Hint at the problem in the "Didn't find op for builtin opcode ... version ..." error.

PiperOrigin-RevId: 350545885
Change-Id: I18528ab009bbb6e6a30e67e683ebdb1fe3ba00d0

tensorflow/lite/c/c_api_experimental_test.cc

@@ -20,6 +20,7 @@ limitations under the License.
 #include <memory>
 #include <vector>
 
+#include <gmock/gmock.h>
 #include <gtest/gtest.h>
 #include "tensorflow/lite/builtin_ops.h"
 #include "tensorflow/lite/c/c_api.h"
@@ -27,6 +28,7 @@ limitations under the License.
 #include "tensorflow/lite/delegates/delegate_test_util.h"
 #include "tensorflow/lite/testing/util.h"
 
+using testing::HasSubstr;
 using tflite::delegates::test_utils::TestDelegate;
 
 namespace {
@@ -108,9 +110,9 @@ TEST(CApiExperimentalTest, MissingBuiltin) {
   // Check that interpreter creation failed, because the model contain a buitin
   // op that wasn't supported, and that we got the expected error messages.
   ASSERT_EQ(interpreter, nullptr);
-  EXPECT_EQ(reporter.error_messages(),
-            "Didn't find op for builtin opcode 'ADD' version '1'\n"
-            "Registration failed.\n");
+  EXPECT_THAT(
+      reporter.error_messages(),
+      HasSubstr("Didn't find op for builtin opcode 'ADD' version '1'."));
   EXPECT_EQ(reporter.num_calls(), 2);
 
   TfLiteInterpreterDelete(interpreter);

tensorflow/lite/core/api/op_resolver.cc

@@ -43,7 +43,9 @@ TfLiteStatus GetRegistrationFromOpCode(
     if (*registration == nullptr) {
       TF_LITE_REPORT_ERROR(
           error_reporter,
-          "Didn't find op for builtin opcode '%s' version '%d'\n",
+          "Didn't find op for builtin opcode '%s' version '%d'. "
+          "An older version of this builtin might be supported. "
+          "Are you using an old TFLite binary with a newer model?\n",
           EnumNameBuiltinOperator(builtin_code), version);
       status = kTfLiteError;
     }