fix(sidecar): stop dropping gestures, selectors and keys in silence

a point outside the screen is refused with OUT_OF_RANGE, a selector that matches nothing with NOT_FOUND, and a key with no device-driver equivalent throws instead of pressing nothing. parseBounds also reads uiautomator's [left,top][right,bottom] form, which is what a device actually reports and which left every by-selector tap on a device resolving to nothing.

sidecar/src/main/kotlin/dev/sanderling/sidecar/DriverBackend.kt

@@ -859,20 +859,43 @@ class MaestroDriverBackend(private val serial: String?) : DriverBackend {
 
     override fun terminate(bundleId: String) = driver.stopApp(bundleId)
 
-    override fun tap(x: Int, y: Int) = driver.tap(maestro.Point(x, y))
+    // requireOnScreen refuses a point the device has no window under. Android
+    // drops such a MotionEvent in InputDispatcher and the on-device server's
+    // TapResponse carries no delivery signal, so this is the last layer that
+    // can tell the runner the gesture reached nothing.
+    private fun requireOnScreen(x: Int, y: Int) {
+        val cached = extent
+        if (cached != null && !offScreen(x, y, cached.first, cached.second)) return
+        val info = driver.deviceInfo()
+        val fresh = Pair(info.widthPixels, info.heightPixels)
+        extent = fresh
+        if (!offScreen(x, y, fresh.first, fresh.second)) return
+        throw io.grpc.Status.OUT_OF_RANGE
+            .withDescription(
+                "gesture point ($x,$y) is outside the ${fresh.first}x${fresh.second} screen",
+            )
+            .asRuntimeException()
+    }
 
-    override fun longPress(x: Int, y: Int) =
+    // A cached extent is re-read before any refusal, so a screen that resized
+    // mid-run cannot make the sidecar invent gesture failures for valid points.
+    @Volatile
+    private var extent: Pair<Int, Int>? = null
+
+    override fun tap(x: Int, y: Int) {
+        requireOnScreen(x, y)
+        driver.tap(maestro.Point(x, y))
+    }
+
+    override fun longPress(x: Int, y: Int) {
+        requireOnScreen(x, y)
         driver.longPress(maestro.Point(x, y))
+    }
 
     override fun tapSelector(selector: String) {
         val root = driver.contentDescriptor(false)
-        val bounds = findBoundsBySelector(root, selector) ?: return
-        driver.tap(
-            maestro.Point(
-                (bounds[0] + bounds[2]) / 2,
-                (bounds[1] + bounds[3]) / 2,
-            ),
-        )
+        val bounds = requireBoundsBySelector(root, selector)
+        tap((bounds[0] + bounds[2]) / 2, (bounds[1] + bounds[3]) / 2)
     }
 
     override fun inputText(text: String) {
@@ -926,14 +949,17 @@ class MaestroDriverBackend(private val serial: String?) : DriverBackend {
         toX: Int,
         toY: Int,
         durationMillis: Long,
-    ) = driver.swipe(
-        maestro.Point(fromX, fromY),
-        maestro.Point(toX, toY),
-        maxOf(durationMillis, 250L),
-    )
+    ) {
+        requireOnScreen(fromX, fromY)
+        driver.swipe(
+            maestro.Point(fromX, fromY),
+            maestro.Point(toX, toY),
+            maxOf(durationMillis, 250L),
+        )
+    }
 
     override fun pressKey(key: String) {
-        maestroKeyFor(key)?.let { driver.pressKey(it) }
+        driver.pressKey(maestroKeyFor(key))
     }
 
     override fun screenshot(): Triple<ByteArray, Int, Int> {
@@ -1026,6 +1052,18 @@ private fun buildDadb(serial: String?): dadb.Dadb =
         )
     }
 
+// requireBoundsBySelector refuses a selector that names nothing on the current
+// screen. Returning quietly dispatched no tap at all and left the step reading
+// as an action that landed. NOT_FOUND keeps it apart from the OUT_OF_RANGE a
+// point outside the screen gets: this one never resolved a point to begin with.
+internal fun requireBoundsBySelector(
+    root: maestro.TreeNode,
+    selector: String,
+): IntArray = findBoundsBySelector(root, selector)
+    ?: throw io.grpc.Status.NOT_FOUND
+        .withDescription("selector $selector matched no element")
+        .asRuntimeException()
+
 internal fun findBoundsBySelector(
     root: maestro.TreeNode,
     selector: String,
@@ -1073,9 +1111,19 @@ internal fun findBoundsInTree(
     return null
 }
 
+// Device trees report bounds as uiautomator's [left,top][right,bottom]; the
+// flat four-number form comes from the trees the stub backend serves. Reading
+// only the flat form left every by-selector tap on a device resolving to
+// nothing, which the caller never heard about.
+private val boundsPairs =
+    Regex("^\\[(-?\\d+),(-?\\d+)\\]\\[(-?\\d+),(-?\\d+)\\]$")
+private val boundsFlat =
+    Regex("^\\[(-?\\d+),(-?\\d+),(-?\\d+),(-?\\d+)\\]$")
+
 internal fun parseBounds(s: String): IntArray? {
-    val pattern = Regex("^\\[(-?\\d+),(-?\\d+),(-?\\d+),(-?\\d+)\\]$")
-    val m = pattern.matchEntire(s) ?: return null
+    val m = boundsPairs.matchEntire(s)
+        ?: boundsFlat.matchEntire(s)
+        ?: return null
     return IntArray(4) { m.groupValues[it + 1].toInt() }
 }
 
@@ -1194,12 +1242,21 @@ internal class WdaRecovery(
     }
 }
 
+// offScreen reports a point outside the device's touch surface. The upper
+// bounds are exclusive: a tap at x == width is dropped by InputDispatcher just
+// as one past it is.
+internal fun offScreen(x: Int, y: Int, width: Int, height: Int): Boolean =
+    x < 0 || y < 0 || x >= width || y >= height
+
 // maestroKeyFor rejects an unknown key (matching StubDriverBackend) so an
-// unmapped or wrong-case key fails loudly instead of being silently dropped.
-internal fun maestroKeyFor(key: String): maestro.KeyCode? {
+// unmapped or wrong-case key fails loudly instead of being silently dropped. A
+// mapped key with no device-driver equivalent is rejected the same way: it
+// returned null, and the caller then dropped the press with no error at all.
+internal fun maestroKeyFor(key: String): maestro.KeyCode {
     val keyCode = StubDriverBackend.KEY_MAP[key.lowercase()]
         ?: throw IllegalArgumentException("unsupported pressKey value: $key")
     return keyCodeToMaestro(keyCode)
+        ?: throw IllegalArgumentException("no device key for $keyCode")
 }
 
 private fun keyCodeToMaestro(adbKeyCode: String): maestro.KeyCode? =

sidecar/src/test/kotlin/dev/sanderling/sidecar/DeviceOutputParserTest.kt

@@ -2,6 +2,7 @@ package dev.sanderling.sidecar
 
 import org.junit.Test
 import kotlin.test.assertEquals
+import kotlin.test.assertFailsWith
 import kotlin.test.assertNull
 import kotlin.test.assertTrue
 
@@ -136,6 +137,20 @@ class DeviceOutputParserTest {
         assertNull(findBoundsBySelector(tree, "id:missing"))
     }
 
+    @Test fun findBoundsBySelectorReadsTheBoundsTheDeviceActuallyReports() {
+        val tree = node("text" to "Sign in", "bounds" to "[129,274][192,292]")
+        assertEquals(listOf(129, 274, 192, 292), findBoundsBySelector(tree, "text:Sign in")?.toList())
+    }
+
+    @Test fun requireBoundsBySelectorRefusesASelectorThatMatchesNothing() {
+        val tree = node("resource-id" to "com.example:id/x", "bounds" to "[0,0,4,4]")
+        assertEquals(listOf(0, 0, 4, 4), requireBoundsBySelector(tree, "id:x").toList())
+        val refused = assertFailsWith<io.grpc.StatusRuntimeException> {
+            requireBoundsBySelector(tree, "id:missing")
+        }
+        assertEquals(io.grpc.Status.Code.NOT_FOUND, refused.status.code)
+    }
+
     @Test fun findBoundsBySelectorReturnsNullWhenMatchHasMalformedBounds() {
         val tree = node("resource-id" to "com.example:id/x", "bounds" to "not-bounds")
         assertNull(findBoundsBySelector(tree, "id:x"))

sidecar/src/test/kotlin/dev/sanderling/sidecar/OffScreenGestureTest.kt

@@ -0,0 +1,29 @@
+package dev.sanderling.sidecar
+
+import kotlin.test.Test
+import kotlin.test.assertFalse
+import kotlin.test.assertTrue
+
+class OffScreenGestureTest {
+
+    @Test
+    fun `a point inside the screen is delivered`() {
+        assertFalse(offScreen(160, 283, 320, 640))
+        assertFalse(offScreen(0, 0, 320, 640))
+        assertFalse(offScreen(319, 639, 320, 640))
+    }
+
+    @Test
+    fun `a point past an edge is off screen`() {
+        assertTrue(offScreen(160, 900, 320, 640))
+        assertTrue(offScreen(900, 283, 320, 640))
+        assertTrue(offScreen(160, -100, 320, 640))
+        assertTrue(offScreen(-1, 283, 320, 640))
+    }
+
+    @Test
+    fun `the far edge is exclusive because InputDispatcher drops it`() {
+        assertTrue(offScreen(320, 283, 320, 640))
+        assertTrue(offScreen(160, 640, 320, 640))
+    }
+}