[Impeller] Validation errors in tests cause GTest failures. (flutter/engine#53786)

Earlier, this used to take down the entire process. Now, the entire set of failures will be listed instead.

engine/src/flutter/impeller/base/validation.cc

@@ -12,11 +12,16 @@ namespace impeller {
 
 static std::atomic_int32_t sValidationLogsDisabledCount = 0;
 static std::atomic_int32_t sValidationLogsAreFatal = 0;
+static ValidationFailureCallback sValidationFailureCallback;
 
 void ImpellerValidationErrorsSetFatal(bool fatal) {
   sValidationLogsAreFatal = fatal;
 }
 
+void ImpellerValidationErrorsSetCallback(ValidationFailureCallback callback) {
+  sValidationFailureCallback = std::move(callback);
+}
+
 ScopedValidationDisable::ScopedValidationDisable() {
   sValidationLogsDisabledCount++;
 }
@@ -47,6 +52,10 @@ std::ostream& ValidationLog::GetStream() {
 }
 
 void ImpellerValidationBreak(const char* message, const char* file, int line) {
+  if (sValidationFailureCallback &&
+      sValidationFailureCallback(message, file, line)) {
+    return;
+  }
   const auto severity =
       ImpellerValidationErrorsAreFatal() ? fml::LOG_FATAL : fml::LOG_ERROR;
   auto fml_log = fml::LogMessage{severity, file, line, nullptr};

engine/src/flutter/impeller/base/validation.h

@@ -5,6 +5,7 @@
 #ifndef FLUTTER_IMPELLER_BASE_VALIDATION_H_
 #define FLUTTER_IMPELLER_BASE_VALIDATION_H_
 
+#include <functional>
 #include <sstream>
 
 namespace impeller {
@@ -37,6 +38,21 @@ void ImpellerValidationErrorsSetFatal(bool fatal);
 
 bool ImpellerValidationErrorsAreFatal();
 
+using ValidationFailureCallback =
+    std::function<bool(const char* message, const char* file, int line)>;
+
+//------------------------------------------------------------------------------
+/// @brief      Sets a callback that callers (usually tests) can set to
+///             intercept validation failures.
+///
+///             Returning true from the callback indicates that Impeller can
+///             continue and avoid any default behavior on tripping validation
+///             (which could include process termination).
+///
+/// @param[in]  callback  The callback
+///
+void ImpellerValidationErrorsSetCallback(ValidationFailureCallback callback);
+
 struct ScopedValidationDisable {
   ScopedValidationDisable();
 

engine/src/flutter/impeller/playground/playground_test.cc

@@ -11,9 +11,26 @@
 namespace impeller {
 
 PlaygroundTest::PlaygroundTest()
-    : Playground(PlaygroundSwitches{flutter::testing::GetArgsForProcess()}) {}
+    : Playground(PlaygroundSwitches{flutter::testing::GetArgsForProcess()}) {
+  ImpellerValidationErrorsSetCallback(
+      [](const char* message, const char* file, int line) -> bool {
+        // GTEST_MESSAGE_AT_ can only be used in a function that returns void.
+        // Hence the goofy lambda. The failure message and location will still
+        // be correct however.
+        //
+        // https://google.github.io/googletest/advanced.html#assertion-placement
+        [message, file, line]() -> void {
+          GTEST_MESSAGE_AT_(file, line, "Impeller Validation Error",
+                            ::testing::TestPartResult::kFatalFailure)
+              << message;
+        }();
+        return true;
+      });
+}
 
-PlaygroundTest::~PlaygroundTest() = default;
+PlaygroundTest::~PlaygroundTest() {
+  ImpellerValidationErrorsSetCallback(nullptr);
+}
 
 namespace {
 bool DoesSupportWideGamutTests() {
@@ -36,8 +53,6 @@ void PlaygroundTest::SetUp() {
     return;
   }
 
-  ImpellerValidationErrorsSetFatal(true);
-
   // Test names that end with "WideGamut" will render with wide gamut support.
   std::string test_name = flutter::testing::GetCurrentTestName();
   PlaygroundSwitches switches = switches_;