Added a customization to allow underscores in shape names.

1. Throw an exception if an invalid shape name is used instead of trying to transform it. This should be backwards-compatible, because our transformation is currently broken.
2. Throw an exception if a customer-visible identifier contains underscores. Added customizations to rename any existing shapes that violate this rule.
3. Add validation to the code generator to verify that certain names will actually compile. This provides a more useful error message when services contain invalid identifiers.
4. Deprecate SsoOidc's "error_description" getters for ones with idiomatic names.

Author: millems

.changes/next-release/deprecation-AWSSSOOIDC-07f569c.json

@@ -0,0 +1,6 @@
+{
+    "type": "deprecation",
+    "category": "AWS SSO OIDC",
+    "contributor": "",
+    "description": "Renamed/deprecated 'error_description' fields in exceptions in favor of 'errorDescription'."
+}

.changes/next-release/feature-AWSSDKforJavav2-a2cc0b1.json

@@ -0,0 +1,6 @@
+{
+    "type": "feature",
+    "category": "AWS SDK for Java v2",
+    "contributor": "",
+    "description": "Added code generation validation that customer-visible identifiers are idiomatic (do not contain underscores). Services with underscores in their models can use rename customizations to fix these issues, or apply the 'underscoresInNameBehavior = ALLOW' customization."
+}

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

@@ -53,7 +53,7 @@ private Map<String, ShapeModel> constructModelShapes(Set<String> shapesToSkip) {
             ShapeType shapeType = getModelShapeType(shape);
 
             if (shapeType != null) {
-                String javaClassName = getNamingStrategy().getJavaClassName(shapeName);
+                String javaClassName = getNamingStrategy().getShapeClassName(shapeName);
                 if (shapesToSkip.contains(javaClassName)) {
                     continue;
                 }

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

@@ -159,7 +159,6 @@ private MemberModel generateMemberModel(String c2jMemberName, Member c2jMemberDe
                                                variableType + " type.");
         }
 
-
         MemberModel memberModel = new MemberModel();
 
         memberModel.withC2jName(c2jMemberName)
@@ -443,7 +442,7 @@ private void fillContainerTypeMemberMetadata(Map<String, Shape> c2jShapes,
                                                  mapValueModel));
 
         } else if (memberC2jShape.getEnumValues() != null) { // enum values
-            memberModel.withEnumType(getNamingStrategy().getJavaClassName(memberC2jShapeName));
+            memberModel.withEnumType(getNamingStrategy().getShapeClassName(memberC2jShapeName));
         }
     }
 

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

@@ -157,6 +157,8 @@ public IntermediateModel build() {
 
         setSimpleMethods(trimmedModel);
 
+        namingStrategy.validateCustomerVisibleNaming(trimmedModel);
+
         return trimmedModel;
     }
 

codegen/src/main/java/software/amazon/awssdk/codegen/internal/TypeUtils.java

@@ -133,7 +133,7 @@ public String getJavaDataType(Map<String, Shape> shapes, String shapeName,
         String shapeType = shape.getType();
 
         if (Structure.getName().equals(shapeType)) {
-            return namingStrategy.getJavaClassName(shapeName);
+            return namingStrategy.getShapeClassName(shapeName);
         } else if (List.getName().equals(shapeType)) {
             String listContainerType = DATA_TYPE_MAPPINGS.get(TypeKey.LIST_INTERFACE);
             return listContainerType + "<" +

codegen/src/main/java/software/amazon/awssdk/codegen/model/config/customization/CustomizationConfig.java

@@ -165,13 +165,19 @@ public class CustomizationConfig {
      * Arnable fields used in s3 control
      */
     private Map<String, S3ArnableFieldConfig> s3ArnableFields;
+
     /**
      * Allow a customer to set an endpoint override AND bypass endpoint discovery on their client even when endpoint discovery
      * enabled is true and endpoint discovery is required for an operation. This customization should almost never be "true"
      * because it creates a confusing customer experience.
      */
     private boolean allowEndpointOverrideForEndpointDiscoveryRequiredOperations = false;
 
+    /**
+     * How the code generator should behave when it encounters shapes with underscores in the name.
+     */
+    private UnderscoresInNameBehavior underscoresInNameBehavior;
+
     private CustomizationConfig() {
     }
 
@@ -434,4 +440,17 @@ public void setAllowEndpointOverrideForEndpointDiscoveryRequiredOperations(
         this.allowEndpointOverrideForEndpointDiscoveryRequiredOperations =
             allowEndpointOverrideForEndpointDiscoveryRequiredOperations;
     }
+
+    public UnderscoresInNameBehavior getUnderscoresInNameBehavior() {
+        return underscoresInNameBehavior;
+    }
+
+    public void setUnderscoresInNameBehavior(UnderscoresInNameBehavior behavior) {
+        this.underscoresInNameBehavior = behavior;
+    }
+
+    public CustomizationConfig withUnderscoresInShapeNameBehavior(UnderscoresInNameBehavior behavior) {
+        this.underscoresInNameBehavior = behavior;
+        return this;
+    }
 }

codegen/src/main/java/software/amazon/awssdk/codegen/model/config/customization/UnderscoresInNameBehavior.java

@@ -0,0 +1,26 @@
+/*
+ * 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.model.config.customization;
+
+/**
+ * Valid values for the {@link CustomizationConfig#setUnderscoresInNameBehavior} customization.
+ */
+public enum UnderscoresInNameBehavior {
+    /**
+     * Allow the underscores in names, and generating shapes with names that are non-idiomatic to the language.
+     */
+    ALLOW
+}

codegen/src/main/java/software/amazon/awssdk/codegen/model/intermediate/IntermediateModel.java

@@ -20,6 +20,7 @@
 import java.io.InputStream;
 import java.io.UncheckedIOException;
 import java.util.Collections;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
@@ -57,9 +58,11 @@ public final class IntermediateModel {
     }
 
     public IntermediateModel() {
+        this.operations = new HashMap<>();
+        this.shapes = new HashMap<>();
         this.endpointOperation = Optional.empty();
-        this.paginators = Collections.emptyMap();
-        this.waiters = Collections.emptyMap();
+        this.paginators = new HashMap<>();
+        this.waiters = new HashMap<>();
         this.namingStrategy = null;
     }
 

codegen/src/main/java/software/amazon/awssdk/codegen/model/intermediate/MemberModel.java

@@ -220,22 +220,6 @@ public MemberModel withBeanStyleSetterMethodName(String beanStyleSetterName) {
         return this;
     }
 
-    // TODO: Remove when all marshallers switch over to new style
-    public String getSetterMethodName() {
-        return getBeanStyleSetterMethodName();
-    }
-
-    // TODO: Remove when all marshallers switch over to new style
-    public void setSetterMethodName(String setterMethodName) {
-        setBeanStyleGetterMethodName(setterMethodName);
-    }
-
-    // TODO: Remove when all marshallers switch over to new style
-    public MemberModel withSetterMethodName(String setterMethodName) {
-        setSetterMethodName(setterMethodName);
-        return this;
-    }
-
     public String getFluentSetterMethodName() {
         return fluentSetterMethodName;
     }

codegen/src/main/java/software/amazon/awssdk/codegen/model/service/Shape.java

@@ -20,7 +20,6 @@
 import java.util.Map;
 
 public class Shape {
-
     private String type;
 
     private Map<String, Member> members = Collections.emptyMap();

codegen/src/main/java/software/amazon/awssdk/codegen/naming/DefaultNamingStrategy.java

@@ -32,15 +32,20 @@
 import java.util.Objects;
 import java.util.Optional;
 import java.util.Set;
+import java.util.regex.Pattern;
 import java.util.stream.Stream;
 import software.amazon.awssdk.codegen.internal.Constant;
 import software.amazon.awssdk.codegen.internal.Utils;
 import software.amazon.awssdk.codegen.model.config.customization.CustomizationConfig;
+import software.amazon.awssdk.codegen.model.config.customization.UnderscoresInNameBehavior;
+import software.amazon.awssdk.codegen.model.intermediate.IntermediateModel;
 import software.amazon.awssdk.codegen.model.intermediate.MemberModel;
+import software.amazon.awssdk.codegen.model.intermediate.Metadata;
 import software.amazon.awssdk.codegen.model.service.ServiceModel;
 import software.amazon.awssdk.codegen.model.service.Shape;
 import software.amazon.awssdk.utils.Logger;
 import software.amazon.awssdk.utils.StringUtils;
+import software.amazon.awssdk.utils.Validate;
 
 /**
  * Default implementation of naming strategy respecting.
@@ -49,6 +54,9 @@ public class DefaultNamingStrategy implements NamingStrategy {
 
     private static final Logger log = Logger.loggerFor(DefaultNamingStrategy.class);
 
+    private static final Pattern VALID_IDENTIFIER_NAME =
+        Pattern.compile("\\p{javaJavaIdentifierStart}\\p{javaJavaIdentifierPart}*");
+
     private static final String COLLISION_DISAMBIGUATION_PREFIX = "Default";
 
     private static final Set<String> RESERVED_KEYWORDS;
@@ -96,7 +104,7 @@ public class DefaultNamingStrategy implements NamingStrategy {
     public DefaultNamingStrategy(ServiceModel serviceModel,
                                  CustomizationConfig customizationConfig) {
         this.serviceModel = serviceModel;
-        this.customizationConfig = customizationConfig;
+        this.customizationConfig = customizationConfig == null ? CustomizationConfig.create() : customizationConfig;
     }
 
     private static boolean isJavaKeyword(String word) {
@@ -178,7 +186,6 @@ public String getSmokeTestPackageName(String serviceName) {
      * if provided or service name with the shared service name.
      */
     private String concatServiceNameIfShareModel(String serviceName) {
-
         if (customizationConfig.getShareModelConfig() != null) {
             return customizationConfig.getShareModelConfig().getShareModelWith() + "." +
                    Optional.ofNullable(customizationConfig.getShareModelConfig().getPackageName()).orElse(serviceName);
@@ -268,11 +275,8 @@ public String getEnumValueName(String enumValue) {
     }
 
     @Override
-    public String getJavaClassName(String shapeName) {
-        return Arrays.stream(shapeName.split("[._-]|\\W"))
-                     .filter(s -> !StringUtils.isEmpty(s))
-                     .map(Utils::capitalize)
-                     .collect(joining());
+    public String getShapeClassName(String shapeName) {
+        return Utils.capitalize(shapeName);
     }
 
     @Override
@@ -374,4 +378,63 @@ private boolean isDisallowedNameForShape(String name, Shape parentShape) {
             return RESERVED_STRUCTURE_METHOD_NAMES.contains(name);
         }
     }
+
+    @Override
+    public void validateCustomerVisibleNaming(IntermediateModel trimmedModel) {
+        Metadata metadata = trimmedModel.getMetadata();
+        validateCustomerVisibleName(metadata.getSyncInterface(), "metadata-derived interface name");
+        validateCustomerVisibleName(metadata.getSyncBuilderInterface(), "metadata-derived builder interface name");
+        validateCustomerVisibleName(metadata.getAsyncInterface(), "metadata-derived async interface name");
+        validateCustomerVisibleName(metadata.getAsyncBuilderInterface(), "metadata-derived async builder interface name");
+        validateCustomerVisibleName(metadata.getBaseBuilderInterface(), "metadata-derived builder interface name");
+        validateCustomerVisibleName(metadata.getBaseExceptionName(), "metadata-derived exception name");
+        validateCustomerVisibleName(metadata.getBaseRequestName(), "metadata-derived request name");
+        validateCustomerVisibleName(metadata.getBaseResponseName(), "metadata-derived response name");
+
+        trimmedModel.getOperations().values().forEach(operation -> {
+            validateCustomerVisibleName(operation.getOperationName(), "operations");
+        });
+
+        trimmedModel.getWaiters().forEach((name, waiter) -> {
+            validateCustomerVisibleName(name, "waiters");
+        });
+
+        trimmedModel.getShapes().values().forEach(shape -> {
+            String shapeName = shape.getShapeName();
+            validateCustomerVisibleName(shapeName, "shapes");
+            shape.getMembers().forEach(member -> {
+                validateCustomerVisibleName(member.getFluentGetterMethodName(), shapeName + " shape");
+                validateCustomerVisibleName(member.getFluentSetterMethodName(), shapeName + " shape");
+                validateCustomerVisibleName(member.getFluentEnumGetterMethodName(), shapeName + " shape");
+                validateCustomerVisibleName(member.getFluentEnumSetterMethodName(), shapeName + " shape");
+                validateCustomerVisibleName(member.getExistenceCheckMethodName(), shapeName + " shape");
+                validateCustomerVisibleName(member.getBeanStyleGetterMethodName(), shapeName + " shape");
+                validateCustomerVisibleName(member.getBeanStyleSetterMethodName(), shapeName + " shape");
+                validateCustomerVisibleName(member.getEnumType(), shapeName + " shape");
+            });
+        });
+    }
+
+    private void validateCustomerVisibleName(String name, String location) {
+        if (name == null) {
+            return;
+        }
+
+        if (name.contains("_")) {
+            UnderscoresInNameBehavior behavior = customizationConfig.getUnderscoresInNameBehavior();
+
+            String supportedBehaviors = Arrays.toString(UnderscoresInNameBehavior.values());
+            Validate.notNull(behavior,
+                             "Encountered a name or identifier that the customer will see (%s in the %s) with an underscore. "
+                             + "This isn't idiomatic in Java. Please either remove the underscores or apply the "
+                             + "'underscoresInNameBehavior' customization for this service (Supported "
+                             + "'underscoresInNameBehavior' values: %s).", name, location, supportedBehaviors);
+            Validate.isTrue(behavior == UnderscoresInNameBehavior.ALLOW,
+                            "Unsupported underscoresInShapeNameBehavior: %s. Supported values: %s", behavior, supportedBehaviors);
+        }
+
+        Validate.isTrue(VALID_IDENTIFIER_NAME.matcher(name).matches(),
+                        "Encountered a name or identifier that is invalid within Java (%s in %s). Please remove invalid "
+                        + "characters.", name, location);
+    }
 }

codegen/src/main/java/software/amazon/awssdk/codegen/naming/NamingStrategy.java

@@ -15,6 +15,7 @@
 
 package software.amazon.awssdk.codegen.naming;
 
+import software.amazon.awssdk.codegen.model.intermediate.IntermediateModel;
 import software.amazon.awssdk.codegen.model.intermediate.MemberModel;
 import software.amazon.awssdk.codegen.model.service.Shape;
 
@@ -97,7 +98,7 @@ public interface NamingStrategy {
      * @param shapeName Name of structure used to derive Java class name.
      * @return Appropriate name to use for a Java class for an arbitrary (not a request, response, error) structure.
      */
-    String getJavaClassName(String shapeName);
+    String getShapeClassName(String shapeName);
 
     /**
      * @param memberName Member name to name getter for.
@@ -154,4 +155,9 @@ public interface NamingStrategy {
      * @return Name of an existence check method.
      */
     String getExistenceCheckMethodName(String memberName, Shape parentShape);
+
+    /**
+     * Verify the customer-visible naming in the provided intermediate model will compile and is idiomatic to Java.
+     */
+    void validateCustomerVisibleNaming(IntermediateModel trimmedModel);
 }