More httpChecksum trait validation for responses

docs/source-2.0/aws/aws-core.rst

@@ -958,7 +958,8 @@ The ``httpChecksum`` trait is a structure that contains the following members:
 The ``httpChecksum`` trait MUST define at least one of the request checksumming
 behavior, by setting the ``requestAlgorithmMember`` or
 ``requestChecksumRequired`` property, or the response checksumming behavior, by
-setting the ``requestValidationModeMember`` property.
+setting the ``requestValidationModeMember`` and ``responseAlgorithms``
+properties.
 
 The following is an example of the ``httpChecksum`` trait that defines required
 request checksum behavior with support for the "CRC32C", "CRC32", "SHA1", and

smithy-aws-traits/src/main/java/software/amazon/smithy/aws/traits/HttpChecksumTraitValidator.java

@@ -74,7 +74,8 @@ private List<ValidationEvent> validateOperation(Model model, OperationShape oper
                 trait.isRequestChecksumRequired() || trait.getRequestAlgorithmMember().isPresent();
 
         // Response checksum behavior is defined when either the `requestValidationModeMember`
-        // property or `responseAlgorithms` property are modeled.
+        // property or `responseAlgorithms` property are modeled. Actually both are needed, but this check helps do
+        // deeper validation later.
         boolean isResponseChecksumConfiguration =
                 !trait.getResponseAlgorithms().isEmpty() || trait.getRequestValidationModeMember().isPresent();
 
@@ -236,6 +237,13 @@ private List<ValidationEvent> validateResponseChecksumConfiguration(
             validateValidationModeMember(model, trait, operation, input).map(events::add);
         }
 
+        // Validate responseAlgorithms is not empty.
+        if (trait.getResponseAlgorithms().isEmpty()) {
+            events.add(error(operation, trait, "The `httpChecksum` trait must model the"
+                    + " `responseAlgorithms` property to support response checksum behavior."));
+            return events;
+        }
+
         // Check for header binding conflicts with each error shape.
         if (!operation.getErrors().isEmpty()) {
             for (ShapeId id : operation.getErrors()) {

smithy-aws-traits/src/test/resources/software/amazon/smithy/aws/traits/errorfiles/http-checksum-trait.errors

@@ -1,5 +1,7 @@
 [SUPPRESSED] smithy.example#NoBehavior: This shape applies a trait that is unstable: aws.protocols#httpChecksum | UnstableTrait
 [SUPPRESSED] smithy.example#NoModeForResponse: This shape applies a trait that is unstable: aws.protocols#httpChecksum | UnstableTrait
 [SUPPRESSED] smithy.example#NoOutputForResponse: This shape applies a trait that is unstable: aws.protocols#httpChecksum | UnstableTrait
+[SUPPRESSED] smithy.example#NoResponseAlgorithms: This shape applies a trait that is unstable: aws.protocols#httpChecksum | UnstableTrait
 [ERROR] smithy.example#NoBehavior: The `httpChecksum` trait must define at least one of the `request` or `response` checksum behaviors. | HttpChecksumTrait
 [ERROR] smithy.example#NoModeForResponse: The `httpChecksum` trait must model the `requestValidationModeMember` property to support response checksum behavior. | HttpChecksumTrait
+[ERROR] smithy.example#NoResponseAlgorithms: The `httpChecksum` trait must model the `responseAlgorithms` property to support response checksum behavior. | HttpChecksumTrait

smithy-aws-traits/src/test/resources/software/amazon/smithy/aws/traits/errorfiles/http-checksum-trait.smithy

@@ -37,6 +37,24 @@ structure NoModeForResponseInput {}
 @output
 structure NoModeForResponseOutput {}
 
+@httpChecksum(
+    requestValidationModeMember: "validationMode"
+)
+@suppress(["UnstableTrait"])
+operation NoResponseAlgorithms {
+    input: NoResponseAlgorithmsInput,
+    output: NoResponseAlgorithmsOutput,
+}
+
+@input
+structure NoResponseAlgorithmsInput {
+    validationMode: ValidationMode
+}
+
+@output
+structure NoResponseAlgorithmsOutput {}
+
+
 @httpChecksum(
     requestAlgorithmMember: "requestAlgorithm",
     requestValidationModeMember: "validationMode",