Privacy-Period-Tracker/build.gradle.kts

// AGP 9 has built-in Kotlin support, so there is no org.jetbrains.kotlin.android
// plugin here — applying it is now an error rather than a redundancy.
// The Compose compiler plugin is still applied separately.
// See https://developer.android.com/build/migrate-to-built-in-kotlin
plugins {
    alias(libs.plugins.android.application) apply false
    alias(libs.plugins.android.library) apply false
    alias(libs.plugins.kotlin.jvm) apply false
    alias(libs.plugins.kotlin.compose) apply false
    alias(libs.plugins.ksp) apply false
    alias(libs.plugins.hilt) apply false
    alias(libs.plugins.room) apply false
}

// ===========================================================================
// Module boundaries
// ===========================================================================
//
// The dependency table in docs/architecture/README.md, as a check.
//
// Two boundaries in this project are load-bearing and neither can be held up by
// people remembering them:
//
//   1. `domain:*` must not see the Android SDK. It is why the prediction
//      engine's tests run in a second instead of on an emulator, and one
//      contributor reaching for a convenient Android API would end that with no
//      test failing.
//   2. The advertising subsystem must never reach cycle data. PRODUCT_PLAN.md
//      §34 states it as non-negotiable: no menstrual date, cycle length,
//      fertility status, ovulation estimate, prediction confidence, prediction
//      history or spotting record may reach advertising, ever.
//
// The second is written down before `core:ads` exists on purpose. A guard added
// alongside the code it constrains is a guard that was shaped around whatever
// exception somebody wanted at the time.
//
// Run: ./gradlew checkModuleBoundaries   (also wired into `check`)
// Prove it fails: bash scripts/prove-guard.sh
//
// Exit is non-zero with every violation listed, not just the first — a guard
// that reports one problem per run turns a five-minute fix into five runs.

/** Project dependencies each module is permitted. Anything else fails. */
val allowedProjectDependencies: Map<String, Set<String>> = mapOf(
    ":app" to setOf(":core:designsystem", ":core:data", ":core:datastore", ":domain:cycle", ":domain:prediction"),
    ":core:designsystem" to emptySet(),
    ":core:database" to setOf(":domain:cycle", ":domain:prediction"),
    ":core:datastore" to emptySet(),
    ":core:data" to setOf(":core:database", ":domain:cycle", ":domain:prediction"),
    ":domain:cycle" to emptySet(),
    ":domain:prediction" to setOf(":domain:cycle"),
    // Batch 07. Empty, and that is the whole point: the ads module may reach
    // NOTHING in this project. It talks to the UI through an AdProvider
    // interface owned by :app.
    ":core:ads" to emptySet(),
)

/** Modules that must never see the Android SDK, by never applying an Android plugin. */
val mustStayPureJvm = setOf(":domain:cycle", ":domain:prediction")

/**
 * Configurations that describe what SHIPS. Test-only dependencies are not a
 * product boundary — a test may reach for a fake or an in-memory database that
 * production must not — so they are deliberately not examined here.
 */
val shippingConfigurations = setOf("implementation", "api", "compileOnly", "runtimeOnly", "ksp")

// ---------------------------------------------------------------------------
// Collected in afterEvaluate, and that is not a detail.
//
// The first version of this read `subprojects.configurations` directly in the
// root build script. The root project is configured BEFORE its subprojects, so
// every configuration was empty, every module had no dependencies, and the task
// printed "7 modules checked, no violations" while checking nothing at all.
//
// It was caught by `scripts/prove-guard.sh` on the first run — a deliberate
// forbidden dependency was added to :domain:prediction and the guard stayed
// green. That is precisely the failure GUARDS.md §1 exists for, and it is why
// no guard here is believed until it has been watched failing.
// ---------------------------------------------------------------------------

val observedProjectDependencies = mutableMapOf<String, Set<String>>()
val observedAndroidPlugins = mutableMapOf<String, List<String>>()
val containerProjects = mutableSetOf<String>()

subprojects {
    afterEvaluate {
        if (!buildFile.exists()) {
            // `include(":core:database")` makes Gradle create an intermediate
            // `:core` project with nothing to build. Containers, not modules —
            // named in the output rather than dropped, because "skipped" and
            // "passed" must not look the same.
            containerProjects += path
            return@afterEvaluate
        }
        observedProjectDependencies[path] = configurations
            .filter { it.name in shippingConfigurations }
            .flatMap { conf -> conf.dependencies.filterIsInstance<ProjectDependency>() }
            .map { it.path }
            .toSet()
        observedAndroidPlugins[path] = plugins.mapNotNull { plugin ->
            plugin::class.qualifiedName?.takeIf { it.contains("com.android.build") }
        }
    }
}

tasks.register("checkModuleBoundaries") {
    group = "verification"
    description = "Every module's project dependencies must match docs/architecture/README.md."

    val allowed = allowedProjectDependencies
    val observed = observedProjectDependencies
    val androidPlugins = observedAndroidPlugins
    val pureJvm = mustStayPureJvm
    val containers = containerProjects

    // Providers, not values: these maps are filled during afterEvaluate, which
    // has not run when this task is being registered. Reading them eagerly here
    // is the same mistake as reading them in the root script.
    inputs.property("allowed", allowed.toString())
    inputs.property("observed", provider { observed.toString() })
    inputs.property("androidPlugins", provider { androidPlugins.toString() })

    doLast {
        val violations = mutableListOf<String>()

        val modules = observed.keys

        // Refuse to report a pass over nothing. An empty map here means the
        // collection above did not run, which is exactly how this guard was
        // green while checking nothing.
        if (modules.isEmpty()) {
            throw GradleException(
                "no modules were examined, so nothing was checked. This is not a pass — " +
                    "see the afterEvaluate note in build.gradle.kts.",
            )
        }

        // A module nobody declared a rule for is not "allowed anything" — it is
        // unmeasured, and reporting it as a pass is how a boundary quietly stops
        // covering half the project.
        (modules - allowed.keys).sorted().forEach {
            violations += "$it has no entry in allowedProjectDependencies, so its dependencies were never checked."
        }

        observed.forEach { (module, deps) ->
            if (module in containers) return@forEach
            val permitted = allowed[module] ?: return@forEach
            (deps - permitted).sorted().forEach { dep ->
                violations += "$module depends on $dep, which the architecture does not permit."
            }
        }

        pureJvm.forEach { module ->
            androidPlugins[module]?.takeIf { it.isNotEmpty() }?.let { plugins ->
                violations += "$module applies an Android plugin (${plugins.first()}). " +
                    "It must stay pure JVM so the prediction engine is testable without an emulator."
            }
        }

        if (violations.isNotEmpty()) {
            logger.error("")
            logger.error("Module boundary violations:")
            violations.forEach { logger.error("  - $it") }
            logger.error("")
            logger.error("These are the rules in docs/architecture/README.md. If the architecture")
            logger.error("changed on purpose, change that table and the map in build.gradle.kts in")
            logger.error("the same commit. If it did not, this dependency is the mistake.")
            throw GradleException("${violations.size} module boundary violation(s).")
        }

        logger.lifecycle(
            "module boundaries: ${modules.size} module(s) checked, " +
                "${pureJvm.size} required to stay pure JVM, no violations.",
        )
        if (containers.isNotEmpty()) {
            logger.lifecycle(
                "  (skipped ${containers.size} container project(s) with no build file: " +
                    "${containers.sorted().joinToString(", ")})",
            )
        }
    }
}

// Wired into `check` so it runs with the tests rather than only when remembered.
subprojects {
    tasks.matching { it.name == "check" }.configureEach {
        dependsOn(rootProject.tasks.named("checkModuleBoundaries"))
    }
}