Generate testing APIs (cashapp#787)

* Generate testing APIs

* Code review feedback

* Generate testing facets for the test-schema

redwood-cli/src/main/kotlin/app/cash/redwood/cli/GenerateCommand.kt

@@ -38,6 +38,7 @@ internal class GenerateCommand : CliktCommand(name = "generate") {
       "--compose" to CodegenType.Compose,
       "--compose-protocol" to ProtocolCodegenType.Compose,
       "--layout-modifiers" to CodegenType.LayoutModifiers,
+      "--testing" to CodegenType.Testing,
       "--widget" to CodegenType.Widget,
       "--widget-protocol" to ProtocolCodegenType.Widget,
     )

redwood-compose-testing/build.gradle

@@ -11,12 +11,16 @@ kotlin {
     commonMain {
       dependencies {
         api libs.jetbrains.compose.runtime
-        api libs.kotlin.test
         api libs.kotlinx.coroutines.core
         api projects.redwoodCompose
         api projects.redwoodRuntime
       }
     }
+    commonTest {
+      dependencies {
+        implementation libs.kotlin.test
+      }
+    }
   }
 }
 

redwood-compose-testing/src/commonMain/kotlin/app/cash/redwood/compose/testing/WidgetValue.kt

@@ -15,10 +15,66 @@
  */
 package app.cash.redwood.compose.testing
 
+import app.cash.redwood.LayoutModifier
+
 /**
  * A widget that's implemented as a value class, appropriate for use in tests.
  *
  * Implementations of this interface may have lambda properties that trigger application behavior.
  * These lambda properties are **excluded** from [Any.equals], [Any.hashCode], and [Any.toString].
  */
-public interface WidgetValue
+public interface WidgetValue {
+  public val layoutModifiers: LayoutModifier
+
+  /** Returns all of the direct children of this widget, grouped by slot. */
+  public val childrenLists: List<List<WidgetValue>>
+    get() = listOf()
+}
+
+/**
+ * Returns a sequence that does a depth-first preorder traversal of the entire widget tree whose
+ * roots are this list. This is the same order elements occur in code.
+ *
+ * For example, given the following structure:
+ *
+ * ```
+ * Column {
+ *   Toolbar {
+ *     Icon(...)
+ *     Title(...)
+ *   }
+ *   Row {
+ *     Text(...)
+ *     Button(...)
+ *   }
+ * }
+ * ```
+ *
+ * The flattened elements are returned in this order:
+ *
+ * ```
+ * Column,
+ * Toolbar,
+ * Icon,
+ * Title,
+ * Row,
+ * Text,
+ * Button
+ * ```
+ */
+public fun List<WidgetValue>.flatten(): Sequence<WidgetValue> {
+  return sequence {
+    for (widget in this@flatten) {
+      flattenRecursive(widget)
+    }
+  }
+}
+
+private suspend fun SequenceScope<WidgetValue>.flattenRecursive(widgetValue: WidgetValue) {
+  yield(widgetValue)
+  for (children in widgetValue.childrenLists) {
+    for (child in children) {
+      flattenRecursive(child)
+    }
+  }
+}

redwood-compose-testing/src/commonTest/kotlin/app/cash/redwood/compose/testing/WidgetValueTest.kt

@@ -0,0 +1,80 @@
+/*
+ * Copyright (C) 2023 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.
+ */
+package app.cash.redwood.compose.testing
+
+import app.cash.redwood.LayoutModifier
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class WidgetValueTest {
+  @Test
+  fun flattenNoHierarchy() {
+    val a = SimpleWidgetValue()
+    val b = SimpleWidgetValue()
+    val c = SimpleWidgetValue()
+
+    assertEquals(
+      listOf(),
+      listOf<WidgetValue>().flatten().toList(),
+    )
+    assertEquals(
+      listOf(a),
+      listOf<WidgetValue>(a).flatten().toList(),
+    )
+    assertEquals(
+      listOf(a, b, c),
+      listOf<WidgetValue>(a, b, c).flatten().toList(),
+    )
+  }
+
+  @Test
+  fun flattenParentsFirst() {
+    val a = SimpleWidgetValue()
+    val aa = SimpleWidgetValue(childrenLists = listOf(listOf(a)))
+    val aaa = SimpleWidgetValue(childrenLists = listOf(listOf(aa)))
+
+    assertEquals(
+      listOf(aa, a),
+      listOf<WidgetValue>(aa).flatten().toList(),
+    )
+    assertEquals(
+      listOf(aaa, aa, a),
+      listOf<WidgetValue>(aaa).flatten().toList(),
+    )
+  }
+
+  @Test
+  fun flattenSiblingSubtreeFirst() {
+    val a = SimpleWidgetValue()
+    val aa = SimpleWidgetValue(childrenLists = listOf(listOf(a)))
+    val aaa = SimpleWidgetValue(childrenLists = listOf(listOf(aa)))
+    val b = SimpleWidgetValue()
+
+    assertEquals(
+      listOf(aa, a, b),
+      listOf<WidgetValue>(aa, b).flatten().toList(),
+    )
+    assertEquals(
+      listOf(aaa, aa, a, b),
+      listOf<WidgetValue>(aaa, b).flatten().toList(),
+    )
+  }
+
+  class SimpleWidgetValue(
+    override val layoutModifiers: LayoutModifier = LayoutModifier,
+    override val childrenLists: List<List<WidgetValue>> = listOf(),
+  ) : WidgetValue
+}

redwood-gradle-plugin/build.gradle

@@ -54,6 +54,12 @@ gradlePlugin {
       description = "Redwood schema layout modifier code generation Gradle plugin"
       implementationClass = "app.cash.redwood.gradle.RedwoodLayoutModifiersGeneratorPlugin"
     }
+    redwoodTestingGenerator {
+      id = "app.cash.redwood.generator.testing"
+      displayName = "Redwood generator (testing)"
+      description = "Redwood schema testing code generation Gradle plugin"
+      implementationClass = "app.cash.redwood.gradle.RedwoodTestingGeneratorPlugin"
+    }
     redwoodWidgetGenerator {
       id = "app.cash.redwood.generator.widget"
       displayName = "Redwood generator (widget)"

redwood-gradle-plugin/src/main/kotlin/app/cash/redwood/gradle/RedwoodGeneratorPlugin.kt

@@ -18,6 +18,7 @@ package app.cash.redwood.gradle
 import app.cash.redwood.gradle.RedwoodGeneratorPlugin.Strategy.Compose
 import app.cash.redwood.gradle.RedwoodGeneratorPlugin.Strategy.ComposeProtocol
 import app.cash.redwood.gradle.RedwoodGeneratorPlugin.Strategy.LayoutModifiers
+import app.cash.redwood.gradle.RedwoodGeneratorPlugin.Strategy.Testing
 import app.cash.redwood.gradle.RedwoodGeneratorPlugin.Strategy.Widget
 import app.cash.redwood.gradle.RedwoodGeneratorPlugin.Strategy.WidgetProtocol
 import org.gradle.api.Plugin
@@ -35,6 +36,9 @@ public class RedwoodComposeProtocolGeneratorPlugin : RedwoodGeneratorPlugin(Comp
 @Suppress("unused") // Invoked reflectively by Gradle.
 public class RedwoodLayoutModifiersGeneratorPlugin : RedwoodGeneratorPlugin(LayoutModifiers)
 
+@Suppress("unused") // Invoked reflectively by Gradle.
+public class RedwoodTestingGeneratorPlugin : RedwoodGeneratorPlugin(Testing)
+
 @Suppress("unused") // Invoked reflectively by Gradle.
 public class RedwoodWidgetGeneratorPlugin : RedwoodGeneratorPlugin(Widget)
 
@@ -51,6 +55,7 @@ public abstract class RedwoodGeneratorPlugin(
     Compose("--compose", "redwood-compose"),
     ComposeProtocol("--compose-protocol", "redwood-protocol-compose"),
     LayoutModifiers("--layout-modifiers", "redwood-runtime"),
+    Testing("--testing", "redwood-compose-testing"),
     Widget("--widget", "redwood-widget"),
     WidgetProtocol("--widget-protocol", "redwood-protocol-widget"),
   }

redwood-layout-testing/build.gradle

@@ -0,0 +1,22 @@
+apply plugin: 'org.jetbrains.kotlin.multiplatform'
+apply plugin: 'app.cash.redwood.generator.testing'
+apply plugin: 'com.vanniktech.maven.publish'
+apply plugin: 'org.jetbrains.dokka' // Must be applied here for publish plugin.
+
+kotlin {
+  apply from: "${rootDir}/addAllTargets.gradle"
+
+  sourceSets {
+    commonMain {
+      dependencies {
+        api projects.redwoodLayoutLayoutmodifiers
+        api projects.redwoodLayoutWidget
+      }
+    }
+  }
+}
+
+redwoodSchema {
+  source = projects.redwoodLayoutSchema
+  type = 'app.cash.redwood.layout.RedwoodLayout'
+}

redwood-layout-testing/gradle.properties

@@ -0,0 +1,2 @@
+POM_ARTIFACT_ID=redwood-layout-testing
+POM_NAME=Redwood Layout Testing

redwood-tooling-codegen/src/main/kotlin/app/cash/redwood/tooling/codegen/codegen.kt

@@ -17,13 +17,15 @@ package app.cash.redwood.tooling.codegen
 
 import app.cash.redwood.tooling.codegen.CodegenType.Compose
 import app.cash.redwood.tooling.codegen.CodegenType.LayoutModifiers
+import app.cash.redwood.tooling.codegen.CodegenType.Testing
 import app.cash.redwood.tooling.codegen.CodegenType.Widget
 import app.cash.redwood.tooling.schema.Schema
 import java.nio.file.Path
 
 public enum class CodegenType {
   Compose,
   LayoutModifiers,
+  Testing,
   Widget,
 }
 
@@ -43,6 +45,14 @@ public fun Schema.generate(type: CodegenType, destination: Path) {
         generateLayoutModifierInterface(this, layoutModifier).writeTo(destination)
       }
     }
+    Testing -> {
+      generateTester(this).writeTo(destination)
+      generateMutableWidgetFactory(this).writeTo(destination)
+      for (widget in widgets) {
+        generateMutableWidget(this, widget).writeTo(destination)
+        generateWidgetValue(this, widget).writeTo(destination)
+      }
+    }
     Widget -> {
       generateWidgetFactories(this).writeTo(destination)
       generateWidgetFactory(this).writeTo(destination)

redwood-tooling-codegen/src/main/kotlin/app/cash/redwood/tooling/codegen/composeGeneration.kt

@@ -22,7 +22,6 @@ import app.cash.redwood.tooling.schema.Widget
 import app.cash.redwood.tooling.schema.Widget.Children
 import app.cash.redwood.tooling.schema.Widget.Event
 import app.cash.redwood.tooling.schema.Widget.Property
-import com.squareup.kotlinpoet.AnnotationSpec
 import com.squareup.kotlinpoet.ClassName
 import com.squareup.kotlinpoet.CodeBlock
 import com.squareup.kotlinpoet.FileSpec
@@ -75,11 +74,7 @@ internal fun generateComposable(
       FunSpec.builder(flatName)
         .addModifiers(PUBLIC)
         .addAnnotation(ComposeRuntime.Composable)
-        .addAnnotation(
-          AnnotationSpec.builder(Stdlib.OptIn)
-            .addMember("%T::class", Redwood.RedwoodCodegenApi)
-            .build(),
-        )
+        .addAnnotation(Redwood.OptInToRedwoodCodegenApi)
         .apply {
           // Set the layout modifier as the last non-child lambda in the function signature.
           // This ensures you can still use trailing lambda syntax.

redwood-tooling-codegen/src/main/kotlin/app/cash/redwood/tooling/codegen/sharedHelpers.kt

@@ -92,6 +92,18 @@ internal fun Schema.getWidgetFactoryType(): ClassName {
   return ClassName(widgetPackage(this), "${name}WidgetFactory")
 }
 
+internal fun Schema.getMutableWidgetFactoryType(): ClassName {
+  return ClassName(widgetPackage(this), "Mutable${name}WidgetFactory")
+}
+
+internal fun Schema.mutableWidgetType(widget: Widget): ClassName {
+  return ClassName(widgetPackage(this), "Mutable${widget.type.flatName}")
+}
+
+internal fun Schema.widgetValueType(widget: Widget): ClassName {
+  return ClassName(widgetPackage(this), "${widget.type.flatName}Value")
+}
+
 internal fun Schema.getWidgetFactoryProviderType(): ClassName {
   return ClassName(widgetPackage(this), "${name}WidgetFactoryProvider")
 }
@@ -120,6 +132,10 @@ internal fun Schema.layoutModifierImpl(layoutModifier: LayoutModifier): ClassNam
   return ClassName(composePackage(), layoutModifier.type.simpleName!! + "Impl")
 }
 
+internal fun Schema.getTesterFunction(): MemberName {
+  return MemberName(widgetPackage(this), "${name}Tester")
+}
+
 internal val Schema.toLayoutModifier: MemberName get() =
   MemberName(widgetPackage(this), "toLayoutModifier")