// Copyright 2014 The Bazel Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package com.google.devtools.common.options;
import com.google.devtools.common.options.OptionsParser.OptionUsageRestrictions;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* An interface for annotating fields in classes (derived from OptionsBase)
* that are options.
*/
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface Option {
/**
* The name of the option ("--name").
*/
String name();
/**
* The single-character abbreviation of the option ("-abbrev").
*/
char abbrev() default '\0';
/**
* A help string for the usage information.
*/
String help() default "";
/**
* A short text string to describe the type of the expected value. E.g., <code>regex</code>. This
* is ignored for boolean, tristate, boolean_or_enum, and void options.
*/
String valueHelp() default "";
/**
* The default value for the option. This method should only be invoked directly by the parser
* implementation. Any access to default values should go via the parser to allow for application
* specific defaults.
*
* <p>There are two reasons this is a string. Firstly, it ensures that explicitly specifying this
* option at its default value (as printed in the usage message) has the same behavior as not
* specifying the option at all; this would be very hard to achieve if the default value was an
* instance of type T, since we'd need to ensure that {@link #toString()} and {@link #converter}
* were dual to each other. The second reason is more mundane but also more restrictive:
* annotation values must be compile-time constants.
*
* <p>If an option's defaultValue() is the string "null", the option's converter will not be
* invoked to interpret it; a null reference will be used instead. (It would be nice if
* defaultValue could simply return null, but bizarrely, the Java Language Specification does not
* consider null to be a compile-time constant.) This special interpretation of the string "null"
* is only applicable when computing the default value; if specified on the command-line, this
* string will have its usual literal meaning.
*
* <p>The default value for flags that set allowMultiple is always the empty list and its default
* value is ignored.
*/
String defaultValue();
/**
* A string describing the role of the option. Some existing categories are "input," "output,"
* "config," "semantics," and "strategy," among others.
*
* <p>The category of options that this belongs to dictates how options are grouped by {@link
* OptionsParser#describeOptions}, for the usage documentation.
*
* <p>For undocumented flags that aren't listed anywhere, this is currently a no-op. Feel free to
* set the value that it would have if it were documented, which might be helpful if a flag is
* part of an experimental feature that might become documented in the future, or just leave it
* unset as the default.
*
* <p>For hidden or internal options, use the category field only if it is helpful for yourself or
* other Bazel developers.
*/
String category() default "misc";
/**
* Options have multiple uses, some flags, some not. For user-visible flags, they are
* "documented," but otherwise, there are 3 types of undocumented options.
*
* <ul>
* <li>{@code UNDOCUMENTED}: undocumented but user-usable flags. These options are useful for
* (some subset of) users, but not meant to be publicly advertised. For example,
* experimental options which are only meant to be used by specific testers or team members.
* These options will not be listed in the usage info displayed for the {@code --help}
* option. They are otherwise normal - {@link
* OptionsParser.UnparsedOptionValueDescription#isHidden()} returns {@code false} for them,
* and they can be parsed normally from the command line or RC files.
* <li>{@code HIDDEN}: flags which users should not pass or know about, but which are used by
* the program (e.g., communication between a command-line client and a backend server).
* Like {@code "undocumented"} options, these options will not be listed in the usage info
* displayed for the {@code --help} option. However, in addition to this, calling {@link
* OptionsParser.UnparsedOptionValueDescription#isHidden()} on these options will return
* {@code true} - for example, this can be checked to strip out such secret options when
* logging or otherwise reporting the command line to the user. This category does not
* affect the option in any other way; it can still be parsed normally from the command line
* or an RC file.
* <li>{@code INTERNAL}: these are not flags, but options which are purely for internal use
* within the JVM, and should never be shown to the user, nor be parsed by the options
* parser. Like {@code "hidden"} options, these options will not be listed in the usage info
* displayed for the --help option, and are considered hidden by {@link
* OptionsParser.UnparsedOptionValueDescription#isHidden()}. Unlike those, this type of
* option cannot be parsed by any call to {@link OptionsParser#parse} - it will be treated
* as if it was not defined.
* </ul>
*/
OptionUsageRestrictions optionUsageRestrictions() default OptionUsageRestrictions.DOCUMENTED;
/**
* The converter that we'll use to convert the string representation of this option's value into
* an object or a simple type. The default is to use the builtin converters ({@link
* Converters#DEFAULT_CONVERTERS}). Custom converters must implement the {@link Converter}
* interface.
*/
@SuppressWarnings({"unchecked", "rawtypes"})
// Can't figure out how to coerce Converter.class into Class<? extends Converter<?>>
Class<? extends Converter> converter() default Converter.class;
/**
* A flag indicating whether the option type should be allowed to occur multiple times in a single
* option list.
*
* <p>If the command can occur multiple times, then the attribute value <em>must</em> be a list
* type {@code List<T>}, and the result type of the converter for this option must either match
* the parameter {@code T} or {@code List<T>}. In the latter case the individual lists are
* concatenated to form the full options value.
*
* <p>The {@link #defaultValue()} field of the annotation is ignored for repeatable flags and the
* default value will be the empty list.
*/
boolean allowMultiple() default false;
/**
* If the option is actually an abbreviation for other options, this field will contain the
* strings to expand this option into. The original option is dropped and the replacement used in
* its stead. It is recommended that such an option be of type {@link Void}.
*
* <p>An expanded option overrides previously specified options of the same name, even if it is
* explicitly specified. This is the original behavior and can be surprising if the user is not
* aware of it, which has led to several requests to change this behavior. This was discussed in
* the blaze team and it was decided that it is not a strong enough case to change the behavior.
*/
String[] expansion() default {};
/**
* A mechanism for specifying an expansion that is a function of the parser's {@link
* IsolatedOptionsData}. This can be used to create an option that expands to different strings
* depending on what other options the parser knows about.
*
* <p>If provided (i.e. not {@link ExpansionFunction}{@code .class}), the {@code expansion} field
* must not be set. The mechanism of expansion is as if the {@code expansion} field were set to
* whatever the return value of this function is.
*/
Class<? extends ExpansionFunction> expansionFunction() default ExpansionFunction.class;
/**
* If the option requires that additional options be implicitly appended, this field will contain
* the additional options. Implicit dependencies are parsed at the end of each {@link
* OptionsParser#parse} invocation, and override options specified in the same call. However, they
* can be overridden by options specified in a later call or by options with a higher priority.
*
* @see OptionPriority
*/
String[] implicitRequirements() default {};
/**
* If this field is a non-empty string, the option is deprecated, and a deprecation warning is
* added to the list of warnings when such an option is used.
*/
String deprecationWarning() default "";
/**
* The old name for this option. If an option has a name "foo" and an old name "bar", --foo=baz
* and --bar=baz will be equivalent. If the old name is used, a warning will be printed indicating
* that the old name is deprecated and the new name should be used.
*/
String oldName() default "";
/**
* Indicates that this option is a wrapper for other options, and will be unwrapped when parsed.
* For example, if foo is a wrapper option, then "--foo=--bar=baz" will be parsed as the flag
* "--bar=baz" (rather than --foo taking the value "--bar=baz"). A wrapper option should have the
* type {@link Void} (if it is something other than Void, the parser will not assign a value to
* it). The {@link Option#implicitRequirements()}, {@link Option#expansion()}, {@link
* Option#converter()} attributes will not be processed. Wrapper options are implicitly repeatable
* (i.e., as though {@link Option#allowMultiple()} is true regardless of its value in the
* annotation).
*
* <p>Wrapper options are provided only for transitioning flags which appear as values to other
* flags, to top-level flags. Wrapper options should not be used in Invocation Policy, as
* expansion flags to other flags, or as implicit requirements to other flags. Use the inner flags
* instead.
*/
boolean wrapperOption() default false;
}