Throw clear model validation error for unresolved member shape targets in codegen

.changes/next-release/bugfix-AWSSDKforJavav2-8aed2cb.json

@@ -0,0 +1,6 @@
+{
+    "type": "bugfix",
+    "category": "AWS SDK for Java v2",
+    "contributor": "",
+    "description": "Codegen now fails with a clear model validation error identifying the offending shape, member, and unresolved target when a shape member references a shape that does not exist in the model, instead of a NullPointerException during code generation."
+}

codegen/src/main/java/software/amazon/awssdk/codegen/IntermediateModelBuilder.java

@@ -46,6 +46,7 @@
 import software.amazon.awssdk.codegen.model.service.Waiters;
 import software.amazon.awssdk.codegen.naming.DefaultNamingStrategy;
 import software.amazon.awssdk.codegen.naming.NamingStrategy;
+import software.amazon.awssdk.codegen.validation.MemberShapeTargetValidator;
 import software.amazon.awssdk.utils.CollectionUtils;
 
 /**
@@ -162,6 +163,7 @@ public IntermediateModel build() {
                                                                service.getClientContextParams());
 
         linkMembersToShapes(trimmedModel);
+        MemberShapeTargetValidator.validate(trimmedModel);
         linkOperationsToInputOutputShapes(trimmedModel);
         linkCustomAuthorizationToRequestShapes(trimmedModel);
 

codegen/src/main/java/software/amazon/awssdk/codegen/validation/MemberShapeTargetValidator.java

@@ -0,0 +1,111 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License").
+ * You may not use this file except in compliance with the License.
+ * A copy of the License is located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ * or in the "license" file accompanying this file. This file is distributed
+ * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ * express or implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+package software.amazon.awssdk.codegen.validation;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import software.amazon.awssdk.codegen.model.intermediate.IntermediateModel;
+import software.amazon.awssdk.codegen.model.intermediate.MapModel;
+import software.amazon.awssdk.codegen.model.intermediate.MemberModel;
+import software.amazon.awssdk.codegen.model.intermediate.ShapeModel;
+
+/**
+ * Validates that every member which is expected to reference a model shape actually resolves to one after member-to-shape
+ * linking. A member can be left referencing a target shape that no longer exists in the intermediate model (missing from the
+ * service model, removed by a customization, or misspelled), which otherwise surfaces as a cryptic {@link NullPointerException}
+ * deep inside code emission.
+ *
+ * <p>The classification of which members reference a shape mirrors {@code RemoveUnusedShapes.resolveMemberShapes} so that
+ * validation and shape retention never disagree.
+ */
+public final class MemberShapeTargetValidator {
+
+    private MemberShapeTargetValidator() {
+    }
+
+    /**
+     * Collects every member whose target shape cannot be resolved and, if any are found, throws a single
+     * {@link ModelInvalidException} carrying one entry per distinct offending member.
+     *
+     * @throws ModelInvalidException if any member references a shape that does not exist in the model.
+     */
+    public static void validate(IntermediateModel model) {
+        List<ValidationEntry> entries = new ArrayList<>();
+        Set<String> reportedKeys = new HashSet<>();
+        for (ShapeModel shape : model.getShapes().values()) {
+            if (shape.getMembers() == null) {
+                continue;
+            }
+            for (MemberModel member : shape.getMembers()) {
+                validateMember(model, shape, member, member, entries, reportedKeys);
+            }
+        }
+        if (!entries.isEmpty()) {
+            throw ModelInvalidException.builder().validationEntries(entries).build();
+        }
+    }
+
+    /**
+     * @param topLevelMember the member declared directly on the shape; for list/map element members this stays pointed at the
+     *                       container member so the error message identifies a member the service team can locate.
+     */
+    private static void validateMember(IntermediateModel model, ShapeModel shape, MemberModel topLevelMember,
+                                       MemberModel member, List<ValidationEntry> entries, Set<String> reportedKeys) {
+        if (member == null) {
+            return;
+        }
+
+        if (member.getEnumType() != null) {
+            requireResolvable(model, shape, topLevelMember, member, member.getEnumType(), entries, reportedKeys);
+        } else if (member.isList()) {
+            validateMember(model, shape, topLevelMember, member.getListModel().getListMemberModel(), entries, reportedKeys);
+        } else if (member.isMap()) {
+            MapModel mapModel = member.getMapModel();
+            validateMember(model, shape, topLevelMember, mapModel.getKeyModel(), entries, reportedKeys);
+            validateMember(model, shape, topLevelMember, mapModel.getValueModel(), entries, reportedKeys);
+        } else if (!member.isSimple()) {
+            requireResolvable(model, shape, topLevelMember, member, member.getVariable().getSimpleType(), entries, reportedKeys);
+        }
+    }
+
+    private static void requireResolvable(IntermediateModel model, ShapeModel shape, MemberModel topLevelMember,
+                                          MemberModel member, String targetName,
+                                          List<ValidationEntry> entries, Set<String> reportedKeys) {
+        // linkMembersToShapes only links members declared directly on a shape, so a list/map element member always carries a
+        // null shape; resolve its target by name (matching shape retention) instead of reading the unset getShape().
+        boolean resolved = member == topLevelMember ? member.getShape() != null
+                                                    : model.getShapes().containsKey(targetName);
+        if (!resolved) {
+            recordDangling(shape, topLevelMember, targetName, entries, reportedKeys);
+        }
+    }
+
+    private static void recordDangling(ShapeModel shape, MemberModel member, String targetName,
+                                       List<ValidationEntry> entries, Set<String> reportedKeys) {
+        String dedupKey = shape.getShapeName() + '|' + member.getC2jName() + '|' + targetName;
+        if (!reportedKeys.add(dedupKey)) {
+            return;
+        }
+        String detail = String.format(
+            "Member '%s' of shape '%s' targets shape '%s' which does not exist in the intermediate model. The target shape "
+            + "may be missing from the service model, removed by a customization, or misspelled.",
+            member.getC2jName(), shape.getShapeName(), targetName);
+
+        entries.add(ValidationEntry.create(ValidationErrorId.UNKNOWN_SHAPE_MEMBER, ValidationErrorSeverity.DANGER, detail));
+    }
+}

codegen/src/test/java/software/amazon/awssdk/codegen/MemberShapeTargetValidationBuildTest.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License").
+ * You may not use this file except in compliance with the License.
+ * A copy of the License is located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ * or in the "license" file accompanying this file. This file is distributed
+ * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ * express or implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+package software.amazon.awssdk.codegen;
+
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+import java.io.File;
+import org.junit.jupiter.api.Test;
+import software.amazon.awssdk.codegen.model.config.customization.CustomizationConfig;
+import software.amazon.awssdk.codegen.model.service.ServiceModel;
+import software.amazon.awssdk.codegen.utils.ModelLoaderUtils;
+import software.amazon.awssdk.codegen.validation.ModelInvalidException;
+import software.amazon.awssdk.codegen.validation.ValidationEntry;
+import software.amazon.awssdk.codegen.validation.ValidationErrorId;
+import software.amazon.awssdk.codegen.validation.ValidationErrorSeverity;
+
+/**
+ * Full-build coverage proving that member-to-shape linking actually leaves a null shape when a referenced target is removed by
+ * a customization, and that {@link IntermediateModelBuilder#build()} fails fast instead of producing a downstream
+ * {@link NullPointerException}. Reproduces P456014803.
+ */
+public class MemberShapeTargetValidationBuildTest {
+
+    @Test
+    public void build_enumTargetRemovedByDeprecatedShapesCustomization_throwsModelInvalid() {
+        File serviceModelFile = new File(MemberShapeTargetValidationBuildTest.class
+            .getResource("poet/client/c2j/dangling-shape-validator/service-2.json").getFile());
+        File customizationFile = new File(MemberShapeTargetValidationBuildTest.class
+            .getResource("poet/client/c2j/dangling-shape-validator/customization.config").getFile());
+
+        C2jModels models = C2jModels.builder()
+            .serviceModel(ModelLoaderUtils.loadModel(ServiceModel.class, serviceModelFile))
+            .customizationConfig(ModelLoaderUtils.loadModel(CustomizationConfig.class, customizationFile))
+            .build();
+
+        assertThatThrownBy(() -> new IntermediateModelBuilder(models).build())
+            .isInstanceOf(ModelInvalidException.class)
+            .hasMessageContaining("GetRequestAuthorizationDetailsResponse")
+            .hasMessageContaining("AuthorizationDetails")
+            .hasMessageContaining("AuthDetailType")
+            .matches(e -> {
+                ValidationEntry entry = ((ModelInvalidException) e).validationEntries().get(0);
+                return entry.getErrorId() == ValidationErrorId.UNKNOWN_SHAPE_MEMBER
+                       && entry.getSeverity() == ValidationErrorSeverity.DANGER;
+            }, "validation entry is UNKNOWN_SHAPE_MEMBER / DANGER");
+    }
+}