Cover KMP source sets with a ktlint namespace-import rule

build-logic/convention/src/main/kotlin/HedvigGradlePlugin.kt

@@ -38,6 +38,14 @@ private fun Project.configureKtlint(libs: LibrariesForLibs) {
     reporters = arrayOf(ReporterType.checkstyle.name)
   }
 
+  // Our own rules run on every source set, which is what gives KMP modules the coverage that
+  // Android Lint cannot reach.
+  if (name != "hedvig-ktlint") {
+    dependencies {
+      add("ktlint", project(":hedvig-ktlint"))
+    }
+  }
+
   tasks.withType<org.jmailen.gradle.kotlinter.tasks.LintTask>().configureEach {
     exclude { it.file.path.contains("generated/") }
     reports.set(

gradle/libs.versions.toml

@@ -27,6 +27,8 @@ kmpNativeCoroutines = "1.0.5"
 kotlin = "2.4.10"
 kotlinpoet = "2.3.0"
 kotlinter = "5.6.0"
+# Must match the ktlint that kotlinter bundles, so the custom ruleset links against the same API
+ktlintCore = "1.8.0"
 ksp = "2.3.10"
 ktor = "3.5.1"
 license = "0.9.9"
@@ -271,6 +273,8 @@ kmpNativeCoroutines-gradlePlugin = { module = "com.rickclephas.kmp.nativecorouti
 kotlin-gradlePlugin = { module = "org.jetbrains.kotlin:kotlin-gradle-plugin", version.ref = "kotlin" }
 kotlinSerialization-gradlePlugin = { module = "org.jetbrains.kotlin:kotlin-serialization", version.ref = "kotlin" }
 kotlinter-gradlePlugin = { module = "org.jmailen.gradle:kotlinter-gradle", version.ref = "kotlinter" }
+ktlint-ruleEngineCore = { module = "com.pinterest.ktlint:ktlint-rule-engine-core", version.ref = "ktlintCore" }
+ktlint-cliRulesetCore = { module = "com.pinterest.ktlint:ktlint-cli-ruleset-core", version.ref = "ktlintCore" }
 ksp-gradlePlugin = { module = "com.google.devtools.ksp:com.google.devtools.ksp.gradle.plugin", version.ref = "ksp" }
 license-gradlePlugin = { module = "com.jaredsburrows.license:com.jaredsburrows.license.gradle.plugin", version.ref = "license" }
 metro-gradlePlugin = { module = "dev.zacsweers.metro:dev.zacsweers.metro.gradle.plugin", version.ref = "metro" }

hedvig-ktlint/build.gradle.kts

@@ -0,0 +1,9 @@
+plugins {
+  id("hedvig.jvm.library")
+  id("hedvig.gradle.plugin")
+}
+
+dependencies {
+  compileOnly(libs.ktlint.ruleEngineCore)
+  compileOnly(libs.ktlint.cliRulesetCore)
+}

hedvig-ktlint/src/main/kotlin/com/hedvig/android/ktlint/HedvigRuleSetProvider.kt

@@ -0,0 +1,13 @@
+package com.hedvig.android.ktlint
+
+import com.pinterest.ktlint.cli.ruleset.core.api.RuleSetProviderV3
+import com.pinterest.ktlint.rule.engine.core.api.RuleProvider
+import com.pinterest.ktlint.rule.engine.core.api.RuleSetId
+
+internal const val CUSTOM_RULE_SET_ID = "hedvig"
+
+class HedvigRuleSetProvider : RuleSetProviderV3(RuleSetId(CUSTOM_RULE_SET_ID)) {
+  override fun getRuleProviders(): Set<RuleProvider> = setOf(
+    RuleProvider { NamespaceImportRule() },
+  )
+}

hedvig-ktlint/src/main/kotlin/com/hedvig/android/ktlint/NamespaceImportRule.kt

@@ -0,0 +1,68 @@
+package com.hedvig.android.ktlint
+
+import com.pinterest.ktlint.rule.engine.core.api.ElementType
+import com.pinterest.ktlint.rule.engine.core.api.Rule
+import com.pinterest.ktlint.rule.engine.core.api.RuleId
+import org.jetbrains.kotlin.com.intellij.lang.ASTNode
+
+/**
+ * Reports imports that shorten a qualified reference past the point where the short name still says
+ * what it is, such as `import hedvig.resources.Res.string` turning `Res.string.FOO` into `string.FOO`.
+ *
+ * This is the multiplatform counterpart of the `NamespaceImport` Android Lint check, which cannot run
+ * on KMP source sets. ktlint has no type resolution, so an owner is recognized by the shape of the
+ * import path rather than by resolving it, and [CAPITALIZED_PACKAGES] carries the exceptions that
+ * costs us.
+ */
+internal class NamespaceImportRule :
+  Rule(
+    ruleId = RuleId("$CUSTOM_RULE_SET_ID:namespace-import"),
+    about = About(
+      maintainer = "Hedvig",
+      repositoryUrl = "https://github.com/HedvigInsurance/android",
+      issueTrackerUrl = "https://github.com/HedvigInsurance/android/issues",
+    ),
+  ) {
+  override fun beforeVisitChildNodes(
+    node: ASTNode,
+    autoCorrect: Boolean,
+    emit: (offset: Int, errorMessage: String, canBeAutoCorrected: Boolean) -> Unit,
+  ) {
+    if (node.elementType != ElementType.IMPORT_DIRECTIVE) return
+    val text = node.text
+    // An alias is a deliberate act of renaming, and gives the use site a name of its own.
+    if (text.contains(" as ")) return
+    val qualifiedName = text.removePrefix("import").trim()
+    if (qualifiedName.isEmpty() || qualifiedName.endsWith("*")) return
+
+    val importedName = qualifiedName.substringAfterLast('.')
+    val ownerPath = qualifiedName.substringBeforeLast('.', "")
+    val ownerName = ownerPath.substringAfterLast('.')
+    if (importedName.isEmpty() || ownerName.isEmpty()) return
+    if (!ownerName.first().isUpperCase()) return
+    // `Duration.Companion.seconds` and friends exist to enable the `5.seconds` receiver idiom.
+    if (ownerName == "Companion") return
+    if (CAPITALIZED_PACKAGES.any { qualifiedName.startsWith(it) }) return
+
+    val importsAMember = importedName.first().isLowerCase()
+    if (!importsAMember && qualifiedName !in DENIED_IMPORTS) return
+
+    emit(
+      node.startOffset,
+      "Import $ownerName and write $ownerName.$importedName at the use site. " +
+        "On its own, $importedName no longer says what it is.",
+      false,
+    )
+  }
+
+  private companion object {
+    /**
+     * Kotlin/Native interop packages are capitalized after the framework they bind, so their
+     * top-level declarations look identical to members of a class.
+     */
+    val CAPITALIZED_PACKAGES = listOf("platform.")
+
+    /** Imports that read as a type but still leave nothing meaningful at the use site. */
+    val DENIED_IMPORTS = setOf("kotlin.time.Clock.System")
+  }
+}

hedvig-ktlint/src/main/resources/META-INF/services/com.pinterest.ktlint.cli.ruleset.core.api.RuleSetProviderV3

@@ -0,0 +1 @@
+com.hedvig.android.ktlint.HedvigRuleSetProvider

hedvig-lint/lint-baseline/lint-baseline-hedvig-ktlint.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<issues format="6" by="lint 9.3.1" type="baseline" client="gradle" dependencies="false" name="AGP (9.3.1)" variant="all" version="9.3.1">
+
+</issues>

hedvig-lint/lint.xml

@@ -8,6 +8,12 @@
        config entry for a check absent from a given module isn't flagged. -->
   <issue id="UnknownIssueId" severity="ignore" />
 
+  <!-- Renovate (renovate.json) owns dependency freshness, so lint's version-staleness notices are
+       duplicate signal. They also resolve against the shared root gradle/libs.versions.toml rather
+       than the module being linted, so they report identically no matter which module runs lint. -->
+  <issue id="GradleDependency" severity="ignore" />
+  <issue id="NewerVersionAvailable" severity="ignore" />
+
   <issue id="ButtonCase" severity="ignore" />
   <issue id="TypographyDashes" severity="ignore" />
   <issue id="TypographyEllipsis" severity="ignore" />

settings.gradle.kts

@@ -69,3 +69,4 @@ include("design-showcase-desktop")
 project(":design-showcase-desktop").projectDir =
   rootProject.projectDir.resolve("micro-apps").resolve("design-showcase-desktop")
 include("hedvig-lint")
+include("hedvig-ktlint")