Custom Detekt Rules

Custom rule set diGuardrails in module :quality:detekt-rules. Enforces DI, Hilt, suppression, and resolver-log privacy conventions at compile time.

Existing Rules

Rule	What It Catches	Why
InjectConstructorDefaultParameter	Default values on @Inject constructor params	Hilt ignores defaults, causing silent behavior mismatch
HiltViewModelApplicationContext	@ApplicationContext in @HiltViewModel constructors	Forces narrower abstractions, improves testability
DisallowNewSuppression	@Suppress without an adjacent ROADMAP-architecture-refactor allowlist comment	Prevents new lint debt from becoming invisible
NoResolverIpInLogs	Resolver or upstream IP identifiers interpolated into log calls	Keeps user-visible network state out of logs

Module Structure

quality/detekt-rules/
  src/main/kotlin/com/poyka/ripdpi/quality/detekt/
    RipDpiRuleSetProvider.kt           -- Registers all rules (id: "diGuardrails")
    AnnotationMatchers.kt              -- Shared helpers: hasAnnotation(), findAnnotation()
    InjectConstructorDefaultParameter.kt
    HiltViewModelApplicationContext.kt
    DisallowNewSuppression.kt
    NoResolverIpInLogs.kt
  src/test/kotlin/com/poyka/ripdpi/quality/detekt/
    InjectConstructorDefaultParameterTest.kt
    HiltViewModelApplicationContextTest.kt
    DisallowNewSuppressionTest.kt
    NoResolverIpInLogsTest.kt

Creating a New Rule

Step 1: Write the Rule Class

Create src/main/kotlin/com/poyka/ripdpi/quality/detekt/YourRuleName.kt:

package com.poyka.ripdpi.quality.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.KtClass

class YourRuleName(config: Config) : Rule(config) {
    override val issue: Issue =
        Issue(
            id = "YourRuleName",
            severity = Severity.Defect,
            description = "One-line description of what this catches.",
            debt = Debt.FIVE_MINS,
        )

    override fun visitClass(klass: KtClass) {
        super.visitClass(klass)
        // Use hasAnnotation() from AnnotationMatchers.kt
        if (!klass.hasAnnotation("SomeAnnotation")) return

        // Check condition and report
        report(
            CodeSmell(
                issue = issue,
                entity = Entity.from(klass),
                message = "Actionable message: what to do instead.",
            ),
        )
    }
}

Step 2: Register in RuleSetProvider

Add to RipDpiRuleSetProvider.kt:

override fun instance(config: Config): RuleSet =
    RuleSet(
        ruleSetId,
        listOf(
            InjectConstructorDefaultParameter(config),
            HiltViewModelApplicationContext(config),
            DisallowNewSuppression(config),
            NoResolverIpInLogs(config),
            YourRuleName(config),  // <-- add here
        ),
    )

Step 3: Activate in detekt.yml

Add to config/detekt/detekt.yml:

diGuardrails:
  active: true
  InjectConstructorDefaultParameter:
    active: true
  HiltViewModelApplicationContext:
    active: true
  NoResolverIpInLogs:
    active: true
  YourRuleName:               # <-- add here
    active: true

DisallowNewSuppression is registered in RipDpiRuleSetProvider and inherits the active diGuardrails rule-set setting; it has no per-rule override in the current config.

Step 4: Write Tests

Create src/test/kotlin/com/poyka/ripdpi/quality/detekt/YourRuleNameTest.kt:

package com.poyka.ripdpi.quality.detekt

import io.gitlab.arturbosch.detekt.api.Config
import io.gitlab.arturbosch.detekt.test.compileAndLint
import org.junit.jupiter.api.Test
import kotlin.test.assertEquals

class YourRuleNameTest {
    private val rule = YourRuleName(Config.empty)

    @Test
    fun `reports violation on annotated class`() {
        val code = """
            @SomeAnnotation
            class Bad { /* violating pattern */ }
        """.trimIndent()
        val findings = rule.compileAndLint(code)
        assertEquals(1, findings.size)
    }

    @Test
    fun `allows non-annotated class`() {
        val code = """
            class Fine { /* same pattern but no annotation */ }
        """.trimIndent()
        val findings = rule.compileAndLint(code)
        assertEquals(0, findings.size)
    }
}

Cover: positive detection, negative (no false positive), edge cases (primary vs secondary constructors, nested classes).

Annotation Matching

Use the shared helpers from AnnotationMatchers.kt:

// Check if a KtAnnotated element has an annotation by simple name
klass.hasAnnotation("HiltViewModel")        // matches @HiltViewModel
constructor.hasAnnotation("Inject")          // matches @Inject

// Find the annotation entry (for Entity.from targeting)
parameter.findAnnotation("ApplicationContext")  // returns KtAnnotationEntry?

Important: These match by simple name, not fully-qualified name. hasAnnotation("Inject") matches both @javax.inject.Inject and @com.google.inject.Inject.

Common PSI Visitor Methods

Method	When To Use
visitClass(KtClass)	Checking class-level patterns
visitPrimaryConstructor(KtPrimaryConstructor)	Constructor parameter rules
visitSecondaryConstructor(KtSecondaryConstructor)	Must handle alongside primary
visitNamedFunction(KtNamedFunction)	Function-level rules
visitProperty(KtProperty)	Property declaration rules

Use getStrictParentOfType<KtClassOrObject>() to navigate from a constructor to its owning class.

Convention Plugin

ripdpi.android.detekt.gradle.kts configures detekt for all modules:

• Parallel: true
• Config: config/detekt/detekt.yml
• Reports: HTML + XML
• JVM target: 17
• Excludes: **/build/**, **/generated/**, **/jni/**, **/cpp/**
• Baseline: Auto-detected from detekt-baseline.xml if present in module
• Plugin deps: Custom rules (:quality:detekt-rules) + detekt-compose-rules

Run detekt:

./gradlew staticAnalysis          # detekt + ktlint + lint
./gradlew detektDebug             # detekt only (single variant)

Common Mistakes

Mistake	Fix
Forgetting to register in RipDpiRuleSetProvider	Rule exists but never runs. Add to the listOf(...) in instance().
Using FQN for annotation matching	hasAnnotation("javax.inject.Inject") won't match. Use simple name: "Inject".
Not activating in detekt.yml	Rule is registered but inactive. Add YourRuleName: { active: true } under diGuardrails:.
Testing only primary constructors	Many rules apply to both primary and secondary. Override both visitor methods.
Reporting on wrong entity	Use Entity.from(specificElement) not Entity.from(constructor) -- highlights the exact problem location.
Missing super.visitX() call	Always call super.visitPrimaryConstructor(constructor) etc. to continue traversal.

See Also

• config/detekt/detekt.yml -- Full detekt configuration
• build-logic/convention/src/main/kotlin/ripdpi.android.detekt.gradle.kts -- Convention plugin