Fix using shapes without TaritDefinition as trait

smithy-cli/src/it/resources/software/amazon/smithy/cli/projects/model-with-warning/model/main.smithy

@@ -2,6 +2,7 @@ $version: "2.0"
 namespace smithy.example
 
 @unstable
+@trait
 structure exampleUnstable {}
 
 @exampleUnstable

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

@@ -4,6 +4,8 @@
  */
 package software.amazon.smithy.model.loader;
 
+import static software.amazon.smithy.model.validation.Severity.ERROR;
+
 import java.util.ArrayDeque;
 import java.util.ArrayList;
 import java.util.Collection;
@@ -18,9 +20,11 @@
 import software.amazon.smithy.model.shapes.Shape;
 import software.amazon.smithy.model.shapes.ShapeId;
 import software.amazon.smithy.model.shapes.ShapeType;
+import software.amazon.smithy.model.traits.TraitDefinition;
 import software.amazon.smithy.model.traits.TraitFactory;
 import software.amazon.smithy.model.validation.ValidationEvent;
 import software.amazon.smithy.model.validation.ValidationEventDecorator;
+import software.amazon.smithy.model.validation.Validator;
 
 final class LoadOperationProcessor implements Consumer<LoadOperation> {
 
@@ -125,9 +129,11 @@ Model buildModel() {
         Model.Builder modelBuilder = Model.builder();
         modelBuilder.metadata(metadata.getData());
         resolveForwardReferences();
-        traitMap.applyTraitsToNonMixinsInShapeMap(shapeMap);
+        List<ShapeId> undefinedTraits = new ArrayList<>();
+        traitMap.applyTraitsToNonMixinsInShapeMap(shapeMap, undefinedTraits);
         shapeMap.buildShapesAndClaimMixinTraits(modelBuilder, traitMap::claimTraitsForShape);
         traitMap.emitUnclaimedTraits();
+        validateTraitWithTraitDefinition(undefinedTraits, modelBuilder);
         if (prelude != null) {
             modelBuilder.addShapes(prelude);
         }
@@ -138,6 +144,28 @@ List<ValidationEvent> events() {
         return events;
     }
 
+    private void validateTraitWithTraitDefinition(List<ShapeId> undefiedTraits, Model.Builder modelBuilder) {
+        Map<ShapeId, Shape> shapes = modelBuilder.getCurrentShapes();
+        for (ShapeId traitId : undefiedTraits) {
+            if (shapes.containsKey(traitId)) {
+                Shape traitShape = shapes.get(traitId);
+                if (!traitShape.hasTrait(TraitDefinition.ID)) {
+                    events.add(ValidationEvent.builder()
+                            .id(Validator.MODEL_ERROR)
+                            .severity(ERROR)
+                            .sourceLocation(traitShape.getSourceLocation())
+                            .shapeId(traitId)
+                            .message(
+                                    String.format(
+                                            "Shape `%s` cannot be applied as a trait. If this is a custom trait, " +
+                                                    "please add `@trait` to this shape.",
+                                            traitId))
+                            .build());
+                }
+            }
+        }
+    }
+
     private void resolveForwardReferences() {
         while (!forwardReferences.isEmpty()) {
             LoadOperation.ForwardReference reference = forwardReferences.poll();

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

@@ -23,6 +23,7 @@
 import software.amazon.smithy.model.shapes.ShapeId;
 import software.amazon.smithy.model.traits.DynamicTrait;
 import software.amazon.smithy.model.traits.Trait;
+import software.amazon.smithy.model.traits.TraitDefinition;
 import software.amazon.smithy.model.traits.TraitFactory;
 import software.amazon.smithy.model.validation.Severity;
 import software.amazon.smithy.model.validation.ValidationEvent;
@@ -46,7 +47,7 @@ final class LoaderTraitMap {
         this.allowUnknownTraits = allowUnknownTraits;
     }
 
-    void applyTraitsToNonMixinsInShapeMap(LoaderShapeMap shapeMap) {
+    void applyTraitsToNonMixinsInShapeMap(LoaderShapeMap shapeMap, List<ShapeId> undefinedTraits) {
         for (Map.Entry<ShapeId, Map<ShapeId, Node>> entry : traits.entrySet()) {
             ShapeId target = entry.getKey();
             ShapeId root = target.withoutMember();
@@ -64,6 +65,7 @@ void applyTraitsToNonMixinsInShapeMap(LoaderShapeMap shapeMap) {
                 Node traitNode = traitEntry.getValue();
                 Trait created = createTrait(target, traitId, traitNode);
                 validateTraitIsKnown(target, traitId, created, traitNode.getSourceLocation(), shapeMap);
+                validateTraitWithTraitDefinition(traitId, undefinedTraits);
 
                 if (target.hasMember()) {
                     // Apply the trait to a member by reaching into the members of each LoadOperation.DefineShape.
@@ -144,6 +146,13 @@ private void validateTraitIsKnown(
         }
     }
 
+    private void validateTraitWithTraitDefinition(ShapeId traitId, List<ShapeId> undefinedTraits) {
+        Map<ShapeId, Node> appliedTraits = traits.get(traitId);
+        if (appliedTraits == null || !appliedTraits.containsKey(TraitDefinition.ID)) {
+            undefinedTraits.add(traitId);
+        }
+    }
+
     private void applyTraitsToShape(AbstractShapeBuilder<?, ?> shape, Trait trait) {
         if (trait != null) {
             shape.addTrait(trait);

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/loader/invalid-other-shapes-as-trait.errors

@@ -0,0 +1 @@
+[ERROR] com.foo#MyDoc: Shape `com.foo#MyDoc` cannot be applied as a trait. If this is a custom trait, please add `@trait` to this shape. | Model

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/loader/invalid-other-shapes-as-trait.smithy

@@ -0,0 +1,8 @@
+$version: "1.0"
+
+namespace com.foo
+
+document MyDoc
+
+@MyDoc(name: "aa")
+structure MyStruct {}