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442 lines
18 KiB
442 lines
18 KiB
/*
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* Copyright (c) 2005, 2013, Oracle and/or its affiliates. All rights reserved.
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* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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*
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*
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*
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*
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*/
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package javax.annotation.processing;
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import java.util.Set;
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import javax.lang.model.util.Elements;
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import javax.lang.model.AnnotatedConstruct;
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import javax.lang.model.element.*;
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import javax.lang.model.SourceVersion;
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/**
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* The interface for an annotation processor.
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*
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* <p>Annotation processing happens in a sequence of {@linkplain
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* javax.annotation.processing.RoundEnvironment rounds}. On each
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* round, a processor may be asked to {@linkplain #process process} a
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* subset of the annotations found on the source and class files
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* produced by a prior round. The inputs to the first round of
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* processing are the initial inputs to a run of the tool; these
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* initial inputs can be regarded as the output of a virtual zeroth
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* round of processing. If a processor was asked to process on a
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* given round, it will be asked to process on subsequent rounds,
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* including the last round, even if there are no annotations for it
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* to process. The tool infrastructure may also ask a processor to
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* process files generated implicitly by the tool's operation.
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*
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* <p> Each implementation of a {@code Processor} must provide a
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* public no-argument constructor to be used by tools to instantiate
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* the processor. The tool infrastructure will interact with classes
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* implementing this interface as follows:
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*
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* <ol>
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*
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* <li>If an existing {@code Processor} object is not being used, to
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* create an instance of a processor the tool calls the no-arg
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* constructor of the processor class.
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*
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* <li>Next, the tool calls the {@link #init init} method with
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* an appropriate {@code ProcessingEnvironment}.
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*
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* <li>Afterwards, the tool calls {@link #getSupportedAnnotationTypes
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* getSupportedAnnotationTypes}, {@link #getSupportedOptions
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* getSupportedOptions}, and {@link #getSupportedSourceVersion
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* getSupportedSourceVersion}. These methods are only called once per
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* run, not on each round.
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*
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* <li>As appropriate, the tool calls the {@link #process process}
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* method on the {@code Processor} object; a new {@code Processor}
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* object is <em>not</em> created for each round.
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*
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* </ol>
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*
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* If a processor object is created and used without the above
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* protocol being followed, then the processor's behavior is not
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* defined by this interface specification.
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*
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* <p> The tool uses a <i>discovery process</i> to find annotation
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* processors and decide whether or not they should be run. By
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* configuring the tool, the set of potential processors can be
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* controlled. For example, for a {@link javax.tools.JavaCompiler
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* JavaCompiler} the list of candidate processors to run can be
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* {@linkplain javax.tools.JavaCompiler.CompilationTask#setProcessors
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* set directly} or controlled by a {@linkplain
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* javax.tools.StandardLocation#ANNOTATION_PROCESSOR_PATH search path}
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* used for a {@linkplain java.util.ServiceLoader service-style}
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* lookup. Other tool implementations may have different
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* configuration mechanisms, such as command line options; for
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* details, refer to the particular tool's documentation. Which
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* processors the tool asks to {@linkplain #process run} is a function
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* of the types of the annotations <em>{@linkplain AnnotatedConstruct present}</em>
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* on the {@linkplain
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* RoundEnvironment#getRootElements root elements}, what {@linkplain
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* #getSupportedAnnotationTypes annotation types a processor
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* supports}, and whether or not a processor {@linkplain #process
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* claims the annotation types it processes}. A processor will be asked to
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* process a subset of the annotation types it supports, possibly an
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* empty set.
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*
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* For a given round, the tool computes the set of annotation types
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* that are present on the elements enclosed within the root elements.
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* If there is at least one annotation type present, then as
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* processors claim annotation types, they are removed from the set of
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* unmatched annotation types. When the set is empty or no more
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* processors are available, the round has run to completion. If
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* there are no annotation types present, annotation processing still
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* occurs but only <i>universal processors</i> which support
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* processing all annotation types, {@code "*"}, can claim the (empty)
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* set of annotation types.
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*
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* <p>An annotation type is considered present if there is at least
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* one annotation of that type present on an element enclosed within
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* the root elements of a round. For this purpose, a type parameter is
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* considered to be enclosed by its {@linkplain
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* TypeParameterElement#getGenericElement generic
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* element}. Annotations on {@linkplain
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* java.lang.annotation.ElementType#TYPE_USE type uses}, as opposed to
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* annotations on elements, are ignored when computing whether or not
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* an annotation type is present.
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*
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* <p>An annotation is present if it meets the definition of being
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* present given in {@link AnnotatedConstruct}. In brief, an
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* annotation is considered present for the purposes of discovery if
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* it is directly present or present via inheritance. An annotation is
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* <em>not</em> considered present by virtue of being wrapped by a
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* container annotation. Operationally, this is equivalent to an
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* annotation being present on an element if and only if it would be
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* included in the results of {@link
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* Elements#getAllAnnotationMirrors(Element)} called on that element. Since
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* annotations inside container annotations are not considered
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* present, to properly process {@linkplain
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* java.lang.annotation.Repeatable repeatable annotation types},
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* processors are advised to include both the repeatable annotation
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* type and its containing annotation type in the set of {@linkplain
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* #getSupportedAnnotationTypes() supported annotation types} of a
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* processor.
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*
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* <p>Note that if a processor supports {@code "*"} and returns {@code
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* true}, all annotations are claimed. Therefore, a universal
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* processor being used to, for example, implement additional validity
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* checks should return {@code false} so as to not prevent other such
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* checkers from being able to run.
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*
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* <p>If a processor throws an uncaught exception, the tool may cease
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* other active annotation processors. If a processor raises an
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* error, the current round will run to completion and the subsequent
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* round will indicate an {@linkplain RoundEnvironment#errorRaised
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* error was raised}. Since annotation processors are run in a
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* cooperative environment, a processor should throw an uncaught
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* exception only in situations where no error recovery or reporting
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* is feasible.
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*
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* <p>The tool environment is not required to support annotation
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* processors that access environmental resources, either {@linkplain
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* RoundEnvironment per round} or {@linkplain ProcessingEnvironment
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* cross-round}, in a multi-threaded fashion.
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*
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* <p>If the methods that return configuration information about the
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* annotation processor return {@code null}, return other invalid
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* input, or throw an exception, the tool infrastructure must treat
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* this as an error condition.
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*
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* <p>To be robust when running in different tool implementations, an
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* annotation processor should have the following properties:
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*
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* <ol>
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*
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* <li>The result of processing a given input is not a function of the presence or absence
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* of other inputs (orthogonality).
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*
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* <li>Processing the same input produces the same output (consistency).
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*
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* <li>Processing input <i>A</i> followed by processing input <i>B</i>
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* is equivalent to processing <i>B</i> then <i>A</i>
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* (commutativity)
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*
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* <li>Processing an input does not rely on the presence of the output
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* of other annotation processors (independence)
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*
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* </ol>
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*
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* <p>The {@link Filer} interface discusses restrictions on how
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* processors can operate on files.
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*
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* <p>Note that implementors of this interface may find it convenient
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* to extend {@link AbstractProcessor} rather than implementing this
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* interface directly.
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*
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* @author Joseph D. Darcy
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* @author Scott Seligman
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* @author Peter von der Ahé
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* @since 1.6
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*/
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public interface Processor {
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/**
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* Returns the options recognized by this processor. An
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* implementation of the processing tool must provide a way to
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* pass processor-specific options distinctly from options passed
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* to the tool itself, see {@link ProcessingEnvironment#getOptions
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* getOptions}.
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*
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* <p>Each string returned in the set must be a period separated
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* sequence of {@linkplain
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* javax.lang.model.SourceVersion#isIdentifier identifiers}:
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*
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* <blockquote>
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* <dl>
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* <dt><i>SupportedOptionString:</i>
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* <dd><i>Identifiers</i>
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*
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* <dt><i>Identifiers:</i>
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* <dd> <i>Identifier</i>
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* <dd> <i>Identifier</i> {@code .} <i>Identifiers</i>
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*
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* <dt><i>Identifier:</i>
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* <dd>Syntactic identifier, including keywords and literals
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* </dl>
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* </blockquote>
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*
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* <p> A tool might use this information to determine if any
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* options provided by a user are unrecognized by any processor,
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* in which case it may wish to report a warning.
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*
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* @return the options recognized by this processor or an
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* empty collection if none
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* @see javax.annotation.processing.SupportedOptions
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*/
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Set<String> getSupportedOptions();
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/**
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* Returns the names of the annotation types supported by this
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* processor. An element of the result may be the canonical
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* (fully qualified) name of a supported annotation type.
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* Alternately it may be of the form "<tt><i>name</i>.*</tt>"
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* representing the set of all annotation types with canonical
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* names beginning with "<tt><i>name.</i></tt>". Finally, {@code
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* "*"} by itself represents the set of all annotation types,
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* including the empty set. Note that a processor should not
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* claim {@code "*"} unless it is actually processing all files;
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* claiming unnecessary annotations may cause a performance
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* slowdown in some environments.
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*
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* <p>Each string returned in the set must be accepted by the
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* following grammar:
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*
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* <blockquote>
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* <dl>
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* <dt><i>SupportedAnnotationTypeString:</i>
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* <dd><i>TypeName</i> <i>DotStar</i><sub><i>opt</i></sub>
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* <dd><tt>*</tt>
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*
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* <dt><i>DotStar:</i>
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* <dd><tt>.</tt> <tt>*</tt>
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* </dl>
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* </blockquote>
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*
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* where <i>TypeName</i> is as defined in
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* <cite>The Java™ Language Specification</cite>.
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*
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* @return the names of the annotation types supported by this processor
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* @see javax.annotation.processing.SupportedAnnotationTypes
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* @jls 3.8 Identifiers
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* @jls 6.5.5 Meaning of Type Names
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*/
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Set<String> getSupportedAnnotationTypes();
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/**
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* Returns the latest source version supported by this annotation
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* processor.
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*
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* @return the latest source version supported by this annotation
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* processor.
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* @see javax.annotation.processing.SupportedSourceVersion
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* @see ProcessingEnvironment#getSourceVersion
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*/
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SourceVersion getSupportedSourceVersion();
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/**
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* Initializes the processor with the processing environment.
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*
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* @param processingEnv environment for facilities the tool framework
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* provides to the processor
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*/
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void init(ProcessingEnvironment processingEnv);
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/**
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* Processes a set of annotation types on type elements
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* originating from the prior round and returns whether or not
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* these annotation types are claimed by this processor. If {@code
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* true} is returned, the annotation types are claimed and subsequent
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* processors will not be asked to process them; if {@code false}
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* is returned, the annotation types are unclaimed and subsequent
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* processors may be asked to process them. A processor may
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* always return the same boolean value or may vary the result
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* based on chosen criteria.
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*
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* <p>The input set will be empty if the processor supports {@code
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* "*"} and the root elements have no annotations. A {@code
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* Processor} must gracefully handle an empty set of annotations.
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*
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* @param annotations the annotation types requested to be processed
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* @param roundEnv environment for information about the current and prior round
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* @return whether or not the set of annotation types are claimed by this processor
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*/
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boolean process(Set<? extends TypeElement> annotations,
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RoundEnvironment roundEnv);
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/**
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* Returns to the tool infrastructure an iterable of suggested
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* completions to an annotation. Since completions are being asked
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* for, the information provided about the annotation may be
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* incomplete, as if for a source code fragment. A processor may
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* return an empty iterable. Annotation processors should focus
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* their efforts on providing completions for annotation members
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* with additional validity constraints known to the processor, for
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* example an {@code int} member whose value should lie between 1
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* and 10 or a string member that should be recognized by a known
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* grammar, such as a regular expression or a URL.
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*
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* <p>Since incomplete programs are being modeled, some of the
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* parameters may only have partial information or may be {@code
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* null}. At least one of {@code element} and {@code userText}
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* must be non-{@code null}. If {@code element} is non-{@code
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* null}, {@code annotation} and {@code member} may be {@code
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* null}. Processors may not throw a {@code NullPointerException}
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* if some parameters are {@code null}; if a processor has no
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* completions to offer based on the provided information, an
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* empty iterable can be returned. The processor may also return
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* a single completion with an empty value string and a message
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* describing why there are no completions.
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*
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* <p>Completions are informative and may reflect additional
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* validity checks performed by annotation processors. For
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* example, consider the simple annotation:
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*
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* <blockquote>
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* <pre>
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* @MersennePrime {
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* int value();
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* }
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* </pre>
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* </blockquote>
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*
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* (A Mersenne prime is prime number of the form
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* 2<sup><i>n</i></sup> - 1.) Given an {@code AnnotationMirror}
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* for this annotation type, a list of all such primes in the
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* {@code int} range could be returned without examining any other
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* arguments to {@code getCompletions}:
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*
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* <blockquote>
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* <pre>
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* import static javax.annotation.processing.Completions.*;
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* ...
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* return Arrays.asList({@link Completions#of(String) of}("3"),
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* of("7"),
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* of("31"),
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* of("127"),
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* of("8191"),
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* of("131071"),
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* of("524287"),
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* of("2147483647"));
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* </pre>
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* </blockquote>
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*
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* A more informative set of completions would include the number
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* of each prime:
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*
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* <blockquote>
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* <pre>
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* return Arrays.asList({@link Completions#of(String, String) of}("3", "M2"),
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* of("7", "M3"),
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* of("31", "M5"),
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* of("127", "M7"),
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* of("8191", "M13"),
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* of("131071", "M17"),
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* of("524287", "M19"),
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* of("2147483647", "M31"));
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* </pre>
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* </blockquote>
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*
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* However, if the {@code userText} is available, it can be checked
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* to see if only a subset of the Mersenne primes are valid. For
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* example, if the user has typed
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*
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* <blockquote>
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* <code>
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* @MersennePrime(1
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* </code>
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* </blockquote>
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*
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* the value of {@code userText} will be {@code "1"}; and only
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* two of the primes are possible completions:
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*
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* <blockquote>
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* <pre>
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* return Arrays.asList(of("127", "M7"),
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* of("131071", "M17"));
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* </pre>
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* </blockquote>
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*
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* Sometimes no valid completion is possible. For example, there
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* is no in-range Mersenne prime starting with 9:
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*
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* <blockquote>
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* <code>
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* @MersennePrime(9
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* </code>
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* </blockquote>
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*
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* An appropriate response in this case is to either return an
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* empty list of completions,
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*
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* <blockquote>
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* <pre>
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* return Collections.emptyList();
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* </pre>
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* </blockquote>
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*
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* or a single empty completion with a helpful message
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*
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* <blockquote>
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* <pre>
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* return Arrays.asList(of("", "No in-range Mersenne primes start with 9"));
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* </pre>
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* </blockquote>
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*
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* @param element the element being annotated
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* @param annotation the (perhaps partial) annotation being
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* applied to the element
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* @param member the annotation member to return possible completions for
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* @param userText source code text to be completed
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*
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* @return suggested completions to the annotation
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*/
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Iterable<? extends Completion> getCompletions(Element element,
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AnnotationMirror annotation,
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ExecutableElement member,
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String userText);
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}
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