Simpler, safer ViewEnvironment and ViewRegistry management.

`ViewEnvironment(Map<ViewEnvironmentKey<*>, Any>)` makes it easy to build a
`ViewEnvironment` whose with values that don't match the type of the
`ViewEnvironmentKey`s. We deprecate it with an eye toward making it
non-public down the road. In its place we introduce `ViewEnvironment.EMPTY`,
and guide people to use it and the type safe `plus` operators.

We introduce a pattern of providing more `plus` operators with new environment
value types.

For `ViewRegistry`, in addition to the `plus` operator we provide a set of
`merge` methods, which finish the long overdue job of making it simpler to
mess with `ViewEnvironment` without stomping on `ViewRegistry` entries, and
to override them. `EnvironmentScreen.withRegistry` and `.withEnvironment` use
these.

Fixes #395.

Author: rjrjr

samples/compose-samples/src/main/java/com/squareup/sample/compose/hellocompose/App.kt

@@ -16,10 +16,9 @@ import com.squareup.workflow1.ui.ViewRegistry
 import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
 import com.squareup.workflow1.ui.compose.WorkflowRendering
 import com.squareup.workflow1.ui.compose.renderAsState
+import com.squareup.workflow1.ui.plus
 
-private val viewRegistry = ViewRegistry(HelloBinding)
-
-private val viewEnvironment = ViewEnvironment(mapOf(ViewRegistry to viewRegistry))
+private val viewEnvironment = ViewEnvironment.EMPTY + ViewRegistry(HelloBinding)
 
 @Composable fun App() {
   MaterialTheme {

samples/compose-samples/src/main/java/com/squareup/sample/compose/hellocomposebinding/HelloBindingActivity.kt

@@ -15,15 +15,13 @@ import com.squareup.workflow1.ui.WorkflowLayout
 import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
 import com.squareup.workflow1.ui.compose.composeViewFactory
 import com.squareup.workflow1.ui.compose.withCompositionRoot
+import com.squareup.workflow1.ui.plus
 import com.squareup.workflow1.ui.renderWorkflowIn
 import kotlinx.coroutines.flow.StateFlow
 
-@OptIn(WorkflowUiExperimentalApi::class)
-private val viewRegistry = ViewRegistry(HelloBinding)
-
 @OptIn(WorkflowUiExperimentalApi::class)
 private val viewEnvironment =
-  ViewEnvironment(mapOf(ViewRegistry to viewRegistry)).withCompositionRoot { content ->
+  (ViewEnvironment.EMPTY + ViewRegistry(HelloBinding)).withCompositionRoot { content ->
     MaterialTheme(content = content)
   }
 
@@ -37,22 +35,22 @@ class HelloBindingActivity : AppCompatActivity() {
 
     val model: HelloBindingModel by viewModels()
     setContentView(
-        WorkflowLayout(this).apply {
-          start(
-              renderings = model.renderings,
-              environment = viewEnvironment
-          )
-        }
+      WorkflowLayout(this).apply {
+        start(
+          renderings = model.renderings,
+          environment = viewEnvironment
+        )
+      }
     )
   }
 
   class HelloBindingModel(savedState: SavedStateHandle) : ViewModel() {
     @OptIn(WorkflowUiExperimentalApi::class)
     val renderings: StateFlow<Any> by lazy {
       renderWorkflowIn(
-          workflow = HelloWorkflow,
-          scope = viewModelScope,
-          savedStateHandle = savedState
+        workflow = HelloWorkflow,
+        scope = viewModelScope,
+        savedStateHandle = savedState
       )
     }
   }

samples/compose-samples/src/main/java/com/squareup/sample/compose/hellocomposeworkflow/HelloComposeWorkflow.kt

@@ -48,5 +48,5 @@ object HelloComposeWorkflow : ComposeWorkflow<String, Toggle>() {
 @Preview(showBackground = true)
 @Composable fun HelloComposeWorkflowPreview() {
   val rendering by HelloComposeWorkflow.renderAsState(props = "hello", onOutput = {})
-  WorkflowRendering(rendering, ViewEnvironment())
+  WorkflowRendering(rendering, ViewEnvironment.EMPTY)
 }

samples/compose-samples/src/main/java/com/squareup/sample/compose/inlinerendering/InlineRenderingWorkflow.kt

@@ -55,7 +55,7 @@ object InlineRenderingWorkflow : StatefulWorkflow<Unit, Int, Nothing, AndroidVie
 @Preview
 @Composable fun InlineRenderingWorkflowPreview() {
   val rendering by InlineRenderingWorkflow.renderAsState(props = Unit, onOutput = {})
-  WorkflowRendering(rendering, ViewEnvironment())
+  WorkflowRendering(rendering, ViewEnvironment.EMPTY)
 }
 
 @OptIn(ExperimentalAnimationApi::class)

samples/compose-samples/src/main/java/com/squareup/sample/compose/nestedrenderings/NestedRenderingsActivity.kt

@@ -15,6 +15,7 @@ import com.squareup.workflow1.ui.ViewRegistry
 import com.squareup.workflow1.ui.WorkflowLayout
 import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
 import com.squareup.workflow1.ui.compose.withCompositionRoot
+import com.squareup.workflow1.ui.plus
 import com.squareup.workflow1.ui.renderWorkflowIn
 import kotlinx.coroutines.flow.StateFlow
 
@@ -26,7 +27,7 @@ private val viewRegistry = ViewRegistry(
 
 @OptIn(WorkflowUiExperimentalApi::class)
 private val viewEnvironment =
-  ViewEnvironment(mapOf(ViewRegistry to viewRegistry)).withCompositionRoot { content ->
+  (ViewEnvironment.EMPTY + viewRegistry).withCompositionRoot { content ->
     CompositionLocalProvider(LocalBackgroundColor provides Color.Green) {
       content()
     }

samples/compose-samples/src/main/java/com/squareup/sample/compose/textinput/App.kt

@@ -1,4 +1,5 @@
 @file:OptIn(WorkflowUiExperimentalApi::class)
+@file:Suppress("FunctionName")
 
 package com.squareup.sample.compose.textinput
 
@@ -11,10 +12,9 @@ import com.squareup.workflow1.ui.ViewRegistry
 import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
 import com.squareup.workflow1.ui.compose.WorkflowRendering
 import com.squareup.workflow1.ui.compose.renderAsState
+import com.squareup.workflow1.ui.plus
 
-private val viewRegistry = ViewRegistry(TextInputViewFactory)
-
-private val viewEnvironment = ViewEnvironment(mapOf(ViewRegistry to viewRegistry))
+private val viewEnvironment = ViewEnvironment.EMPTY + ViewRegistry(TextInputViewFactory)
 
 @Composable fun TextInputApp() {
   MaterialTheme {

samples/containers/android/src/main/java/com/squareup/sample/container/overviewdetail/OverviewDetailConfig.kt

@@ -1,7 +1,8 @@
 package com.squareup.sample.container.overviewdetail
 
-import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
+import com.squareup.workflow1.ui.ViewEnvironment
 import com.squareup.workflow1.ui.ViewEnvironmentKey
+import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
 
 /**
  * [com.squareup.workflow1.ui.ViewEnvironment] value that informs views
@@ -34,3 +35,7 @@ enum class OverviewDetailConfig {
     override val default = None
   }
 }
+
+@WorkflowUiExperimentalApi
+operator fun ViewEnvironment.plus(config: OverviewDetailConfig): ViewEnvironment =
+  this + (OverviewDetailConfig to config)

samples/containers/android/src/main/java/com/squareup/sample/container/overviewdetail/OverviewDetailContainer.kt

@@ -56,14 +56,14 @@ class OverviewDetailContainer(view: View) : ScreenViewRunner<OverviewDetailScree
       // Since we have two sibling back stacks, we need to give them each different
       // SavedStateRegistry key prefixes.
       val overviewViewEnvironment = viewEnvironment
-        .withBackStackStateKeyPrefix(OverviewBackStackKey) + (OverviewDetailConfig to Overview)
+        .withBackStackStateKeyPrefix(OverviewBackStackKey) + Overview
       overviewStub!!.show(rendering.overviewRendering, overviewViewEnvironment)
       rendering.detailRendering
         ?.let { detail ->
           detailStub!!.actual.visibility = VISIBLE
           detailStub.show(
             detail,
-            viewEnvironment + (OverviewDetailConfig to Detail)
+            viewEnvironment + Detail
           )
         }
         ?: run {
@@ -81,7 +81,7 @@ class OverviewDetailContainer(view: View) : ScreenViewRunner<OverviewDetailScree
       ?.let { rendering.overviewRendering + it }
       ?: rendering.overviewRendering
 
-    stub.show(combined, viewEnvironment + (OverviewDetailConfig to Single))
+    stub.show(combined, viewEnvironment + Single)
   }
 
   companion object : ScreenViewFactory<OverviewDetailScreen> by ScreenViewRunner.bind(

workflow-ui/compose-tooling/src/androidTest/java/com/squareup/workflow1/ui/compose/tooling/PreviewViewFactoryTest.kt

@@ -79,7 +79,7 @@ internal class PreviewViewFactoryTest {
     composeRule.onNodeWithText("two").assertIsNotDisplayed()
   }
 
-  @Test fun customViewEnvironment() {
+  @Test fun customViewEnvironment.EMPTY {
     composeRule.setContent {
       ParentConsumesCustomKeyPreview()
     }

workflow-ui/compose-tooling/src/main/java/com/squareup/workflow1/ui/compose/tooling/PreviewViewEnvironment.kt

@@ -11,6 +11,7 @@ import com.squareup.workflow1.ui.ViewEnvironment
 import com.squareup.workflow1.ui.ViewFactory
 import com.squareup.workflow1.ui.ViewRegistry
 import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
+import com.squareup.workflow1.ui.plus
 import kotlin.reflect.KClass
 
 /**
@@ -30,7 +31,7 @@ import kotlin.reflect.KClass
     PreviewViewRegistry(mainFactory, placeholderViewFactory(placeholderModifier))
   }
   return remember(viewRegistry, viewEnvironmentUpdater) {
-    ViewEnvironment(mapOf(ViewRegistry to viewRegistry)).let { environment ->
+    (ViewEnvironment.EMPTY + viewRegistry).let { environment ->
       // Give the preview a chance to add its own elements to the ViewEnvironment.
       viewEnvironmentUpdater?.let { it(environment) } ?: environment
     }