Allow examples for service level errors

This commit enables validating error examples for operations with errors
that are bound to services. All services the operation with said example
are bound to must bind the error.

smithy-model/src/main/java/software/amazon/smithy/model/validation/validators/ExamplesTraitValidator.java

@@ -18,10 +18,14 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Optional;
+import java.util.Set;
 import software.amazon.smithy.model.Model;
+import software.amazon.smithy.model.knowledge.TopDownIndex;
 import software.amazon.smithy.model.node.ObjectNode;
 import software.amazon.smithy.model.shapes.OperationShape;
+import software.amazon.smithy.model.shapes.ServiceShape;
 import software.amazon.smithy.model.shapes.Shape;
+import software.amazon.smithy.model.shapes.ShapeId;
 import software.amazon.smithy.model.traits.ExamplesTrait;
 import software.amazon.smithy.model.validation.AbstractValidator;
 import software.amazon.smithy.model.validation.NodeValidationVisitor;
@@ -75,7 +79,11 @@ private List<ValidationEvent> validateExamples(Model model, OperationShape shape
             } else if (isErrorDefined) {
                 ExamplesTrait.ErrorExample errorExample = example.getError().get();
                 Optional<Shape> errorShape = model.getShape(errorExample.getShapeId());
-                if (errorShape.isPresent() && shape.getErrors().contains(errorExample.getShapeId())) {
+                if (errorShape.isPresent() && (
+                        // The error is directly bound to the operation.
+                        shape.getErrors().contains(errorExample.getShapeId())
+                        // The error is bound to all services that contain the operation.
+                        || servicesContainError(model, shape, errorExample.getShapeId()))) {
                     NodeValidationVisitor validator = createVisitor(
                             "error", errorExample.getContent(), model, shape, example);
                     events.addAll(errorShape.get().accept(validator));
@@ -90,6 +98,30 @@ private List<ValidationEvent> validateExamples(Model model, OperationShape shape
         return events;
     }
 
+    private boolean servicesContainError(Model model, OperationShape shape, ShapeId errorId) {
+        TopDownIndex topDownIndex = TopDownIndex.of(model);
+
+        Set<ServiceShape> services = model.getServiceShapes();
+        if (services.isEmpty()) {
+            return false;
+        }
+
+        for (ServiceShape service : services) {
+            // Skip if the service doesn't have the operation.
+            if (!topDownIndex.getContainedOperations(service).contains(shape)) {
+                continue;
+            }
+
+            // We've already checked if the operation contains the error,
+            // so a service having no errors means we've failed.
+            if (service.getErrors().isEmpty() || !service.getErrors().contains(errorId)) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
     private NodeValidationVisitor createVisitor(
             String name,
             ObjectNode value,

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/examples-trait-service-errors.errors

@@ -0,0 +1,3 @@
+[ERROR] ns.foo#WithError: Error parameters provided for operation without the `ns.foo#ServiceError` error: `Testing 2` | ExamplesTrait
+[ERROR] ns.foo#WithoutError: Error parameters provided for operation without the `ns.foo#OperationError` error: `Testing 3` | ExamplesTrait
+[ERROR] ns.foo#WithoutError: Error parameters provided for operation without the `ns.foo#ServiceError` error: `Testing 4` | ExamplesTrait

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/examples-trait-service-errors.smithy

@@ -0,0 +1,109 @@
+$version: "2"
+
+namespace ns.foo
+
+service ErrorBound {
+    version: "2020-07-02"
+    operations: [
+        WithError
+        WithoutError
+    ]
+    errors: [ServiceError]
+}
+
+service ErrorBound2 {
+    version: "2020-07-02"
+    operations: [
+        WithoutError2
+    ]
+    errors: [ServiceError2]
+}
+
+service NoError {
+    version: "2020-07-02"
+    operations: [
+        WithError
+        WithoutError
+    ]
+}
+
+@examples([
+    {
+        "title": "Testing 1",
+        "error": {
+            "shapeId": "ns.foo#OperationError"
+            "content": {
+                "foo": "baz"
+            }
+        }
+    }
+    {
+        "title": "Testing 2"
+        "error": {
+            "shapeId": "ns.foo#ServiceError"
+            "content": {
+                "foo": "baz"
+            }
+        }
+    }
+])
+operation WithError {
+    input := {}
+    errors: [OperationError]
+}
+
+@examples([
+    {
+        "title": "Testing 3",
+        "error": {
+            "shapeId": "ns.foo#OperationError"
+            "content": {
+                "foo": "baz"
+            }
+        }
+    }
+    {
+        "title": "Testing 4"
+        "error": {
+            "shapeId": "ns.foo#ServiceError"
+            "content": {
+                "foo": "baz"
+            }
+        }
+    }
+])
+operation WithoutError {
+    input := {}
+    output := {}
+}
+
+@examples([
+    {
+        "title": "Testing 5"
+        "error": {
+            "shapeId": "ns.foo#ServiceError2"
+            "content": {
+                "foo": "baz"
+            }
+        }
+    }
+])
+operation WithoutError2 {
+    input := {}
+    output := {}
+}
+
+@error("client")
+structure ServiceError {
+    foo: String
+}
+
+@error("client")
+structure ServiceError2 {
+    foo: String
+}
+
+@error("client")
+structure OperationError {
+    foo: String
+}