Allow jsonName trait on union members

docs/source/1.0/spec/core/protocol-traits.rst

@@ -143,11 +143,11 @@ support configuration settings.
 
 Summary
     Allows a serialized object property name in a JSON document to differ from
-    a structure member name used in the model.
+    a structure or union member name used in the model.
 Trait selector
-    ``structure > member``
+    ``:is(structure, union) > member``
 
-    *Any structure member*
+    *Any structure or union member*
 Value type
     ``string``
 
@@ -203,6 +203,11 @@ following document:
         "bar": "def"
     }
 
+.. note::
+
+    No two members of the same structure or union can use the
+    same case-sensitive ``@jsonName``.
+
 
 .. smithy-trait:: smithy.api#mediaType
 .. _mediaType-trait:

smithy-aws-protocol-tests/model/restJson1/unions.smithy

@@ -512,3 +512,156 @@ apply PostPlayerAction @httpResponseTests([
         }
     }
 ])
+
+
+/// This operation defines a union that uses jsonName on some members.
+@http(uri: "/PostUnionWithJsonName", method: "POST")
+operation PostUnionWithJsonName {
+    input: PostUnionWithJsonNameInput,
+    output: PostUnionWithJsonNameOutput
+}
+
+@input
+structure PostUnionWithJsonNameInput {
+    @required
+    value: UnionWithJsonName
+}
+
+@output
+structure PostUnionWithJsonNameOutput {
+    @required
+    value: UnionWithJsonName
+}
+
+union UnionWithJsonName {
+    @jsonName("FOO")
+    foo: String,
+
+    bar: String,
+
+    @jsonName("_baz")
+    baz: String
+}
+
+apply PostUnionWithJsonName @httpRequestTests([
+    {
+        id: "PostUnionWithJsonNameRequest1",
+        documentation: "Tests that jsonName works with union members.",
+        protocol: restJson1,
+        method: "POST",
+        uri: "/PostUnionWithJsonName",
+        body: """
+            {
+                "value": {
+                    "FOO": "hi"
+                }
+            }""",
+        bodyMediaType: "application/json",
+        headers: {"Content-Type": "application/json"},
+        params: {
+            value: {
+                foo: "hi"
+            }
+        }
+    },
+    {
+        id: "PostUnionWithJsonNameRequest2",
+        documentation: "Tests that jsonName works with union members.",
+        protocol: restJson1,
+        method: "POST",
+        uri: "/PostUnionWithJsonName",
+        body: """
+            {
+                "value": {
+                    "_baz": "hi"
+                }
+            }""",
+        bodyMediaType: "application/json",
+        headers: {"Content-Type": "application/json"},
+        params: {
+            value: {
+                baz: "hi"
+            }
+        }
+    },
+    {
+        id: "PostUnionWithJsonNameRequest3",
+        documentation: "Tests that jsonName works with union members.",
+        protocol: restJson1,
+        method: "POST",
+        uri: "/PostUnionWithJsonName",
+        body: """
+            {
+                "value": {
+                    "bar": "hi"
+                }
+            }""",
+        bodyMediaType: "application/json",
+        headers: {"Content-Type": "application/json"},
+        params: {
+            value: {
+                bar: "hi"
+            }
+        }
+    }
+])
+
+apply PostUnionWithJsonName @httpResponseTests([
+    {
+        id: "PostUnionWithJsonNameResponse1",
+        documentation: "Tests that jsonName works with union members.",
+        protocol: restJson1,
+        code: 200,
+        body: """
+            {
+                "value": {
+                    "FOO": "hi"
+                }
+            }""",
+        bodyMediaType: "application/json",
+        headers: {"Content-Type": "application/json"},
+        params: {
+            value: {
+                foo: "hi"
+            }
+        }
+    },
+    {
+        id: "PostUnionWithJsonNameResponse2",
+        documentation: "Tests that jsonName works with union members.",
+        protocol: restJson1,
+        code: 200,
+        body: """
+            {
+                "value": {
+                    "_baz": "hi"
+                }
+            }""",
+        bodyMediaType: "application/json",
+        headers: {"Content-Type": "application/json"},
+        params: {
+            value: {
+                baz: "hi"
+            }
+        }
+    },
+    {
+        id: "PostUnionWithJsonNameResponse3",
+        documentation: "Tests that jsonName works with union members.",
+        protocol: restJson1,
+        code: 200,
+        body: """
+            {
+                "value": {
+                    "bar": "hi"
+                }
+            }""",
+        bodyMediaType: "application/json",
+        headers: {"Content-Type": "application/json"},
+        params: {
+            value: {
+                bar: "hi"
+            }
+        }
+    }
+])

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

@@ -0,0 +1,69 @@
+/*
+ * Copyright 2022 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.smithy.model.validation.validators;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.TreeMap;
+import java.util.TreeSet;
+import java.util.stream.Collectors;
+import software.amazon.smithy.model.Model;
+import software.amazon.smithy.model.shapes.MemberShape;
+import software.amazon.smithy.model.shapes.Shape;
+import software.amazon.smithy.model.shapes.ShapeId;
+import software.amazon.smithy.model.traits.JsonNameTrait;
+import software.amazon.smithy.model.validation.AbstractValidator;
+import software.amazon.smithy.model.validation.ValidationEvent;
+
+public final class JsonNameValidator extends AbstractValidator {
+    @Override
+    public List<ValidationEvent> validate(Model model) {
+        List<ValidationEvent> events = new ArrayList<>();
+        Set<ShapeId> visitedContainers = new HashSet<>();
+
+        // Find every member marked with a jsonName trait. The containing shapes of these members are
+        // the only structure/union shapes that need to be validated.
+        for (MemberShape member : model.getMemberShapesWithTrait(JsonNameTrait.class)) {
+            // If the container hasn't been visited yet, then validate it's members.
+            if (visitedContainers.add(member.getContainer())) {
+                validateMembersOfContainer(model.expectShape(member.getContainer()), events);
+            }
+        }
+        return events;
+    }
+
+    private void validateMembersOfContainer(Shape container, List<ValidationEvent> events) {
+        Map<String, Set<MemberShape>> memberMappings = new TreeMap<>();
+        for (MemberShape m : container.members()) {
+            String jsonName = m.getTrait(JsonNameTrait.class)
+                    .map(JsonNameTrait::getValue)
+                    .orElseGet(m::getMemberName);
+            memberMappings.computeIfAbsent(jsonName, n -> new TreeSet<>()).add(m);
+        }
+
+        for (Map.Entry<String, Set<MemberShape>> entry : memberMappings.entrySet()) {
+            if (entry.getValue().size() > 1) {
+                events.add(error(container, String.format(
+                        "This shape contains members with conflicting JSON names that resolve to '%s': %s",
+                        entry.getKey(),
+                        entry.getValue().stream().map(MemberShape::getMemberName).collect(Collectors.joining(", ")))));
+            }
+        }
+    }
+}

smithy-model/src/main/resources/META-INF/services/software.amazon.smithy.model.validation.Validator

@@ -16,6 +16,7 @@ software.amazon.smithy.model.validation.validators.HttpQueryParamsTraitValidator
 software.amazon.smithy.model.validation.validators.HttpQueryTraitValidator
 software.amazon.smithy.model.validation.validators.HttpResponseCodeSemanticsValidator
 software.amazon.smithy.model.validation.validators.HttpUriConflictValidator
+software.amazon.smithy.model.validation.validators.JsonNameValidator
 software.amazon.smithy.model.validation.validators.LengthTraitValidator
 software.amazon.smithy.model.validation.validators.MediaTypeValidator
 software.amazon.smithy.model.validation.validators.NoInlineDocumentSupportValidator

smithy-model/src/main/resources/software/amazon/smithy/model/loader/prelude.smithy

@@ -293,7 +293,7 @@ structure internal {}
 
 /// The jsonName trait allows a serialized object property name to differ
 /// from a structure member name used in the model.
-@trait(selector: "structure > member")
+@trait(selector: ":is(structure, union) > member")
 @tags(["diff.error.const"])
 string jsonName
 

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/json-name.errors

@@ -1 +1 @@
-[ERROR] ns.foo#B: Trait `jsonName` cannot be applied to `ns.foo#B`. This trait may only be applied to shapes that match the following selector: structure > member | TraitTarget
+[ERROR] ns.foo#B: Trait `jsonName` cannot be applied to `ns.foo#B`. This trait may only be applied to shapes that match the following selector: :is(structure, union) | TraitTarget

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/jsonName-conflict.errors

@@ -0,0 +1,2 @@
+[ERROR] ns.foo#A: This shape contains members with conflicting JSON names that resolve to 'b': a, b | JsonName
+[ERROR] ns.foo#B: This shape contains members with conflicting JSON names that resolve to 'b': a, b | JsonName

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

@@ -0,0 +1,45 @@
+{
+    "smithy": "1.0",
+    "shapes": {
+        "ns.foo#A": {
+            "type": "structure",
+            "members": {
+                "a": {
+                    "target": "smithy.api#String",
+                    "traits": {
+                        "smithy.api#jsonName": "b"
+                    }
+                },
+                "b": {
+                    "target": "smithy.api#String"
+                },
+                "c": {
+                    "target": "smithy.api#String",
+                    "traits": {
+                        "smithy.api#jsonName": "a"
+                    }
+                }
+            }
+        },
+        "ns.foo#B": {
+            "type": "union",
+            "members": {
+                "a": {
+                    "target": "smithy.api#String",
+                    "traits": {
+                        "smithy.api#jsonName": "b"
+                    }
+                },
+                "b": {
+                    "target": "smithy.api#String"
+                },
+                "c": {
+                    "target": "smithy.api#String",
+                    "traits": {
+                        "smithy.api#jsonName": "a"
+                    }
+                }
+            }
+        }
+    }
+}