[ML] fix NLP inference_config bwc serialization tests (elastic#89011)

The tests were failing because of span not being nulled out for question_answering and text_similarity tasks.

But, this change also attempts to make it more future proof so that if changes occur to the nlp task or tokenization configurations it will cause a failure more quickly and require handling the bwc testing.

closes: elastic#89008
(cherry picked from commit 480479d)

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/ZeroShotClassificationConfig.java

@@ -248,8 +248,8 @@ public String getHypothesisTemplate() {
         return hypothesisTemplate;
     }
 
-    public List<String> getLabels() {
-        return Optional.ofNullable(labels).orElse(List.of());
+    public Optional<List<String>> getLabels() {
+        return Optional.ofNullable(labels);
     }
 
     @Override

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/ZeroShotClassificationConfigUpdate.java

@@ -147,13 +147,13 @@ public InferenceConfig apply(InferenceConfig originalConfig) {
             tokenizationUpdate == null ? zeroShotConfig.getTokenization() : tokenizationUpdate.apply(zeroShotConfig.getTokenization()),
             zeroShotConfig.getHypothesisTemplate(),
             Optional.ofNullable(isMultiLabel).orElse(zeroShotConfig.isMultiLabel()),
-            Optional.ofNullable(labels).orElse(zeroShotConfig.getLabels()),
+            Optional.ofNullable(labels).orElse(zeroShotConfig.getLabels().orElse(null)),
             Optional.ofNullable(resultsField).orElse(zeroShotConfig.getResultsField())
         );
     }
 
     boolean isNoop(ZeroShotClassificationConfig originalConfig) {
-        return (labels == null || labels.equals(originalConfig.getLabels()))
+        return (labels == null || labels.equals(originalConfig.getLabels().orElse(null)))
             && (isMultiLabel == null || isMultiLabel.equals(originalConfig.isMultiLabel()))
             && (resultsField == null || resultsField.equals(originalConfig.getResultsField()))
             && super.isNoop();

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/InferenceConfigItemTestCase.java

@@ -15,6 +15,24 @@
 import org.elasticsearch.xcontent.NamedXContentRegistry;
 import org.elasticsearch.xcontent.ToXContent;
 import org.elasticsearch.xpack.core.ml.AbstractBWCSerializationTestCase;
+import org.elasticsearch.xpack.core.ml.inference.trainedmodel.FillMaskConfig;
+import org.elasticsearch.xpack.core.ml.inference.trainedmodel.FillMaskConfigTests;
+import org.elasticsearch.xpack.core.ml.inference.trainedmodel.InferenceConfig;
+import org.elasticsearch.xpack.core.ml.inference.trainedmodel.NerConfig;
+import org.elasticsearch.xpack.core.ml.inference.trainedmodel.NerConfigTests;
+import org.elasticsearch.xpack.core.ml.inference.trainedmodel.NlpConfig;
+import org.elasticsearch.xpack.core.ml.inference.trainedmodel.PassThroughConfig;
+import org.elasticsearch.xpack.core.ml.inference.trainedmodel.PassThroughConfigTests;
+import org.elasticsearch.xpack.core.ml.inference.trainedmodel.QuestionAnsweringConfig;
+import org.elasticsearch.xpack.core.ml.inference.trainedmodel.QuestionAnsweringConfigTests;
+import org.elasticsearch.xpack.core.ml.inference.trainedmodel.TextClassificationConfig;
+import org.elasticsearch.xpack.core.ml.inference.trainedmodel.TextClassificationConfigTests;
+import org.elasticsearch.xpack.core.ml.inference.trainedmodel.TextEmbeddingConfig;
+import org.elasticsearch.xpack.core.ml.inference.trainedmodel.TextEmbeddingConfigTests;
+import org.elasticsearch.xpack.core.ml.inference.trainedmodel.TextSimilarityConfig;
+import org.elasticsearch.xpack.core.ml.inference.trainedmodel.TextSimilarityConfigTests;
+import org.elasticsearch.xpack.core.ml.inference.trainedmodel.ZeroShotClassificationConfig;
+import org.elasticsearch.xpack.core.ml.inference.trainedmodel.ZeroShotClassificationConfigTests;
 
 import java.util.ArrayList;
 import java.util.Collections;
@@ -25,6 +43,29 @@
 
 public abstract class InferenceConfigItemTestCase<T extends VersionedNamedWriteable & ToXContent> extends AbstractBWCSerializationTestCase<
     T> {
+
+    static InferenceConfig mutateForVersion(NlpConfig inferenceConfig, Version version) {
+        if (inferenceConfig instanceof TextClassificationConfig textClassificationConfig) {
+            return TextClassificationConfigTests.mutateForVersion(textClassificationConfig, version);
+        } else if (inferenceConfig instanceof FillMaskConfig fillMaskConfig) {
+            return FillMaskConfigTests.mutateForVersion(fillMaskConfig, version);
+        } else if (inferenceConfig instanceof QuestionAnsweringConfig questionAnsweringConfig) {
+            return QuestionAnsweringConfigTests.mutateForVersion(questionAnsweringConfig, version);
+        } else if (inferenceConfig instanceof NerConfig nerConfig) {
+            return NerConfigTests.mutateForVersion(nerConfig, version);
+        } else if (inferenceConfig instanceof PassThroughConfig passThroughConfig) {
+            return PassThroughConfigTests.mutateForVersion(passThroughConfig, version);
+        } else if (inferenceConfig instanceof TextEmbeddingConfig textEmbeddingConfig) {
+            return TextEmbeddingConfigTests.mutateForVersion(textEmbeddingConfig, version);
+        } else if (inferenceConfig instanceof TextSimilarityConfig textSimilarityConfig) {
+            return TextSimilarityConfigTests.mutateForVersion(textSimilarityConfig, version);
+        } else if (inferenceConfig instanceof ZeroShotClassificationConfig zeroShotClassificationConfig) {
+            return ZeroShotClassificationConfigTests.mutateForVersion(zeroShotClassificationConfig, version);
+        } else {
+            throw new IllegalArgumentException("unknown inference config [" + inferenceConfig.getName() + "]");
+        }
+    }
+
     @Override
     protected NamedXContentRegistry xContentRegistry() {
         List<NamedXContentRegistry.Entry> namedXContent = new ArrayList<>();

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/TrainedModelConfigTests.java

@@ -28,9 +28,9 @@
 import org.elasticsearch.xpack.core.ml.inference.trainedmodel.IndexLocationTests;
 import org.elasticsearch.xpack.core.ml.inference.trainedmodel.InferenceConfig;
 import org.elasticsearch.xpack.core.ml.inference.trainedmodel.NerConfigTests;
+import org.elasticsearch.xpack.core.ml.inference.trainedmodel.NlpConfig;
 import org.elasticsearch.xpack.core.ml.inference.trainedmodel.PassThroughConfigTests;
 import org.elasticsearch.xpack.core.ml.inference.trainedmodel.RegressionConfigTests;
-import org.elasticsearch.xpack.core.ml.inference.trainedmodel.TextClassificationConfig;
 import org.elasticsearch.xpack.core.ml.inference.trainedmodel.TextClassificationConfigTests;
 import org.elasticsearch.xpack.core.ml.inference.trainedmodel.TextEmbeddingConfigTests;
 import org.elasticsearch.xpack.core.ml.job.messages.Messages;
@@ -391,8 +391,8 @@ protected TrainedModelConfig mutateInstanceForVersion(TrainedModelConfig instanc
             builder.setModelType(null);
             builder.setLocation(null);
         }
-        if (instance.getInferenceConfig()instanceof TextClassificationConfig textClassificationConfig) {
-            builder.setInferenceConfig(TextClassificationConfigTests.mutateInstance(textClassificationConfig, version));
+        if (instance.getInferenceConfig()instanceof NlpConfig nlpConfig) {
+            builder.setInferenceConfig(InferenceConfigItemTestCase.mutateForVersion(nlpConfig, version));
         }
         return builder.build();
     }

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/BertTokenizationTests.java

@@ -19,6 +19,19 @@ public class BertTokenizationTests extends AbstractBWCSerializationTestCase<Bert
 
     private boolean lenient;
 
+    public static BertTokenization mutateForVersion(BertTokenization instance, Version version) {
+        if (version.before(Version.V_8_2_0)) {
+            return new BertTokenization(
+                instance.doLowerCase,
+                instance.withSpecialTokens,
+                instance.maxSequenceLength,
+                instance.truncate,
+                null
+            );
+        }
+        return instance;
+    }
+
     @Before
     public void chooseStrictOrLenient() {
         lenient = randomBoolean();
@@ -41,7 +54,7 @@ protected BertTokenization createTestInstance() {
 
     @Override
     protected BertTokenization mutateInstanceForVersion(BertTokenization instance, Version version) {
-        return instance;
+        return mutateForVersion(instance, version);
     }
 
     public static BertTokenization createRandom() {

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/FillMaskConfigTests.java

@@ -22,6 +22,15 @@ protected boolean supportsUnknownFields() {
         return true;
     }
 
+    public static FillMaskConfig mutateForVersion(FillMaskConfig instance, Version version) {
+        return new FillMaskConfig(
+            instance.getVocabularyConfig(),
+            InferenceConfigTestScaffolding.mutateTokenizationForVersion(instance.getTokenization(), version),
+            instance.getNumTopClasses(),
+            instance.getResultsField()
+        );
+    }
+
     @Override
     protected Predicate<String> getRandomFieldsExcludeFilter() {
         return field -> field.isEmpty() == false;
@@ -44,7 +53,7 @@ protected FillMaskConfig createTestInstance() {
 
     @Override
     protected FillMaskConfig mutateInstanceForVersion(FillMaskConfig instance, Version version) {
-        return instance;
+        return mutateForVersion(instance, version);
     }
 
     public static FillMaskConfig createRandom() {

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/InferenceConfigTestScaffolding.java

@@ -7,8 +7,22 @@
 
 package org.elasticsearch.xpack.core.ml.inference.trainedmodel;
 
+import org.elasticsearch.Version;
+
 public final class InferenceConfigTestScaffolding {
 
+    static Tokenization mutateTokenizationForVersion(Tokenization tokenization, Version version) {
+        if (tokenization instanceof BertTokenization bertTokenization) {
+            return BertTokenizationTests.mutateForVersion(bertTokenization, version);
+        } else if (tokenization instanceof MPNetTokenization mpNetTokenization) {
+            return MPNetTokenizationTests.mutateForVersion(mpNetTokenization, version);
+        } else if (tokenization instanceof RobertaTokenization robertaTokenization) {
+            return RobertaTokenizationTests.mutateForVersion(robertaTokenization, version);
+        } else {
+            throw new IllegalArgumentException("unknown tokenization [" + tokenization.getName() + "]");
+        }
+    }
+
     static Tokenization cloneWithNewTruncation(Tokenization tokenization, Tokenization.Truncate truncate) {
         if (tokenization instanceof MPNetTokenization) {
             return new MPNetTokenization(

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/MPNetTokenizationTests.java

@@ -19,6 +19,19 @@ public class MPNetTokenizationTests extends AbstractBWCSerializationTestCase<MPN
 
     private boolean lenient;
 
+    static MPNetTokenization mutateForVersion(MPNetTokenization instance, Version version) {
+        if (version.before(Version.V_8_2_0)) {
+            return new MPNetTokenization(
+                instance.doLowerCase,
+                instance.withSpecialTokens,
+                instance.maxSequenceLength,
+                instance.truncate,
+                null
+            );
+        }
+        return instance;
+    }
+
     @Before
     public void chooseStrictOrLenient() {
         lenient = randomBoolean();
@@ -41,7 +54,7 @@ protected MPNetTokenization createTestInstance() {
 
     @Override
     protected MPNetTokenization mutateInstanceForVersion(MPNetTokenization instance, Version version) {
-        return instance;
+        return mutateForVersion(instance, version);
     }
 
     public static MPNetTokenization createRandom() {

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/NerConfigTests.java

@@ -21,6 +21,15 @@
 
 public class NerConfigTests extends InferenceConfigItemTestCase<NerConfig> {
 
+    public static NerConfig mutateForVersion(NerConfig instance, Version version) {
+        return new NerConfig(
+            instance.getVocabularyConfig(),
+            InferenceConfigTestScaffolding.mutateTokenizationForVersion(instance.getTokenization(), version),
+            instance.getClassificationLabels(),
+            instance.getResultsField()
+        );
+    }
+
     @Override
     protected boolean supportsUnknownFields() {
         return true;
@@ -48,7 +57,7 @@ protected NerConfig createTestInstance() {
 
     @Override
     protected NerConfig mutateInstanceForVersion(NerConfig instance, Version version) {
-        return instance;
+        return mutateForVersion(instance, version);
     }
 
     public static NerConfig createRandom() {

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/PassThroughConfigTests.java

@@ -17,6 +17,14 @@
 
 public class PassThroughConfigTests extends InferenceConfigItemTestCase<PassThroughConfig> {
 
+    public static PassThroughConfig mutateForVersion(PassThroughConfig instance, Version version) {
+        return new PassThroughConfig(
+            instance.getVocabularyConfig(),
+            InferenceConfigTestScaffolding.mutateTokenizationForVersion(instance.getTokenization(), version),
+            instance.getResultsField()
+        );
+    }
+
     @Override
     protected boolean supportsUnknownFields() {
         return true;
@@ -44,7 +52,7 @@ protected PassThroughConfig createTestInstance() {
 
     @Override
     protected PassThroughConfig mutateInstanceForVersion(PassThroughConfig instance, Version version) {
-        return instance;
+        return mutateForVersion(instance, version);
     }
 
     public static PassThroughConfig createRandom() {

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/QuestionAnsweringConfigTests.java

@@ -17,6 +17,16 @@
 
 public class QuestionAnsweringConfigTests extends InferenceConfigItemTestCase<QuestionAnsweringConfig> {
 
+    public static QuestionAnsweringConfig mutateForVersion(QuestionAnsweringConfig instance, Version version) {
+        return new QuestionAnsweringConfig(
+            instance.getNumTopClasses(),
+            instance.getMaxAnswerLength(),
+            instance.getVocabularyConfig(),
+            InferenceConfigTestScaffolding.mutateTokenizationForVersion(instance.getTokenization(), version),
+            instance.getResultsField()
+        );
+    }
+
     @Override
     protected boolean supportsUnknownFields() {
         return true;
@@ -44,7 +54,7 @@ protected QuestionAnsweringConfig createTestInstance() {
 
     @Override
     protected QuestionAnsweringConfig mutateInstanceForVersion(QuestionAnsweringConfig instance, Version version) {
-        return instance;
+        return mutateForVersion(instance, version);
     }
 
     public static QuestionAnsweringConfig createRandom() {

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/RobertaTokenizationTests.java

@@ -19,6 +19,19 @@ public class RobertaTokenizationTests extends AbstractBWCSerializationTestCase<R
 
     private boolean lenient;
 
+    public static RobertaTokenization mutateForVersion(RobertaTokenization instance, Version version) {
+        if (version.before(Version.V_8_2_0)) {
+            return new RobertaTokenization(
+                instance.withSpecialTokens,
+                instance.isAddPrefixSpace(),
+                instance.maxSequenceLength,
+                instance.truncate,
+                null
+            );
+        }
+        return instance;
+    }
+
     @Before
     public void chooseStrictOrLenient() {
         lenient = randomBoolean();
@@ -41,7 +54,7 @@ protected RobertaTokenization createTestInstance() {
 
     @Override
     protected RobertaTokenization mutateInstanceForVersion(RobertaTokenization instance, Version version) {
-        return instance;
+        return mutateForVersion(instance, version);
     }
 
     public static RobertaTokenization createRandom() {

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/TextClassificationConfigTests.java

@@ -21,37 +21,14 @@
 
 public class TextClassificationConfigTests extends InferenceConfigItemTestCase<TextClassificationConfig> {
 
-    public static TextClassificationConfig mutateInstance(TextClassificationConfig instance, Version version) {
-        if (version.before(Version.V_8_2_0)) {
-            final Tokenization tokenization;
-            if (instance.getTokenization() instanceof BertTokenization) {
-                tokenization = new BertTokenization(
-                    instance.getTokenization().doLowerCase,
-                    instance.getTokenization().withSpecialTokens,
-                    instance.getTokenization().maxSequenceLength,
-                    instance.getTokenization().truncate,
-                    null
-                );
-            } else if (instance.getTokenization() instanceof MPNetTokenization) {
-                tokenization = new MPNetTokenization(
-                    instance.getTokenization().doLowerCase,
-                    instance.getTokenization().withSpecialTokens,
-                    instance.getTokenization().maxSequenceLength,
-                    instance.getTokenization().truncate,
-                    null
-                );
-            } else {
-                throw new UnsupportedOperationException("unknown tokenization type: " + instance.getTokenization().getName());
-            }
-            return new TextClassificationConfig(
-                instance.getVocabularyConfig(),
-                tokenization,
-                instance.getClassificationLabels(),
-                instance.getNumTopClasses(),
-                instance.getResultsField()
-            );
-        }
-        return instance;
+    public static TextClassificationConfig mutateForVersion(TextClassificationConfig instance, Version version) {
+        return new TextClassificationConfig(
+            instance.getVocabularyConfig(),
+            InferenceConfigTestScaffolding.mutateTokenizationForVersion(instance.getTokenization(), version),
+            instance.getClassificationLabels(),
+            instance.getNumTopClasses(),
+            instance.getResultsField()
+        );
     }
 
     @Override
@@ -81,7 +58,7 @@ protected TextClassificationConfig createTestInstance() {
 
     @Override
     protected TextClassificationConfig mutateInstanceForVersion(TextClassificationConfig instance, Version version) {
-        return mutateInstance(instance, version);
+        return mutateForVersion(instance, version);
     }
 
     public void testInvalidClassificationLabels() {

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/TextEmbeddingConfigTests.java

@@ -17,6 +17,14 @@
 
 public class TextEmbeddingConfigTests extends InferenceConfigItemTestCase<TextEmbeddingConfig> {
 
+    public static TextEmbeddingConfig mutateForVersion(TextEmbeddingConfig instance, Version version) {
+        return new TextEmbeddingConfig(
+            instance.getVocabularyConfig(),
+            InferenceConfigTestScaffolding.mutateTokenizationForVersion(instance.getTokenization(), version),
+            instance.getResultsField()
+        );
+    }
+
     @Override
     protected boolean supportsUnknownFields() {
         return true;
@@ -44,7 +52,7 @@ protected TextEmbeddingConfig createTestInstance() {
 
     @Override
     protected TextEmbeddingConfig mutateInstanceForVersion(TextEmbeddingConfig instance, Version version) {
-        return instance;
+        return mutateForVersion(instance, version);
     }
 
     public static TextEmbeddingConfig createRandom() {