback.
* @param nodeTypes the nodes to include/exclude in the traversal
* @param include whether to include or exclude the nodes in the traversal
*/
public AbstractNodeTypePruningCallback(Set nodeTypes,
boolean include) {
this.nodeTypes = nodeTypes;
this.include = include;
}
@Override
public boolean shouldTraverse(NodeTraversal nodeTraversal, Node n,
Node parent) {
return include == nodeTypes.contains(n.getType());
}
}
/**
* Creates a node traversal using the specified callback interface.
*/
public NodeTraversal(AbstractCompiler compiler, Callback cb) {
this(compiler, cb, compiler.getLanguageMode().isEs6OrHigher()
? new Es6SyntacticScopeCreator(compiler)
: SyntacticScopeCreator.makeUntyped(compiler));
}
/**
* Creates a node traversal using the specified callback interface
* and the scope creator.
*/
public NodeTraversal(AbstractCompiler compiler, Callback cb,
ScopeCreator scopeCreator) {
this.callback = cb;
if (cb instanceof ScopedCallback) {
this.scopeCallback = (ScopedCallback) cb;
}
this.compiler = compiler;
this.inputId = null;
this.sourceName = "";
this.scopeCreator = scopeCreator;
this.useBlockScope = scopeCreator.hasBlockScope();
}
private void throwUnexpectedException(Exception unexpectedException) {
// If there's an unexpected exception, try to get the
// line number of the code that caused it.
String message = unexpectedException.getMessage();
// TODO(user): It is possible to get more information if curNode or
// its parent is missing. We still have the scope stack in which it is still
// very useful to find out at least which function caused the exception.
if (inputId != null) {
message =
unexpectedException.getMessage() + "\n" +
formatNodeContext("Node", curNode) +
(curNode == null ?
"" :
formatNodeContext("Parent", curNode.getParent()));
}
compiler.throwInternalError(message, unexpectedException);
}
private String formatNodeContext(String label, Node n) {
if (n == null) {
return " " + label + ": NULL";
}
return " " + label + "(" + n.toString(false, false, false) + "): "
+ formatNodePosition(n);
}
/**
* Traverses a parse tree recursively.
*/
public void traverse(Node root) {
try {
inputId = NodeUtil.getInputId(root);
sourceName = "";
curNode = root;
pushScope(root);
// null parent ensures that the shallow callbacks will traverse root
traverseBranch(root, null);
popScope();
} catch (Exception unexpectedException) {
throwUnexpectedException(unexpectedException);
}
}
void traverseRoots(Node externs, Node root) {
try {
Node scopeRoot = externs.getParent();
Preconditions.checkNotNull(scopeRoot);
inputId = NodeUtil.getInputId(scopeRoot);
sourceName = "";
curNode = scopeRoot;
pushScope(scopeRoot);
traverseBranch(externs, scopeRoot);
Preconditions.checkState(root.getParent() == scopeRoot);
traverseBranch(root, scopeRoot);
popScope();
} catch (Exception unexpectedException) {
throwUnexpectedException(unexpectedException);
}
}
private static final String MISSING_SOURCE = "[source unknown]";
private String formatNodePosition(Node n) {
String sourceFileName = getBestSourceFileName(n);
if (sourceFileName == null) {
return MISSING_SOURCE + "\n";
}
int lineNumber = n.getLineno();
int columnNumber = n.getCharno();
String src = compiler.getSourceLine(sourceFileName, lineNumber);
if (src == null) {
src = MISSING_SOURCE;
}
return sourceFileName + ":" + lineNumber + ":" + columnNumber + "\n"
+ src + "\n";
}
/**
* Traverses a parse tree recursively with a scope, starting with the given
* root. This should only be used in the global scope. Otherwise, use
* {@link #traverseAtScope}.
*/
void traverseWithScope(Node root, Scope s) {
Preconditions.checkState(s.isGlobal());
try {
inputId = null;
sourceName = "";
curNode = root;
pushScope(s);
traverseBranch(root, null);
popScope();
} catch (Exception unexpectedException) {
throwUnexpectedException(unexpectedException);
}
}
/**
* Traverses a parse tree recursively with a scope, starting at that scope's
* root.
*/
void traverseAtScope(Scope s) {
Node n = s.getRootNode();
if (n.isFunction()) {
// We need to do some extra magic to make sure that the scope doesn't
// get re-created when we dive into the function.
if (inputId == null) {
inputId = NodeUtil.getInputId(n);
}
sourceName = getSourceName(n);
curNode = n;
pushScope(s);
Node args = n.getSecondChild();
Node body = args.getNext();
traverseBranch(args, n);
traverseBranch(body, n);
popScope();
} else if (n.isBlock()) {
if (inputId == null) {
inputId = NodeUtil.getInputId(n);
}
sourceName = getSourceName(n);
curNode = n;
pushScope(s);
// traverseBranch is not called here to avoid re-creating the block scope.
for (Node child = n.getFirstChild(); child != null; ) {
Node next = child.getNext();
traverseBranch(child, n);
child = next;
}
popScope();
} else {
Preconditions.checkState(s.isGlobal(), "Expected global scope. Got:", s);
traverseWithScope(n, s);
}
}
/**
* Traverse a function out-of-band of normal traversal.
*
* @param node The function node.
* @param scope The scope the function is contained in. Does not fire enter/exit
* callback events for this scope.
*/
public void traverseFunctionOutOfBand(Node node, Scope scope) {
Preconditions.checkNotNull(scope);
Preconditions.checkState(node.isFunction());
Preconditions.checkState(scope.getRootNode() != null);
if (inputId == null) {
inputId = NodeUtil.getInputId(node);
}
curNode = node.getParent();
pushScope(scope, true /* quietly */);
traverseBranch(node, curNode);
popScope(true /* quietly */);
}
/**
* Traverses an inner node recursively with a refined scope. An inner node may
* be any node with a non {@code null} parent (i.e. all nodes except the
* root).
*
* @param node the node to traverse
* @param parent the node's parent, it may not be {@code null}
* @param refinedScope the refined scope of the scope currently at the top of
* the scope stack or in trivial cases that very scope or {@code null}
*/
void traverseInnerNode(Node node, Node parent, Scope refinedScope) {
Preconditions.checkNotNull(parent);
if (inputId == null) {
inputId = NodeUtil.getInputId(node);
}
if (refinedScope != null && getScope() != refinedScope) {
curNode = node;
pushScope(refinedScope);
traverseBranch(node, parent);
popScope();
} else {
traverseBranch(node, parent);
}
}
public AbstractCompiler getCompiler() {
return compiler;
}
/**
* Gets the current line number, or zero if it cannot be determined. The line
* number is retrieved lazily as a running time optimization.
*/
public int getLineNumber() {
Node cur = curNode;
while (cur != null) {
int line = cur.getLineno();
if (line >= 0) {
return line;
}
cur = cur.getParent();
}
return 0;
}
/**
* Gets the current char number, or zero if it cannot be determined. The line
* number is retrieved lazily as a running time optimization.
*/
public int getCharno() {
Node cur = curNode;
while (cur != null) {
int line = cur.getCharno();
if (line >= 0) {
return line;
}
cur = cur.getParent();
}
return 0;
}
/**
* Gets the current input source name.
*
* @return A string that may be empty, but not null
*/
public String getSourceName() {
return sourceName;
}
/**
* Gets the current input source.
*/
public CompilerInput getInput() {
return compiler.getInput(inputId);
}
/**
* Gets the current input module.
*/
public JSModule getModule() {
CompilerInput input = getInput();
return input == null ? null : input.getModule();
}
/** Returns the node currently being traversed. */
public Node getCurrentNode() {
return curNode;
}
/**
* Traversal for passes that work only on changed functions.
* Suppose a loopable pass P1 uses this traversal.
* Then, if a function doesn't change between two runs of P1, it won't look at
* the function the second time.
* (We're assuming that P1 runs to a fixpoint, o/w we may miss optimizations.)
*
* Most changes are reported with calls to Compiler.reportCodeChange(), which
* doesn't know which scope changed. We keep track of the current scope by
* calling Compiler.setScope inside pushScope and popScope.
* The automatic tracking can be wrong in rare cases when a pass changes scope
* w/out causing a call to pushScope or popScope. It's very hard to find the
* places where this happens unless a bug is triggered.
* Passes that do cross-scope modifications call
* Compiler.reportChangeToEnclosingScope(Node n).
*/
public static void traverseChangedFunctions(
AbstractCompiler compiler, FunctionCallback callback) {
final AbstractCompiler comp = compiler;
final FunctionCallback cb = callback;
final Node jsRoot = comp.getJsRoot();
NodeTraversal.traverseEs6(comp, jsRoot,
new AbstractPreOrderCallback() {
@Override
public final boolean shouldTraverse(NodeTraversal t, Node n, Node p) {
if ((n == jsRoot || n.isFunction()) && comp.hasScopeChanged(n)) {
cb.enterFunction(comp, n);
}
return true;
}
});
}
/**
* Traverses a node recursively.
* @deprecated Use traverseEs6 whenever possible.
*/
@Deprecated
public static void traverse(AbstractCompiler compiler, Node root, Callback cb) {
NodeTraversal t = new NodeTraversal(compiler, cb);
t.traverse(root);
}
/**
* Traverses using the ES6SyntacticScopeCreator
*/
// TODO (stephshi): rename to "traverse" when the old traverse method is no longer used
public static void traverseEs6(AbstractCompiler compiler, Node root, Callback cb) {
NodeTraversal t = new NodeTraversal(compiler, cb, new Es6SyntacticScopeCreator(compiler));
t.traverse(root);
}
public static void traverseTyped(AbstractCompiler compiler, Node root, Callback cb) {
NodeTraversal t = new NodeTraversal(compiler, cb, SyntacticScopeCreator.makeTyped(compiler));
t.traverse(root);
}
@Deprecated
public static void traverseRoots(
AbstractCompiler compiler, Callback cb, Node externs, Node root) {
NodeTraversal t = new NodeTraversal(compiler, cb);
t.traverseRoots(externs, root);
}
public static void traverseRootsEs6(
AbstractCompiler compiler, Callback cb, Node externs, Node root) {
NodeTraversal t = new NodeTraversal(compiler, cb, new Es6SyntacticScopeCreator(compiler));
t.traverseRoots(externs, root);
}
public static void traverseRootsTyped(
AbstractCompiler compiler, Callback cb, Node externs, Node root) {
NodeTraversal t = new NodeTraversal(compiler, cb, SyntacticScopeCreator.makeTyped(compiler));
t.traverseRoots(externs, root);
}
/**
* Traverses a branch.
*/
private void traverseBranch(Node n, Node parent) {
int type = n.getType();
if (type == Token.SCRIPT) {
inputId = n.getInputId();
sourceName = getSourceName(n);
}
curNode = n;
if (!callback.shouldTraverse(this, n, parent)) {
return;
}
if (type == Token.FUNCTION) {
traverseFunction(n, parent);
} else if (type == Token.CLASS) {
traverseClass(n, parent);
} else if (useBlockScope && NodeUtil.createsBlockScope(n)) {
traverseBlockScope(n);
} else {
for (Node child = n.getFirstChild(); child != null; ) {
// child could be replaced, in which case our child node
// would no longer point to the true next
Node next = child.getNext();
traverseBranch(child, n);
child = next;
}
}
curNode = n;
callback.visit(this, n, parent);
}
/** Traverses a function. */
private void traverseFunction(Node n, Node parent) {
final Node fnName = n.getFirstChild();
boolean isFunctionExpression = (parent != null)
&& NodeUtil.isFunctionExpression(n);
if (!isFunctionExpression) {
// Function declarations are in the scope containing the declaration.
traverseBranch(fnName, n);
}
curNode = n;
pushScope(n);
if (isFunctionExpression) {
// Function expression names are only accessible within the function
// scope.
traverseBranch(fnName, n);
}
final Node args = fnName.getNext();
final Node body = args.getNext();
// Args
traverseBranch(args, n);
// Body
// ES6 "arrow" function may not have a block as a body.
traverseBranch(body, n);
popScope();
}
/** Traverses a class. */
private void traverseClass(Node n, Node parent) {
final Node className = n.getFirstChild();
boolean isClassExpression = NodeUtil.isClassExpression(n);
if (!isClassExpression) {
// Class declarations are in the scope containing the declaration.
traverseBranch(className, n);
}
curNode = n;
pushScope(n);
if (isClassExpression) {
// Class expression names are only accessible within the function
// scope.
traverseBranch(className, n);
}
final Node extendsClause = className.getNext();
final Node body = extendsClause.getNext();
// Extends
traverseBranch(extendsClause, n);
// Body
traverseBranch(body, n);
popScope();
}
/** Traverses a non-function block. */
private void traverseBlockScope(Node n) {
pushScope(n);
for (Node child : n.children()) {
traverseBranch(child, n);
}
popScope();
}
/** Examines the functions stack for the last instance of a function node. When possible, prefer
* this method over NodeUtil.getEnclosingFunction() because this in general looks at less nodes.
*/
public Node getEnclosingFunction() {
Node root = getCfgRoot();
return root.isFunction() ? root : null;
}
/** Creates a new scope (e.g. when entering a function). */
private void pushScope(Node node) {
Preconditions.checkState(curNode != null);
Preconditions.checkState(node != null);
compiler.setScope(node);
scopeRoots.push(node);
if (NodeUtil.isValidCfgRoot(node)) {
cfgRoots.push(node);
cfgs.push(null);
}
if (scopeCallback != null) {
scopeCallback.enterScope(this);
}
}
/** Creates a new scope (e.g. when entering a function). */
private void pushScope(Scope s) {
pushScope(s, false);
}
/**
* Creates a new scope (e.g. when entering a function).
* @param quietly Don't fire an enterScope callback.
*/
private void pushScope(Scope s, boolean quietly) {
Preconditions.checkState(curNode != null);
compiler.setScope(s.getRootNode());
scopes.push(s);
if (NodeUtil.isValidCfgRoot(s.getRootNode())) {
cfgRoots.push(s.getRootNode());
cfgs.push(null);
}
if (!quietly && scopeCallback != null) {
scopeCallback.enterScope(this);
}
}
private void popScope() {
popScope(false);
}
/**
* Pops back to the previous scope (e.g. when leaving a function).
* @param quietly Don't fire the exitScope callback.
*/
private void popScope(boolean quietly) {
if (!quietly && scopeCallback != null) {
scopeCallback.exitScope(this);
}
Node scopeRoot;
if (scopeRoots.isEmpty()) {
scopeRoot = scopes.pop().getRootNode();
} else {
scopeRoot = scopeRoots.pop();
}
if (NodeUtil.isValidCfgRoot(scopeRoot)) {
Preconditions.checkState(!cfgRoots.isEmpty());
Preconditions.checkState(cfgRoots.pop() == scopeRoot);
cfgs.pop();
}
if (hasScope()) {
compiler.setScope(getScopeRoot());
}
}
/** Gets the current scope. */
public Scope getScope() {
Scope scope = scopes.isEmpty() ? null : scopes.peek();
if (scopeRoots.isEmpty()) {
return scope;
}
Iterator it = scopeRoots.descendingIterator();
while (it.hasNext()) {
scope = scopeCreator.createScope(it.next(), scope);
scopes.push(scope);
}
scopeRoots.clear();
// No need to call compiler.setScope; the top scopeRoot is now the top scope
return scope;
}
public Scope getClosestHoistScope() {
// TODO(moz): This should not call getScope(). We should find the root of the closest hoist
// scope and effectively getScope() from there, which avoids scanning inner scopes that might
// not be needed.
return getScope().getClosestHoistScope();
}
public TypedScope getTypedScope() {
Scope s = getScope();
Preconditions.checkState(s instanceof TypedScope,
"getTypedScope called for untyped traversal");
return (TypedScope) s;
}
/** Gets the control flow graph for the current JS scope. */
public ControlFlowGraph getControlFlowGraph() {
if (cfgs.peek() == null) {
ControlFlowAnalysis cfa = new ControlFlowAnalysis(compiler, false, true);
cfa.process(null, getCfgRoot());
cfgs.pop();
cfgs.push(cfa.getCfg());
}
return cfgs.peek();
}
/** Returns the current scope's root. */
public Node getScopeRoot() {
if (scopeRoots.isEmpty()) {
return scopes.peek().getRootNode();
} else {
return scopeRoots.peek();
}
}
private Node getCfgRoot() {
return cfgRoots.peek();
}
/**
* Determines whether the traversal is currently in the global scope. Note that this returns false
* in a global block scope.
*/
public boolean inGlobalScope() {
return getScopeDepth() == 0;
}
/**
* Determines whether the hoist scope of the current traversal is global.
*/
public boolean inGlobalHoistScope() {
return !getCfgRoot().isFunction();
}
int getScopeDepth() {
int sum = scopes.size() + scopeRoots.size();
Preconditions.checkState(sum > 0);
return sum - 1; // Use 0-based scope depth to be consistent within the compiler
}
public boolean hasScope() {
return !(scopes.isEmpty() && scopeRoots.isEmpty());
}
/** Reports a diagnostic (error or warning) */
public void report(Node n, DiagnosticType diagnosticType,
String... arguments) {
JSError error = JSError.make(n, diagnosticType, arguments);
compiler.report(error);
}
private static String getSourceName(Node n) {
String name = n.getSourceFileName();
return nullToEmpty(name);
}
InputId getInputId() {
return inputId;
}
/**
* Creates a JSError during NodeTraversal.
*
* @param n Determines the line and char position within the source file name
* @param type The DiagnosticType
* @param arguments Arguments to be incorporated into the message
*/
public JSError makeError(Node n, CheckLevel level, DiagnosticType type,
String... arguments) {
return JSError.make(n, level, type, arguments);
}
/**
* Creates a JSError during NodeTraversal.
*
* @param n Determines the line and char position within the source file name
* @param type The DiagnosticType
* @param arguments Arguments to be incorporated into the message
*/
public JSError makeError(Node n, DiagnosticType type, String... arguments) {
return JSError.make(n, type, arguments);
}
private String getBestSourceFileName(Node n) {
return n == null ? sourceName : n.getSourceFileName();
}
}