src/main/java/com/google/devtools/common/options/Option.java - bazel - Git at Google

 // 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 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.
  *
  * <p>The fields of this annotation have matching getters in {@link OptionDefinition}. Please do not
  * access these fields directly, but instead go through that class.
  *
  * <p>A number of checks are run on an Option's fields' values at compile time. See
  * {@link com.google.devtools.common.options.processor.OptionProcessor} for details.
  */
 @Target(ElementType.FIELD)
 @Retention(RetentionPolicy.RUNTIME)
 public @interface Option {
   /** The name of the option ("--name"). */
   String name();

   /** The single-character abbreviation of the option ("-a"). */
   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();

   /**
    * This category field is deprecated. Bazel is in the process of migrating all options to use the
    * better defined enums in OptionDocumentationCategory and the tags in the option_filters.proto
    * file. It will still be used for the usage documentation until a sufficient proportion of
    * options are using the new system.
    *
    * <p>Please leave the old category field in existing options to minimize disruption to the Help
    * output during the transition period. All uses of this field will be removed when transition is
    * complete. This category field has no effect on the other fields below, having both set is not a
    * problem.
    */
   @Deprecated
   String category() default "misc";

   /**
    * Grouping categories used for usage documentation. See the enum's definition for details.
    *
    * <p>For undocumented flags that aren't listed anywhere, set this to
    * OptionDocumentationCategory.UNDOCUMENTED.
    */
   OptionDocumentationCategory documentationCategory();

   /**
    * Tag about the intent or effect of this option. Unless this option is a no-op (and the reason
    * for this should be documented) all options should have some effect, so this needs to have at
    * least one value, and as many as apply.
    *
    * <p>No option should list NO_OP or UNKNOWN with other effects listed, but all other combinations
    * are allowed.
    */
   OptionEffectTag[] effectTags();

   /**
    * Tag about the option itself, not its effect, such as option state (experimental) or intended
    * use (a value that isn't a flag but is used internally, for example, is "internal")
    *
    * <p>If one or more of the OptionMetadataTag values apply, please include, but otherwise, this
    * list can be left blank.
    *
    * <p>Hidden or internal options must be UNDOCUMENTED (set in {@link #documentationCategory()}).
    */
   OptionMetadataTag[] metadataTags() default {};

   /**
    * 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 boolean value indicating whether the option type should be allowed to occur multiple times in
    * a single arg list.
    *
    * <p>If the option 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;

   /**
    * Additional options that need to be implicitly added for this option.
    *
    * <p>Nothing guarantees that these options are not overridden by later or higher-priority values
    * for the same options, so if this is truly a requirement, the user should check that the correct
    * set of options is set.
    *
    * <p>These requirements are added for ANY mention of this option, so may not work as intended: in
    * the case where a user is trying to explicitly turn off a flag (say, by setting a boolean flag
    * to its default value of false), the mention will still turn on its requirements. For this
    * reason, it is best not to use this feature, and rely on expansion flags if multi-flag groupings
    * are needed.
    */
   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 "";
 }
	// 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 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.
	*
	* <p>The fields of this annotation have matching getters in {@link OptionDefinition}. Please do not
	* access these fields directly, but instead go through that class.
	*
	* <p>A number of checks are run on an Option's fields' values at compile time. See
	* {@link com.google.devtools.common.options.processor.OptionProcessor} for details.
	*/
	@Target(ElementType.FIELD)
	@Retention(RetentionPolicy.RUNTIME)
	public @interface Option {
	/** The name of the option ("--name"). */
	String name();

	/** The single-character abbreviation of the option ("-a"). */
	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();

	/**
	* This category field is deprecated. Bazel is in the process of migrating all options to use the
	* better defined enums in OptionDocumentationCategory and the tags in the option_filters.proto
	* file. It will still be used for the usage documentation until a sufficient proportion of
	* options are using the new system.
	*
	* <p>Please leave the old category field in existing options to minimize disruption to the Help
	* output during the transition period. All uses of this field will be removed when transition is
	* complete. This category field has no effect on the other fields below, having both set is not a
	* problem.
	*/
	@Deprecated
	String category() default "misc";

	/**
	* Grouping categories used for usage documentation. See the enum's definition for details.
	*
	* <p>For undocumented flags that aren't listed anywhere, set this to
	* OptionDocumentationCategory.UNDOCUMENTED.
	*/
	OptionDocumentationCategory documentationCategory();

	/**
	* Tag about the intent or effect of this option. Unless this option is a no-op (and the reason
	* for this should be documented) all options should have some effect, so this needs to have at
	* least one value, and as many as apply.
	*
	* <p>No option should list NO_OP or UNKNOWN with other effects listed, but all other combinations
	* are allowed.
	*/
	OptionEffectTag[] effectTags();

	/**
	* Tag about the option itself, not its effect, such as option state (experimental) or intended
	* use (a value that isn't a flag but is used internally, for example, is "internal")
	*
	* <p>If one or more of the OptionMetadataTag values apply, please include, but otherwise, this
	* list can be left blank.
	*
	* <p>Hidden or internal options must be UNDOCUMENTED (set in {@link #documentationCategory()}).
	*/
	OptionMetadataTag[] metadataTags() default {};

	/**
	* 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 boolean value indicating whether the option type should be allowed to occur multiple times in
	* a single arg list.
	*
	* <p>If the option 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;

	/**
	* Additional options that need to be implicitly added for this option.
	*
	* <p>Nothing guarantees that these options are not overridden by later or higher-priority values
	* for the same options, so if this is truly a requirement, the user should check that the correct
	* set of options is set.
	*
	* <p>These requirements are added for ANY mention of this option, so may not work as intended: in
	* the case where a user is trying to explicitly turn off a flag (say, by setting a boolean flag
	* to its default value of false), the mention will still turn on its requirements. For this
	* reason, it is best not to use this feature, and rely on expansion flags if multi-flag groupings
	* are needed.
	*/
	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 "";
	}