Honor EmptyImageSource.isExpectedEmpty in controllers

Differential Revision: D113540276

fbshipit-source-id: 8b435eec1780fe3cd5eb117040deb7daca92ba2b

Author: oprisnik

vito/core-impl/src/main/java/com/facebook/fresco/vito/core/impl/KFrescoController.kt

@@ -42,6 +42,7 @@ import com.facebook.fresco.vito.source.BitmapImageSource
 import com.facebook.fresco.vito.source.ColorImageSource
 import com.facebook.fresco.vito.source.DrawableImageSource
 import com.facebook.fresco.vito.source.DrawableResImageSource
+import com.facebook.fresco.vito.source.EmptyImageSource
 import com.facebook.imagepipeline.image.CloseableBitmap
 import com.facebook.imagepipeline.image.CloseableImage
 import com.facebook.imagepipeline.image.CloseableStaticBitmap
@@ -236,6 +237,24 @@ class KFrescoController(
           setDrawableAsActualImage(drawable, resourceDrawable, imageRequest, imageId)
           return true
         }
+        is EmptyImageSource -> {
+          // Expected empty: caller opted in via `isExpectedEmpty` and the config flag is on. Route
+          // through `onEmptyEvent` + placeholder — skipping the default fetch path where
+          // `ImageSourceToImagePipelineAdapter.NO_REQUEST_SUPPLIER` produces an immediate failure
+          // with `"No image request was specified!"`. The config read is the LAST condition so we
+          // only exercise the new path when the source is genuinely expected-empty. Non-expected
+          // empty sources fall through to today's failure path.
+          if (source.isExpectedEmpty && config.handleExpectedEmptyImageSource()) {
+            drawable.listenerManager.onEmptyEvent(callerContext)
+            drawable.placeholderLayer.setPlaceholder(imageRequest.resources, options)
+            drawable.listenerManager.onPlaceholderSet(
+                imageId,
+                imageRequest,
+                drawable.placeholderLayer.getDataModel().maybeGetDrawable(),
+            )
+            return true
+          }
+        }
       }
 
       // Check if the image is in cache

vito/core-java-impl/src/main/java/com/facebook/fresco/vito/core/impl/FrescoController2Impl.kt

@@ -95,8 +95,17 @@ open class FrescoController2Impl(
       FLog.e(TAG, "Drawable not supported $drawable")
       return false
     }
-    // Fast path for null-URIs
-    if (config.fastPathForEmptyRequests() && imageRequest.imageSource is EmptyImageSource) {
+    // Fast path for null-URIs. Two entry points: (a) the existing global
+    // `fastPathForEmptyRequests` toggle, or (b) a per-source opt-in via
+    // `EmptyImageSource.isExpectedEmpty` (callers who know "no image" is the legitimate outcome and
+    // want it counted as onEmptyEvent rather than onFailure). The config read is the LAST condition
+    // so (b) only exercises the new path when the source is genuinely expected-empty.
+    val emptySource = imageRequest.imageSource as? EmptyImageSource
+    if (
+        emptySource != null &&
+            (config.fastPathForEmptyRequests() ||
+                (emptySource.isExpectedEmpty && config.handleExpectedEmptyImageSource()))
+    ) {
       emptyRequestFastPath(drawable, imageRequest, callerContext)
       return true
     }

vito/core/src/main/java/com/facebook/fresco/vito/core/DefaultFrescoVitoConfig.kt

@@ -52,6 +52,8 @@ constructor(override val prefetchConfig: PrefetchConfig = DefaultPrefetchConfig(
 
   override fun fastPathForEmptyRequests(): Boolean = false
 
+  override fun handleExpectedEmptyImageSource(): Boolean = false
+
   override fun enableWindowWideColorGamut(): Boolean = false
 
   override fun handleImageResultInBackground(): Boolean = false

vito/core/src/main/java/com/facebook/fresco/vito/core/FrescoVitoConfig.kt

@@ -48,6 +48,14 @@ interface FrescoVitoConfig {
 
   fun fastPathForEmptyRequests(): Boolean
 
+  /**
+   * When on, controllers honor [EmptyImageSource.isExpectedEmpty] and route "expected empty"
+   * requests through the `onEmptyEvent` success-with-no-image callback path instead of firing
+   * `onFailure` with `"No image request was specified!"`. Default off preserves legacy failure
+   * semantics for all callers.
+   */
+  fun handleExpectedEmptyImageSource(): Boolean = false
+
   fun enableWindowWideColorGamut(): Boolean
 
   fun handleImageResultInBackground(): Boolean