/*
 * Copyright (c) 2006, 2017, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package com.sun.tools.javac.main;

import java.io.FileWriter;
import java.io.PrintWriter;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.text.Collator;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.EnumSet;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.Locale;
import java.util.ServiceLoader;
import java.util.Set;
import java.util.TreeSet;
import java.util.regex.Pattern;
import java.util.stream.Collectors;
import java.util.stream.StreamSupport;

import javax.lang.model.SourceVersion;

import com.sun.tools.doclint.DocLint;
import com.sun.tools.javac.code.Lint;
import com.sun.tools.javac.code.Lint.LintCategory;
import com.sun.tools.javac.code.Source;
import com.sun.tools.javac.code.Type;
import com.sun.tools.javac.jvm.Profile;
import com.sun.tools.javac.jvm.Target;
import com.sun.tools.javac.platform.PlatformProvider;
import com.sun.tools.javac.processing.JavacProcessingEnvironment;
import com.sun.tools.javac.util.Assert;
import com.sun.tools.javac.util.JDK9Wrappers;
import com.sun.tools.javac.util.Log;
import com.sun.tools.javac.util.Log.PrefixKind;
import com.sun.tools.javac.util.Log.WriterKind;
import com.sun.tools.javac.util.Options;
import com.sun.tools.javac.util.StringUtils;

import static com.sun.tools.javac.main.Option.ChoiceKind.*;
import static com.sun.tools.javac.main.Option.OptionGroup.*;
import static com.sun.tools.javac.main.Option.OptionKind.*;

Options for javac. The specific Option to handle a command-line option can be found by calling lookup, which search some or all of the members of this enum in order, looking for the first match. The action for an Option is performed handleOption, which determines whether an argument is needed and where to find it; handleOption then calls process providing a suitable OptionHelper to provide access the compiler state. 
This is NOT part of any supported API.
If you write code that depends on this, you do so at your own
risk.  This code and its internal interfaces are subject to change
or deletion without notice.
/**
 * Options for javac.
 * The specific Option to handle a command-line option can be found by calling
 * {@link #lookup}, which search some or all of the members of this enum in order,
 * looking for the first {@link #matches match}.
 * The action for an Option is performed {@link #handleOption}, which determines
 * whether an argument is needed and where to find it;
 * {@code handleOption} then calls {@link #process process} providing a suitable
 * {@link OptionHelper} to provide access the compiler state.
 *
 * <p><b>This is NOT part of any supported API.
 * If you write code that depends on this, you do so at your own
 * risk.  This code and its internal interfaces are subject to change
 * or deletion without notice.</b></p>
 */
public enum Option {
    G("-g", "opt.g", STANDARD, BASIC),

    G_NONE("-g:none", "opt.g.none", STANDARD, BASIC) {
        @Override
        public void process(OptionHelper helper, String option) {
            helper.put("-g:", "none");
        }
    },

    G_CUSTOM("-g:",  "opt.g.lines.vars.source",
            STANDARD, BASIC, ANYOF, "lines", "vars", "source"),

    XLINT("-Xlint", "opt.Xlint", EXTENDED, BASIC),

    XLINT_CUSTOM("-Xlint:", "opt.arg.Xlint", "opt.Xlint.custom", EXTENDED, BASIC, ANYOF, getXLintChoices()) {
        private final String LINT_KEY_FORMAT = LARGE_INDENT + "  %-" +
                (DEFAULT_SYNOPSIS_WIDTH + SMALL_INDENT.length() - LARGE_INDENT.length() - 2) + "s %s";
        @Override
        protected void help(Log log) {
            super.help(log);
            log.printRawLines(WriterKind.STDOUT,
                              String.format(LINT_KEY_FORMAT,
                                            "all",
                                            log.localize(PrefixKind.JAVAC, "opt.Xlint.all")));
            for (LintCategory lc : LintCategory.values()) {
                log.printRawLines(WriterKind.STDOUT,
                                  String.format(LINT_KEY_FORMAT,
                                                lc.option,
                                                log.localize(PrefixKind.JAVAC,
                                                             "opt.Xlint.desc." + lc.option)));
            }
            log.printRawLines(WriterKind.STDOUT,
                              String.format(LINT_KEY_FORMAT,
                                            "none",
                                            log.localize(PrefixKind.JAVAC, "opt.Xlint.none")));
        }
    },

    XDOCLINT("-Xdoclint", "opt.Xdoclint", EXTENDED, BASIC),

    XDOCLINT_CUSTOM("-Xdoclint:", "opt.Xdoclint.subopts", "opt.Xdoclint.custom", EXTENDED, BASIC) {
        @Override
        public boolean matches(String option) {
            return DocLint.isValidOption(
                    option.replace(XDOCLINT_CUSTOM.primaryName, DocLint.XMSGS_CUSTOM_PREFIX));
        }

        @Override
        public void process(OptionHelper helper, String option) {
            String prev = helper.get(XDOCLINT_CUSTOM);
            String next = (prev == null) ? option : (prev + " " + option);
            helper.put(XDOCLINT_CUSTOM.primaryName, next);
        }
    },

    XDOCLINT_PACKAGE("-Xdoclint/package:", "opt.Xdoclint.package.args", "opt.Xdoclint.package.desc", EXTENDED, BASIC) {
        @Override
        public boolean matches(String option) {
            return DocLint.isValidOption(
                    option.replace(XDOCLINT_PACKAGE.primaryName, DocLint.XCHECK_PACKAGE));
        }

        @Override
        public void process(OptionHelper helper, String option) {
            String prev = helper.get(XDOCLINT_PACKAGE);
            String next = (prev == null) ? option : (prev + " " + option);
            helper.put(XDOCLINT_PACKAGE.primaryName, next);
        }
    },

    DOCLINT_FORMAT("--doclint-format", "opt.doclint.format", EXTENDED, BASIC, ONEOF, "html4", "html5"),

    // -nowarn is retained for command-line backward compatibility
    NOWARN("-nowarn", "opt.nowarn", STANDARD, BASIC) {
        @Override
        public void process(OptionHelper helper, String option) {
            helper.put("-Xlint:none", option);
        }
    },

    VERBOSE("-verbose", "opt.verbose", STANDARD, BASIC),

    // -deprecation is retained for command-line backward compatibility
    DEPRECATION("-deprecation", "opt.deprecation", STANDARD, BASIC) {
        @Override
        public void process(OptionHelper helper, String option) {
            helper.put("-Xlint:deprecation", option);
        }
    },

    CLASS_PATH("--class-path -classpath -cp", "opt.arg.path", "opt.classpath", STANDARD, FILEMANAGER),

    SOURCE_PATH("--source-path -sourcepath", "opt.arg.path", "opt.sourcepath", STANDARD, FILEMANAGER),

    MODULE_SOURCE_PATH("--module-source-path", "opt.arg.mspath", "opt.modulesourcepath", STANDARD, FILEMANAGER),

    MODULE_PATH("--module-path -p", "opt.arg.path", "opt.modulepath", STANDARD, FILEMANAGER),

    UPGRADE_MODULE_PATH("--upgrade-module-path", "opt.arg.path", "opt.upgrademodulepath", STANDARD, FILEMANAGER),

    SYSTEM("--system", "opt.arg.jdk", "opt.system", STANDARD, FILEMANAGER),

    PATCH_MODULE("--patch-module", "opt.arg.patch", "opt.patch", EXTENDED, FILEMANAGER) {
        // The deferred filemanager diagnostics mechanism assumes a single value per option,
        // but --patch-module can be used multiple times, once per module. Therefore we compose
        // a value for the option containing the last value specified for each module, and separate
        // the the module=path pairs by an invalid path character, NULL.
        // The standard file manager code knows to split apart the NULL-separated components.
        @Override
        public void process(OptionHelper helper, String option, String arg) throws InvalidValueException {
            if (arg.isEmpty()) {
                throw helper.newInvalidValueException("err.no.value.for.option", option);
            } else if (getPattern().matcher(arg).matches()) {
                String prev = helper.get(PATCH_MODULE);
                if (prev == null) {
                    super.process(helper, option, arg);
                } else {
                    String argModulePackage = arg.substring(0, arg.indexOf('='));
                    boolean isRepeated = Arrays.stream(prev.split("\0"))
                            .map(s -> s.substring(0, s.indexOf('=')))
                            .collect(Collectors.toSet())
                            .contains(argModulePackage);
                    if (isRepeated) {
                        throw helper.newInvalidValueException("err.repeated.value.for.patch.module", argModulePackage);
                    } else {
                        super.process(helper, option, prev + '\0' + arg);
                    }
                }
            } else {
                throw helper.newInvalidValueException("err.bad.value.for.option", option, arg);
            }
        }

        @Override
        public Pattern getPattern() {
            return Pattern.compile("([^/]+)=(,*[^,].*)");
        }
    },

    BOOT_CLASS_PATH("--boot-class-path -bootclasspath", "opt.arg.path", "opt.bootclasspath", STANDARD, FILEMANAGER) {
        @Override
        public void process(OptionHelper helper, String option, String arg) throws InvalidValueException {
            helper.remove("-Xbootclasspath/p:");
            helper.remove("-Xbootclasspath/a:");
            super.process(helper, option, arg);
        }
    },

    XBOOTCLASSPATH_PREPEND("-Xbootclasspath/p:", "opt.arg.path", "opt.Xbootclasspath.p", EXTENDED, FILEMANAGER),

    XBOOTCLASSPATH_APPEND("-Xbootclasspath/a:", "opt.arg.path", "opt.Xbootclasspath.a", EXTENDED, FILEMANAGER),

    XBOOTCLASSPATH("-Xbootclasspath:", "opt.arg.path", "opt.bootclasspath", EXTENDED, FILEMANAGER) {
        @Override
        public void process(OptionHelper helper, String option, String arg) throws InvalidValueException {
            helper.remove("-Xbootclasspath/p:");
            helper.remove("-Xbootclasspath/a:");
            super.process(helper, "-bootclasspath", arg);
        }
    },

    EXTDIRS("-extdirs", "opt.arg.dirs", "opt.extdirs", STANDARD, FILEMANAGER),

    DJAVA_EXT_DIRS("-Djava.ext.dirs=", "opt.arg.dirs", "opt.extdirs", EXTENDED, FILEMANAGER) {
        @Override
        public void process(OptionHelper helper, String option, String arg) throws InvalidValueException {
            EXTDIRS.process(helper, "-extdirs", arg);
        }
    },

    ENDORSEDDIRS("-endorseddirs", "opt.arg.dirs", "opt.endorseddirs", STANDARD, FILEMANAGER),

    DJAVA_ENDORSED_DIRS("-Djava.endorsed.dirs=", "opt.arg.dirs", "opt.endorseddirs", EXTENDED, FILEMANAGER) {
        @Override
        public void process(OptionHelper helper, String option, String arg) throws InvalidValueException {
            ENDORSEDDIRS.process(helper, "-endorseddirs", arg);
        }
    },

    PROC("-proc:", "opt.proc.none.only", STANDARD, BASIC,  ONEOF, "none", "only"),

    PROCESSOR("-processor", "opt.arg.class.list", "opt.processor", STANDARD, BASIC),

    PROCESSOR_PATH("--processor-path -processorpath", "opt.arg.path", "opt.processorpath", STANDARD, FILEMANAGER),

    PROCESSOR_MODULE_PATH("--processor-module-path", "opt.arg.path", "opt.processormodulepath", STANDARD, FILEMANAGER),

    PARAMETERS("-parameters","opt.parameters", STANDARD, BASIC),

    D("-d", "opt.arg.directory", "opt.d", STANDARD, FILEMANAGER),

    S("-s", "opt.arg.directory", "opt.sourceDest", STANDARD, FILEMANAGER),

    H("-h", "opt.arg.directory", "opt.headerDest", STANDARD, FILEMANAGER),

    IMPLICIT("-implicit:", "opt.implicit", STANDARD, BASIC, ONEOF, "none", "class"),

    ENCODING("-encoding", "opt.arg.encoding", "opt.encoding", STANDARD, FILEMANAGER),

    SOURCE("-source", "opt.arg.release", "opt.source", STANDARD, BASIC) {
        @Override
        public void process(OptionHelper helper, String option, String operand) throws InvalidValueException {
            Source source = Source.lookup(operand);
            if (source == null) {
                throw helper.newInvalidValueException("err.invalid.source", operand);
            }
            super.process(helper, option, operand);
        }
    },

    TARGET("-target", "opt.arg.release", "opt.target", STANDARD, BASIC) {
        @Override
        public void process(OptionHelper helper, String option, String operand) throws InvalidValueException {
            Target target = Target.lookup(operand);
            if (target == null) {
                throw helper.newInvalidValueException("err.invalid.target", operand);
            }
            super.process(helper, option, operand);
        }
    },

    RELEASE("--release", "opt.arg.release", "opt.release", STANDARD, BASIC) {
        @Override
        protected void help(Log log) {
            Iterable<PlatformProvider> providers =
                    ServiceLoader.load(PlatformProvider.class, Arguments.class.getClassLoader());
            Set<String> platforms = StreamSupport.stream(providers.spliterator(), false)
                                                 .flatMap(provider -> StreamSupport.stream(provider.getSupportedPlatformNames()
                                                                                                   .spliterator(),
                                                                                           false))
                                                 .collect(Collectors.toCollection(TreeSet :: new));

            StringBuilder targets = new StringBuilder();
            String delim = "";
            for (String platform : platforms) {
                targets.append(delim);
                targets.append(platform);
                delim = ", ";
            }

            super.help(log, log.localize(PrefixKind.JAVAC, descrKey, targets.toString()));
        }
    },

    PROFILE("-profile", "opt.arg.profile", "opt.profile", STANDARD, BASIC) {
        @Override
        public void process(OptionHelper helper, String option, String operand) throws InvalidValueException {
            Profile profile = Profile.lookup(operand);
            if (profile == null) {
                throw helper.newInvalidValueException("err.invalid.profile", operand);
            }
            super.process(helper, option, operand);
        }
    },

    VERSION("--version -version", "opt.version", STANDARD, INFO) {
        @Override
        public void process(OptionHelper helper, String option) throws InvalidValueException {
            Log log = helper.getLog();
            String ownName = helper.getOwnName();
            log.printLines(WriterKind.STDOUT, PrefixKind.JAVAC, "version", ownName,  JavaCompiler.version());
            super.process(helper, option);
        }
    },

    FULLVERSION("--full-version -fullversion", null, HIDDEN, INFO) {
        @Override
        public void process(OptionHelper helper, String option) throws InvalidValueException {
            Log log = helper.getLog();
            String ownName = helper.getOwnName();
            log.printLines(WriterKind.STDOUT, PrefixKind.JAVAC, "fullVersion", ownName,  JavaCompiler.fullVersion());
            super.process(helper, option);
        }
    },

    // Note: -h is already taken for "native header output directory".
    HELP("--help -help", "opt.help", STANDARD, INFO) {
        @Override
        public void process(OptionHelper helper, String option) throws InvalidValueException {
            Log log = helper.getLog();
            String ownName = helper.getOwnName();
            log.printLines(WriterKind.STDOUT, PrefixKind.JAVAC, "msg.usage.header", ownName);
            showHelp(log, OptionKind.STANDARD);
            log.printNewline(WriterKind.STDOUT);
            super.process(helper, option);
        }
    },

    A("-A", "opt.arg.key.equals.value", "opt.A", STANDARD, BASIC, ArgKind.ADJACENT) {
        @Override
        public boolean matches(String arg) {
            return arg.startsWith("-A");
        }

        @Override
        public boolean hasArg() {
            return false;
        }
        // Mapping for processor options created in
        // JavacProcessingEnvironment
        @Override
        public void process(OptionHelper helper, String option) throws InvalidValueException {
            int argLength = option.length();
            if (argLength == 2) {
                throw helper.newInvalidValueException("err.empty.A.argument");
            }
            int sepIndex = option.indexOf('=');
            String key = option.substring(2, (sepIndex != -1 ? sepIndex : argLength) );
            if (!JavacProcessingEnvironment.isValidOptionName(key)) {
                throw helper.newInvalidValueException("err.invalid.A.key", option);
            }
            helper.put(option, option);
        }
    },

    DEFAULT_MODULE_FOR_CREATED_FILES("--default-module-for-created-files",
                                     "opt.arg.default.module.for.created.files",
                                     "opt.default.module.for.created.files", EXTENDED, BASIC) {
        @Override
        public void process(OptionHelper helper, String option, String arg) throws InvalidValueException {
            String prev = helper.get(DEFAULT_MODULE_FOR_CREATED_FILES);
            if (prev != null) {
                throw helper.newInvalidValueException("err.option.too.many",
                                                      DEFAULT_MODULE_FOR_CREATED_FILES.primaryName);
            } else if (arg.isEmpty()) {
                throw helper.newInvalidValueException("err.no.value.for.option", option);
            } else if (getPattern().matcher(arg).matches()) {
                helper.put(DEFAULT_MODULE_FOR_CREATED_FILES.primaryName, arg);
            } else {
                throw helper.newInvalidValueException("err.bad.value.for.option", option, arg);
            }
        }

        @Override
        public Pattern getPattern() {
            return Pattern.compile("[^,].*");
        }
    },

    X("--help-extra -X", "opt.X", STANDARD, INFO) {
        @Override
        public void process(OptionHelper helper, String option) throws InvalidValueException {
            Log log = helper.getLog();
            showHelp(log, OptionKind.EXTENDED);
            log.printNewline(WriterKind.STDOUT);
            log.printLines(WriterKind.STDOUT, PrefixKind.JAVAC, "msg.usage.nonstandard.footer");
            super.process(helper, option);
        }
    },

    // This option exists only for the purpose of documenting itself.
    // It's actually implemented by the launcher.
    J("-J", "opt.arg.flag", "opt.J", STANDARD, INFO, ArgKind.ADJACENT) {
        @Override
        public void process(OptionHelper helper, String option) {
            throw new AssertionError("the -J flag should be caught by the launcher.");
        }
    },

    MOREINFO("-moreinfo", null, HIDDEN, BASIC) {
        @Override
        public void process(OptionHelper helper, String option) throws InvalidValueException {
            Type.moreInfo = true;
            super.process(helper, option);
        }
    },

    // treat warnings as errors
    WERROR("-Werror", "opt.Werror", STANDARD, BASIC),

    // prompt after each error
    // new Option("-prompt",                                        "opt.prompt"),
    PROMPT("-prompt", null, HIDDEN, BASIC),

    // dump stack on error
    DOE("-doe", null, HIDDEN, BASIC),

    // output source after type erasure
    PRINTSOURCE("-printsource", null, HIDDEN, BASIC),

    // display warnings for generic unchecked operations
    WARNUNCHECKED("-warnunchecked", null, HIDDEN, BASIC) {
        @Override
        public void process(OptionHelper helper, String option) {
            helper.put("-Xlint:unchecked", option);
        }
    },

    XMAXERRS("-Xmaxerrs", "opt.arg.number", "opt.maxerrs", EXTENDED, BASIC),

    XMAXWARNS("-Xmaxwarns", "opt.arg.number", "opt.maxwarns", EXTENDED, BASIC),

    XSTDOUT("-Xstdout", "opt.arg.file", "opt.Xstdout", EXTENDED, INFO) {
        @Override
        public void process(OptionHelper helper, String option, String arg) throws InvalidValueException {
            try {
                Log log = helper.getLog();
                log.setWriters(new PrintWriter(new FileWriter(arg), true));
            } catch (java.io.IOException e) {
                throw helper.newInvalidValueException("err.error.writing.file", arg, e);
            }
            super.process(helper, option, arg);
        }
    },

    XPRINT("-Xprint", "opt.print", EXTENDED, BASIC),

    XPRINTROUNDS("-XprintRounds", "opt.printRounds", EXTENDED, BASIC),

    XPRINTPROCESSORINFO("-XprintProcessorInfo", "opt.printProcessorInfo", EXTENDED, BASIC),

    XPREFER("-Xprefer:", "opt.prefer", EXTENDED, BASIC, ONEOF, "source", "newer"),

    XXUSERPATHSFIRST("-XXuserPathsFirst", "opt.userpathsfirst", HIDDEN, BASIC),

    // see enum PkgInfo
    XPKGINFO("-Xpkginfo:", "opt.pkginfo", EXTENDED, BASIC, ONEOF, "always", "legacy", "nonempty"),

    /* -O is a no-op, accepted for backward compatibility. */
    O("-O", null, HIDDEN, BASIC),

    /* -Xjcov produces tables to support the code coverage tool jcov. */
    XJCOV("-Xjcov", null, HIDDEN, BASIC),

    PLUGIN("-Xplugin:", "opt.arg.plugin", "opt.plugin", EXTENDED, BASIC) {
        @Override
        public void process(OptionHelper helper, String option) {
            String p = option.substring(option.indexOf(':') + 1).trim();
            String prev = helper.get(PLUGIN);
            helper.put(PLUGIN.primaryName, (prev == null) ? p : prev + '\0' + p);
        }
    },

    XDIAGS("-Xdiags:", "opt.diags", EXTENDED, BASIC, ONEOF, "compact", "verbose"),

    DEBUG("--debug:", null, HIDDEN, BASIC) {
        @Override
        public void process(OptionHelper helper, String option) throws InvalidValueException {
            HiddenGroup.DEBUG.process(helper, option);
        }
    },

    SHOULDSTOP("--should-stop:", null, HIDDEN, BASIC) {
        @Override
        public void process(OptionHelper helper, String option) throws InvalidValueException {
            HiddenGroup.SHOULDSTOP.process(helper, option);
        }
    },

    DIAGS("--diags:", null, HIDDEN, BASIC) {
        @Override
        public void process(OptionHelper helper, String option) throws InvalidValueException {
            HiddenGroup.DIAGS.process(helper, option);
        }
    },

    /* This is a back door to the compiler's option table.
     * -XDx=y sets the option x to the value y.
     * -XDx sets the option x to the value x.
     */
    XD("-XD", null, HIDDEN, BASIC) {
        @Override
        public boolean matches(String s) {
            return s.startsWith(primaryName);
        }
        @Override
        public void process(OptionHelper helper, String option) {
            process(helper, option, option.substring(primaryName.length()));
        }

        @Override
        public void process(OptionHelper helper, String option, String arg) {
            int eq = arg.indexOf('=');
            String key = (eq < 0) ? arg : arg.substring(0, eq);
            String value = (eq < 0) ? arg : arg.substring(eq+1);
            helper.put(key, value);
        }
    },

    ADD_EXPORTS("--add-exports", "opt.arg.addExports", "opt.addExports", EXTENDED, BASIC) {
        @Override
        public void process(OptionHelper helper, String option, String arg) throws InvalidValueException {
            if (arg.isEmpty()) {
                throw helper.newInvalidValueException("err.no.value.for.option", option);
            } else if (getPattern().matcher(arg).matches()) {
                String prev = helper.get(ADD_EXPORTS);
                helper.put(ADD_EXPORTS.primaryName, (prev == null) ? arg : prev + '\0' + arg);
            } else {
                throw helper.newInvalidValueException("err.bad.value.for.option", option, arg);
            }
        }

        @Override
        public Pattern getPattern() {
            return Pattern.compile("([^/]+)/([^=]+)=(,*[^,].*)");
        }
    },

    ADD_OPENS("--add-opens", null, null, HIDDEN, BASIC),

    ADD_READS("--add-reads", "opt.arg.addReads", "opt.addReads", EXTENDED, BASIC) {
        @Override
        public void process(OptionHelper helper, String option, String arg) throws InvalidValueException {
            if (arg.isEmpty()) {
                throw helper.newInvalidValueException("err.no.value.for.option", option);
            } else if (getPattern().matcher(arg).matches()) {
                String prev = helper.get(ADD_READS);
                helper.put(ADD_READS.primaryName, (prev == null) ? arg : prev + '\0' + arg);
            } else {
                throw helper.newInvalidValueException("err.bad.value.for.option", option, arg);
            }
        }

        @Override
        public Pattern getPattern() {
            return Pattern.compile("([^=]+)=(,*[^,].*)");
        }
    },

    MODULE("--module -m", "opt.arg.m", "opt.m", STANDARD, BASIC),

    ADD_MODULES("--add-modules", "opt.arg.addmods", "opt.addmods", STANDARD, BASIC) {
        @Override
        public void process(OptionHelper helper, String option, String arg) throws InvalidValueException {
            if (arg.isEmpty()) {
                throw helper.newInvalidValueException("err.no.value.for.option", option);
            } else if (getPattern().matcher(arg).matches()) {
                String prev = helper.get(ADD_MODULES);
                // since the individual values are simple names, we can simply join the
                // values of multiple --add-modules options with ','
                helper.put(ADD_MODULES.primaryName, (prev == null) ? arg : prev + ',' + arg);
            } else {
                throw helper.newInvalidValueException("err.bad.value.for.option", option, arg);
            }
        }

        @Override
        public Pattern getPattern() {
            return Pattern.compile(",*[^,].*");
        }
    },

    LIMIT_MODULES("--limit-modules", "opt.arg.limitmods", "opt.limitmods", STANDARD, BASIC) {
        @Override
        public void process(OptionHelper helper, String option, String arg) throws InvalidValueException {
            if (arg.isEmpty()) {
                throw helper.newInvalidValueException("err.no.value.for.option", option);
            } else if (getPattern().matcher(arg).matches()) {
                helper.put(LIMIT_MODULES.primaryName, arg); // last one wins
            } else {
                throw helper.newInvalidValueException("err.bad.value.for.option", option, arg);
            }
        }

        @Override
        public Pattern getPattern() {
            return Pattern.compile(",*[^,].*");
        }
    },

    MODULE_VERSION("--module-version", "opt.arg.module.version", "opt.module.version", STANDARD, BASIC) {
        @Override
        public void process(OptionHelper helper, String option, String arg) throws InvalidValueException {
            if (arg.isEmpty()) {
                throw helper.newInvalidValueException("err.no.value.for.option", option);
            } else {
                try {
                    Class.forName(JDK9Wrappers.ModuleDescriptor.Version.CLASSNAME);
                    // use official parser if available
                    try {
                        JDK9Wrappers.ModuleDescriptor.Version.parse(arg);
                    } catch (IllegalArgumentException e) {
                        throw helper.newInvalidValueException("err.bad.value.for.option", option, arg);
                    }
                } catch (ClassNotFoundException ex) {
                    // fall-back to simplistic rules when running on older platform
                    if (!(arg.charAt(0) >= '0' && arg.charAt(0) <= '9') ||
                        arg.endsWith("-") ||
                        arg.endsWith("+")) {
                        throw helper.newInvalidValueException("err.bad.value.for.option", option, arg);
                    }
                }
            }
            super.process(helper, option, arg);
        }
    },

    // This option exists only for the purpose of documenting itself.
    // It's actually implemented by the CommandLine class.
    AT("@", "opt.arg.file", "opt.AT", STANDARD, INFO, ArgKind.ADJACENT) {
        @Override
        public void process(OptionHelper helper, String option) {
            throw new AssertionError("the @ flag should be caught by CommandLine.");
        }
    },

    // Standalone positional argument: source file or type name.
    SOURCEFILE("sourcefile", null, HIDDEN, INFO) {
        @Override
        public boolean matches(String s) {
            if (s.endsWith(".java"))  // Java source file
                return true;
            int sep = s.indexOf('/');
            if (sep != -1) {
                return SourceVersion.isName(s.substring(0, sep))
                        && SourceVersion.isName(s.substring(sep + 1));
            } else {
                return SourceVersion.isName(s);   // Legal type name
            }
        }
        @Override
        public void process(OptionHelper helper, String option) throws InvalidValueException {
            if (option.endsWith(".java") ) {
                Path p = Paths.get(option);
                if (!Files.exists(p)) {
                    throw helper.newInvalidValueException("err.file.not.found", p);
                }
                if (!Files.isRegularFile(p)) {
                    throw helper.newInvalidValueException("err.file.not.file", p);
                }
                helper.addFile(p);
            } else {
                helper.addClassName(option);
            }
        }
    },

    MULTIRELEASE("--multi-release", "opt.arg.multi-release", "opt.multi-release", HIDDEN, FILEMANAGER),

    INHERIT_RUNTIME_ENVIRONMENT("--inherit-runtime-environment", "opt.inherit_runtime_environment",
            HIDDEN, BASIC) {
        @Override
        public void process(OptionHelper helper, String option) throws InvalidValueException {
            try {
                Class.forName(JDK9Wrappers.VMHelper.CLASSNAME);
                String[] runtimeArgs = JDK9Wrappers.VMHelper.getRuntimeArguments();
                for (String arg : runtimeArgs) {
                    // Handle any supported runtime options; ignore all others.
                    // The runtime arguments always use the single token form, e.g. "--name=value".
                    for (Option o : getSupportedRuntimeOptions()) {
                        if (o.matches(arg)) {
                            switch (o) {
                                case ADD_MODULES:
                                    int eq = arg.indexOf('=');
                                    Assert.check(eq > 0, () -> ("invalid runtime option:" + arg));
                                    // --add-modules=ALL-DEFAULT is not supported at compile-time
                                    // so remove it from list, and only process the rest
                                    // if the set is non-empty.
                                    // Note that --add-modules=ALL-DEFAULT is automatically added
                                    // by the standard javac launcher.
                                    String mods = Arrays.stream(arg.substring(eq + 1).split(","))
                                            .filter(s -> !s.isEmpty() && !s.equals("ALL-DEFAULT"))
                                            .collect(Collectors.joining(","));
                                    if (!mods.isEmpty()) {
                                        String updatedArg = arg.substring(0, eq + 1) + mods;
                                        o.handleOption(helper, updatedArg, Collections.emptyIterator());
                                    }
                                    break;
                                default:
                                    o.handleOption(helper, arg, Collections.emptyIterator());
                                    break;
                            }
                            break;
                        }
                    }
                }
            } catch (ClassNotFoundException | SecurityException e) {
                throw helper.newInvalidValueException("err.cannot.access.runtime.env");
            }
        }

        private Option[] getSupportedRuntimeOptions() {
            Option[] supportedRuntimeOptions = {
                ADD_EXPORTS,
                ADD_MODULES,
                LIMIT_MODULES,
                MODULE_PATH,
                UPGRADE_MODULE_PATH,
                PATCH_MODULE
            };
            return supportedRuntimeOptions;
        }
    };

    
This exception is thrown when an invalid value is given for an option.
The detail string gives a detailed, localized message, suitable for use
in error messages reported to the user.
/**
     * This exception is thrown when an invalid value is given for an option.
     * The detail string gives a detailed, localized message, suitable for use
     * in error messages reported to the user.
     */
    public static class InvalidValueException extends Exception {
        private static final long serialVersionUID = -1;

        public InvalidValueException(String msg) {
            super(msg);
        }

        public InvalidValueException(String msg, Throwable cause) {
            super(msg, cause);
        }
    }

    
The kind of argument, if any, accepted by this option. The kind is augmented
by characters in the name of the option.
/**
     * The kind of argument, if any, accepted by this option. The kind is augmented
     * by characters in the name of the option.
     */
    public enum ArgKind {
        
This option does not take any argument. /** This option does not take any argument. */
        NONE,

// Not currently supported
//        /**
//         * This option takes an optional argument, which may be provided directly after an '='
//         * separator, or in the following argument position if that word does not itself appear
//         * to be the name of an option.
//         */
//        OPTIONAL,

        
This option takes an argument.
If the name of option ends with ':' or '=', the argument must be provided directly
after that separator.
Otherwise, it may appear after an '=' or in the following argument position.
/**
         * This option takes an argument.
         * If the name of option ends with ':' or '=', the argument must be provided directly
         * after that separator.
         * Otherwise, it may appear after an '=' or in the following argument position.
         */
        REQUIRED,

        
This option takes an argument immediately after the option name, with no separator
character.
/**
         * This option takes an argument immediately after the option name, with no separator
         * character.
         */
        ADJACENT
    }

    
The kind of an Option. This is used by the -help and -X options.
/**
     * The kind of an Option. This is used by the -help and -X options.
     */
    public enum OptionKind {
        
A standard option, documented by -help. /** A standard option, documented by -help. */
        STANDARD,
        
An extended option, documented by -X. /** An extended option, documented by -X. */
        EXTENDED,
        
A hidden option, not documented. /** A hidden option, not documented. */
        HIDDEN,
    }

    
The group for an Option. This determines the situations in which the
option is applicable.
/**
     * The group for an Option. This determines the situations in which the
     * option is applicable.
     */
    enum OptionGroup {
        
A basic option, available for use on the command line or via the
 Compiler API. /** A basic option, available for use on the command line or via the
         *  Compiler API. */
        BASIC,
        
An option for javac's standard JavaFileManager. Other file managers
 may or may not support these options. /** An option for javac's standard JavaFileManager. Other file managers
         *  may or may not support these options. */
        FILEMANAGER,
        
A command-line option that requests information, such as -help. /** A command-line option that requests information, such as -help. */
        INFO,
        
A command-line "option" representing a file or class name. /** A command-line "option" representing a file or class name. */
        OPERAND
    }

    
The kind of choice for "choice" options.
/**
     * The kind of choice for "choice" options.
     */
    enum ChoiceKind {
        
The expected value is exactly one of the set of choices. /** The expected value is exactly one of the set of choices. */
        ONEOF,
        
The expected value is one of more of the set of choices. /** The expected value is one of more of the set of choices. */
        ANYOF
    }

    enum HiddenGroup {
        DIAGS("diags"),
        DEBUG("debug"),
        SHOULDSTOP("should-stop");

        static final Set<String> skipSet = new java.util.HashSet<>(
                Arrays.asList("--diags:", "--debug:", "--should-stop:"));

        final String text;

        HiddenGroup(String text) {
            this.text = text;
        }

        public void process(OptionHelper helper, String option) throws InvalidValueException {
            String p = option.substring(option.indexOf(':') + 1).trim();
            String[] subOptions = p.split(";");
            for (String subOption : subOptions) {
                subOption = text + "." + subOption.trim();
                XD.process(helper, subOption, subOption);
            }
        }

        static boolean skip(String name) {
            return skipSet.contains(name);
        }
    }

    
The "primary name" for this option. This is the name that is used to put values in the Options table. /**
     * The "primary name" for this option.
     * This is the name that is used to put values in the {@link Options} table.
     */
    public final String primaryName;

    
The set of names (primary name and aliases) for this option.
Note that some names may end in a separator, to indicate that an argument must immediately
follow the separator (and cannot appear in the following argument position.
/**
     * The set of names (primary name and aliases) for this option.
     * Note that some names may end in a separator, to indicate that an argument must immediately
     * follow the separator (and cannot appear in the following argument position.
     */
    public final String[] names;

    
Documentation key for arguments. /** Documentation key for arguments. */
    protected final String argsNameKey;

    
Documentation key for description.
/** Documentation key for description.
     */
    protected final String descrKey;

    
The kind of this option. /** The kind of this option. */
    private final OptionKind kind;

    
The group for this option. /** The group for this option. */
    private final OptionGroup group;

    
The kind of argument for this option. /** The kind of argument for this option. */
    private final ArgKind argKind;

    
The kind of choices for this option, if any. /** The kind of choices for this option, if any. */
    private final ChoiceKind choiceKind;

    
The choices for this option, if any. /** The choices for this option, if any. */
    private final Set<String> choices;

    
Looks up the first option matching the given argument in the full set of options.
Params:
arg – the argument to be matches
Returns:
the first option that matches, or null if none./**
     * Looks up the first option matching the given argument in the full set of options.
     * @param arg the argument to be matches
     * @return the first option that matches, or null if none.
     */
    public static Option lookup(String arg) {
        return lookup(arg, EnumSet.allOf(Option.class));
    }

    
Looks up the first option matching the given argument within a set of options.
Params:
arg – the argument to be matched
options – the set of possible options
Returns:
the first option that matches, or null if none./**
     * Looks up the first option matching the given argument within a set of options.
     * @param arg the argument to be matched
     * @param options the set of possible options
     * @return the first option that matches, or null if none.
     */
    public static Option lookup(String arg, Set<Option> options) {
        for (Option option: options) {
            if (option.matches(arg))
                return option;
        }
        return null;
    }

    
Writes the "command line help" for given kind of option to the log.
Params:
log – the log
kind –  the kind of options to select/**
     * Writes the "command line help" for given kind of option to the log.
     * @param log the log
     * @param kind  the kind of options to select
     */
    private static void showHelp(Log log, OptionKind kind) {
        Comparator<Option> comp = new Comparator<Option>() {
            final Collator collator = Collator.getInstance(Locale.US);
            { collator.setStrength(Collator.PRIMARY); }

            @Override
            public int compare(Option o1, Option o2) {
                return collator.compare(o1.primaryName, o2.primaryName);
            }
        };

        getJavaCompilerOptions()
                .stream()
                .filter(o -> o.kind == kind)
                .sorted(comp)
                .forEach(o -> {
                    o.help(log);
                });
    }

    Option(String text, String descrKey,
            OptionKind kind, OptionGroup group) {
        this(text, null, descrKey, kind, group, null, null, ArgKind.NONE);
    }

    Option(String text, String argsNameKey, String descrKey,
            OptionKind kind, OptionGroup group) {
        this(text, argsNameKey, descrKey, kind, group, null, null, ArgKind.REQUIRED);
    }

    Option(String text, String argsNameKey, String descrKey,
            OptionKind kind, OptionGroup group, ArgKind ak) {
        this(text, argsNameKey, descrKey, kind, group, null, null, ak);
    }

    Option(String text, String argsNameKey, String descrKey, OptionKind kind, OptionGroup group,
            ChoiceKind choiceKind, Set<String> choices) {
        this(text, argsNameKey, descrKey, kind, group, choiceKind, choices, ArgKind.REQUIRED);
    }

    Option(String text, String descrKey,
            OptionKind kind, OptionGroup group,
            ChoiceKind choiceKind, String... choices) {
        this(text, null, descrKey, kind, group, choiceKind,
                new LinkedHashSet<>(Arrays.asList(choices)), ArgKind.REQUIRED);
    }

    private Option(String text, String argsNameKey, String descrKey,
            OptionKind kind, OptionGroup group,
            ChoiceKind choiceKind, Set<String> choices,
            ArgKind argKind) {
        this.names = text.trim().split("\\s+");
        Assert.check(names.length >= 1);
        this.primaryName = names[0];
        this.argsNameKey = argsNameKey;
        this.descrKey = descrKey;
        this.kind = kind;
        this.group = group;
        this.choiceKind = choiceKind;
        this.choices = choices;
        this.argKind = argKind;
    }

    public String getPrimaryName() {
        return primaryName;
    }

    public OptionKind getKind() {
        return kind;
    }

    public ArgKind getArgKind() {
        return argKind;
    }

    public boolean hasArg() {
        return (argKind != ArgKind.NONE);
    }

    public boolean hasSeparateArg() {
        return getArgKind() == ArgKind.REQUIRED &&
               !primaryName.endsWith(":") && !primaryName.endsWith("=");
    }

    public boolean matches(String option) {
        for (String name: names) {
            if (matches(option, name))
                return true;
        }
        return false;
    }

    private boolean matches(String option, String name) {
        if (name.startsWith("--") && !HiddenGroup.skip(name)) {
            return option.equals(name)
                    || hasArg() && option.startsWith(name + "=");
        }

        boolean hasSuffix = (argKind == ArgKind.ADJACENT)
                || name.endsWith(":") || name.endsWith("=");

        if (!hasSuffix)
            return option.equals(name);

        if (!option.startsWith(name))
            return false;

        if (choices != null) {
            String arg = option.substring(name.length());
            if (choiceKind == ChoiceKind.ONEOF)
                return choices.contains(arg);
            else {
                for (String a: arg.split(",+")) {
                    if (!choices.contains(a))
                        return false;
                }
            }
        }

        return true;
    }

    
Handles an option. If an argument for the option is required, depending on spec of the option, it will be found as part of the current arg (following ':' or '=') or in the following argument. This is the recommended way to handle an option directly, instead of calling the underlying process methods. 
Params:
helper – a helper to provide access to the environment
arg – the arg string that identified this option
rest – the remaining strings to be analysed
Throws:
InvalidValueException – if the value of the option was invalid
Implementation Note:
The return value is the opposite of that used by process./**
     * Handles an option.
     * If an argument for the option is required, depending on spec of the option, it will be found
     * as part of the current arg (following ':' or '=') or in the following argument.
     * This is the recommended way to handle an option directly, instead of calling the underlying
     * {@link #process process} methods.
     * @param helper a helper to provide access to the environment
     * @param arg the arg string that identified this option
     * @param rest the remaining strings to be analysed
     * @throws InvalidValueException if the value of the option was invalid
     * @implNote The return value is the opposite of that used by {@link #process}.
     */
    public void handleOption(OptionHelper helper, String arg, Iterator<String> rest) throws InvalidValueException {
        if (hasArg()) {
            String option;
            String operand;
            int sep = findSeparator(arg);
            if (getArgKind() == Option.ArgKind.ADJACENT) {
                option = primaryName; // aliases not supported
                operand = arg.substring(primaryName.length());
            } else if (sep > 0) {
                option = arg.substring(0, sep);
                operand = arg.substring(sep + 1);
            } else {
                if (!rest.hasNext()) {
                    throw helper.newInvalidValueException("err.req.arg", arg);
                }
                option = arg;
                operand = rest.next();
            }
            process(helper, option, operand);
        } else {
            process(helper, arg);
        }
    }

    
Processes an option that either does not need an argument,
or which contains an argument within it, following a separator.
Params:
helper – a helper to provide access to the environment
option – the option to be processed
Throws:
InvalidValueException – if an error occurred/**
     * Processes an option that either does not need an argument,
     * or which contains an argument within it, following a separator.
     * @param helper a helper to provide access to the environment
     * @param option the option to be processed
     * @throws InvalidValueException if an error occurred
     */
    public void process(OptionHelper helper, String option) throws InvalidValueException {
        if (argKind == ArgKind.NONE) {
            process(helper, primaryName, option);
        } else {
            int sep = findSeparator(option);
            process(helper, primaryName, option.substring(sep + 1));
        }
    }

    
Processes an option by updating the environment via a helper object.
Params:
helper – a helper to provide access to the environment
option – the option to be processed
arg – the value to associate with the option, or a default value
 to be used if the option does not otherwise take an argument.
Throws:
InvalidValueException – if an error occurred/**
     * Processes an option by updating the environment via a helper object.
     * @param helper a helper to provide access to the environment
     * @param option the option to be processed
     * @param arg the value to associate with the option, or a default value
     *  to be used if the option does not otherwise take an argument.
     * @throws InvalidValueException if an error occurred
     */
    public void process(OptionHelper helper, String option, String arg) throws InvalidValueException {
        if (choices != null) {
            if (choiceKind == ChoiceKind.ONEOF) {
                // some clients like to see just one of option+choice set
                for (String s : choices)
                    helper.remove(primaryName + s);
                String opt = primaryName + arg;
                helper.put(opt, opt);
                // some clients like to see option (without trailing ":")
                // set to arg
                String nm = primaryName.substring(0, primaryName.length() - 1);
                helper.put(nm, arg);
            } else {
                // set option+word for each word in arg
                for (String a: arg.split(",+")) {
                    String opt = primaryName + a;
                    helper.put(opt, opt);
                }
            }
        }
        helper.put(primaryName, arg);
        if (group == OptionGroup.FILEMANAGER)
            helper.handleFileManagerOption(this, arg);
    }

    
Returns a pattern to analyze the value for an option.
Throws:
UnsupportedOperationException – if an option does not provide a pattern.
Returns:
the pattern/**
     * Returns a pattern to analyze the value for an option.
     * @return the pattern
     * @throws UnsupportedOperationException if an option does not provide a pattern.
     */
    public Pattern getPattern() {
        throw new UnsupportedOperationException();
    }

    
Scans a word to find the first separator character, either colon or equals.
Params:
word – the word to be scanned
Returns:
the position of the first':' or '=' character in the word,
 or -1 if none found/**
     * Scans a word to find the first separator character, either colon or equals.
     * @param word the word to be scanned
     * @return the position of the first':' or '=' character in the word,
     *  or -1 if none found
     */
    private static int findSeparator(String word) {
        for (int i = 0; i < word.length(); i++) {
            switch (word.charAt(i)) {
                case ':': case '=':
                    return i;
            }
        }
        return -1;
    }

    
The indent for the option synopsis. /** The indent for the option synopsis. */
    private static final String SMALL_INDENT = "  ";
    
The automatic indent for the description. /** The automatic indent for the description. */
    private static final String LARGE_INDENT = "        ";
    
The space allowed for the synopsis, if the description is to be shown on the same line. /** The space allowed for the synopsis, if the description is to be shown on the same line. */
    private static final int DEFAULT_SYNOPSIS_WIDTH = 28;
    
The nominal maximum line length, when seeing if text will fit on a line. /** The nominal maximum line length, when seeing if text will fit on a line. */
    private static final int DEFAULT_MAX_LINE_LENGTH = 80;
    
The format for a single-line help entry. /** The format for a single-line help entry. */
    private static final String COMPACT_FORMAT = SMALL_INDENT + "%-" + DEFAULT_SYNOPSIS_WIDTH + "s %s";

    
Writes help text for this option to the log.
Params:
log – the log/**
     * Writes help text for this option to the log.
     * @param log the log
     */
    protected void help(Log log) {
        help(log, log.localize(PrefixKind.JAVAC, descrKey));
    }

    protected void help(Log log, String descr) {
        String synopses = Arrays.stream(names)
                .map(s -> helpSynopsis(s, log))
                .collect(Collectors.joining(", "));

        // If option synopses and description fit on a single line of reasonable length,
        // display using COMPACT_FORMAT
        if (synopses.length() < DEFAULT_SYNOPSIS_WIDTH
                && !descr.contains("\n")
                && (SMALL_INDENT.length() + DEFAULT_SYNOPSIS_WIDTH + 1 + descr.length() <= DEFAULT_MAX_LINE_LENGTH)) {
            log.printRawLines(WriterKind.STDOUT, String.format(COMPACT_FORMAT, synopses, descr));
            return;
        }

        // If option synopses fit on a single line of reasonable length, show that;
        // otherwise, show 1 per line
        if (synopses.length() <= DEFAULT_MAX_LINE_LENGTH) {
            log.printRawLines(WriterKind.STDOUT, SMALL_INDENT + synopses);
        } else {
            for (String name: names) {
                log.printRawLines(WriterKind.STDOUT, SMALL_INDENT + helpSynopsis(name, log));
            }
        }

        // Finally, show the description
        log.printRawLines(WriterKind.STDOUT, LARGE_INDENT + descr.replace("\n", "\n" + LARGE_INDENT));
    }

    
Composes the initial synopsis of one of the forms for this option.
Params:
name – the name of this form of the option
log – the log used to localize the description of the arguments
Returns:
 the synopsis/**
     * Composes the initial synopsis of one of the forms for this option.
     * @param name the name of this form of the option
     * @param log the log used to localize the description of the arguments
     * @return  the synopsis
     */
    private String helpSynopsis(String name, Log log) {
        StringBuilder sb = new StringBuilder();
        sb.append(name);
        if (argsNameKey == null) {
            if (choices != null) {
                if (!name.endsWith(":"))
                    sb.append(" ");
                String sep = "{";
                for (String choice : choices) {
                    sb.append(sep);
                    sb.append(choice);
                    sep = ",";
                }
                sb.append("}");
            }
        } else {
            if (!name.matches(".*[=:]$") && argKind != ArgKind.ADJACENT)
                sb.append(" ");
            sb.append(log.localize(PrefixKind.JAVAC, argsNameKey));
        }

        return sb.toString();
    }

    // For -XpkgInfo:value
    public enum PkgInfo {
        
Always generate package-info.class for every package-info.java file.
The file may be empty if there annotations with a RetentionPolicy
of CLASS or RUNTIME.  This option may be useful in conjunction with
build systems (such as Ant) that expect javac to generate at least
one .class file for every .java file.
/**
         * Always generate package-info.class for every package-info.java file.
         * The file may be empty if there annotations with a RetentionPolicy
         * of CLASS or RUNTIME.  This option may be useful in conjunction with
         * build systems (such as Ant) that expect javac to generate at least
         * one .class file for every .java file.
         */
        ALWAYS,
        
Generate a package-info.class file if package-info.java contains
annotations. The file may be empty if all the annotations have
a RetentionPolicy of SOURCE.
This value is just for backwards compatibility with earlier behavior.
Either of the other two values are to be preferred to using this one.
/**
         * Generate a package-info.class file if package-info.java contains
         * annotations. The file may be empty if all the annotations have
         * a RetentionPolicy of SOURCE.
         * This value is just for backwards compatibility with earlier behavior.
         * Either of the other two values are to be preferred to using this one.
         */
        LEGACY,
        
Generate a package-info.class file if and only if there are annotations
in package-info.java to be written into it.
/**
         * Generate a package-info.class file if and only if there are annotations
         * in package-info.java to be written into it.
         */
        NONEMPTY;

        public static PkgInfo get(Options options) {
            String v = options.get(XPKGINFO);
            return (v == null
                    ? PkgInfo.LEGACY
                    : PkgInfo.valueOf(StringUtils.toUpperCase(v)));
        }
    }

    private static Set<String> getXLintChoices() {
        Set<String> choices = new LinkedHashSet<>();
        choices.add("all");
        for (Lint.LintCategory c : Lint.LintCategory.values()) {
            choices.add(c.option);
            choices.add("-" + c.option);
        }
        choices.add("none");
        return choices;
    }

    
Returns the set of options supported by the command line tool.
Returns:
the set of options./**
     * Returns the set of options supported by the command line tool.
     * @return the set of options.
     */
    static Set<Option> getJavaCompilerOptions() {
        return EnumSet.allOf(Option.class);
    }

    
Returns the set of options supported by the built-in file manager.
Returns:
the set of options./**
     * Returns the set of options supported by the built-in file manager.
     * @return the set of options.
     */
    public static Set<Option> getJavacFileManagerOptions() {
        return getOptions(FILEMANAGER);
    }

    
Returns the set of options supported by this implementation of the JavaCompiler API, via JavaCompiler.getTask. 
Returns:
the set of options./**
     * Returns the set of options supported by this implementation of
     * the JavaCompiler API, via {@link JavaCompiler#getTask}.
     * @return the set of options.
     */
    public static Set<Option> getJavacToolOptions() {
        return getOptions(BASIC);
    }

    private static Set<Option> getOptions(OptionGroup group) {
        return Arrays.stream(Option.values())
                .filter(o -> o.group == group)
                .collect(Collectors.toCollection(() -> EnumSet.noneOf(Option.class)));
    }

}