# Java Completion Proposal Computer

###### Identifier:

org.eclipse.jdt.ui.javaCompletionProposalComputer

###### Since:

3.2

###### Description:

This extension point allows to contribute Java completion proposal computers to participate in the content assist process of the Java editor.

This extension point supports the `<enablement>` element. The default variable is the containing `org.eclipse.jdt.core.IJavaProject`.
Defined variables for `<with>` expressions are:

- "project": type `org.eclipse.jdt.core.IJavaProject`; the current project (same as the default variable)

###### Configuration Markup:

<!ELEMENT extension (javaCompletionProposalComputer | proposalCategory)>

<!ATTLIST extension

point CDATA #REQUIRED

id CDATA #REQUIRED

name CDATA #IMPLIED>

- point - a fully qualified identifier of the target extension point
- id - the proposal category id
- name - an optional name of the extension instance

<!ELEMENT javaCompletionProposalComputer (partition)*>

<!ATTLIST javaCompletionProposalComputer

class CDATA #REQUIRED

activate (true | false) "false"

categoryId IDREF "org.eclipse.jdt.ui.defaultProposalCategory"

needsSortingAfterFiltering (true | false) "false"

requiresUIThread (true | false) "true">

A proposal computer contribution. If no partition types are specified, the computer is added to all partition types.

- class - the name of the class that implements the contributed computer. The class must be public and implement `org.eclipse.jdt.ui.text.java.IJavaCompletionProposalComputer` and must have a public 0-argument constructor.
- activate - if the attribute is set to "true" it will force this plug-in to be loaded on content assist invocation. @since 3.8.1 activation will not happen if the enablement expression for the category is not met.
- categoryId - the id of a `proposalCategory`
- needsSortingAfterFiltering - if the attribute is set to "true" it forces the content assist processor to resort the list of proposals every time a new token is entered or removed to the completion prefix. @since 3.8
- requiresUIThread - Whether the given extension requires to run in UI Thread. If extension doesn't require to run in UI Thread to work, this should be set to "false". It's recommended for an extension to not require UI Thread and have this set to "false" in order to improve performance. If "false", the completion proposal may run in a non-UI Thread, in parallel with other completion computers. If "true", the completion proposal will run in UI Thread, freezing the UI while computing, and in sequence with other completion computers that also require UI Thread. @since 3.16

<!ELEMENT partition EMPTY>

<!ATTLIST partition

type (__dftl_partition_content_type|__java_singleline_comment|__java_multiline_comment|__java_javadoc|__java_string|__java_character) >

- type - a Java partition type for which the specified computer can provide completion proposals. See `IDocument.DEFAULT_CONTENT_TYPE` and `IJavaPartitions` for valid values.

<!ELEMENT proposalCategory (enablement?)>

<!ATTLIST proposalCategory

icon CDATA #IMPLIED>

A proposal category contribution defines categories of proposals used to group them in the UI.

- icon - an optional icon of the category, which can be displayed in the user preferences

<!ELEMENT enablement (not , and , or , instanceof , test , systemTest , equals , count , with , resolve , adapt , iterate , reference)*>

A generic root element. The element can be used inside an extension point to define its enablement expression. The children of an enablement expression are combined using the "and" operator.

<!ELEMENT not (not | and | or | instanceof | test | systemTest | equals | count | with | resolve | adapt | iterate | reference)>

This element represents a NOT operation on the result of evaluating its sub-element expression.

<!ELEMENT and (not , and , or , instanceof , test , systemTest , equals , count , with , resolve , adapt , iterate , reference)*>

This element represents an AND operation on the result of evaluating all its sub-elements expressions.

<!ELEMENT or (not , and , or , instanceof , test , systemTest , equals , count , with , resolve , adapt , iterate , reference)*>

This element represent an OR operation on the result of evaluating all its sub-element expressions.

<!ELEMENT instanceof EMPTY>

<!ATTLIST instanceof

value CDATA #REQUIRED>

This element is used to perform an instanceof check of the object in focus. The expression returns EvaluationResult.TRUE if the object's type is a sub type of the type specified by the attribute value. Otherwise EvaluationResult.FALSE is returned.

- value - a fully qualified name of a class or interface.

<!ELEMENT test EMPTY>

<!ATTLIST test

property CDATA #REQUIRED

args CDATA #IMPLIED

value CDATA #IMPLIED

forcePluginActivation (true | false) >

This element is used to evaluate the property state of the object in focus. The set of testable properties can be extended using the org.eclipse.core.expressions.propertyTesters extension point. The test expression returns EvaluationResult.NOT_LOADED if the property tester doing the actual testing isn't loaded yet and the attribute forcePluginActivation is set to false. If forcePluginActivation is set to true and the evaluation context used to evaluate this expression support plug-in activation then evaluating the property will result in activating the plug-in defining the tester.

- property - the name of an object's property to test.
- args - additional arguments passed to the property tester. Multiple arguments are separated by commas. Each individual argument is converted into a Java base type using the same rules as defined for the value attribute of the test expression.
- value - the expected value of the property. Can be omitted if the property is a boolean property (value will be Boolean.TRUE). The test expression is supposed to return EvaluationResult.TRUE if the property matches the value and EvaluationResult.FALSE otherwise. The value attribute is converted into a Java base type using the following rules:
  - the string "true" is converted into Boolean.TRUE
  - the string "false" is converted into Boolean.FALSE
  - if the string contains a dot then the interpreter tries to convert the value into a Float object. If this fails the string is treated as a java.lang.String
  - if the string only consists of numbers then the interpreter converts the value into an Integer object.
  - in all other cases the string is treated as a java.lang.String
  - the conversion of the string into a Boolean, Float, or Integer can be suppressed by surrounding the string with single quotes. For example, the attribute value="'true'" is converted into the string "true"
- forcePluginActivation - a flag indicating whether the plug-in contributing the property tester should be loaded if necessary. As such, this flag should be used judiciously, in order to avoid unnecessary plug-in activations. Most clients should avoid setting this flag to true. This flag is only honored if the evaluation context used to evaluate this expression allows plug-in activation. Otherwise the flag is ignored and no plug-in loading takes place.

<!ELEMENT systemTest EMPTY>

<!ATTLIST systemTest

property CDATA #REQUIRED

value CDATA #REQUIRED>

Tests a system property by calling the System.getProperty method and compares the result with the value specified through the value attribute.

- property - the name of an system property to test.
- value - the expected value of the property. The value is interpreted as a string value.

<!ELEMENT equals EMPTY>

<!ATTLIST equals

value CDATA #REQUIRED>

This element is used to perform an equals check of the object in focus. The expression returns EvaluationResult.TRUE if the object is equal to the value provided by the attribute value. Otherwise EvaluationResult.FALSE is returned.

- value - the expected value. The value provided as a string is converted into a Java base type using the same rules as for the value attribute of the test expression.

<!ELEMENT count EMPTY>

<!ATTLIST count

value CDATA #REQUIRED>

This element is used to test the number of elements in a collection.

- value - an expression to specify the number of elements in a list. Following wildcard characters can be used:
  *
    any number of elements
  ?
    no elements or one element
  +
    one or more elements
  !
    no elements
  -N)
    less than N elements
  (N-
    greater than N elements
  integer value
    the list must contain the exact number of elements

<!ELEMENT with (not , and , or , instanceof , test , systemTest , equals , count , with , resolve , adapt , iterate , reference)*>

<!ATTLIST with

variable CDATA #REQUIRED>

This element changes the object to be inspected for all its child element to the object referenced by the given variable. If the variable can not be resolved then the expression will throw an ExpressionException when evaluating it. The children of a with expression are combined using the "and" operator.

- variable - the name of the variable to be used for further inspection. It is up to the evaluator of an extension point to provide the variable in the variable pool.

<!ELEMENT resolve (not , and , or , instanceof , test , systemTest , equals , count , with , resolve , adapt , iterate , reference)*>

<!ATTLIST resolve

variable CDATA #REQUIRED

args CDATA #IMPLIED>

This element changes the object to be inspected for all its child element to the object referenced by the given variable. If the variable can not be resolved then the expression will throw an ExpressionException when evaluating it. The children of a resolve expression are combined using the "and" operator.

- variable - the name of the variable to be resolved. This variable is then used as the object in focus for child element evaluation. It is up to the evaluator of an extension point to provide a corresponding variable resolver (see IVariableResolver) through the evaluation context passed to the root expression element when evaluating the expression.
- args - additional arguments passed to the variable resolver. Multiple arguments are separated by commas. Each individual argument is converted into a Java base type using the same rules as defined for the value attribute of the test expression.

<!ELEMENT adapt (not , and , or , instanceof , test , systemTest , equals , count , with , resolve , adapt , iterate , reference)*>

<!ATTLIST adapt

type CDATA #REQUIRED>

This element is used to adapt the object in focus to the type specified by the attribute type. The expression returns EvaluationResult.NOT_LOADED if either the adapter or the type referenced isn't loaded yet. It throws an ExpressionException during evaluation if the type name doesn't exist at all. The children of an adapt expression are combined using the "and" operator.

- type - the type to which the object in focus is to be adapted.

<!ELEMENT iterate (not , and , or , instanceof , test , systemTest , equals , count , with , resolve , adapt , iterate , reference)*>

<!ATTLIST iterate

operator (or|and)

ifEmpty (true | false) >

This element is used to iterate over a variable that is of type java.util.Collection, or a variable that adapts to org.eclipse.core.expressions.IIterable. If the object in focus is not one of the above then a CoreException with an ExpressionStatus will be thrown while evaluating the expression. The child expressions of an iterate expression are combined using the "and" operator.

- operator - either "and" or "or". The operator defines how the results of all the child expressions applied to each child of the Collection or IIterable will be combined and what (if any) short circuit evaluation will be used. If not specified, "and" will be used.
- ifEmpty - the value returned from the "iterate" expression if the collection is empty. If not specified then EvaluationResult.TRUE is returned when the operator equals "and" and EvaluationResult.FALSE is returned if the operator equals "or".

<!ELEMENT reference EMPTY>

<!ATTLIST reference

definitionId IDREF #REQUIRED>

This element is used to reference an expression from the org.eclipse.core.expressions.definitions extension point. The expression definition will be evaluated within the current expression element using the current evaluation context.

- definitionId - The unique id of an expression from org.eclipse.core.expressions.definitions.

###### Examples:

The following is an example of a Java completion proposal computer contribution:

     <extension point="org.eclipse.jdt.ui.javaCompletionProposalComputer"
       id="textual_proposals"
       name="Text Proposals">
       <proposalCategory icon="icons/wordcompletions.png"/>
     </extension>
     <extension point="org.eclipse.jdt.ui.javaCompletionProposalComputer"
       id="WordCompletionProposalComputer"
       name="Word Completion Proposal Computer">
       <javaCompletionProposalComputer
          class="org.eclipse.jdt.internal.ui.text.java.HippieProposalComputer"
          categoryId="org.eclipse.ui.texteditor.textual_proposals">
          <partition type="__java_javadoc"/>
       </javaCompletionProposalComputer>
     </extension>

###### API Information:

The contributed class must extend `org.eclipse.jdt.ui.text.java.IJavaCompletionProposalComputer`

###### Supplied Implementation:

see `org.eclipse.jdt.internal.ui.text.java.HippieProposalComputer` for an example.

Copyright (c) 2006, 2013 IBM Corporation and others.
This program and the accompanying materials are made available under the terms of the Eclipse Public License 2.0 which accompanies this distribution, and is available at https://www.eclipse.org/legal/epl-v20.html/ SPDX-License-Identifier: EPL-2.0