Honor the PlatformColor fallback in ColorPropConverter on Android

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/bridge/ColorPropConverter.kt

@@ -23,6 +23,7 @@ public object ColorPropConverter {
   private fun supportWideGamut(): Boolean = Build.VERSION.SDK_INT >= Build.VERSION_CODES.O
 
   private const val JSON_KEY = "resource_paths"
+  private const val FALLBACK_KEY = "fallback"
   private const val PREFIX_RESOURCE = "@"
   private const val PREFIX_ATTR = "?"
   private const val PACKAGE_DELIMITER = ":"
@@ -65,15 +66,18 @@ public object ColorPropConverter {
         }
       }
 
+      val fallback = resolveFallback(value)
+      if (fallback != null) {
+        return fallback
+      }
+
       val attemptedPaths = (0 until resourcePaths.size()).map { resourcePaths.getString(it) }
       FLog.w(
           ReactConstants.TAG,
           "ColorValue: Failed to resolve resource paths: ${attemptedPaths.joinToString(", ")}",
       )
 
-      throw JSApplicationCausedNativeException(
-          "ColorValue: None of the paths in the `$JSON_KEY` array resolved to a color resource.",
-      )
+      return Color.TRANSPARENT
     }
 
     throw JSApplicationCausedNativeException("ColorValue: the value must be a number or Object.")
@@ -121,12 +125,21 @@ public object ColorPropConverter {
         }
       }
 
+      val fallback = resolveFallback(value)
+      if (supportWideGamut() && fallback != null) {
+        return Color.valueOf(fallback)
+      }
+
       val attemptedPaths = (0 until resourcePaths.size()).map { resourcePaths.getString(it) }
       FLog.w(
           ReactConstants.TAG,
           "ColorValue: Failed to resolve resource paths: ${attemptedPaths.joinToString(", ")}",
       )
 
+      if (supportWideGamut()) {
+        return Color.valueOf(Color.TRANSPARENT)
+      }
+
       throw JSApplicationCausedNativeException(
           "ColorValue: None of the paths in the `$JSON_KEY` array resolved to a color resource.",
       )
@@ -162,6 +175,14 @@ public object ColorPropConverter {
     }
   }
 
+  private fun resolveFallback(value: ReadableMap): Int? {
+    if (!value.hasKey(FALLBACK_KEY)) {
+      return null
+    }
+    val fallback = value.getString(FALLBACK_KEY) ?: return null
+    return RawColorParser.nativeParse(fallback)
+  }
+
   @JvmStatic
   public fun resolveResourcePath(context: Context, resourcePath: String?): Int? {
     if (resourcePath.isNullOrEmpty()) {

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/bridge/RawColorParser.kt

@@ -0,0 +1,19 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+package com.facebook.react.bridge
+
+import com.facebook.proguard.annotations.DoNotStrip
+
+@DoNotStrip
+internal object RawColorParser {
+  init {
+    ReactNativeJNISoLoader.staticInit()
+  }
+
+  @DoNotStrip @JvmStatic external fun nativeParse(value: String): Int?
+}

packages/react-native/ReactAndroid/src/main/jni/react/jni/CMakeLists.txt

@@ -64,6 +64,7 @@ add_library(
           MethodInvoker.cpp
           ModuleRegistryBuilder.cpp
           OnLoad.cpp
+          RawColorParser.cpp
         SafeReleaseJniRef.cpp
           ScrollEventHelper.cpp
           TouchesHelper.cpp
@@ -83,6 +84,7 @@ target_link_libraries(reactnativejni
         logger
         react_cxxreact
         react_cxxstableapi
+        react_renderer_css
         react_renderer_runtimescheduler
         reactnativejni_common
         rrc_view

packages/react-native/ReactAndroid/src/main/jni/react/jni/OnLoad.cpp

@@ -11,6 +11,7 @@
 #include <fbjni/fbjni.h>
 
 #include "InspectorNetworkRequestListener.h"
+#include "RawColorParser.h"
 #include "ScrollEventHelper.h"
 #include "TouchesHelper.h"
 #include "TransformHelper.h"
@@ -36,6 +37,7 @@ extern "C" JNIEXPORT jint JNI_OnLoad(JavaVM* vm, void* reserved) {
     FLAGS_minloglevel = 0;
 #endif
     InspectorNetworkRequestListener::registerNatives();
+    RawColorParser::registerNatives();
     ScrollEventHelper::registerNatives();
     TouchesHelper::registerNatives();
     TransformHelper::registerNatives();

packages/react-native/ReactAndroid/src/main/jni/react/jni/RawColorParser.cpp

@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include "RawColorParser.h"
+
+#include <react/renderer/css/CSSColor.h>
+#include <react/renderer/css/CSSValueParser.h>
+#include <react/renderer/graphics/Color.h>
+
+namespace facebook::react {
+
+namespace {
+
+jni::local_ref<jni::JInteger> parse(
+    jni::alias_ref<jclass> /*unused*/,
+    std::string value) {
+  auto cssColor = parseCSSProperty<CSSColor>(value);
+  if (std::holds_alternative<CSSColor>(cssColor)) {
+    auto c = std::get<CSSColor>(cssColor);
+    return jni::JInteger::valueOf(
+        hostPlatformColorFromRGBA(c.r, c.g, c.b, c.a));
+  }
+  return nullptr;
+}
+
+} // namespace
+
+void RawColorParser::registerNatives() {
+  javaClassLocal()->registerNatives({
+      makeNativeMethod("nativeParse", parse),
+  });
+}
+
+} // namespace facebook::react

packages/react-native/ReactAndroid/src/main/jni/react/jni/RawColorParser.h

@@ -0,0 +1,21 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#pragma once
+
+#include <fbjni/fbjni.h>
+
+namespace facebook::react {
+
+class RawColorParser : public jni::JavaClass<RawColorParser> {
+ public:
+  static auto constexpr *kJavaDescriptor = "Lcom/facebook/react/bridge/RawColorParser;";
+
+  static void registerNatives();
+};
+
+} // namespace facebook::react

packages/react-native/ReactAndroid/src/test/java/com/facebook/react/bridge/ColorPropConverterTest.kt

@@ -8,16 +8,21 @@
 package com.facebook.react.bridge
 
 import android.content.Context
+import android.graphics.Color
 import android.view.ContextThemeWrapper
+import com.facebook.testutils.shadows.ShadowRawColorParser
+import com.facebook.testutils.shadows.ShadowSoLoader
 import org.assertj.core.api.Assertions.assertThat
 import org.junit.Before
 import org.junit.Test
 import org.junit.runner.RunWith
 import org.robolectric.RobolectricTestRunner
 import org.robolectric.RuntimeEnvironment
+import org.robolectric.annotation.Config
 
 /** Tests for [ColorPropConverter] */
 @RunWith(RobolectricTestRunner::class)
+@Config(shadows = [ShadowSoLoader::class, ShadowRawColorParser::class])
 class ColorPropConverterTest {
 
   private lateinit var context: Context
@@ -45,6 +50,58 @@ class ColorPropConverterTest {
     assertThat(result).isEqualTo(themeColor(android.R.attr.textColorPrimary))
   }
 
+  @Test
+  fun unresolvedPathUsesFallback() {
+    val result = ColorPropConverter.getColor(platformColor("@color/missing", "#ff0000"), context)
+
+    assertThat(result).isEqualTo(Color.RED)
+  }
+
+  @Test
+  fun unresolvedPathUsesFallbackOverDefault() {
+    val result = ColorPropConverter.getColor(platformColor("@color/missing", "#ff0000"), context, 0)
+
+    assertThat(result).isEqualTo(Color.RED)
+  }
+
+  @Test
+  fun unresolvedPathUsesTransparentFallback() {
+    val result = ColorPropConverter.getColor(platformColor("?attr/missing", "transparent"), context)
+
+    assertThat(result).isEqualTo(Color.TRANSPARENT)
+  }
+
+  @Test
+  fun resolvedPathIgnoresFallback() {
+    val result =
+        ColorPropConverter.getColor(platformColor("?android:attr/colorAccent", "#ff0000"), context)
+
+    assertThat(result).isEqualTo(themeColor(android.R.attr.colorAccent))
+  }
+
+  @Test
+  fun unresolvedPathWithoutFallbackIsTransparent() {
+    val result = ColorPropConverter.getColor(platformColor("@color/missing"), context)
+
+    assertThat(result).isEqualTo(Color.TRANSPARENT)
+  }
+
+  @Test
+  fun unresolvedPathWithInvalidFallbackIsTransparent() {
+    val result =
+        ColorPropConverter.getColor(platformColor("@color/missing", "not-a-color"), context)
+
+    assertThat(result).isEqualTo(Color.TRANSPARENT)
+  }
+
+  private fun platformColor(path: String, fallback: String? = null): ReadableMap {
+    val map = JavaOnlyMap.of("resource_paths", JavaOnlyArray.of(path))
+    if (fallback != null) {
+      map.putString("fallback", fallback)
+    }
+    return map
+  }
+
   private fun themeColor(attr: Int): Int {
     val typedArray = context.obtainStyledAttributes(intArrayOf(attr))
     val color = typedArray.getColor(0, 0)

packages/react-native/ReactAndroid/src/test/java/com/facebook/testutils/shadows/ShadowRawColorParser.kt

@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+package com.facebook.testutils.shadows
+
+import android.graphics.Color
+import com.facebook.react.bridge.RawColorParser
+import org.robolectric.annotation.Implementation
+import org.robolectric.annotation.Implements
+
+@Implements(RawColorParser::class)
+class ShadowRawColorParser {
+  companion object {
+    /** Stands in for the native CSS color parser with a fixed lookup table. */
+    @JvmStatic
+    @Implementation
+    fun nativeParse(value: String): Int? =
+        when (value) {
+          "#ff0000" -> Color.RED
+          "transparent" -> Color.TRANSPARENT
+          else -> null
+        }
+  }
+}

scripts/cxx-api/api-snapshots/ReactAndroidDebugCxx.api

@@ -2128,6 +2128,11 @@ class facebook::react::PullToRefreshViewProps : public facebook::react::HostPlat
   public virtual folly::dynamic getDiffProps(const facebook::react::Props* prevProps) const override;
 }
 
+class facebook::react::RawColorParser : public facebook::jni::JavaClass<facebook::react::RawColorParser> {
+  public static constexpr auto * kJavaDescriptor;
+  public static void registerNatives();
+}
+
 class facebook::react::RawProps {
   public RawProps();
   public RawProps(const facebook::react::RawProps& other) noexcept;

scripts/cxx-api/api-snapshots/ReactAndroidFrameworksCxx.api

@@ -3275,6 +3275,11 @@ class facebook::react::PullToRefreshViewProps : public facebook::react::HostPlat
   public virtual folly::dynamic getDiffProps(const facebook::react::Props* prevProps) const override;
 }
 
+class facebook::react::RawColorParser : public facebook::jni::JavaClass<facebook::react::RawColorParser> {
+  public static constexpr auto * kJavaDescriptor;
+  public static void registerNatives();
+}
+
 class facebook::react::RawProps {
   public RawProps();
   public RawProps(const facebook::react::RawProps& other) noexcept;

scripts/cxx-api/api-snapshots/ReactAndroidNewarchCxx.api

@@ -2127,6 +2127,11 @@ class facebook::react::PullToRefreshViewProps : public facebook::react::HostPlat
   public virtual folly::dynamic getDiffProps(const facebook::react::Props* prevProps) const override;
 }
 
+class facebook::react::RawColorParser : public facebook::jni::JavaClass<facebook::react::RawColorParser> {
+  public static constexpr auto * kJavaDescriptor;
+  public static void registerNatives();
+}
+
 class facebook::react::RawProps {
   public RawProps();
   public RawProps(const facebook::react::RawProps& other) noexcept;

scripts/cxx-api/api-snapshots/ReactAndroidReleaseCxx.api

@@ -2127,6 +2127,11 @@ class facebook::react::PullToRefreshViewProps : public facebook::react::HostPlat
   public virtual folly::dynamic getDiffProps(const facebook::react::Props* prevProps) const override;
 }
 
+class facebook::react::RawColorParser : public facebook::jni::JavaClass<facebook::react::RawColorParser> {
+  public static constexpr auto * kJavaDescriptor;
+  public static void registerNatives();
+}
+
 class facebook::react::RawProps {
   public RawProps();
   public RawProps(const facebook::react::RawProps& other) noexcept;