akarshy21 · Nov 5, 2026 · Nov 11, 2026
@@ -4,7 +4,13 @@
  */
 package software.amazon.smithy.python.codegen.types;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.io.IOException;
+import java.nio.file.Files;
 import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.List;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.io.TempDir;
 import software.amazon.smithy.build.FileManifest;
@@ -56,4 +62,119 @@ public void testCodegenWithoutService(@TempDir Path tempDir) {
                 .build();
         plugin.execute(context);
     }
+
+    @Test
+    public void testEveryShapeIsGeneratedAlongsideErrors(@TempDir Path tempDir) throws IOException {
+        // Error shapes get their own synthetic operation; the shapes next to them must too.
+        String models = generate(tempDir, errors() + structures(8), settings());
+
+        assertEquals(List.of(), missing(models, errorNames(), structureNames(8)), "shapes missing from models.py");
+    }
+
+    @Test
+    public void testInputsAndOutputsAreGeneratedWhenEnabled(@TempDir Path tempDir) throws IOException {
+        // @input and @output shapes get synthetic operations too, and are generated when asked for.
+        String models = generate(
+                tempDir,
+                errors() + structures(4) + operations(),
+                settings().withMember("generateInputsAndOutputs", true));
+
+        List<String> expected = new ArrayList<>(structureNames(4));
+        expected.addAll(ioNames());
+        assertEquals(List.of(), missing(models, errorNames(), expected), "shapes missing from models.py");
+    }
+
+    @Test
+    public void testInputsAndOutputsAreGeneratedForServiceWhenEnabled(@TempDir Path tempDir) throws IOException {
+        String service =
+                "service IoService { operations: [OpA, OpB, OpC, OpD, OpE, OpF], errors: [ErrorA, ErrorB, ErrorC, ErrorD, ErrorE] }\n";
+        String models = generate(
+                tempDir,
+                errors() + operations() + service,
+                settings().withMember("service", "example.types#IoService")
+                        .withMember("generateInputsAndOutputs", true));
+
+        assertEquals(List.of(), missing(models, errorNames(), ioNames()), "shapes missing from models.py");
+    }
+
+    @Test
+    public void testInputsAndOutputsAreSkippedByDefault(@TempDir Path tempDir) throws IOException {
+        String models = generate(tempDir, errors() + structures(4) + operations(), settings());
+
+        assertEquals(List.of(), missing(models, errorNames(), structureNames(4)), "shapes missing from models.py");
+        List<String> generatedIo = ioNames().stream().filter(name -> models.contains("class " + name + ":")).toList();
+        assertEquals(List.of(), generatedIo, "input/output shapes generated without generateInputsAndOutputs");
+    }
+
+    private static final List<String> OPERATIONS = List.of("OpA", "OpB", "OpC", "OpD", "OpE", "OpF");
+
+    private static List<String> errorNames() {
+        return List.of("ErrorA", "ErrorB", "ErrorC", "ErrorD", "ErrorE");
+    }
+
+    private static List<String> structureNames(int count) {
+        return List.of("ShapeA", "ShapeB", "ShapeC", "ShapeD", "ShapeE", "ShapeF", "ShapeG", "ShapeH")
+                .subList(0, count);
+    }
+
+    private static List<String> ioNames() {
+        List<String> names = new ArrayList<>();
+        for (String operation : OPERATIONS) {
+            names.add(operation + "Input");
+            names.add(operation + "Output");
+        }
+        return names;
+    }
+
+    private static String errors() {
+        StringBuilder source = new StringBuilder();
+        for (String error : errorNames()) {
+            source.append("@error(\"client\")\nstructure ").append(error).append(" { message: String }\n");
+        }
+        return source.toString();
+    }
+
+    private static String structures(int count) {
+        StringBuilder source = new StringBuilder();
+        for (String structure : structureNames(count)) {
+            source.append("structure ").append(structure).append(" { value: String }\n");
+        }
+        return source.toString();
+    }
+
+    private static String operations() {
+        StringBuilder source = new StringBuilder();
+        for (String operation : OPERATIONS) {
+            source.append("operation ")
+                    .append(operation)
+                    .append(" { input := { value: String }, output := { value: String } }\n");
+        }
+        return source.toString();
+    }
+
+    private static ObjectNode.Builder settings() {
+        return ObjectNode.builder().withMember("module", "types_test").withMember("moduleVersion", "0.0.1");
+    }
+
+    private static String generate(Path tempDir, String shapes, ObjectNode.Builder settings) throws IOException {
+        Model model = Model.assembler()
+                .addUnparsedModel("test.smithy", "$version: \"2.0\"\nnamespace example.types\n" + shapes)
+                .assemble()
+                .unwrap();
+        PluginContext context = PluginContext.builder()
+                .fileManifest(FileManifest.create(tempDir))
+                .settings(settings.build())
+                .model(model)
+                .build();
+        new PythonTypeCodegenPlugin().execute(context);
+        return Files.readString(tempDir.resolve("src/types_test/models.py"));
+    }
+
+    // Errors are declared as `class Name(...)`, other structures as `class Name:`.
+    private static List<String> missing(String models, List<String> errors, List<String> structures) {
+        List<String> missing = new ArrayList<>();
+        errors.stream().filter(name -> !models.contains("class " + name + "(")).forEach(missing::add);
+        structures.stream().filter(name -> !models.contains("class " + name + ":")).forEach(missing::add);
+        return missing;
+    }
 }
@@ -72,13 +72,14 @@ Model transform(ModelTransformer transformer, Model model) {
                         .addTrait(new InputTrait())
                         .addMember("member", shape.getId())
                         .build();
-                index++;
                 operationBuilder.input(input);
                 addedShapes.add(input);
             }
 
             serviceBuilder.addOperation(operationId);
             addedShapes.add(operationBuilder.build());
+            // Every shape needs its own operation; a reused ID replaces the earlier one.
+            index++;
         }
 
         addedShapes.add(serviceBuilder.build());

@@ -40,6 +40,13 @@
 
 final class DirectedPythonTypeCodegen
         implements DirectedCodegen<GenerationContext, PythonSettings, PythonIntegration> {
+
+    private final boolean generateInputsAndOutputs;
+
+    DirectedPythonTypeCodegen(boolean generateInputsAndOutputs) {
+        this.generateInputsAndOutputs = generateInputsAndOutputs;
+    }
+
     @Override
     public SymbolProvider createSymbolProvider(CreateSymbolProviderDirective<PythonSettings> directive) {
         return new PythonSymbolProvider(directive.model(), directive.settings());
@@ -79,7 +86,7 @@ public void generateService(GenerateServiceDirective<GenerationContext, PythonSe
 
     @Override
     public void generateStructure(GenerateStructureDirective<GenerationContext, PythonSettings> directive) {
-        // If we're only generating data shapes, there's no need to generate input or output shapes.
+        // Types-only codegen skips input and output shapes unless generateInputsAndOutputs is set.
         if (!shouldGenerateStructure(directive.settings(), directive.shape())) {
             return;
         }
@@ -98,8 +105,9 @@ private boolean shouldGenerateStructure(PythonSettings settings, Shape shape) {
         if (shape.getId().getNamespace().equals("smithy.synthetic")) {
             return false;
         }
-        return !(settings.artifactType().equals(PythonSettings.ArtifactType.TYPES)
-                && (shape.hasTrait(InputTrait.class) || shape.hasTrait(OutputTrait.class)));
+        return generateInputsAndOutputs
+                || !(settings.artifactType().equals(PythonSettings.ArtifactType.TYPES)
+                        && (shape.hasTrait(InputTrait.class) || shape.hasTrait(OutputTrait.class)));
     }
 
     @Override

@@ -39,7 +39,7 @@ public void execute(PluginContext context) {
         }
 
         runner.settings(pythonSettings);
-        runner.directedCodegen(new DirectedPythonTypeCodegen());
+        runner.directedCodegen(new DirectedPythonTypeCodegen(typeSettings.generateInputsAndOutputs()));
         runner.fileManifest(context.getFileManifest());
         runner.service(pythonSettings.service());
         runner.model(model);

@@ -84,7 +84,13 @@ public PythonSettings toPythonSettings() {
      * @return Returns the extracted settings.
      */
     public static PythonTypeCodegenSettings fromNode(ObjectNode config) {
-        config.warnIfAdditionalProperties(Arrays.asList(SERVICE, MODULE_NAME, MODULE_DESCRIPTION, MODULE_VERSION));
+        config.warnIfAdditionalProperties(Arrays.asList(
+                SERVICE,
+                MODULE_NAME,
+                MODULE_DESCRIPTION,
+                MODULE_VERSION,
+                SELECTOR,
+                GENERATE_INPUTS_AND_OUTPUTS));
 
         String moduleName = config.expectStringMember(MODULE_NAME).getValue();
         Builder builder = builder()