Create Hilt Navigation artifact.

Add androidx.hilt:hilt-navigation and androidx.hilt:hilt-navigation-fragment containing APIs for using @HiltViewModel and Hilt's ViewModelFactory with AndroidX Navigation.
The APIs will allow users to retrieve a HiltViewModelFactory whose view model owner and saved state owner is the NavBackStackEntry. Additionally it provide a kotlin extension, `hiltNavGraphViewModels` which mimics `navGraphViewModels`.

These artifacts essentially tackle:
* google/dagger#2152
* google/dagger#2166

Test: HiltNavGraphViewModelLazyTest
Relnote: Provide APIs for using @HiltViewModel with Navigation.

Change-Id: I00e675363f5af3922205a30f4670a4c33877a7b3

buildSrc/build_dependencies.gradle

@@ -26,7 +26,7 @@ build_versions.kotlin = "1.4.21"
 build_versions.kotlin_coroutines = "1.4.1"
 build_versions.ksp = "1.4.20-dev-experimental-20201204"
 
-build_versions.hilt = "2.29.1-alpha"
+build_versions.hilt = "DEV-SNAPSHOT"
 
 def agpOverride = System.getenv("GRADLE_PLUGIN_VERSION")
 if (agpOverride != null) {

hilt/hilt-navigation-fragment/api/api_lint.ignore

@@ -0,0 +1,3 @@
+// Baseline format: 1.0
+MissingNullability: androidx.hilt.navigation.fragment.HiltNavGraphViewModelLazyKt#hiltNavGraphViewModels(androidx.fragment.app.Fragment, int):
+    Missing nullability on method `hiltNavGraphViewModels` return

hilt/hilt-navigation-fragment/api/current.txt

@@ -0,0 +1,9 @@
+// Signature format: 4.0
+package androidx.hilt.navigation.fragment {
+
+  public final class HiltNavGraphViewModelLazyKt {
+    method @MainThread public static inline <reified VM extends androidx.lifecycle.ViewModel> kotlin.Lazy<? extends VM>! hiltNavGraphViewModels(androidx.fragment.app.Fragment, @IdRes int navGraphId);
+  }
+
+}
+

hilt/hilt-navigation-fragment/api/public_plus_experimental_current.txt

@@ -0,0 +1,9 @@
+// Signature format: 4.0
+package androidx.hilt.navigation.fragment {
+
+  public final class HiltNavGraphViewModelLazyKt {
+    method @MainThread public static inline <reified VM extends androidx.lifecycle.ViewModel> kotlin.Lazy<? extends VM>! hiltNavGraphViewModels(androidx.fragment.app.Fragment, @IdRes int navGraphId);
+  }
+
+}
+

hilt/hilt-navigation-fragment/api/restricted_current.txt

@@ -0,0 +1,9 @@
+// Signature format: 4.0
+package androidx.hilt.navigation.fragment {
+
+  public final class HiltNavGraphViewModelLazyKt {
+    method @MainThread public static inline <reified VM extends androidx.lifecycle.ViewModel> kotlin.Lazy<? extends VM>! hiltNavGraphViewModels(androidx.fragment.app.Fragment, @IdRes int navGraphId);
+  }
+
+}
+

hilt/hilt-navigation-fragment/build.gradle

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+
+import androidx.build.LibraryGroups
+import androidx.build.LibraryVersions
+import androidx.build.Publish
+
+import static androidx.build.dependencies.DependenciesKt.*
+
+plugins {
+    id("AndroidXPlugin")
+    id("com.android.library")
+    id("kotlin-android")
+    id("kotlin-kapt")
+    id("dagger.hilt.android.plugin")
+}
+
+android {
+    defaultConfig {
+        testInstrumentationRunner "androidx.hilt.navigation.fragment.TestRunner"
+    }
+}
+
+dependencies {
+    api(KOTLIN_STDLIB)
+    api(project(":hilt:hilt-navigation"))
+    api("androidx.navigation:navigation-fragment-ktx:2.3.2")
+
+    androidTestImplementation(projectOrArtifact(":fragment:fragment-testing"))
+    androidTestImplementation(ANDROIDX_TEST_EXT_JUNIT)
+    androidTestImplementation(ANDROIDX_TEST_CORE)
+    androidTestImplementation(ANDROIDX_TEST_RUNNER)
+    androidTestImplementation(ANDROIDX_TEST_RULES)
+    androidTestImplementation(TRUTH)
+    androidTestImplementation(HILT_ANDROID)
+    androidTestImplementation(HILT_ANDROID_TESTING)
+    kaptAndroidTest(HILT_COMPILER)
+    androidTestImplementation(project(":internal-testutils-runtime"))
+    androidTestImplementation(project(":internal-testutils-navigation"), {
+        exclude group: 'androidx.navigation', module: 'navigation-common-ktx'
+    })
+}
+
+androidx {
+    name = "Android Navigation Fragment Hilt Extension"
+    publish = Publish.SNAPSHOT_AND_RELEASE
+    mavenVersion = LibraryVersions.HILT
+    mavenGroup = LibraryGroups.HILT
+    inceptionYear = "2021"
+    description = "Android Navigation Fragment Hilt Extension"
+}

hilt/hilt-navigation-fragment/src/androidTest/AndroidManifest.xml

@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~ Copyright (C) 2017 The Android Open Source Project
+  ~
+  ~ Licensed under the Apache License, Version 2.0 (the "License");
+  ~ you may not use this file except in compliance with the License.
+  ~ You may obtain a copy of the License at
+  ~
+  ~      http://www.apache.org/licenses/LICENSE-2.0
+  ~
+  ~ Unless required by applicable law or agreed to in writing, software
+  ~ distributed under the License is distributed on an "AS IS" BASIS,
+  ~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  ~ See the License for the specific language governing permissions and
+  ~ limitations under the License.
+  -->
+
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+          package="androidx.navigation.fragment.ktx">
+    <application>
+        <activity android:name="androidx.hilt.navigation.fragment.NavGraphActivity" />
+    </application>
+</manifest>

hilt/hilt-navigation-fragment/src/androidTest/java/androidx/hilt/navigation/fragment/HiltNavGraphViewModelLazyTest.kt

@@ -0,0 +1,149 @@
+/*
+ * Copyright 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package androidx.hilt.navigation.fragment
+
+import android.os.Bundle
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import androidx.fragment.app.Fragment
+import androidx.fragment.app.FragmentActivity
+import androidx.hilt.navigation.fragment.test.R
+import androidx.lifecycle.SavedStateHandle
+import androidx.lifecycle.ViewModel
+import androidx.navigation.findNavController
+import androidx.test.core.app.ActivityScenario
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import androidx.test.filters.LargeTest
+import androidx.testutils.withActivity
+import com.google.common.truth.Truth.assertThat
+import dagger.hilt.android.AndroidEntryPoint
+import dagger.hilt.android.lifecycle.HiltViewModel
+import dagger.hilt.android.testing.HiltAndroidRule
+import dagger.hilt.android.testing.HiltAndroidTest
+import org.junit.Rule
+import org.junit.Test
+import org.junit.runner.RunWith
+import javax.inject.Inject
+
+/*
+ * Copyright 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+@LargeTest
+@HiltAndroidTest
+@RunWith(AndroidJUnit4::class)
+class HiltNavGraphViewModelLazyTest {
+
+    @get:Rule
+    val testRule = HiltAndroidRule(this)
+
+    @Test
+    fun sameViewModelAcrossFragments() {
+        with(ActivityScenario.launch(NavGraphActivity::class.java)) {
+            val navController = withActivity { findNavController(R.id.nav_host_fragment) }
+            val firstFragment: TestVMFragment = withActivity {
+                val navHostFragment = supportFragmentManager
+                    .findFragmentById(R.id.nav_host_fragment)!!
+                navHostFragment.childFragmentManager.primaryNavigationFragment as TestVMFragment
+            }
+            val viewModel = withActivity { firstFragment.viewModel }
+            val savedStateViewModel = withActivity { firstFragment.savedStateViewModel }
+            assertThat(viewModel).isNotNull()
+            assertThat(savedStateViewModel).isNotNull()
+
+            // First assert that we don't have any default value since the
+            // navigation graph wasn't sent any arguments
+            val initialState: String? = savedStateViewModel.savedStateHandle["test"]
+            assertThat(initialState).isNull()
+
+            // Now set arguments
+            savedStateViewModel.savedStateHandle.set("test", "test")
+
+            // Navigate to the second destination and ensure it
+            // gets the same ViewModels and data
+            withActivity {
+                navController.navigate(R.id.second_destination)
+            }
+            val secondFragment: TestVMFragment = withActivity {
+                val navHostFragment = supportFragmentManager
+                    .findFragmentById(R.id.nav_host_fragment)!!
+                navHostFragment.childFragmentManager.primaryNavigationFragment as TestVMFragment
+            }
+            assertThat(secondFragment.viewModel)
+                .isSameInstanceAs(viewModel)
+            assertThat(secondFragment.savedStateViewModel)
+                .isSameInstanceAs(savedStateViewModel)
+            val savedValue: String? = secondFragment.savedStateViewModel
+                .savedStateHandle["test"]
+            assertThat(savedValue).isEqualTo("test")
+
+            // Now recreate the Activity and ensure that when we
+            // first request the nav graph ViewModel on the second destination
+            // that we get the same ViewModel and data back
+            recreate()
+            val recreatedFragment: TestVMFragment = withActivity {
+                val navHostFragment = supportFragmentManager
+                    .findFragmentById(R.id.nav_host_fragment)!!
+                navHostFragment.childFragmentManager.primaryNavigationFragment as TestVMFragment
+            }
+            assertThat(recreatedFragment.viewModel)
+                .isSameInstanceAs(viewModel)
+            assertThat(recreatedFragment.savedStateViewModel)
+                .isSameInstanceAs(savedStateViewModel)
+            val recreatedValue: String? = recreatedFragment.savedStateViewModel
+                .savedStateHandle["test"]
+            assertThat(recreatedValue).isEqualTo("test")
+        }
+    }
+}
+
+@AndroidEntryPoint
+class NavGraphActivity : FragmentActivity(R.layout.activity_nav_graph)
+
+@AndroidEntryPoint
+class TestVMFragment : Fragment() {
+    val viewModel: TestViewModel by hiltNavGraphViewModels(R.id.vm_graph)
+    val savedStateViewModel: TestSavedStateViewModel by hiltNavGraphViewModels(R.id.vm_graph)
+    override fun onCreateView(
+        inflater: LayoutInflater,
+        container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View? {
+        return View(activity)
+    }
+}
+
+@HiltViewModel
+class TestViewModel @Inject constructor() : ViewModel()
+
+@HiltViewModel
+class TestSavedStateViewModel @Inject constructor(
+    val savedStateHandle: SavedStateHandle
+) : ViewModel()

hilt/hilt-navigation-fragment/src/androidTest/java/androidx/hilt/navigation/fragment/TestRunner.kt

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package androidx.hilt.navigation.fragment
+
+import android.app.Application
+import android.content.Context
+import androidx.test.runner.AndroidJUnitRunner
+import dagger.hilt.android.testing.HiltTestApplication
+
+class TestRunner : AndroidJUnitRunner() {
+    override fun newApplication(
+        cl: ClassLoader?,
+        className: String?,
+        context: Context?
+    ): Application {
+        return super.newApplication(cl, HiltTestApplication::class.java.name, context)
+    }
+}

hilt/hilt-navigation-fragment/src/androidTest/res/layout/activity_nav_graph.xml

@@ -0,0 +1,26 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  Copyright 2021 The Android Open Source Project
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+  -->
+
+<fragment
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:id="@+id/nav_host_fragment"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:name="androidx.navigation.fragment.NavHostFragment"
+    app:defaultNavHost="true"
+    app:navGraph="@navigation/vm_graph" />

hilt/hilt-navigation-fragment/src/androidTest/res/navigation/vm_graph.xml

@@ -0,0 +1,37 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  Copyright 2021 The Android Open Source Project
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+  -->
+
+<navigation
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:id="@+id/vm_graph"
+    app:startDestination="@+id/start_destination">
+    <fragment
+        android:id="@+id/start_destination"
+        android:name="androidx.hilt.navigation.fragment.TestVMFragment">
+        <argument
+            android:name="test"
+            android:defaultValue="first"/>
+    </fragment>
+    <fragment
+        android:id="@+id/second_destination"
+        android:name="androidx.hilt.navigation.fragment.TestVMFragment">
+        <argument
+            android:name="test"
+            android:defaultValue="second" />
+    </fragment>
+</navigation>