Notable Changes in IntelliJ Platform and Plugins API 2021.*

Allows integration of standalone tools like shfmt: External Code Formatter.

Use new method CustomComponentAction.updateCustomComponent(Component, Presentation) to synchronize given Presentation and component state.

Use getPriorityRange() in AnnotationSession/LocalInspectionToolSession to optimize highlighting for coarse-grained files (e.g., PsiPlainTextFile files with single node).

Now com.intellij.ui.IconManager.createDeferredIcon() doesn't use iconProducer which might result in "wrong" composite icons and failed assertions. Override UsefulTestCase.isIconRequired() returning true to restore production icons. Alternatively, invoke Registry.get("psi.deferIconLoading").setValue(false) in setUp() and Registry.get("psi.deferIconLoading").resetToDefault() in tearDown().

Please obtain necessary components only when needed (logged as ERROR now).

Use LanguageInjectionContributor (com.intellij.languageInjectionContributor extension point) and LanguageInjectionPerformer (com.intellij.languageInjectionPerformer extension point) to customize language injection.

Several plugins (Arquillian, AspectJ, CoffeeScript, Debugger Support for JSP (JSR45), Drools, Guice, Helidon, Java EE: Enterprise Java Beans (EJB), Spring OSGi, Spring Web Flow) have been unbundled. The IDE will suggest installation if the project contains related framework dependency. If a plugin depends on them, users will need to install them from the JetBrains Marketplace.

Override ReferenceImporter#isAddUnambiguousImportsOnTheFlyEnabled() and provide corresponding user setting. Implement HintAction with fixSilently() and hook it up to highlighting as a quick fix for unresolved reference.

Implement FileEncodingProvider and register in com.intellij.fileEncodingProvider extension point.

JBCefOsrHandlerBrowser forwards to custom CefRenderHandler, e.g., for off-screen rendering.

Use LightJavaCodeInsightFixtureTestCase4.