[Impeller] fail CI if validations are enabled but not available. (flutter#51378)

Fixes flutter#145041

Will test this by unsetting the VVL configuration

Author: Jonah Williams

impeller/playground/backend/vulkan/playground_impl_vk.cc

@@ -88,6 +88,9 @@ PlaygroundImplVK::PlaygroundImplVK(PlaygroundSwitches switches)
   context_settings.shader_libraries_data = ShaderLibraryMappingsForPlayground();
   context_settings.cache_directory = fml::paths::GetCachesDirectory();
   context_settings.enable_validation = switches_.enable_vulkan_validation;
+  context_settings.fatal_missing_validations =
+      switches_.enable_vulkan_validation;
+  ;
 
   auto context_vk = ContextVK::Create(std::move(context_settings));
   if (!context_vk || !context_vk->IsValid()) {

impeller/renderer/backend/vulkan/capabilities_vk.cc

@@ -14,7 +14,8 @@ namespace impeller {
 
 static constexpr const char* kInstanceLayer = "ImpellerInstance";
 
-CapabilitiesVK::CapabilitiesVK(bool enable_validations) {
+CapabilitiesVK::CapabilitiesVK(bool enable_validations,
+                               bool fatal_missing_validations) {
   auto extensions = vk::enumerateInstanceExtensionProperties();
   auto layers = vk::enumerateInstanceLayerProperties();
 
@@ -45,6 +46,9 @@ CapabilitiesVK::CapabilitiesVK(bool enable_validations) {
         << "Requested Impeller context creation with validations but the "
            "validation layers could not be found. Expect no Vulkan validation "
            "checks!";
+    if (fatal_missing_validations) {
+      FML_LOG(FATAL) << "Validation missing. Exiting.";
+    }
   }
   if (validations_enabled_) {
     FML_LOG(INFO) << "Vulkan validations are enabled.";

impeller/renderer/backend/vulkan/capabilities_vk.h

@@ -113,7 +113,8 @@ enum class OptionalDeviceExtensionVK : uint32_t {
 class CapabilitiesVK final : public Capabilities,
                              public BackendCast<CapabilitiesVK, Capabilities> {
  public:
-  explicit CapabilitiesVK(bool enable_validations);
+  explicit CapabilitiesVK(bool enable_validations,
+                          bool fatal_missing_validations = false);
 
   ~CapabilitiesVK();
 

impeller/renderer/backend/vulkan/context_vk.cc

@@ -168,8 +168,8 @@ void ContextVK::Setup(Settings settings) {
   enable_validation = true;
 #endif
 
-  auto caps =
-      std::shared_ptr<CapabilitiesVK>(new CapabilitiesVK(enable_validation));
+  auto caps = std::shared_ptr<CapabilitiesVK>(new CapabilitiesVK(
+      enable_validation, settings.fatal_missing_validations));
 
   if (!caps->IsValid()) {
     VALIDATION_LOG << "Could not determine device capabilities.";

impeller/renderer/backend/vulkan/context_vk.h

@@ -49,6 +49,8 @@ class ContextVK final : public Context,
     fml::UniqueFD cache_directory;
     bool enable_validation = false;
     bool enable_gpu_tracing = false;
+    /// If validations are requested but cannot be enabled, log a fatal error.
+    bool fatal_missing_validations = false;
 
     Settings() = default;
 

impeller/renderer/backend/vulkan/context_vk_unittests.cc

@@ -222,6 +222,17 @@ TEST(ContextVKTest, WarmUpFunctionCreatesRenderPass) {
                         "vkCreateRenderPass") != functions->end());
 }
 
+TEST(ContextVKTest, FatalMissingValidations) {
+  EXPECT_DEATH(const std::shared_ptr<ContextVK> context =
+                   MockVulkanContextBuilder()
+                       .SetSettingsCallback([](ContextVK::Settings& settings) {
+                         settings.enable_validation = true;
+                         settings.fatal_missing_validations = true;
+                       })
+                       .Build(),
+               "");
+}
+
 TEST(ContextVKTest, HasDefaultColorFormat) {
   std::shared_ptr<ContextVK> context = MockVulkanContextBuilder().Build();