Improve SmithyBuilder error messages

smithy-build/src/main/java/software/amazon/smithy/build/SmithyBuildImpl.java

@@ -289,6 +289,9 @@ private ProjectionResult applyProjection(
                         "The model could not be merged with the following imports: [%s]",
                         projection.getImports()));
                 return ProjectionResult.builder()
+                        // Create an empty model so that ProjectionResult can be created when
+                        // the Model can't be assembled.
+                        .model(Model.builder().build())
                         .projectionName(projectionName)
                         .events(baseModel.getValidationEvents())
                         .build();

smithy-build/src/test/java/software/amazon/smithy/build/SmithyBuildTest.java

@@ -18,6 +18,7 @@
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.containsInAnyOrder;
 import static org.hamcrest.Matchers.containsString;
+import static org.hamcrest.Matchers.empty;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.hasItem;
 import static org.hamcrest.Matchers.is;
@@ -46,12 +47,18 @@
 import software.amazon.smithy.build.model.SmithyBuildConfig;
 import software.amazon.smithy.build.model.TransformConfig;
 import software.amazon.smithy.model.Model;
+import software.amazon.smithy.model.SourceException;
+import software.amazon.smithy.model.SourceLocation;
 import software.amazon.smithy.model.node.Node;
 import software.amazon.smithy.model.node.ObjectNode;
 import software.amazon.smithy.model.shapes.ShapeId;
 import software.amazon.smithy.model.traits.DocumentationTrait;
 import software.amazon.smithy.model.traits.SensitiveTrait;
 import software.amazon.smithy.model.traits.TagsTrait;
+import software.amazon.smithy.model.traits.Trait;
+import software.amazon.smithy.model.traits.TraitFactory;
+import software.amazon.smithy.model.validation.Severity;
+import software.amazon.smithy.model.validation.ValidationEvent;
 import software.amazon.smithy.utils.IoUtils;
 import software.amazon.smithy.utils.ListUtils;
 import software.amazon.smithy.utils.MapUtils;
@@ -590,4 +597,63 @@ public void execute(PluginContext context) {
         assertThat(e.getMessage(), containsString("(exampleProjection): java.lang.RuntimeException: Hi"));
         assertThat(e.getSuppressed(), equalTo(new Throwable[]{canned}));
     }
+
+    /*
+     This test causes SmithyBuild to fail in a way that it's unable to create Model as part of the
+     projection while using imports. This trigger a specific code path that needs to be able to create
+     a ProjectionResult with no model, so an empty model is provided. To achieve this, a test trait is
+     used with a custom trait factory that always throws when toNode is called on the trait (this is
+     something that's used for lots of stuff like trait hash code and equality). Smithy's model
+     assembler will catch the thrown SourceException, turn it into a validation event, and then bail
+     on trying to finish to build the model, triggering the code path under test here.
+     */
+    @Test
+    public void projectionsThatCannotCreateModelsFailGracefully() throws URISyntaxException {
+        Path config = Paths.get(getClass().getResource("test-bad-trait-serializer-config.json").toURI());
+        Model model = Model.assembler()
+                .addImport(getClass().getResource("test-bad-trait-serializer.smithy"))
+                .assemble()
+                .unwrap();
+        ShapeId badId = ShapeId.from("smithy.test#badTrait");
+        TraitFactory baseFactory = TraitFactory.createServiceFactory();
+        SmithyBuild builder = new SmithyBuild()
+                .config(config)
+                .model(model)
+                .fileManifestFactory(MockManifest::new)
+                .modelAssemblerSupplier(() -> {
+                    // Hook in a TraitFactory that knows about our custom, failing trait.
+                    return Model.assembler()
+                            .traitFactory((id, target, node) -> {
+                                if (id.equals(badId)) {
+                                    return Optional.of(new BadCustomTrait());
+                                } else {
+                                    return baseFactory.createTrait(id, target, node);
+                                }
+                            });
+                });
+
+        SmithyBuildResult result = builder.build();
+
+        // The project must have failed.
+        assertTrue(result.anyBroken());
+
+        // Now validate that we got the failure to serialize the model.
+        List<ValidationEvent> events = result.getProjectionResults().get(0).getEvents();
+        assertThat(events, not(empty()));
+        assertThat(events.get(0).getSeverity(), is(Severity.ERROR));
+        assertThat(events.get(0).getMessage(), containsString("Unable to serialize trait"));
+    }
+
+    // A test trait that always throws when toNode is called.
+    private static final class BadCustomTrait implements Trait {
+        @Override
+        public ShapeId toShapeId() {
+            return ShapeId.from("smithy.test#badTrait");
+        }
+
+        @Override
+        public Node toNode() {
+            throw new SourceException("Unable to serialize trait!", SourceLocation.none());
+        }
+    }
 }

smithy-build/src/test/resources/software/amazon/smithy/build/test-bad-trait-serializer-config.json

@@ -0,0 +1,8 @@
+{
+    "version": "1.0",
+    "projections": {
+        "foo": {
+            "imports": ["test-bad-trait-serializer-import.smithy"]
+        }
+    }
+}

smithy-build/src/test/resources/software/amazon/smithy/build/test-bad-trait-serializer-import.smithy

@@ -0,0 +1,9 @@
+$version: "1.0"
+
+namespace smithy.test
+
+@trait
+string badTrait
+
+@badTrait
+string shape

smithy-build/src/test/resources/software/amazon/smithy/build/test-bad-trait-serializer.smithy

@@ -0,0 +1,3 @@
+$version: "1.0"
+
+namespace smithy.test

smithy-utils/src/main/java/software/amazon/smithy/utils/SmithyBuilder.java

@@ -41,7 +41,16 @@ public interface SmithyBuilder<T> {
      */
     static <T> T requiredState(String method, T value) {
         if (value == null) {
-            throw new IllegalStateException(method + " was not set on the builder");
+            StringBuilder message = new StringBuilder(method).append(" was not set on the builder");
+
+            // Include the builder class that could not be built.
+            StackTraceElement[] elements = Thread.currentThread().getStackTrace();
+            if (elements.length >= 2) {
+                String builder = elements[2].getClassName();
+                message.append(" (builder class is probably ").append(builder).append(')');
+            }
+
+            throw new IllegalStateException(message.toString());
         }
         return value;
     }

smithy-utils/src/test/java/software/amazon/smithy/utils/SmithyBuilderTest.java

@@ -0,0 +1,38 @@
+/*
+ * 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.utils;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.equalTo;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class SmithyBuilderTest {
+    @Test
+    public void includesCallingClassName() {
+        IllegalStateException e = Assertions.assertThrows(IllegalStateException.class, () -> new Foo().test());
+
+        assertThat(e.getMessage(), equalTo("foo was not set on the builder (builder class is probably "
+                                           + "software.amazon.smithy.utils.SmithyBuilderTest$Foo)"));
+    }
+
+    private static final class Foo {
+        public void test() {
+            SmithyBuilder.requiredState("foo", null);
+        }
+    }
+}