Add a sufix to distinguish added required traits to structures or unions (#2793)

Author: sugmanue

gradle/libs.versions.toml

@@ -1,5 +1,6 @@
 [versions]
 junit5 = "5.13.4"
+junit-platform = "1.13.4"
 hamcrest = "3.0"
 jmh = "0.7.2"
 spotbugs = "6.2.4"
@@ -40,7 +41,7 @@ junit-bom = { module = "org.junit:junit-bom", version.ref = "junit5" }
 junit-jupiter-api = { module = "org.junit.jupiter:junit-jupiter-api", version.ref = "junit5" }
 junit-jupiter-engine = { module = "org.junit.jupiter:junit-jupiter-engine", version.ref = "junit5" }
 junit-jupiter-params = { module = "org.junit.jupiter:junit-jupiter-params", version.ref = "junit5" }
-junit-platform-launcher = { module = "org.junit.platform:junit-platform-launcher" }
+junit-platform-launcher = { module = "org.junit.platform:junit-platform-launcher", version.ref = "junit-platform" }
 hamcrest = { module = "org.hamcrest:hamcrest", version.ref = "hamcrest" }
 assertj-core = { module = "org.assertj:assertj-core", version.ref = "assertj" }
 mockserver = { module = "org.mock-server:mockserver-netty", version.ref = "mockserver" }

smithy-diff/src/main/java/software/amazon/smithy/diff/evaluators/ChangedNullability.java

@@ -124,12 +124,24 @@ private void createErrors(
             }
             // Can't add required to a member unless the member is marked as @clientOptional or part of @input.
             if (change.isTraitAdded(RequiredTrait.ID) && !newMember.hasTrait(ClientOptionalTrait.ID)) {
-                eventsToAdd.add(emit(Severity.ERROR,
-                        "AddedRequiredTrait",
-                        shape,
-                        oldMemberSourceLocation,
-                        message,
-                        "The @required trait was added to a member."));
+                if (newTarget.isStructureShape() || newTarget.isUnionShape()) {
+                    eventsToAdd.add(emit(Severity.WARNING,
+                            "AddedRequiredTrait.StructureOrUnion",
+                            shape,
+                            oldMemberSourceLocation,
+                            message,
+                            "The @required trait was added to a member "
+                                    + "that targets a " + newTarget.getType() + ". This is backward compatible in "
+                                    + "generators that always treat structures and unions as optional "
+                                    + "(e.g., AWS generators)"));
+                } else {
+                    eventsToAdd.add(emit(Severity.ERROR,
+                            "AddedRequiredTrait",
+                            shape,
+                            oldMemberSourceLocation,
+                            message,
+                            "The @required trait was added to a member."));
+                }
             }
             // Can't add the default trait to a member unless the member was previously required.
             if (change.isTraitAdded(DefaultTrait.ID) && !change.isTraitRemoved(RequiredTrait.ID)) {

smithy-diff/src/test/java/software/amazon/smithy/diff/evaluators/ChangedNullabilityTest.java

@@ -396,7 +396,7 @@ public void specialHandlingForRequiredStructureMembers() {
     }
 
     @Test
-    public void specialHandlingForRequiredUnionMembers() {
+    public void specialHandlingForRemovedRequiredUnionMembers() {
         SourceLocation memberSource = new SourceLocation("b.smithy", 3, 4);
         MemberShape memberA = MemberShape.builder().id("smithy.example#Baz$a").target("smithy.api#String").build();
         MemberShape memberB = MemberShape.builder().id("smithy.example#Baz$B").target("smithy.api#String").build();
@@ -418,7 +418,37 @@ public void specialHandlingForRequiredUnionMembers() {
 
         List<ValidationEvent> events = TestHelper.findEvents(
                 ModelDiff.compare(oldModel, newModel),
-                "ChangedNullability");
+                "ChangedNullability.RemovedRequiredTrait.StructureOrUnion");
+
+        assertThat(events, hasSize(1));
+        assertThat(events.get(0).getSeverity(), is(Severity.WARNING));
+        assertThat(events.get(0).getSourceLocation(), equalTo(memberSource));
+    }
+
+    @Test
+    public void specialHandlingForAddedRequiredUnionMembers() {
+        SourceLocation memberSource = new SourceLocation("b.smithy", 3, 4);
+        MemberShape memberA = MemberShape.builder().id("smithy.example#Baz$a").target("smithy.api#String").build();
+        MemberShape memberB = MemberShape.builder().id("smithy.example#Baz$B").target("smithy.api#String").build();
+        UnionShape union = UnionShape.builder().id("smithy.example#Baz").addMember(memberA).addMember(memberB).build();
+        MemberShape memberBaz = MemberShape.builder()
+                .id("smithy.example#Foo$baz")
+                .addTrait(new RequiredTrait())
+                .target(union)
+                .source(memberSource)
+                .build();
+        StructureShape struct = StructureShape.builder().id("smithy.example#Foo").addMember(memberBaz).build();
+        Model newModel = Model.assembler().addShapes(union, struct, memberA, memberB, memberBaz).assemble().unwrap();
+        Model oldModel = ModelTransformer.create()
+                .replaceShapes(newModel,
+                        ListUtils.of(
+                                Shape.shapeToBuilder(newModel.expectShape(ShapeId.from("smithy.example#Foo$baz")))
+                                        .removeTrait(RequiredTrait.ID)
+                                        .build()));
+
+        List<ValidationEvent> events = TestHelper.findEvents(
+                ModelDiff.compare(oldModel, newModel),
+                "ChangedNullability.AddedRequiredTrait.StructureOrUnion");
 
         assertThat(events, hasSize(1));
         assertThat(events.get(0).getSeverity(), is(Severity.WARNING));