Brian Wilkerson
d1a2a43d54
R=scheglov@google.com Review-Url: https://codereview.chromium.org/3006703002 .
82 lines
3.1 KiB
Markdown
82 lines
3.1 KiB
Markdown
# Providing Occurrences Information
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Occurrences information is used by clients to help users identify all of the
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references to a single program element, such as a class, field, or local
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variable, within a single file.
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## Implementation details
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Occurrences information is available through a subscription. If the server has
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subscribed for occurrences information in some set of files, then the plugin
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should send the information in an `analysis.occurrences` notification whenever
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the information needs to be updated.
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When a notification needs to be sent, the method `sendOccurrencesNotification`
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will be invoked. This method is responsible for sending the notification.
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The easiest way to add support for this notification is by adding the classes
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`OccurrencesMixin` and `DartOccurrencesMixin` (from
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`package:analyzer_plugin/plugin/occurrences_mixin.dart`) to the list of mixins
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for your subclass of `ServerPlugin`. This will leave you with one abstract
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method that you need to implement: `getOccurrencesContributors`. That method is
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responsible for returning a list of `OccurrencesContributor`s. It is the
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occurrences contributors that produce the actual occurrences information. (Most
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plugins will only need a single occurrences contributor.)
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To write an occurrences contributor, create a class that implements
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`OccurrencesContributor`. The interface defines a single method named
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`computeOccurrences`. The method has two arguments: an `OccurrencesRequest` that
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describes the file for which occurrences information is being requested and an
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`OccurrencesCollector` through which occurrences information is to be added.
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If you mix in the class `DartOccurrencesMixin`, then the request will be an
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instance of `DartOccurrencesRequest`, which also has analysis results.
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## Example
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Start by creating a class that implements `OccurrencesContributor`, then
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implement the method `computeOccurrences`. This method is typically implemented
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by creating a visitor (such as an AstVisitor) that can visit the results of the
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analysis (such as a CompilationUnit) and extract the occurrences information
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from the analysis result.
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For example, your contributor might look something like the following:
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```dart
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class MyOccurrencesContributor implements OccurrencesContributor {
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@override
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void computeOccurrences(
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OccurrencesRequest request, OccurrencesCollector collector) {
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if (request is DartOccurrencesRequest) {
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OccurrencesVisitor visitor = new OccurrencesVisitor(collector);
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request.result.unit.accept(visitor);
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}
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}
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}
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class OccurrencesVisitor extends RecursiveAstVisitor {
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final OccurrencesCollector collector;
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OccurrencesVisitor(this.collector);
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@override
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void visitSimpleIdentifier(SimpleIdentifier node) {
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// ...
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}
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}
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```
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Given a contributor like the one above, you can implement your plugin similar to
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the following:
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```dart
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class MyPlugin extends ServerPlugin with OccurrencesMixin, DartOccurrencesMixin {
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// ...
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@override
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List<OccurrencesContributor> getOccurrencesContributors(String path) {
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return <OccurrencesContributor>[new MyOccurrencesContributor()];
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}
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}
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```
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