annotator.md

title
7. Annotator

Annotator helps highlight and annotate any code based on specific rules.

7.1. Define an annotator

In this tutorial we will annotate usages of our properties within Java code. Let's consider a literal which starts with "simple:" as a usage of our property.

package com.simpleplugin;

import com.intellij.lang.annotation.*;
import com.intellij.openapi.editor.DefaultLanguageHighlighterColors;
import com.intellij.openapi.project.Project;
import com.intellij.openapi.util.TextRange;
import com.intellij.psi.*;
import com.simpleplugin.psi.SimpleProperty;
import org.jetbrains.annotations.NotNull;

import java.util.List;

public class SimpleAnnotator implements Annotator {
  @Override
  public void annotate(@NotNull final PsiElement element, @NotNull AnnotationHolder holder) {
    if (element instanceof PsiLiteralExpression) {
      PsiLiteralExpression literalExpression = (PsiLiteralExpression) element;
      String value = literalExpression.getValue() instanceof String ? (String) literalExpression.getValue() : null;

      if (value != null && value.startsWith("simple" + ":")) {
        Project project = element.getProject();
        String key = value.substring(7);
        List<SimpleProperty> properties = SimpleUtil.findProperties(project, key);
        if (properties.size() == 1) {
          TextRange range = new TextRange(element.getTextRange().getStartOffset() + 8,
                                          element.getTextRange().getEndOffset() - 1);
          Annotation annotation = holder.createInfoAnnotation(range, null);
          annotation.setTextAttributes(DefaultLanguageHighlighterColors.LINE_COMMENT);
        } else if (properties.size() == 0) {
          TextRange range = new TextRange(element.getTextRange().getStartOffset() + 8,
                                          element.getTextRange().getEndOffset() - 1);
          holder.createErrorAnnotation(range, "Unresolved property");
        }
      }
    }
  }
}

7.2. Register the annotator

<annotator language="JAVA" implementationClass="com.simpleplugin.SimpleAnnotator"/>

7.3. Run the project

Let's define the following Java file and check if the IDE resolves a property.

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

If we type an undefined property name, it will annotate the code with a error.