com.google.javascript.jscomp.Es6RewriteModulesToCommonJsModules Maven / Gradle / Ivy
/*
* Copyright 2018 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.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
import com.google.auto.value.AutoValue;
import com.google.common.annotations.VisibleForTesting;
import com.google.javascript.jscomp.NodeTraversal.AbstractPostOrderCallback;
import com.google.javascript.jscomp.deps.ModuleLoader;
import com.google.javascript.jscomp.deps.ModuleLoader.ModulePath;
import com.google.javascript.jscomp.parsing.parser.FeatureSet.Feature;
import com.google.javascript.rhino.IR;
import com.google.javascript.rhino.Node;
import com.google.javascript.rhino.Token;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;
import javax.annotation.Nullable;
/**
* Rewrites an ES6 module to a CommonJS-like module for the sake of per-file transpilation +
* bunlding (e.g. Closure Bundler). Output is not meant to be type checked.
*/
public class Es6RewriteModulesToCommonJsModules implements CompilerPass {
private static final String JSCOMP_DEFAULT_EXPORT = "$$default";
private static final String MODULE = "$$module";
private static final String EXPORTS = "$$exports";
private static final String REQUIRE = "$$require";
private final AbstractCompiler compiler;
private final String pragma;
public Es6RewriteModulesToCommonJsModules(AbstractCompiler compiler) {
this(compiler, "use strict");
}
@VisibleForTesting
Es6RewriteModulesToCommonJsModules(AbstractCompiler compiler, String pragma) {
this.compiler = compiler;
this.pragma = pragma;
}
@Override
public void process(Node externs, Node root) {
for (Node script : root.children()) {
if (Es6RewriteModules.isEs6ModuleRoot(script)) {
NodeTraversal.traverse(compiler, script, new Rewriter(compiler, script));
script.putBooleanProp(Node.TRANSPILED, true);
}
}
compiler.setFeatureSet(compiler.getFeatureSet().without(Feature.MODULES));
}
private static class LocalQName {
final String qName;
/**
* Node to use for source information. All exported properties are transpiled to ES5 getters so
* debuggers will automatically step into these, even with source maps. When stepping in this
* node will be displayed in the source map. In general it should either be the export itself
* (e.g. export function or class) or the specific name being exported (export specs, const,
* etc).
*/
final Node nodeForSourceInfo;
LocalQName(String qName, Node nodeForSourceInfo) {
this.qName = qName;
this.nodeForSourceInfo = nodeForSourceInfo;
}
}
/**
* Normalizes a registered or import path.
*
* Absolute import paths need to match the registered path exactly. Some {@link
* ModuleLoader.ModulePath}s will have a leading slash and some won't. So in order to have
* everything line up AND preserve schemes (if they exist) then just strip leading /.
*
*
Additionally if any path contains a protocol it will be stripped only the path part will
* remain. This is done heuristically as we cannot use {@link java.net.URL} or {@link
* java.nio.file.Path} due to GWT. As a result of stripping this cross-domain imports are not
* compatible with this pass.
*/
private static String normalizePath(String path) {
int indexOfProtocol = path.indexOf("://");
if (indexOfProtocol > -1) {
path = path.substring(indexOfProtocol + 3);
int indexOfSlash = path.indexOf('/');
if (indexOfSlash > -1) {
path = path.substring(indexOfSlash + 1);
}
} else if (path.startsWith("/")) {
path = path.substring(1);
}
return path;
}
// package public only for @AutoValue
@AutoValue
abstract static class ModuleRequest {
abstract String specifier();
abstract String varName();
private static ModuleRequest create(String specifier, String varName) {
return new AutoValue_Es6RewriteModulesToCommonJsModules_ModuleRequest(specifier, varName);
}
}
/**
* Rewrites a single ES6 module into a CommonJS like module designed to be loaded in the
* compiler's module runtime.
*/
private class Rewriter extends AbstractPostOrderCallback {
private Node requireInsertSpot;
private final Node script;
private final Map exportedNameToLocalQName;
private final Set imports;
private final Set importRequests;
private final AbstractCompiler compiler;
private final ModulePath modulePath;
Rewriter(AbstractCompiler compiler, Node script) {
this.compiler = compiler;
this.script = script;
requireInsertSpot = null;
// TreeMap because ES6 orders the export key using natural ordering.
exportedNameToLocalQName = new TreeMap<>();
importRequests = new LinkedHashSet<>();
imports = new HashSet<>();
modulePath = compiler.getInput(script.getInputId()).getPath();
}
@Override
public void visit(NodeTraversal t, Node n, Node parent) {
switch (n.getToken()) {
case IMPORT:
visitImport(t.getInput().getPath(), n);
break;
case EXPORT:
visitExport(t, n, parent);
break;
case SCRIPT:
visitScript(t, n);
break;
case NAME:
maybeRenameImportedValue(t, n);
break;
default:
break;
}
}
/**
* Given an import node gets the name of the var to use for the imported module.
*
* Example: {@code import {v} from './foo.js'; use(v);} Can become:
*
* const module$foo = require('./foo.js');
* use(module$foo.v);
*
* This method would return "module$foo".
*
* Note that if there is a star import the name will be preserved.
*
*
Example:
*
* import defaultValue, * as foo from './foo.js';
* use(defaultValue, foo.bar);
*
*
* Can become:
*
* const foo = require('./foo.js'); use(foo.defaultValue, foo.bar);
*
*
* This makes debugging quite a bit easier as source maps are not great with renaming.
*/
private String getVarNameOfImport(Node importDecl) {
checkState(importDecl.isImport());
if (importDecl.getSecondChild().isImportStar()) {
return importDecl.getSecondChild().getString();
}
return getVarNameOfImport(importDecl.getLastChild().getString());
}
private String getVarNameOfImport(String importRequest) {
return modulePath.resolveModuleAsPath(importRequest).toModuleName();
}
/**
* @return qualified name to use to reference an imported value.
*
Examples:
*
* - If referencing an import spec like v in "import {v} from './foo.js'" then this
* would return "module$foo.v".
*
- If referencing an import star like m in "import * as m from './foo.js'" then this
* would return "m".
*
- If referencing an import default like d in "import d from './foo.js'" then this
* would return "module$foo.default".
*
Used to rename references to imported values within this module.
*/
private String getNameOfImportedValue(Node nameNode) {
Node importDecl = nameNode;
while (!importDecl.isImport()) {
importDecl = importDecl.getParent();
}
String moduleName = getVarNameOfImport(importDecl);
if (nameNode.getParent().isImportSpec()) {
return moduleName + "." + nameNode.getParent().getFirstChild().getString();
} else if (nameNode.isImportStar()) {
return moduleName;
} else {
checkState(nameNode.getParent().isImport());
return moduleName + ".default";
}
}
/**
* @param nameNode any variable name that is potentially from an import statement
* @return qualified name to use to reference an imported value if the given node is an imported
* name or null if the value is not imported or if it is in the import statement itself
*/
@Nullable
private String maybeGetNameOfImportedValue(Scope s, Node nameNode) {
checkState(nameNode.isName());
Var var = s.getVar(nameNode.getString());
if (var != null
// variables added implicitly to the scope, like arguments, have a null name node
&& var.getNameNode() != null
&& NodeUtil.isImportedName(var.getNameNode())
&& nameNode != var.getNameNode()) {
return getNameOfImportedValue(var.getNameNode());
}
return null;
}
/** Renames the given name node if it is an imported value. */
private void maybeRenameImportedValue(NodeTraversal t, Node n) {
checkState(n.isName());
Node parent = n.getParent();
if (parent.isExport()
|| parent.isExportSpec()
|| parent.isImport()
|| parent.isImportSpec()) {
return;
}
String qName = maybeGetNameOfImportedValue(t.getScope(), n);
if (qName != null) {
n.replaceWith(NodeUtil.newQName(compiler, qName));
t.reportCodeChange();
}
}
private void visitScript(NodeTraversal t, Node script) {
checkState(this.script == script);
Node moduleNode = script.getFirstChild();
checkState(moduleNode.isModuleBody());
moduleNode.detach();
script.addChildrenToFront(moduleNode.removeChildren());
// Order here is important. We want the end result to be:
// $jscomp.registerAndLoadModule(function($$require, $$exports, $$module) {
// // First to ensure circular deps can see exports of this module before we require them,
// // and also so that temporal deadzone is respected.
// //
// // Second so the module definition can reference imported modules, and so any require'd
// // modules are loaded.
// //
// // And finally last is the actual module definition.
// //
// }, /* */, [/* */]);
// As a result the calls below are in *inverse* order to what we want above so they can keep
// adding to the front of the script.
addRequireCalls();
addExportDef();
registerAndLoadModule(t);
}
/** Adds one call to require per imported module. */
private void addRequireCalls() {
if (!importRequests.isEmpty()) {
for (Node importDecl : imports) {
importDecl.detach();
}
Set importedNames = new HashSet<>();
for (ModuleRequest request : importRequests) {
String varName = request.varName();
if (importedNames.add(varName)) {
Node requireCall = IR.call(IR.name(REQUIRE), IR.string(request.specifier()));
requireCall.putBooleanProp(Node.FREE_CALL, true);
Node var = IR.var(IR.name(varName), requireCall);
var.useSourceInfoIfMissingFromForTree(script);
script.addChildAfter(var, requireInsertSpot);
requireInsertSpot = var;
}
}
}
}
/** Wraps the entire current module definition in a $jscomp.registerAndLoadModule function. */
private void registerAndLoadModule(NodeTraversal t) {
Node block = IR.block();
block.addChildrenToFront(script.removeChildren());
block.addChildToFront(IR.exprResult(IR.string(pragma)));
Node moduleFunction =
IR.function(
IR.name(""),
IR.paramList(IR.name(REQUIRE), IR.name(EXPORTS), IR.name(MODULE)),
block);
Node shallowDeps = new Node(Token.ARRAYLIT);
for (ModuleRequest request : importRequests) {
shallowDeps.addChildToBack(IR.string(request.specifier()));
}
Node exprResult =
IR.exprResult(
IR.call(
IR.getprop(IR.name("$jscomp"), IR.string("registerAndLoadModule")),
moduleFunction,
// Resolving this path enables removing module roots from this path.
IR.string(
normalizePath(
compiler.getModuleLoader().resolve(t.getInput().getName()).toString())),
shallowDeps));
script.addChildToBack(exprResult.useSourceInfoIfMissingFromForTree(script));
compiler.reportChangeToChangeScope(script);
compiler.reportChangeToChangeScope(moduleFunction);
t.reportCodeChange();
}
/** Adds exports to the exports object using Object.defineProperties. */
private void addExportDef() {
if (!exportedNameToLocalQName.isEmpty()) {
Node definePropertiesLit = IR.objectlit();
for (Map.Entry entry : exportedNameToLocalQName.entrySet()) {
addExport(definePropertiesLit, entry.getKey(), entry.getValue());
}
script.addChildToFront(
IR.exprResult(
IR.call(
NodeUtil.newQName(compiler, "Object.defineProperties"),
IR.name(EXPORTS),
definePropertiesLit))
.useSourceInfoIfMissingFromForTree(script));
}
}
/** Adds an ES5 getter to the given object literal to use an an export. */
private void addExport(Node definePropertiesLit, String exportedName, LocalQName localQName) {
Node exportedValue = NodeUtil.newQName(compiler, localQName.qName);
Node getterFunction =
IR.function(IR.name(""), IR.paramList(), IR.block(IR.returnNode(exportedValue)));
getterFunction.useSourceInfoFromForTree(localQName.nodeForSourceInfo);
Node objLit =
IR.objectlit(
IR.stringKey("enumerable", IR.trueNode()), IR.stringKey("get", getterFunction));
definePropertiesLit.addChildToBack(IR.stringKey(exportedName, objLit));
compiler.reportChangeToChangeScope(getterFunction);
}
private void visitImport(ModuleLoader.ModulePath path, Node importDecl) {
if (importDecl.getLastChild().getString().contains("://")) {
compiler.report(
JSError.make(
importDecl, Es6ToEs3Util.CANNOT_CONVERT, "Module requests with protocols."));
}
// Normalize the import path according to the module resolution scheme so that bundles are
// compatible with the compiler's module loader options.
importRequests.add(
ModuleRequest.create(
normalizePath(
path.resolveModuleAsPath(importDecl.getLastChild().getString()).toString()),
getVarNameOfImport(importDecl)));
imports.add(importDecl);
}
private void visitExportDefault(NodeTraversal t, Node export, Node parent) {
Node child = export.getFirstChild();
String name = null;
if (child.isFunction() || child.isClass()) {
name = NodeUtil.getName(child);
}
if (name != null) {
Node decl = child.detach();
parent.replaceChild(export, decl);
} else {
name = JSCOMP_DEFAULT_EXPORT;
// Default exports are constant in more ways than one. Not only can they not be
// overwritten but they also act like a const for temporal dead-zone purposes.
Node var = IR.constNode(IR.name(name), export.removeFirstChild());
parent.replaceChild(export, var.useSourceInfoIfMissingFromForTree(export));
NodeUtil.addFeatureToScript(t.getCurrentScript(), Feature.CONST_DECLARATIONS);
}
exportedNameToLocalQName.put("default", new LocalQName(name, export));
t.reportCodeChange();
}
private void visitExportFrom(NodeTraversal t, Node export, Node parent) {
// export {x, y as z} from 'moduleIdentifier';
Node moduleIdentifier = export.getLastChild();
Node importNode = IR.importNode(IR.empty(), IR.empty(), moduleIdentifier.cloneNode());
importNode.useSourceInfoFrom(export);
parent.addChildBefore(importNode, export);
visit(t, importNode, parent);
String moduleName = getVarNameOfImport(moduleIdentifier.getString());
for (Node exportSpec : export.getFirstChild().children()) {
exportedNameToLocalQName.put(
exportSpec.getLastChild().getString(),
new LocalQName(moduleName + "." + exportSpec.getFirstChild().getString(), exportSpec));
}
parent.removeChild(export);
t.reportCodeChange();
}
private void visitExportSpecs(NodeTraversal t, Node export, Node parent) {
// export {Foo};
for (Node exportSpec : export.getFirstChild().children()) {
String localName = exportSpec.getFirstChild().getString();
Var var = t.getScope().getVar(localName);
if (var != null && NodeUtil.isImportedName(var.getNameNode())) {
localName = maybeGetNameOfImportedValue(t.getScope(), exportSpec.getFirstChild());
checkNotNull(localName);
}
exportedNameToLocalQName.put(
exportSpec.getLastChild().getString(), new LocalQName(localName, exportSpec));
}
parent.removeChild(export);
t.reportCodeChange();
}
private void visitExportNameDeclaration(Node declaration) {
// export var Foo;
// export let {a, b:[c,d]} = {};
List lhsNodes = NodeUtil.findLhsNodesInNode(declaration);
for (Node lhs : lhsNodes) {
checkState(lhs.isName());
String name = lhs.getString();
exportedNameToLocalQName.put(name, new LocalQName(name, lhs));
}
}
private void visitExportDeclaration(NodeTraversal t, Node export, Node parent) {
// export var Foo;
// export function Foo() {}
// etc.
Node declaration = export.getFirstChild();
if (NodeUtil.isNameDeclaration(declaration)) {
visitExportNameDeclaration(declaration);
} else {
checkState(declaration.isFunction() || declaration.isClass());
String name = declaration.getFirstChild().getString();
exportedNameToLocalQName.put(name, new LocalQName(name, export));
}
parent.replaceChild(export, declaration.detach());
t.reportCodeChange();
}
private void visitExportStar(NodeTraversal t, Node export, Node parent) {
// export * from 'moduleIdentifier';
Node moduleIdentifier = export.getLastChild();
// Make an "import 'spec'" from this export node and then visit it to rewrite to a require().
Node importNode = IR.importNode(IR.empty(), IR.empty(), moduleIdentifier.cloneNode());
importNode.useSourceInfoFrom(export);
parent.addChildBefore(importNode, export);
visit(t, importNode, parent);
String moduleName = getVarNameOfImport(moduleIdentifier.getString());
export.replaceWith(
IR.exprResult(
IR.call(
IR.getprop(IR.name("$$module"), IR.string("exportAllFrom")),
IR.name(moduleName)))
.useSourceInfoFromForTree(export));
t.reportCodeChange();
}
private void visitExport(NodeTraversal t, Node export, Node parent) {
if (export.getBooleanProp(Node.EXPORT_DEFAULT)) {
visitExportDefault(t, export, parent);
} else if (export.getBooleanProp(Node.EXPORT_ALL_FROM)) {
visitExportStar(t, export, parent);
} else if (export.hasTwoChildren()) {
visitExportFrom(t, export, parent);
} else {
if (export.getFirstChild().getToken() == Token.EXPORT_SPECS) {
visitExportSpecs(t, export, parent);
} else {
visitExportDeclaration(t, export, parent);
}
}
}
}
}