Introduce tooling module with support for previewing ViewBindings with Compose's Preview.

.buildscript/android-sample-app.gradle

@@ -1,8 +1,8 @@
 apply from: rootProject.file('.buildscript/configure-android-defaults.gradle')
 
 dependencies {
+  implementation(project(":compose-tooling"))
   implementation(Deps.get("androidx.appcompat"))
-  implementation(Deps.get("compose.tooling"))
   implementation(Deps.get("timber"))
   implementation(Deps.get("workflow.core"))
   implementation(Deps.get("workflow.runtime"))

compose-tooling/api/compose-tooling.api

@@ -0,0 +1,17 @@
+public final class com/squareup/workflow/ui/compose/tooling/BuildConfig {
+	public static final field BUILD_TYPE Ljava/lang/String;
+	public static final field DEBUG Z
+	public static final field LIBRARY_PACKAGE_NAME Ljava/lang/String;
+	public fun <init> ()V
+}
+
+public final class com/squareup/workflow/ui/compose/tooling/ComposeWorkflowsKt {
+	public static final fun preview (Lcom/squareup/workflow/compose/ComposeWorkflow;Ljava/lang/Object;Landroidx/ui/core/Modifier;Landroidx/ui/core/Modifier;Lkotlin/jvm/functions/Function1;Landroidx/compose/Composer;)V
+	public static synthetic fun preview$default (Lcom/squareup/workflow/compose/ComposeWorkflow;Ljava/lang/Object;Landroidx/ui/core/Modifier;Landroidx/ui/core/Modifier;Lkotlin/jvm/functions/Function1;Landroidx/compose/Composer;ILjava/lang/Object;)V
+}
+
+public final class com/squareup/workflow/ui/compose/tooling/ViewFactoriesKt {
+	public static final fun preview (Lcom/squareup/workflow/ui/ViewFactory;Ljava/lang/Object;Landroidx/ui/core/Modifier;Landroidx/ui/core/Modifier;Lkotlin/jvm/functions/Function1;Landroidx/compose/Composer;)V
+	public static synthetic fun preview$default (Lcom/squareup/workflow/ui/ViewFactory;Ljava/lang/Object;Landroidx/ui/core/Modifier;Landroidx/ui/core/Modifier;Lkotlin/jvm/functions/Function1;Landroidx/compose/Composer;ILjava/lang/Object;)V
+}
+

compose-tooling/build.gradle.kts

@@ -0,0 +1,43 @@
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+
+/*
+ * Copyright 2020 Square Inc.
+ *
+ * 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.
+ */
+plugins {
+  id("com.android.library")
+  kotlin("android")
+}
+
+java {
+  sourceCompatibility = JavaVersion.VERSION_1_8
+  targetCompatibility = JavaVersion.VERSION_1_8
+}
+
+apply(from = rootProject.file(".buildscript/configure-maven-publish.gradle"))
+apply(from = rootProject.file(".buildscript/configure-android-defaults.gradle"))
+apply(from = rootProject.file(".buildscript/android-ui-tests.gradle"))
+
+apply(from = rootProject.file(".buildscript/configure-compose.gradle"))
+tasks.withType<KotlinCompile> {
+  kotlinOptions.apiVersion = "1.3"
+}
+
+dependencies {
+  api(project(":core-compose"))
+  api(Dependencies.Compose.tooling)
+  api(Dependencies.Kotlin.stdlib)
+
+  implementation(Dependencies.Compose.foundation)
+}

compose-tooling/gradle.properties

@@ -0,0 +1,18 @@
+#
+# Copyright 2020 Square Inc.
+#
+# 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.
+#
+POM_ARTIFACT_ID=workflow-ui-compose-tooling
+POM_NAME=Workflow UI Compose Tooling
+POM_PACKAGING=aar

compose-tooling/src/androidTest/java/com/squareup/workflow/ui/compose/tooling/PreviewComposeWorkflowTest.kt

@@ -0,0 +1,154 @@
+/*
+ * Copyright 2020 Square Inc.
+ *
+ * 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.
+ */
+@file:Suppress("TestFunctionName", "PrivatePropertyName")
+
+package com.squareup.workflow.ui.compose.tooling
+
+import androidx.compose.Composable
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import androidx.ui.core.Modifier
+import androidx.ui.foundation.Text
+import androidx.ui.layout.Column
+import androidx.ui.layout.size
+import androidx.ui.semantics.Semantics
+import androidx.ui.test.assertIsDisplayed
+import androidx.ui.test.assertIsNotDisplayed
+import androidx.ui.test.createComposeRule
+import androidx.ui.test.findByText
+import androidx.ui.tooling.preview.Preview
+import androidx.ui.unit.dp
+import com.squareup.workflow.Workflow
+import com.squareup.workflow.compose.composed
+import com.squareup.workflow.ui.ViewEnvironmentKey
+import com.squareup.workflow.ui.compose.showRendering
+import org.junit.Rule
+import org.junit.Test
+import org.junit.runner.RunWith
+
+/**
+ * Duplicate of [PreviewViewFactoryTest] but for [com.squareup.workflow.compose.ComposeWorkflow].
+ */
+@RunWith(AndroidJUnit4::class)
+class PreviewComposeWorkflowTest {
+
+  @Rule @JvmField val composeRule = createComposeRule()
+
+  @Test fun singleChild() {
+    composeRule.setContent {
+      ParentWithOneChildPreview()
+    }
+
+    findByText("one").assertIsDisplayed()
+    findByText("two").assertIsDisplayed()
+  }
+
+  @Test fun twoChildren() {
+    composeRule.setContent {
+      ParentWithTwoChildrenPreview()
+    }
+
+    findByText("one").assertIsDisplayed()
+    findByText("two").assertIsDisplayed()
+    findByText("three").assertIsDisplayed()
+  }
+
+  @Test fun modifierIsApplied() {
+    composeRule.setContent {
+      ParentWithModifier()
+    }
+
+    // The view factory will be rendered with size (0,0), so it should be reported as not displayed.
+    findByText("one").assertIsNotDisplayed()
+    findByText("two").assertIsNotDisplayed()
+  }
+
+  @Test fun placeholderModifierIsApplied() {
+    composeRule.setContent {
+      ParentWithPlaceholderModifier()
+    }
+
+    // The child will be rendered with size (0,0), so it should be reported as not displayed.
+    findByText("one").assertIsDisplayed()
+    findByText("two").assertIsNotDisplayed()
+  }
+
+  @Test fun customViewEnvironment() {
+    composeRule.setContent {
+      ParentConsumesCustomKeyPreview()
+    }
+
+    findByText("foo").assertIsDisplayed()
+  }
+
+  private val ParentWithOneChild =
+    Workflow.composed<Pair<String, String>, Nothing> { props, _, environment ->
+      Column {
+        Text(props.first)
+        Semantics(container = true, mergeAllDescendants = true) {
+          environment.showRendering(rendering = props.second)
+        }
+      }
+    }
+
+  @Preview @Composable private fun ParentWithOneChildPreview() {
+    ParentWithOneChild.preview(Pair("one", "two"))
+  }
+
+  private val ParentWithTwoChildren =
+    Workflow.composed<Triple<String, String, String>, Nothing> { props, _, environment ->
+      Column {
+        Semantics(container = true) {
+          environment.showRendering(rendering = props.first)
+        }
+        Text(props.second)
+        Semantics(container = true) {
+          environment.showRendering(rendering = props.third)
+        }
+      }
+    }
+
+  @Preview @Composable private fun ParentWithTwoChildrenPreview() {
+    ParentWithTwoChildren.preview(Triple("one", "two", "three"))
+  }
+
+  @Preview @Composable private fun ParentWithModifier() {
+    ParentWithOneChild.preview(
+        Pair("one", "two"),
+        modifier = Modifier.size(0.dp)
+    )
+  }
+
+  @Preview @Composable private fun ParentWithPlaceholderModifier() {
+    ParentWithOneChild.preview(
+        Pair("one", "two"),
+        placeholderModifier = Modifier.size(0.dp)
+    )
+  }
+
+  object TestEnvironmentKey : ViewEnvironmentKey<String>(String::class) {
+    override val default: String get() = error("Not specified")
+  }
+
+  private val ParentConsumesCustomKey = Workflow.composed<Unit, Nothing> { _, _, environment ->
+    Text(environment[TestEnvironmentKey])
+  }
+
+  @Preview @Composable private fun ParentConsumesCustomKeyPreview() {
+    ParentConsumesCustomKey.preview(Unit) {
+      it + (TestEnvironmentKey to "foo")
+    }
+  }
+}