Brian Wilkerson
608bf972b0
R=scheglov@google.com Review-Url: https://codereview.chromium.org/3004733002 .
80 lines
2.8 KiB
Markdown
80 lines
2.8 KiB
Markdown
# Providing Folding Information
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Folding information is used by clients to allow users to collapse portions of
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the code that are not interesting for their current task.
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## Implementation details
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Folding information is available through a subscription. If the server has
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subscribed for folding information in some set of files, then the plugin
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should send the information in an `analysis.folding` 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 `sendFoldingNotification`
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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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`FoldingMixin` and `DartFoldingMixin` (from
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`package:analyzer_plugin/plugin/folding_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: `getFoldingContributors`. That method is
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responsible for returning a list of `FoldingContributor`s. It is the folding
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contributors that produce the actual folding regions. (Most plugins will only
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need a single folding contributor.)
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To write a folding contributor, create a class that implements
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`FoldingContributor`. The interface defines a single method named
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`computeFolding`. The method has two arguments: an `FoldingRequest` that
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describes the file for which folding information is being requested and an
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`FoldingCollector` through which folding regions are to be added.
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If you mix in the class `DartFoldingMixin`, then the request will be an
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instance of `DartFoldingRequest`, which also has analysis results.
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## Example
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Start by creating a class that implements `FoldingContributor`, then implement
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the method `computeFolding`. This method is typically implemented by creating a
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visitor (such as an AstVisitor) that can visit the results of the analysis (such
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as a CompilationUnit) and extract the folding regions 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 MyFoldingContributor implements FoldingContributor {
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@override
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void computeFolding(
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FoldingRequest request, FoldingCollector collector) {
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if (request is DartFoldingRequest) {
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FoldingVisitor visitor = new FoldingVisitor(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 FoldingVisitor extends RecursiveAstVisitor {
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final FoldingCollector collector;
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FoldingVisitor(this.collector);
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@override
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void visitClassDeclaration(ClassDeclaration 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 FoldingMixin, DartFoldingMixin {
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// ...
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@override
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List<FoldingContributor> getFoldingContributors(String path) {
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return <FoldingContributor>[new MyFoldingContributor()];
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}
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}
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```
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