IntelliJ Platform Plugin SDK Help

7. Annotator

An Annotator helps highlight and annotate any code based on specific rules. This section adds annotation functionality to support the Simple Language in the context of Java code.

Reference: Annotator

Required Project Configuration Changes

Classes defined in this step of the tutorial depend on com.intellij.psi.PsiLiteralExpression at runtime. Using PsiLiteralExpression introduces a dependency on Beginning in version 2019.2 of the IntelliJ Platform these dependencies are declared in plugin.xml:


The dependency is also declared in the build.gradle file:

intellij { plugins = [''] }

Or the following line in the project's build.gradle.kts file:

intellij { setPlugins ("") }

Define an Annotator

The SimpleAnnotator subclasses Annotator. Consider a literal string that starts with "simple:" as a prefix of a Simple Language key. It isn't part of the Simple Language, but it is a useful convention for detecting Simple Language keys embedded as string literals in other languages, like Java. Annotate the simple:key literal expression, and differentiate between a well-formed vs. an unresolved property.

// Copyright 2000-2020 JetBrains s.r.o. and other contributors. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file. package org.intellij.sdk.language; import com.intellij.codeInspection.ProblemHighlightType; import com.intellij.lang.annotation.AnnotationHolder; import com.intellij.lang.annotation.Annotator; import com.intellij.lang.annotation.HighlightSeverity; import com.intellij.openapi.editor.DefaultLanguageHighlighterColors; import com.intellij.openapi.util.TextRange; import com.intellij.psi.PsiElement; import com.intellij.psi.PsiLiteralExpression; import org.intellij.sdk.language.psi.SimpleProperty; import org.jetbrains.annotations.NotNull; import java.util.List; public class SimpleAnnotator implements Annotator { // Define strings for the Simple language prefix - used for annotations, line markers, etc. public static final String SIMPLE_PREFIX_STR = "simple"; public static final String SIMPLE_SEPARATOR_STR = ":"; @Override public void annotate(@NotNull final PsiElement element, @NotNull AnnotationHolder holder) { // Ensure the Psi Element is an expression if (!(element instanceof PsiLiteralExpression)) { return; } // Ensure the Psi element contains a string that starts with the prefix and separator PsiLiteralExpression literalExpression = (PsiLiteralExpression) element; String value = literalExpression.getValue() instanceof String ? (String) literalExpression.getValue() : null; if ((value == null) || !value.startsWith(SIMPLE_PREFIX_STR + SIMPLE_SEPARATOR_STR)) { return; } // Define the text ranges (start is inclusive, end is exclusive) // "simple:key" // 01234567890 TextRange prefixRange = TextRange.from(element.getTextRange().getStartOffset(), SIMPLE_PREFIX_STR.length() + 1); TextRange separatorRange = TextRange.from(prefixRange.getEndOffset(), SIMPLE_SEPARATOR_STR.length()); TextRange keyRange = new TextRange(separatorRange.getEndOffset(), element.getTextRange().getEndOffset() - 1); // highlight "simple" prefix and ":" separator holder.newSilentAnnotation(HighlightSeverity.INFORMATION) .range(prefixRange).textAttributes(DefaultLanguageHighlighterColors.KEYWORD).create(); holder.newSilentAnnotation(HighlightSeverity.INFORMATION) .range(separatorRange).textAttributes(SimpleSyntaxHighlighter.SEPARATOR).create(); // Get the list of properties for given key String key = value.substring(SIMPLE_PREFIX_STR.length() + SIMPLE_SEPARATOR_STR.length()); List<SimpleProperty> properties = SimpleUtil.findProperties(element.getProject(), key); if (properties.isEmpty()) { holder.newAnnotation(HighlightSeverity.ERROR, "Unresolved property") .range(keyRange) .highlightType(ProblemHighlightType.LIKE_UNKNOWN_SYMBOL) // ** Tutorial step 18.3 - Add a quick fix for the string containing possible properties .withFix(new SimpleCreatePropertyQuickFix(key)) .create(); } else { // Found at least one property, force the text attributes to Simple syntax value character holder.newSilentAnnotation(HighlightSeverity.INFORMATION) .range(keyRange).textAttributes(SimpleSyntaxHighlighter.VALUE).create(); } } }

Register the Annotator

Using the com.intellij.annotator extension point in the plugin configuration file, register the Simple Language annotator class with the IntelliJ Platform:

<extensions defaultExtensionNs="com.intellij"> <annotator language="JAVA" implementationClass="org.intellij.sdk.language.SimpleAnnotator"/> </extensions>

Run the Project

As a test, define the following Java file containing a Simple Language prefix:value pair:

public class Test { public static void main(String[] args) { System.out.println("simple:website"); } }

Open this Java file in an IDE Development Instance running the simple_language_plugin to check if the IDE resolves a property:


If the property is an undefined name, the annotator flags the code with an error.

Unresolved property

Try changing the Simple Language color settings to differentiate the annotation from the default language color settings.

Last modified: 16 February 2021