StupidLintRule.kt

import com.android.tools.lint.client.api.UElementHandler
import com.android.tools.lint.detector.api.Category
import com.android.tools.lint.detector.api.Detector
import com.android.tools.lint.detector.api.Implementation
import com.android.tools.lint.detector.api.Issue
import com.android.tools.lint.detector.api.JavaContext
import com.android.tools.lint.detector.api.Scope
import com.android.tools.lint.detector.api.Severity
import com.android.tools.lint.detector.api.SourceCodeScanner
import org.jetbrains.uast.UClass

class StupidLintRule : Detector(), SourceCodeScanner {

  override fun getApplicableUastTypes() = listOf(UClass::class.java)

  override fun createUastHandler(context: JavaContext) = ConstructorVisitor(context)

  class ConstructorVisitor(private val context: JavaContext) : UElementHandler() {

    override fun visitClass(node: UClass) {
      val constructorCount = node.constructors.count()
      if (constructorCount != 42) {
        context.report(
          ISSUE,
          node,
          context.getLocation(node.containingFile),
          "Class doesn't have 42 constructors"
        )
      }
    }
  }

  companion object {
    val ISSUE = Issue.create(
      id = "42Constructors",
      briefDescription = "42Constructors",
      explanation = "Every class needs 42 constructors.",
      category = Category.CORRECTNESS,
      priority = 6,
      severity = Severity.FATAL,
      androidSpecific = false,
      implementation = Implementation(StupidLintRule::class.java, Scope.JAVA_FILE_SCOPE)
    )
  }
}

StupidLintRuleTest.kt

import com.android.tools.lint.checks.infrastructure.LintDetectorTest
import com.android.tools.lint.detector.api.Detector
import org.intellij.lang.annotations.Language
import org.junit.Test
import org.junit.runner.RunWith
import org.junit.runners.JUnit4

@RunWith(JUnit4::class)
class StupidLintRuleTest : LintDetectorTest() {

  override fun getIssues() = listOf(StupidLintRule.ISSUE)

  override fun getDetector(): Detector = StupidLintRule()

  @Test
  fun test() {
    @Language("kotlin")
    val user = """
          package my.package
          
          data class User(
            val name: String
          )
          """.trimIndent()
    lint()
      .files(kotlin(user))
      .allowMissingSdk()
      .run()
      .expectErrorCount(1)
  }
}