Remove OperationMissingInput|Output

These validators nudged modelers to define explicit input and output
references for every operation, but added a lot of noise and don't
achieve the core objective of defining a dedicated input and output
shape for every operation. Better validation could be added through a
linter that discourages the use of Unit for operations at all.

designs/operation-input-output-and-unit-types.md

@@ -180,11 +180,6 @@ structure GetFooOutput {}
 To encourage models to utilize the `@input` and `@output` traits, built-in
 validation will be added to Smithy.
 
-When an operation does not define input or output explicitly a WARNING
-validation event will be emitted with the ID `OperationMissingInput` or
-`OperationMissingOutput`. This can be avoided by explicitly assigning the input
-or output of an operation to a shape, including `smithy.api#Unit`.
-
 If an operation input targets a shape other than `smithy.api#Unit` that is
 not marked with the `@input` trait, a WARNING validation event is emitted with
 the ID `OperationMissingInputTrait`. A similar event with an ID of

smithy-aws-protocol-tests/model/awsJson1_0/empty-input-output.smithy

@@ -12,7 +12,6 @@ use smithy.test#httpResponseTests
 /// The example tests how requests and responses are serialized when there's
 /// no request or response payload because the operation has no input or output.
 /// While this should be rare, code generators must support this.
-@suppress(["OperationMissingInput", "OperationMissingOutput"])
 operation NoInputAndNoOutput {}
 
 apply NoInputAndNoOutput @httpRequestTests([
@@ -114,7 +113,6 @@ apply NoInputAndNoOutput @httpResponseTests([
 /// no request or response payload because the operation has no input and the
 /// output is empty. While this should be rare, code generators must support
 /// this.
-@suppress(["OperationMissingInput"])
 operation NoInputAndOutput {
     output: NoInputAndOutputOutput
 }

smithy-aws-protocol-tests/model/awsJson1_0/endpoint-paths.smithy

@@ -20,5 +20,4 @@ use smithy.test#httpRequestTests
         appliesTo: "client"
     }
 ])
-@suppress(["OperationMissingInput", "OperationMissingOutput"])
 operation HostWithPathOperation {}

smithy-aws-protocol-tests/model/awsJson1_0/endpoints.smithy

@@ -23,7 +23,6 @@ use smithy.test#httpRequestTests
     }
 ])
 @endpoint(hostPrefix: "foo.")
-@suppress(["OperationMissingInput", "OperationMissingOutput"])
 operation EndpointOperation {}
 
 
@@ -47,7 +46,6 @@ operation EndpointOperation {}
     }
 ])
 @endpoint(hostPrefix: "foo.{label}.")
-@suppress(["OperationMissingOutput"])
 operation EndpointWithHostLabelOperation {
     input: EndpointWithHostLabelOperationInput,
 }

smithy-aws-protocol-tests/model/shared-types.smithy

@@ -33,20 +33,6 @@ metadata suppressions = [
         reason: """
             This is a temporary solution until we rewrite these tests to define input, output,
             and use the `@input` and `@output` traits."""
-    },
-    {
-        id: "OperationMissingInput",
-        namespace: "*",
-        reason: """
-            This is a temporary solution until we rewrite these tests to define input, output,
-            and use the `@input` and `@output` traits."""
-    },
-    {
-        id: "OperationMissingOutput",
-        namespace: "*",
-        reason: """
-            This is a temporary solution until we rewrite these tests to define input, output,
-            and use the `@input` and `@output` traits."""
     }
 ]
 

smithy-aws-traits/src/test/resources/software/amazon/smithy/aws/traits/errorfiles/clientendpointdiscovery/no-input.errors

@@ -1 +0,0 @@
-[WARNING] ns.foo#PutObject: This operation does not define output | OperationMissingOutput

smithy-aws-traits/src/test/resources/software/amazon/smithy/aws/traits/errorfiles/clientendpointdiscovery/no-output.errors

@@ -1,2 +1 @@
-[WARNING] ns.foo#DescribeEndpoints: This operation does not define output | OperationMissingOutput
 [ERROR] ns.foo#DescribeEndpoints: Endpoint discovery operation output must only contain an `Endpoints` member, but found: [] | ClientEndpointDiscovery

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

@@ -15,7 +15,7 @@ structure NoBehaviorInput {}
 @httpChecksum(
     requestChecksumRequired: true,
 )
-@suppress(["UnstableTrait", "OperationMissingInput"])
+@suppress(["UnstableTrait"])
 operation NoInput {
     output: Unit
 }

smithy-linters/src/test/resources/software/amazon/smithy/linters/errorfiles/contains-reserved-words-validator.json

@@ -202,8 +202,6 @@
     },
     "metadata": {
         "suppressions": [
-            {"id": "OperationMissingInput", "namespace": "ns.foo"},
-            {"id": "OperationMissingOutput", "namespace": "ns.foo"},
             {"id": "OperationInputOutputName", "namespace": "ns.foo"}
         ],
         "validators": [

smithy-linters/src/test/resources/software/amazon/smithy/linters/errorfiles/input-output-structure-reuse.json

@@ -106,8 +106,6 @@
     },
     "metadata": {
         "suppressions": [
-            {"id": "OperationMissingInput", "namespace": "ns.foo"},
-            {"id": "OperationMissingOutput", "namespace": "ns.foo"},
             {"id": "OperationMissingInputTrait", "namespace": "ns.foo"},
             {"id": "OperationMissingOutputTrait", "namespace": "ns.foo"}
         ],

smithy-linters/src/test/resources/software/amazon/smithy/linters/errorfiles/missing-paginated-trait-validator.json

@@ -256,10 +256,6 @@
         }
     },
     "metadata": {
-        "suppressions": [
-            {"id": "OperationMissingInput", "namespace": "ns.foo"},
-            {"id": "OperationMissingOutput", "namespace": "ns.foo"}
-        ],
         "validators": [
             {
                 "name": "MissingPaginatedTrait"

smithy-linters/src/test/resources/software/amazon/smithy/linters/errorfiles/standard-operation-verb-validator-test.json

@@ -42,10 +42,6 @@
         }
     },
     "metadata": {
-        "suppressions": [
-            {"id":  "OperationMissingInput", "namespace": "ns.foo"},
-            {"id":  "OperationMissingOutput", "namespace": "ns.foo"}
-        ],
         "validators": [
             {
                 "name": "StandardOperationVerb",

smithy-model/src/main/java/software/amazon/smithy/model/loader/AstModelLoader.java

@@ -246,15 +246,6 @@ private void loadOperation(ShapeId id, ObjectNode node, FullyResolvedModelFile m
                 .id(id)
                 .source(node.getSourceLocation())
                 .addErrors(loadOptionalTargetList(modelFile, id, node, ERRORS));
-
-        if (!node.getMember("input").isPresent()) {
-            modelFile.events().add(LoaderUtils.createOperationMissingInput(id, node.getSourceLocation()));
-        }
-
-        if (!node.getMember("output").isPresent()) {
-            modelFile.events().add(LoaderUtils.createOperationMissingOutput(id, node.getSourceLocation()));
-        }
-
         loadOptionalTarget(modelFile, id, node, "input").ifPresent(builder::input);
         loadOptionalTarget(modelFile, id, node, "output").ifPresent(builder::output);
         modelFile.onShape(builder);

smithy-model/src/main/java/software/amazon/smithy/model/loader/IdlModelParser.java

@@ -549,15 +549,6 @@ private void parseOperationStatement(ShapeId id, SourceLocation location) {
         ObjectNode node = IdlNodeParser.parseObjectNode(this, id.toString());
         LoaderUtils.checkForAdditionalProperties(node, id, OPERATION_PROPERTY_NAMES, modelFile.events());
         modelFile.onShape(builder);
-
-        if (!node.getMember("input").isPresent()) {
-            modelFile.events().add(LoaderUtils.createOperationMissingInput(id, location));
-        }
-
-        if (!node.getMember("output").isPresent()) {
-            modelFile.events().add(LoaderUtils.createOperationMissingOutput(id, location));
-        }
-
         optionalId(node, "input", builder::input);
         optionalId(node, "output", builder::output);
         optionalIdList(node, ERRORS_KEYS, builder::addError);

smithy-model/src/main/java/software/amazon/smithy/model/loader/LoaderUtils.java

@@ -110,42 +110,4 @@ static boolean containsErrorEvents(List<ValidationEvent> events) {
         }
         return false;
     }
-
-    /**
-     * Helper method to create a validation event when input is not explicitly defined.
-     *
-     * @param id Shape ID of the operation.
-     * @param location Where the operation is defined.
-     * @return Returns the event.
-     */
-    static ValidationEvent createOperationMissingInput(ShapeId id, SourceLocation location) {
-        return ValidationEvent.builder()
-                .id("OperationMissingInput")
-                .severity(Severity.WARNING)
-                .shapeId(id)
-                .sourceLocation(location)
-                .message("This operation does not define input, so it defaults to smithy.api#Unit. Defining input "
-                         + "for an operation, even if you don't need it today, future-proofs the operation by "
-                         + "allowing input members to be added later.")
-                .build();
-    }
-
-    /**
-     * Helper method to create a validation event when output is not explicitly defined.
-     *
-     * @param id Shape ID of the operation.
-     * @param location Where the operation is defined.
-     * @return Returns the event.
-     */
-    static ValidationEvent createOperationMissingOutput(ShapeId id, SourceLocation location) {
-        return ValidationEvent.builder()
-                .id("OperationMissingOutput")
-                .severity(Severity.WARNING)
-                .shapeId(id)
-                .sourceLocation(location)
-                .message("This operation does not define output, so it defaults to smithy.api#Unit. Defining output "
-                         + "for an operation, even if you don't need it today, future-proofs the operation by "
-                         + "allowing output members to be added later.")
-                .build();
-    }
 }

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/auth/auth-trait-invalid-shape-id.json

@@ -1,11 +1,5 @@
 {
     "smithy": "1.0",
-    "metadata": {
-        "suppressions": [
-            {"id":  "OperationMissingInput", "namespace": "ns.foo"},
-            {"id":  "OperationMissingOutput", "namespace": "ns.foo"}
-        ]
-    },
     "shapes": {
         "ns.foo#InvalidShapeId": {
             "type": "operation",

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/auth/auth-trait-must-target-auth-definitions.json

@@ -1,11 +1,5 @@
 {
     "smithy": "1.0",
-    "metadata": {
-        "suppressions": [
-            {"id":  "OperationMissingInput", "namespace": "ns.foo"},
-            {"id":  "OperationMissingOutput", "namespace": "ns.foo"}
-        ]
-    },
     "shapes": {
         "ns.foo#Valid1": {
             "type": "operation",

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/auth/auth-trait-must-target-service-schemes.json

@@ -1,11 +1,5 @@
 {
     "smithy": "1.0",
-    "metadata": {
-        "suppressions": [
-            {"id":  "OperationMissingInput", "namespace": "ns.foo"},
-            {"id":  "OperationMissingOutput", "namespace": "ns.foo"}
-        ]
-    },
     "shapes": {
         "ns.foo#Service": {
             "type": "service",

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/examples-trait-validator.json

@@ -1,11 +1,5 @@
 {
     "smithy": "1.0",
-    "metadata": {
-        "suppressions": [
-            {"id": "OperationMissingInput", "namespace": "*"},
-            {"id": "OperationMissingOutput", "namespace": "*"}
-        ]
-    },
     "shapes": {
         "ns.foo#Operation": {
             "type": "operation",

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/host-request-validator.json

@@ -2,8 +2,6 @@
     "smithy": "1.0",
     "metadata": {
         "suppressions": [
-            {"id": "OperationMissingInput", "namespace": "*"},
-            {"id": "OperationMissingOutput", "namespace": "*"},
             {"id": "OperationMissingInputTrait", "namespace": "*"},
             {"id": "OperationMissingOutputTrait", "namespace": "*"}
         ]

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/http-checksum-required-trait.json

@@ -2,8 +2,6 @@
   "smithy": "1.0",
   "metadata": {
     "suppressions": [
-      {"id": "OperationMissingInput", "namespace": "*"},
-      {"id": "OperationMissingOutput", "namespace": "*"},
       {"id": "OperationMissingInputTrait", "namespace": "*"},
       {"id": "OperationMissingOutputTrait", "namespace": "*"}
     ]

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/http-method-semantics-validator.json

@@ -1,11 +1,5 @@
 {
     "smithy": "1.0",
-    "metadata": {
-        "suppressions": [
-            {"id":  "OperationMissingInput", "namespace": "ns.foo"},
-            {"id":  "OperationMissingOutput", "namespace": "ns.foo"}
-        ]
-    },
     "shapes": {
         "ns.foo#A": {
             "type": "operation",

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/http-request-response-validator.json

@@ -2,8 +2,6 @@
     "smithy": "1.0",
     "metadata": {
         "suppressions": [
-            {"id":  "OperationMissingInput", "namespace": "ns.foo"},
-            {"id":  "OperationMissingOutput", "namespace": "ns.foo"},
             {"id":  "OperationMissingInputTrait", "namespace": "ns.foo"},
             {"id":  "OperationMissingOutputTrait", "namespace": "ns.foo"}
         ]

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/http-response-code-semantics-validator.json

@@ -1,11 +1,5 @@
 {
     "smithy": "1.0",
-    "metadata": {
-        "suppressions": [
-            {"id": "OperationMissingInput", "namespace": "*"},
-            {"id": "OperationMissingOutput", "namespace": "*"}
-        ]
-    },
     "shapes": {
         "ns.foo#A": {
             "type": "operation",

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/http-uri-conflict-validator.json

@@ -2,8 +2,6 @@
     "smithy": "1.0",
     "metadata": {
         "suppressions": [
-            {"id": "OperationMissingInput", "namespace": "*"},
-            {"id": "OperationMissingOutput", "namespace": "*"},
             {"id": "OperationMissingInputTrait", "namespace": "*"},
             {"id": "OperationMissingOutputTrait", "namespace": "*"}
         ]

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/lifecycle/valid-implicit-lifecycles.json

@@ -2,8 +2,6 @@
     "smithy": "1.0",
     "metadata": {
         "suppressions": [
-            {"id": "OperationMissingInput", "namespace": "*"},
-            {"id": "OperationMissingOutput", "namespace": "*"},
             {"id": "OperationMissingInputTrait", "namespace": "*"},
             {"id": "OperationMissingOutputTrait", "namespace": "*"}
         ]

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/lifecycle/validates-idempotent-lifecycles.json

@@ -2,8 +2,6 @@
     "smithy": "1.0",
     "metadata": {
         "suppressions": [
-            {"id": "OperationMissingInput", "namespace": "*"},
-            {"id": "OperationMissingOutput", "namespace": "*"},
             {"id": "OperationMissingInputTrait", "namespace": "*"},
             {"id": "OperationMissingOutputTrait", "namespace": "*"}
         ]

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/lifecycle/validates-instance-and-collection-operations.json

@@ -2,8 +2,6 @@
     "smithy": "1.0",
     "metadata": {
         "suppressions": [
-            {"id": "OperationMissingInput", "namespace": "*"},
-            {"id": "OperationMissingOutput", "namespace": "*"},
             {"id": "OperationMissingInputTrait", "namespace": "*"},
             {"id": "OperationMissingOutputTrait", "namespace": "*"}
         ]

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/lifecycle/validates-readonly-lifecycles.json

@@ -2,8 +2,6 @@
     "smithy": "1.0",
     "metadata": {
         "suppressions": [
-            {"id": "OperationMissingInput", "namespace": "*"},
-            {"id": "OperationMissingOutput", "namespace": "*"},
             {"id": "OperationMissingInputTrait", "namespace": "*"},
             {"id": "OperationMissingOutputTrait", "namespace": "*"}
         ]

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/linters/emit-each-selector-validator.json

@@ -128,9 +128,6 @@
             "type": "operation",
             "input": {
                 "target": "ns.foo#OperationBInput"
-            },
-            "traits": {
-                "smithy.api#suppress": ["OperationMissingOutput"]
             }
         },
         "ns.foo#OperationBInput": {

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/paginated/paginated-invalid.json

@@ -2,8 +2,6 @@
     "smithy": "1.0",
     "metadata": {
         "suppressions": [
-            {"id": "OperationMissingInput", "namespace": "*"},
-            {"id": "OperationMissingOutput", "namespace": "*"},
             {"id": "OperationMissingInputTrait", "namespace": "*"},
             {"id": "OperationMissingOutputTrait", "namespace": "*"}
         ]

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/paginated/paginated-valid.json

@@ -2,8 +2,6 @@
     "smithy": "1.0",
     "metadata": {
         "suppressions": [
-            {"id": "OperationMissingInput", "namespace": "*"},
-            {"id": "OperationMissingOutput", "namespace": "*"},
             {"id": "OperationMissingInputTrait", "namespace": "*"},
             {"id": "OperationMissingOutputTrait", "namespace": "*"}
         ]

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/service-conflict-validator.json

@@ -1,11 +1,5 @@
 {
     "smithy": "1.0",
-    "metadata": {
-        "suppressions": [
-            {"id":  "OperationMissingInput", "namespace": "*"},
-            {"id":  "OperationMissingOutput", "namespace": "*"}
-        ]
-    },
     "shapes": {
         "ns.foo#MyService": {
             "type": "service",

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/single-operation-binding.json

@@ -1,11 +1,5 @@
 {
     "smithy": "1.0",
-    "metadata": {
-        "suppressions": [
-            {"id":  "OperationMissingInput", "namespace": "ns.foo"},
-            {"id":  "OperationMissingOutput", "namespace": "ns.foo"}
-        ]
-    },
     "shapes": {
         "ns.foo#MyService": {
             "type": "service",

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/streaming-trait-event.json

@@ -2,8 +2,6 @@
     "smithy": "1.0",
     "metadata": {
         "suppressions": [
-            {"id":  "OperationMissingInput", "namespace": "ns.foo"},
-            {"id":  "OperationMissingOutput", "namespace": "ns.foo"},
             {"id":  "OperationMissingInputTrait", "namespace": "ns.foo"},
             {"id":  "OperationMissingOutputTrait", "namespace": "ns.foo"}
         ]

smithy-mqtt-traits/src/test/resources/software/amazon/smithy/mqtt/traits/errorfiles/job-service.smithy

@@ -1,9 +1,7 @@
 $version: "1.0"
 
 metadata suppressions = [
-    {id: "OperationMissingInput", namespace: "aws.iotjobs"},
     {id: "OperationMissingInputTrait", namespace: "aws.iotjobs"},
-    {id: "OperationMissingOutput", namespace: "aws.iotjobs"},
     {id: "OperationMissingOutputTrait", namespace: "aws.iotjobs"},
 ]
 

smithy-mqtt-traits/src/test/resources/software/amazon/smithy/mqtt/traits/errorfiles/mqtt-topic-labels.smithy

@@ -2,7 +2,6 @@ namespace smithy.example
 
 // Missing input for {foo} property.
 @smithy.mqtt#publish("events1/{foo}")
-@suppress(["OperationMissingInput", "OperationMissingOutput"])
 operation Operation1 {}
 
 
@@ -51,7 +50,6 @@ structure Operation4Input {
 
 // No errors.
 @smithy.mqtt#publish("events5/{foo}")
-@suppress(["OperationMissingOutput"])
 operation Operation5 {
     input: Operation5Input
 }

smithy-mqtt-traits/src/test/resources/software/amazon/smithy/mqtt/traits/errorfiles/subscribe-missing-output.smithy

@@ -3,5 +3,4 @@
 namespace smithy.example
 
 @smithy.mqtt#subscribe("events")
-@suppress(["OperationMissingInput", "OperationMissingOutput"])
 operation Foo {}

smithy-waiters/src/test/resources/software/amazon/smithy/waiters/errorfiles/cannot-wait-on-streaming-operations.smithy

@@ -13,7 +13,6 @@ use smithy.waiters#waitable
         ]
     }
 )
-@suppress(["OperationMissingOutput"])
 operation StreamingInput {
     input: StreamingInputInput
 }
@@ -41,7 +40,6 @@ structure SuccessMessage {}
         ]
     }
 )
-@suppress(["OperationMissingInput"])
 operation StreamingOutput {
     output: StreamingOutputOutput
 }

smithy-waiters/src/test/resources/software/amazon/smithy/waiters/errorfiles/inputOutput-operation-with-no-input.smithy

@@ -19,7 +19,6 @@ use smithy.waiters#waitable
         ]
     }
 )
-@suppress(["OperationMissingInput"])
 operation A {
     output: AOutput
 }

smithy-waiters/src/test/resources/software/amazon/smithy/waiters/errorfiles/inputOutput-operation-with-no-output.smithy

@@ -19,7 +19,6 @@ use smithy.waiters#waitable
         ]
     }
 )
-@suppress(["OperationMissingOutput"])
 operation A {
     input: AInput
 }

smithy-waiters/src/test/resources/software/amazon/smithy/waiters/errorfiles/output-on-bad-shapes.smithy

@@ -18,5 +18,4 @@ use smithy.waiters#waitable
         ]
     }
 )
-@suppress(["OperationMissingInput", "OperationMissingOutput"])
 operation A {}