Merge pull request #6 from Doist/piotr/no_not_null_operator

NoNotNullOperator rule

README.md

@@ -68,4 +68,8 @@ val a = when {
 ### MutableObservablePropertyIsPrivate
 
 This rule reports exposed `MutableLive...` and `MutableStateFlow` properties. They should be 
-private.   
+private.
+
+### NoNotNullOperator
+
+This rule reports `!!` usage. `requireNotNull` should be used instead.

src/main/kotlin/com/doist/detekt/NoNotNullOperator.kt

@@ -0,0 +1,32 @@
+package com.doist.detekt
+
+import io.gitlab.arturbosch.detekt.api.CodeSmell
+import io.gitlab.arturbosch.detekt.api.Config
+import io.gitlab.arturbosch.detekt.api.Debt
+import io.gitlab.arturbosch.detekt.api.Entity
+import io.gitlab.arturbosch.detekt.api.Issue
+import io.gitlab.arturbosch.detekt.api.Rule
+import io.gitlab.arturbosch.detekt.api.Severity
+import org.jetbrains.kotlin.psi.KtPostfixExpression
+
+class NoNotNullOperator(config: Config) : Rule(config) {
+    override val issue = Issue(
+        javaClass.simpleName,
+        Severity.Style,
+        "Detects !! operator",
+        Debt.FIVE_MINS,
+    )
+
+    override fun visitPostfixExpression(expression: KtPostfixExpression) {
+        super.visitPostfixExpression(expression)
+
+        if (expression.text.endsWith("!!")) {
+            val codeSmell = CodeSmell(
+                issue = issue,
+                entity = Entity.from(expression),
+                message = "Use requireNotNull instead of !! operator",
+            )
+            report(codeSmell)
+        }
+    }
+}

src/main/resources/config/config.yml

@@ -7,3 +7,5 @@ DoistRuleSet:
     active: true
   MutableObservablePropertyIsPrivate:
     active: true
+  NoNotNullOperator:
+    active: true

src/test/kotlin/com/doist/detekt/NoNotNullOperatorTest.kt

@@ -0,0 +1,33 @@
+package com.doist.detekt
+
+import io.gitlab.arturbosch.detekt.api.Config
+import io.gitlab.arturbosch.detekt.rules.KotlinCoreEnvironmentTest
+import io.gitlab.arturbosch.detekt.test.compileAndLintWithContext
+import io.kotest.matchers.collections.shouldHaveSize
+import org.jetbrains.kotlin.cli.jvm.compiler.KotlinCoreEnvironment
+import org.junit.jupiter.api.Test
+
+@KotlinCoreEnvironmentTest
+internal class NoNotNullOperatorTest(private val env: KotlinCoreEnvironment) {
+    @Test
+    fun `reports !! usage`() {
+        val code = """
+            val a: String? = ""
+            val b = a!!
+        """
+        val rule = NoNotNullOperator(Config.empty)
+        val findings = rule.compileAndLintWithContext(env, code)
+        findings shouldHaveSize 1
+    }
+
+    @Test
+    fun `doesn't reports requireNoteNull usage`() {
+        val code = """
+            val a: String? = ""
+            val b = requireNotNull(a)
+        """
+        val rule = NoNotNullOperator(Config.empty)
+        val findings = rule.compileAndLintWithContext(env, code)
+        findings shouldHaveSize 0
+    }
+}