Add Feature Module

Feature Module Creation Skill

This skill creates a new feature module in the feature/ package.

Prerequisites & Pre-steps

Before generating the module, confirm:

1. Screen Definition (Crucial): Before creating a new feature module, you MUST first add the new Screen definition to com.metasearch.android.feature.screens.Screens.kt.
   • Ensure the new Screen (object or data class) is defined and registered in that file.
2. Module Naming:
   • {module}: Must be snake_case (e.g., person_detail).
   • {Module}: Must be PascalCase (e.g., PersonDetail).
3. Module Purpose (What feature/screen this is for)
4. Domain Dependencies (Which domain.*.api modules are needed)

Implementation Steps

1. Gradle Configuration (build.gradle.kts)

Each feature module must use the standard feature plugins. Note: All feature modules automatically depend on feature.screens, so you do not need to add it manually.

plugins {
    alias(libs.plugins.metasearch.android.feature)
    alias(libs.plugins.metasearch.test)
}

android {
    namespace = "com.metasearch.android.feature.{module}"
}

dependencies {
    // Note: projects.feature.screens is already provided by the feature plugin.

    // Add required Domain APIs here
    // implementation(projects.domain.{domain}.api)
}

2. File Structure

Create the source directory structure: feature/{module}/src/main/java/com/metasearch/android/feature/{module}/

Screen Definition

All Screen classes should be defined in the feature.screens module. Do not define new Screen classes inside the feature module. Instead, reference the existing Screen from com.metasearch.android.feature.screens.

Screen Definition Example

When adding a new screen to feature/screens/Screens.kt, follow these patterns:

1. For simple screens (No parameters):

@Parcelize
data object {Module}Screen : Screen

2. For screens with parameters:

@Parcelize
data class {Module}Screen(
    val id: Long,
) : Screen

Key Files to Create

(using {Module} as PascalCase):

1. {Module}Presenter.kt: Handles business logic.

package com.metasearch.android.feature.{module}

import androidx.compose.runtime.Composable
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.rememberCoroutineScope
import androidx.compose.runtime.setValue
import com.metasearch.android.feature.screens.{Module}Screen
import com.slack.circuit.codegen.annotations.CircuitInject
import com.slack.circuit.runtime.Navigator
import com.slack.circuit.runtime.presenter.Presenter
import dev.zacsweers.metro.AppScope
import dev.zacsweers.metro.Assisted
import dev.zacsweers.metro.AssistedFactory
import dev.zacsweers.metro.AssistedInject

@AssistedInject
class {Module}Presenter(
    @Assisted private val navigator: Navigator,
    // TODO: Inject UseCases or Repository
) : Presenter<{Module}UiState> {

    @CircuitInject({Module}Screen::class, AppScope::class)
    @AssistedFactory
    fun interface Factory {
        fun create(navigator: Navigator): {Module}Presenter
    }

    @Composable
    override fun present(): {Module}UiState {
        val scope = rememberCoroutineScope()

        // TODO: Define states (remember / rememberRetained)

        fun handleEvent(event: {Module}UiEvent) {
            when (event) {
                // TODO: Handle events
            }
        }

        return {Module}UiState(
            eventSink = ::handleEvent,
            // TODO: Assign states
        )
    }
}

2. {Module}Ui.kt: UI components, annotated with @CircuitInject({Module}Screen::class, AppScope::class).

package com.metasearch.android.feature.{module}

import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import com.metasearch.android.feature.screens.{Module}Screen
import com.slack.circuit.codegen.annotations.CircuitInject
import dev.zacsweers.metro.AppScope

@CircuitInject({Module}Screen::class, AppScope::class)
@Composable
fun {Module}Ui(
    state: {Module}UiState,
    modifier: Modifier = Modifier,
) {
    // TODO: Implement UI using MetaSearchTheme
}

3. {Module}UiState.kt: UI state data class.

package com.metasearch.android.feature.{module}

import com.slack.circuit.runtime.CircuitUiEvent
import com.slack.circuit.runtime.CircuitUiState

data class {Module}UiState(
    val eventSink: ({Module}UiEvent) -> Unit,
    // TODO: Add state properties
) : CircuitUiState

sealed interface {Module}UiEvent : CircuitUiEvent {
    // TODO: Add events
}

3. Registration

Add the new module to the project and link it to the app module.

1. settings.gradle.kts Include the new module in the feature modules block (maintain alphabetical order):

include(":feature:{module}")

2. app/build.gradle.kts Add the dependency using the type-safe Gradle accessor.

• Note: Gradle automatically generates a camelCase accessor for every snake_case module name you define in settings.gradle.kts.
• Mapping Rule: person_detail (snake_case) → personDetail (camelCase)

// Always use the camelCase accessor (e.g., personDetail)
implementation(projects.feature.{Module})

3. Sync & Verify:

./gradlew :feature:{module}:compileDebugKotlin

Naming & Architecture Rules

Best Practices

• Screen Definition: Always define new Screen classes in feature/screens/Screens.kt first. Never define them inside feature modules.
• Design System: Always use MetaSearchTheme tokens from :core:designsystem. Do not hardcode colors or spacing.
• Circuit Inject: Every UI Composable must be annotated with @CircuitInject.
• UI: UI Composables should be stateless and take State and Event lambdas as parameters.