Remove model inference

This removes the ability to infer which service should be generated
for in a model, instead relying on the setting being explicit.

codegen/smithy-go-codegen/src/main/java/software/amazon/smithy/go/codegen/CodegenVisitor.java

@@ -44,7 +44,7 @@ final class CodegenVisitor extends ShapeVisitor.Default<Void> {
     private final GoDelegator writers;
 
     CodegenVisitor(PluginContext context) {
-        settings = GoSettings.from(context.getModel(), context.getSettings());
+        settings = GoSettings.from(context.getSettings());
         model = context.getModel();
         modelWithoutTraitShapes = context.getModelWithoutTraitShapes();
         service = settings.getService(model);

codegen/smithy-go-codegen/src/main/java/software/amazon/smithy/go/codegen/GoSettings.java

@@ -16,25 +16,18 @@
 package software.amazon.smithy.go.codegen;
 
 import java.util.Arrays;
-import java.util.List;
 import java.util.Objects;
-import java.util.logging.Logger;
-import java.util.stream.Collectors;
 import software.amazon.smithy.codegen.core.CodegenException;
 import software.amazon.smithy.model.Model;
 import software.amazon.smithy.model.node.ObjectNode;
-import software.amazon.smithy.model.node.StringNode;
 import software.amazon.smithy.model.shapes.ServiceShape;
-import software.amazon.smithy.model.shapes.Shape;
 import software.amazon.smithy.model.shapes.ShapeId;
 
 /**
  * Settings used by {@link GoCodegenPlugin}.
  */
 public final class GoSettings {
 
-    private static final Logger LOGGER = Logger.getLogger(GoSettings.class.getName());
-
     private static final String SERVICE = "service";
     private static final String MODULE_NAME = "module";
     private static final String MODULE_DESCRIPTION = "moduleDescription";
@@ -48,19 +41,14 @@ public final class GoSettings {
     /**
      * Create a settings object from a configuration object node.
      *
-     * @param model Model to infer the service to generate if not explicitly provided.
      * @param config Config object to load.
      * @return Returns the extracted settings.
      */
-    public static GoSettings from(Model model, ObjectNode config) {
+    public static GoSettings from(ObjectNode config) {
         GoSettings settings = new GoSettings();
         config.warnIfAdditionalProperties(Arrays.asList(SERVICE, MODULE_NAME, MODULE_DESCRIPTION, MODULE_VERSION));
 
-        // Get the service from the settings or infer one from the given model.
-        settings.setService(config.getStringMember(SERVICE)
-                .map(StringNode::expectShapeId)
-                .orElseGet(() -> inferService(model)));
-
+        settings.setService(config.expectStringMember(SERVICE).expectShapeId());
         settings.setModuleName(config.expectStringMember(MODULE_NAME).getValue());
         settings.setModuleVersion(config.expectStringMember(MODULE_VERSION).getValue());
         settings.setModuleDescription(config.getStringMemberOrDefault(
@@ -69,25 +57,6 @@ public static GoSettings from(Model model, ObjectNode config) {
         return settings;
     }
 
-    private static ShapeId inferService(Model model) {
-        List<ShapeId> services = model
-                .shapes(ServiceShape.class)
-                .map(Shape::getId)
-                .sorted()
-                .collect(Collectors.toList());
-
-        if (services.isEmpty()) {
-            throw new CodegenException("Cannot infer a service to generate because the model does not "
-                    + "contain any service shapes");
-        } else if (services.size() > 1) {
-            throw new CodegenException("Cannot infer a service to generate because the model contains "
-                    + "multiple service shapes: " + services);
-        } else {
-            LOGGER.info("Inferring service to generate as " + services.get(0));
-            return services.get(0);
-        }
-    }
-
     /**
      * Gets the id of the service that is being generated.
      *