fix: 命令处理器在执行时读 props，不用组合期捕获的值

compose/build.gradle.kts

@@ -50,6 +50,11 @@ kotlin {
         iosMain.dependencies {
             implementation(libs.ktor.client.darwin)
         }
+        // composition-level tests run on the simulator; the Android host tests have no window
+        iosTest.dependencies {
+            @OptIn(org.jetbrains.compose.ExperimentalComposeLibrary::class)
+            implementation(compose.uiTest)
+        }
         commonTest.dependencies {
             implementation(libs.kotlin.test)
             implementation(libs.kotlinx.coroutines.test)

compose/src/commonMain/kotlin/app/tinyui/components/Builtins.kt

@@ -263,8 +263,9 @@ private fun boxAlignment(name: String?): Alignment = when (name) {
  */
 @Composable
 private fun TextFieldComponent(scope: NodeScope) {
-    val maxLength = scope.get<Double>("maxLength")?.toInt()?.takeIf { it > 0 }
-    fun clip(t: String) = clipTo(t, maxLength)
+    // read when used, not captured: a command runs before the recomposition that would refresh a captured value
+    fun clip(t: String) = clipTo(t, scope.get<Double>("maxLength")?.toInt()?.takeIf { it > 0 })
+    val maxLength = scope.get<Double>("maxLength")
     var text by retain { mutableStateOf(clip(scope.get<String>("initialText") ?: "")) }
     var focused by remember { mutableStateOf(false) }
     val focusRequester = remember { FocusRequester() }
@@ -330,19 +331,22 @@ private fun TextFieldComponent(scope: NodeScope) {
  */
 @Composable
 private fun CodeFieldComponent(scope: NodeScope) {
-    val length = (scope.get<Double>("length")?.toInt() ?: 6).coerceIn(1, MAX_CODE_LENGTH)
+    fun length() = (scope.get<Double>("length")?.toInt() ?: 6).coerceIn(1, MAX_CODE_LENGTH)
+    val length = length()
     var value by retain { mutableStateOf(TextFieldValue("")) }
     val focusRequester = remember { FocusRequester() }
     val focusManager = LocalFocusManager.current
     var focused by remember { mutableStateOf(false) }
     // [force]: commands report onChange even when nothing changed, like TextField.setText
     fun update(raw: String, force: Boolean = false) {
-        val t = raw.filter { it in '0'..'9' }.take(length)
+        // the live prop, like TextField.clip: a command may run before this composition saw a new length
+        val max = length()
+        val t = raw.filter { it in '0'..'9' }.take(max)
         val changed = t != value.text
         value = TextFieldValue(t, selection = TextRange(t.length))
         if (!changed && !force) return
         if (scope.has("onChange")) scope.dispatch("onChange", payload("text", t))
-        if (changed && t.length == length && scope.has("onComplete")) scope.dispatch("onComplete", payload("text", t))
+        if (changed && t.length == max && scope.has("onComplete")) scope.dispatch("onComplete", payload("text", t))
     }
     // fewer cells drop the digits that no longer fit at once, rather than keeping them hidden until the next edit
     LaunchedEffect(length) { if (value.text.length > length) update(value.text) }

compose/src/commonMain/kotlin/app/tinyui/schema/NodeScope.kt

@@ -43,7 +43,11 @@ interface NodeScope {
     fun RenderChild(child: UINode)
 }
 
-/** Consumes this node's commands as they arrive, oldest first; one-shot, after composition (docs/adr-004 §3.2). */
+/**
+ * Consumes this node's commands as they arrive, oldest first; one-shot, after composition (docs/adr-004 §3.2).
+ * A command arrives once its flush is applied, but before the recomposition that flush causes: the handler must read
+ * the props it depends on through [NodeScope.get] when it runs, not use values captured during composition.
+ */
 @Composable
 fun NodeScope.Commands(handler: suspend (Command) -> Unit) {
     val node = node

compose/src/iosTest/kotlin/app/tinyui/components/CommandPropsTest.kt

@@ -0,0 +1,63 @@
+package app.tinyui.components
+
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.test.ExperimentalTestApi
+import androidx.compose.ui.test.v2.runComposeUiTest
+import app.tinyui.node.NodeTree
+import app.tinyui.node.PatchProblem
+import app.tinyui.node.UINode
+import app.tinyui.schema.ComponentRegistry
+import app.tinyui.schema.NodeScope
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+
+/** A command arrives after its flush is applied but before the recomposition it causes (docs/components.md §4). */
+@OptIn(ExperimentalTestApi::class)
+class CommandPropsTest {
+    private val problems = ArrayList<PatchProblem>()
+    private val registry = ComponentRegistry().registerBuiltins()
+    private val tree = NodeTree(registry) { problems += it }
+    private val events = ArrayList<String>()
+
+    /** The page's scope without a page: props and events from the node, dispatch recorded. */
+    private fun scopeOf(node: UINode) = object : NodeScope {
+        override val node = node
+        @Suppress("UNCHECKED_CAST")
+        override fun <T> get(key: String): T? = (node.props[key] ?: registry.schema(node.type)?.prop(key)?.default) as T?
+        override fun has(event: String) = node.events[event] == true
+        override fun dispatch(event: String, payload: String) { events += "$event $payload" }
+        @Composable override fun modifier(clickable: Boolean) = Modifier
+        @Composable override fun Children() {}
+        @Composable override fun RenderChild(child: UINode) {}
+    }
+
+    @Test
+    fun textFieldSetTextClipsToTheLimitOfItsOwnFlush() = runComposeUiTest {
+        tree.apply("""[["c",1,"TextField"],["p",1,"maxLength",4],["p",1,"onChange",true],["i",0,1,0]]""")
+        val scope = scopeOf(tree.node(1)!!)
+        setContent { MaterialTheme { registry.Render("TextField", scope) } }
+        waitForIdle()
+        // one flush raises the limit and sets text longer than the old one
+        tree.apply("""[["p",1,"maxLength",10],["x",1,"setText",{"text":"123456"}]]""")
+        waitForIdle()
+        assertTrue(problems.isEmpty(), problems.toString())
+        assertEquals(1, events.size, events.toString())
+        assertTrue("123456" in events.single(), "clipped with the limit of an earlier composition: ${events.single()}")
+    }
+
+    @Test
+    fun codeFieldSetTextTakesTheLengthOfItsOwnFlush() = runComposeUiTest {
+        tree.apply("""[["c",1,"CodeField"],["p",1,"length",4],["p",1,"onChange",true],["i",0,1,0]]""")
+        val scope = scopeOf(tree.node(1)!!)
+        setContent { MaterialTheme { registry.Render("CodeField", scope) } }
+        waitForIdle()
+        tree.apply("""[["p",1,"length",6],["x",1,"setText",{"text":"123456"}]]""")
+        waitForIdle()
+        assertTrue(problems.isEmpty(), problems.toString())
+        assertEquals(1, events.size, events.toString())
+        assertTrue("123456" in events.single(), "took the length of an earlier composition: ${events.single()}")
+    }
+}

docs/components.md

@@ -181,6 +181,8 @@ const [open, setOpen] = signal(false);
 
 命令进节点的 `commands` 队列（不是 props），组件用 `scope.Commands { command -> … }` 在组合后按到达顺序消费，一次性。`LazyColumn` 的 `scrollTo` 与新增行同一 flush 到达时，行先进 children，命令随后执行，index 已经有效。
 
+**处理器要在执行时读 props**：命令在它那批 flush 提交后送达，但早于这批引起的重组。处理器若用组合期捕获的值（`val maxLength = scope.get(...)` 再闭包进去），同一批里改 prop 又发命令时就用了旧值。`TextField.setText` 裁剪、`CodeField.setText` 取位数都在处理器里现读 `scope.get`，自定义组件照此办。
+
 ## 5. `Placeholder`
 
 未注册的类型渲染 `Placeholder`，同时 E5 上报。debug 构建（Android `FLAG_DEBUGGABLE`、iOS debug binary）画红框加类型名与 id；release 渲染零尺寸的空 `Box`。