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// Copyright 2017 The Bazel Authors. All rights reserved.
//
// 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.devtools.skylark.skylint;
import com.google.common.base.Preconditions;
import com.google.devtools.build.lib.syntax.ASTNode;
import com.google.devtools.build.lib.syntax.AbstractComprehension;
import com.google.devtools.build.lib.syntax.AugmentedAssignmentStatement;
import com.google.devtools.build.lib.syntax.BuildFileAST;
import com.google.devtools.build.lib.syntax.DotExpression;
import com.google.devtools.build.lib.syntax.Expression;
import com.google.devtools.build.lib.syntax.FunctionDefStatement;
import com.google.devtools.build.lib.syntax.Identifier;
import com.google.devtools.build.lib.syntax.LValue;
import com.google.devtools.build.lib.syntax.ListComprehension;
import com.google.devtools.build.lib.syntax.ListLiteral;
import com.google.devtools.build.lib.syntax.LoadStatement;
import com.google.devtools.build.lib.syntax.Parameter;
import com.google.devtools.build.lib.syntax.Statement;
import com.google.devtools.build.lib.syntax.SyntaxTreeVisitor;
import java.util.Collection;
import java.util.Map;
/**
* AST visitor that keeps track of which symbols are in scope.
*
* <p>The methods {@code enterBlock}, {@code exitBlock}, {@code declare} and {@code reassign} can be
* overridden by a subclass to handle these "events" during AST traversal.
*/
public class AstVisitorWithNameResolution extends SyntaxTreeVisitor {
protected Environment env;
public AstVisitorWithNameResolution() {
this(Environment.defaultBazel());
}
public AstVisitorWithNameResolution(Environment env) {
this.env = env;
}
@Override
public void visit(BuildFileAST node) {
enterBlock();
// First process all global symbols ...
for (Statement stmt : node.getStatements()) {
if (stmt instanceof FunctionDefStatement) {
Identifier fun = ((FunctionDefStatement) stmt).getIdentifier();
env.addFunction(fun.getName(), fun);
declare(fun.getName(), fun);
} else {
visit(stmt);
}
}
// ... then check the functions
for (Statement stmt : node.getStatements()) {
if (stmt instanceof FunctionDefStatement) {
visit(stmt);
}
}
visitAll(node.getComments());
Preconditions.checkState(env.inGlobalBlock(), "didn't exit some blocks");
exitBlock();
}
@Override
public void visit(LoadStatement node) {
Map<Identifier, String> symbolMap = node.getSymbolMap();
for (Map.Entry<Identifier, String> entry : symbolMap.entrySet()) {
String name = entry.getKey().getName();
env.addImported(name, entry.getKey());
declare(name, entry.getKey());
}
}
@Override
public void visit(Identifier identifier) {
use(identifier);
}
@Override
public void visit(LValue node) {
initializeOrReassignLValue(node);
visitLvalue(node.getExpression());
}
protected void visitLvalue(Expression expr) {
if (expr instanceof Identifier) {
super.visit((Identifier) expr); // don't call this.visit because it doesn't count as usage
} else if (expr instanceof ListLiteral) {
for (Expression e : ((ListLiteral) expr).getElements()) {
visitLvalue(e);
}
} else {
visit(expr);
}
}
@Override
public void visit(AugmentedAssignmentStatement node) {
for (Identifier ident : node.getLValue().boundIdentifiers()) {
use(ident);
}
super.visit(node);
}
@Override
public void visit(FunctionDefStatement node) {
// First visit the default values for parameters in the global environment ...
for (Parameter<Expression, Expression> param : node.getParameters()) {
Expression expr = param.getDefaultValue();
if (expr != null) {
visit(expr);
}
}
// ... then visit everything else in the local environment
enterBlock();
for (Parameter<Expression, Expression> param : node.getParameters()) {
String name = param.getName();
if (name != null) {
env.addParameter(name, param);
declare(name, param);
}
}
// The function identifier was already added to the globals before, so we skip it
visitAll(node.getParameters());
visitBlock(node.getStatements());
exitBlock();
}
@Override
public void visit(DotExpression node) {
// Don't visit the identifier field because it's not a variable and would confuse the identifier
// visitor
visit(node.getObject());
}
@Override
public void visit(AbstractComprehension node) {
enterBlock();
for (ListComprehension.Clause clause : node.getClauses()) {
visit(clause.getExpression());
LValue lvalue = clause.getLValue();
if (lvalue != null) {
Collection<Identifier> boundIdents = lvalue.boundIdentifiers();
for (Identifier ident : boundIdents) {
env.addIdentifier(ident.getName(), ident);
declare(ident.getName(), ident);
}
visit(lvalue);
}
}
visitAll(node.getOutputExpressions());
exitBlock();
}
private void initializeOrReassignLValue(LValue lvalue) {
Iterable<Identifier> identifiers = lvalue.boundIdentifiers();
for (Identifier identifier : identifiers) {
if (env.isDefinedInCurrentScope(identifier.getName())) {
reassign(identifier);
} else {
env.addIdentifier(identifier.getName(), identifier);
declare(identifier.getName(), identifier);
}
}
}
/**
* Invoked when a symbol is defined during AST traversal.
*
* <p>This method is there to be overridden in subclasses, it doesn't do anything by itself.
*
* @param name name of the variable declared
* @param node {@code ASTNode} where it was declared
*/
void declare(String name, ASTNode node) {}
/**
* Invoked when a variable is reassigned during AST traversal.
*
* <p>This method is there to be overridden in subclasses, it doesn't do anything by itself.
*
* @param ident {@code Identifier} that was reassigned
*/
void reassign(Identifier ident) {}
/**
* Invoked when a variable is used during AST traversal.
*
* <p>This method is there to be overridden in subclasses, it doesn't do anything by itself.
*
* @param ident {@code Identifier} that was reassigned
*/
void use(Identifier ident) {}
/**
* Invoked when a lexical block is entered during AST traversal.
*
* <p>This method is there to be overridden in subclasses.
*/
void enterBlock() {
env.enterBlock();
}
/**
* Invoked when a lexical block is entered during AST traversal.
*
* <p>This method is there to be overridden in subclasses.
*/
void exitBlock() {
env.exitBlock();
}
}
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