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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 2014 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.deps;
import com.google.common.base.Strings;
import com.google.common.io.CharSource;
import com.google.common.io.Files;
import com.google.javascript.jscomp.transpile.BaseTranspiler;
import com.google.javascript.jscomp.transpile.TranspileResult;
import com.google.javascript.jscomp.transpile.Transpiler;
import java.io.File;
import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;
import java.nio.charset.Charset;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
/**
* A utility class to assist in creating JS bundle files.
*/
public final class ClosureBundler {
private final Transpiler transpiler;
private final Transpiler es6ModuleTranspiler;
private final EvalMode mode;
private final String sourceUrl;
private final String path;
// TODO(sdh): This cache should be moved out into a higher level, but is
// currently required due to the API that source maps must be accessible
// via just a path (and not the file contents).
private final Map sourceMapCache;
public ClosureBundler() {
this(Transpiler.NULL);
}
public ClosureBundler(Transpiler transpiler) {
this(transpiler, BaseTranspiler.LATEST_TRANSPILER);
}
public ClosureBundler(Transpiler transpiler, Transpiler es6ModuleTranspiler) {
this(
transpiler,
es6ModuleTranspiler,
EvalMode.NORMAL,
/* sourceUrl= */ null,
/* path= */ "unknown_source",
new ConcurrentHashMap<>());
}
private ClosureBundler(
Transpiler transpiler,
Transpiler es6ModuleTranspiler,
EvalMode mode,
String sourceUrl,
String path,
Map sourceMapCache) {
this.transpiler = transpiler;
this.mode = mode;
this.sourceUrl = sourceUrl;
this.path = path;
this.sourceMapCache = sourceMapCache;
this.es6ModuleTranspiler = es6ModuleTranspiler;
}
public ClosureBundler withTranspilers(
Transpiler newTranspiler, Transpiler newEs6ModuleTranspiler) {
return new ClosureBundler(
newTranspiler, newEs6ModuleTranspiler, mode, sourceUrl, path, sourceMapCache);
}
public ClosureBundler withTranspiler(Transpiler newTranspiler) {
return withTranspilers(newTranspiler, es6ModuleTranspiler);
}
public ClosureBundler withEs6ModuleTranspiler(Transpiler newEs6ModuleTranspiler) {
return withTranspilers(transpiler, newEs6ModuleTranspiler);
}
public final ClosureBundler useEval(boolean useEval) {
EvalMode newMode = useEval ? EvalMode.EVAL : EvalMode.NORMAL;
return new ClosureBundler(
transpiler, es6ModuleTranspiler, newMode, sourceUrl, path, sourceMapCache);
}
public final ClosureBundler withSourceUrl(String newSourceUrl) {
return new ClosureBundler(
transpiler, es6ModuleTranspiler, mode, newSourceUrl, path, sourceMapCache);
}
public final ClosureBundler withPath(String newPath) {
return new ClosureBundler(
transpiler, es6ModuleTranspiler, mode, sourceUrl, newPath, sourceMapCache);
}
/** Append the contents of the string to the supplied appendable. */
public static void appendInput(
Appendable out,
DependencyInfo info,
String contents) throws IOException {
new ClosureBundler().appendTo(out, info, contents);
}
/** Append the contents of the string to the supplied appendable. */
public void appendTo(
Appendable out,
DependencyInfo info,
String content) throws IOException {
appendTo(out, info, CharSource.wrap(content));
}
/** Append the contents of the file to the supplied appendable. */
public void appendTo(
Appendable out,
DependencyInfo info,
File content, Charset contentCharset) throws IOException {
appendTo(out, info, Files.asCharSource(content, contentCharset));
}
/** Append the contents of the CharSource to the supplied appendable. */
public void appendTo(
Appendable out,
DependencyInfo info,
CharSource content) throws IOException {
if (info.isModule()) {
mode.appendGoogModule(transpile(content.read()), out, sourceUrl);
} else if ("es6".equals(info.getLoadFlags().get("module")) && transpiler == Transpiler.NULL) {
// TODO(johnplaisted): Make the default transpiler the ES_MODULE_TO_CJS_TRANSPILER. Currently
// some code is passing in unicode identifiers in non-ES6 modules the compiler fails to parse.
// Once this compiler bug is fixed we can always transpile.
mode.appendTraditional(transpileEs6Module(content.read()), out, sourceUrl);
} else {
mode.appendTraditional(transpile(content.read()), out, sourceUrl);
}
}
public void appendRuntimeTo(Appendable out) throws IOException {
String runtime = transpiler.runtime();
if (!runtime.isEmpty()) {
mode.appendTraditional(runtime, out, null);
}
if (transpiler == Transpiler.NULL) {
mode.appendTraditional(es6ModuleTranspiler.runtime(), out, null);
}
}
/**
* Subclasses that need to provide a source map for any transformed input can return it with this
* method.
*/
public String getSourceMap(String path) {
return Strings.nullToEmpty(sourceMapCache.get(path));
}
private String transpile(String s, Transpiler t) {
TranspileResult result;
try {
result = t.transpile(new URI(path), s);
} catch (URISyntaxException e) {
throw new RuntimeException(e);
}
sourceMapCache.put(path, result.sourceMap());
return result.transpiled();
}
private String transpile(String s) {
return transpile(s, transpiler);
}
private String transpileEs6Module(String s) {
return transpile(s, es6ModuleTranspiler);
}
private enum EvalMode {
EVAL {
@Override
void appendTraditional(String s, Appendable out, String sourceUrl) throws IOException {
out.append("eval(\"");
EscapeMode.ESCAPED.append(s, out);
appendSourceUrl(out, EscapeMode.ESCAPED, sourceUrl);
out.append("\");\n");
}
@Override
void appendGoogModule(String s, Appendable out, String sourceUrl) throws IOException {
out.append("goog.loadModule(\"");
EscapeMode.ESCAPED.append(s, out);
appendSourceUrl(out, EscapeMode.ESCAPED, sourceUrl);
out.append("\");\n");
}
},
NORMAL {
@Override
void appendTraditional(String s, Appendable out, String sourceUrl) throws IOException {
EscapeMode.NORMAL.append(s, out);
appendSourceUrl(out, EscapeMode.NORMAL, sourceUrl);
}
@Override
void appendGoogModule(String s, Appendable out, String sourceUrl) throws IOException {
// add the prefix on the first line so the line numbers aren't affected.
out.append(
"goog.loadModule(function(exports) {"
+ "'use strict';");
EscapeMode.NORMAL.append(s, out);
out.append(
"\n" // terminate any trailing single line comment.
+ ";" // terminate any trailing expression.
+ "return exports;});\n");
appendSourceUrl(out, EscapeMode.NORMAL, sourceUrl);
}
};
abstract void appendTraditional(String s, Appendable out, String sourceUrl) throws IOException;
abstract void appendGoogModule(String s, Appendable out, String sourceUrl) throws IOException;
}
private enum EscapeMode {
ESCAPED {
@Override void append(String s, Appendable out) throws IOException {
SourceCodeEscapers.appendWithJavascriptEscaper(s, out);
}
},
NORMAL {
@Override void append(String s, Appendable out) throws IOException {
out.append(s);
}
};
abstract void append(String s, Appendable out) throws IOException;
}
private static void appendSourceUrl(Appendable out, EscapeMode mode, String sourceUrl)
throws IOException {
if (sourceUrl == null) {
return;
}
String toAppend = "\n//# sourceURL=" + sourceUrl + "\n";
// Don't go through #append. That method relies on #transformInput,
// but source URLs generally aren't valid JS inputs.
mode.append(toAppend, out);
}
}