129 lines
4.5 KiB
Java
129 lines
4.5 KiB
Java
// Copyright 2014 The Bazel Authors. All rights reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package com.google.devtools.common.options;
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import com.google.common.escape.CharEscaperBuilder;
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import com.google.common.escape.Escaper;
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import java.lang.reflect.Field;
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import java.util.LinkedHashMap;
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import java.util.List;
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import java.util.Map;
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/**
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* Base class for all options classes. Extend this class, adding public instance fields annotated
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* with {@link Option}. Then you can create instances either programmatically:
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*
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* <pre>
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* X x = Options.getDefaults(X.class);
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* x.host = "localhost";
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* x.port = 80;
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* </pre>
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*
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* or from an array of command-line arguments:
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*
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* <pre>
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* OptionsParser parser = OptionsParser.newOptionsParser(X.class);
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* parser.parse("--host", "localhost", "--port", "80");
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* X x = parser.getOptions(X.class);
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* </pre>
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*
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* <p>Subclasses of {@code OptionsBase} <i>must</i> be constructed reflectively, i.e. using not
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* {@code new MyOptions()}, but one of the above methods instead. (Direct construction creates an
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* empty instance, not containing default values. This leads to surprising behavior and often {@code
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* NullPointerExceptions}, etc.)
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*/
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public abstract class OptionsBase {
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private static final Escaper ESCAPER = new CharEscaperBuilder()
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.addEscape('\\', "\\\\").addEscape('"', "\\\"").toEscaper();
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/**
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* Subclasses must provide a default (no argument) constructor.
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*/
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protected OptionsBase() {
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// There used to be a sanity check here that checks the stack trace of this constructor
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// invocation; unfortunately, that makes the options construction about 10x slower. So be
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// careful with how you construct options classes.
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}
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/**
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* Returns a mapping from option names to values, for each option on this object, including
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* inherited ones. The mapping is a copy, so subsequent mutations to it or to this object are
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* independent. Entries are sorted alphabetically.
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*/
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public final <O extends OptionsBase> Map<String, Object> asMap() {
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// Generic O is needed to tell the type system that the toMap() call is safe.
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// The casts are safe because "this" is an instance of "getClass()"
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// which subclasses OptionsBase.
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@SuppressWarnings("unchecked")
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O castThis = (O) this;
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@SuppressWarnings("unchecked")
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Class<O> castClass = (Class<O>) getClass();
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Map<String, Object> map = new LinkedHashMap<>();
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for (Map.Entry<Field, Object> entry : OptionsParser.toMap(castClass, castThis).entrySet()) {
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OptionDefinition optionDefinition = OptionDefinition.extractOptionDefinition(entry.getKey());
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map.put(optionDefinition.getOptionName(), entry.getValue());
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}
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return map;
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}
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@Override
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public final String toString() {
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return getClass().getName() + asMap();
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}
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/**
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* Returns a string that uniquely identifies the options. This value is
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* intended for analysis caching.
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*/
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public final String cacheKey() {
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StringBuilder result = new StringBuilder(getClass().getName()).append("{");
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for (Map.Entry<String, Object> entry : asMap().entrySet()) {
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result.append(entry.getKey()).append("=");
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Object value = entry.getValue();
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// This special case is needed because List.toString() prints the same
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// ("[]") for an empty list and for a list with a single empty string.
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if (value instanceof List<?> && ((List<?>) value).isEmpty()) {
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result.append("EMPTY");
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} else if (value == null) {
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result.append("NULL");
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} else {
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result
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.append('"')
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.append(ESCAPER.escape(value.toString()))
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.append('"');
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}
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result.append(", ");
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}
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return result.append("}").toString();
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}
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@Override
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public final boolean equals(Object that) {
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return that != null &&
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this.getClass() == that.getClass() &&
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this.asMap().equals(((OptionsBase) that).asMap());
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}
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@Override
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public final int hashCode() {
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return this.getClass().hashCode() + asMap().hashCode();
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}
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}
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