Add ScopeFactory API

README.md

@@ -206,6 +206,13 @@ interface MainScope extends Creatable<MainDependencies> {
 interface MainDependencies {}
 ```
 
+Extending `Creatable<D>` also enables instantiation of a "root" `Scope` without referencing generated code using Motif's `ScopeFactory.create` API:
+
+```java
+MainDependencies dependencies = ...;
+MainScope mainScope = ScopeFactory.create(MainScope.class, dependencies)
+```
+
 ## Convenience APIs
 
 Factory methods that pass parameters through to a constructor without modification can be converted to parameterless abstract methods:

lib/src/main/java/motif/ScopeFactory.java

@@ -0,0 +1,66 @@
+package motif;
+
+import java.lang.reflect.Constructor;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.util.HashMap;
+import java.util.Map;
+
+public class ScopeFactory {
+
+    private ScopeFactory() {}
+
+    private static final Map<Class<?>, Constructor<?>> scopeClassToCreateMethod = new HashMap<>();
+
+    public static <S extends Creatable<D>, D> S create(Class<S> scopeClass, D dependencies) {
+        Constructor<?> constructor = getConstructor(scopeClass);
+        try {
+            return (S) constructor.newInstance(dependencies);
+        } catch (IllegalAccessException e) {
+            throw new RuntimeException(e);
+        } catch (InvocationTargetException e) {
+            throw new RuntimeException(e);
+        } catch (InstantiationException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    private synchronized static Constructor<?> getConstructor(Class<?> scopeClass) {
+        Constructor<?> constructor = scopeClassToCreateMethod.get(scopeClass);
+        if (constructor == null) {
+            Class<?> scopeImplClass = getScopeImplClass(scopeClass);
+            constructor = scopeImplClass.getDeclaredConstructors()[0];
+            scopeClassToCreateMethod.put(scopeClass, constructor);
+        }
+        return constructor;
+    }
+
+    private static Class<?> getScopeImplClass(Class<?> scopeClass) {
+        String scopeImplClassName = getScopeImplClassName(scopeClass);
+        try {
+            return Class.forName(scopeImplClassName, false, scopeClass.getClassLoader());
+        } catch (ClassNotFoundException e) {
+            throw new RuntimeException("Could not find Scope implementation class " + scopeImplClassName + ". Ensure " +
+                    "that the Motif annotation processor is enabled.");
+        }
+    }
+
+    // Inspired by https://github.com/square/javapoet/issues/295
+    private static String getScopeImplClassName(Class<?> scopeClass) {
+        StringBuilder sb = new StringBuilder();
+        sb.append("Impl");
+        Class<?> clazz = scopeClass;
+        while (true) {
+            sb.insert(0, clazz.getSimpleName());
+            Class<?> enclosing = clazz.getEnclosingClass();
+            if (enclosing == null) break;
+            clazz = enclosing;
+        }
+        int lastDot = clazz.getName().lastIndexOf('.');
+        if (lastDot != -1) {
+            sb.insert(0, '.');
+            sb.insert(0, clazz.getName().substring(0, lastDot));
+        }
+        return sb.toString();
+    }
+}

tests/src/main/java/testcases/T068_scope_factory/GRAPH.txt

@@ -0,0 +1,32 @@
+########################################################################
+#                                                                      #
+# This file is auto-generated by running the Motif compiler tests and  #
+# serves a as validation of graph correctness. IntelliJ plugin tests   #
+# also rely on this file to ensure that the plugin graph understanding #
+# is equivalent to the compiler's.                                     #
+#                                                                      #
+# - Do not edit manually.                                              #
+# - Commit changes to source control.                                  #
+# - Since this file is autogenerated, code review changes carefully to #
+#   ensure correctness.                                                #
+#                                                                      #
+########################################################################
+
+ -------
+| Scope |
+ -------
+
+  ==== Required ====
+
+    ---- String ----
+      [ Provided By ]
+      [ Consumed By ]
+        * Scope | Scope.string()
+
+  ==== Provides ====
+
+    ---- Scope | implicit ----
+      [ Required ]
+      [ Consumed By ]
+
+

tests/src/main/java/testcases/T068_scope_factory/Scope.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2018-2019 Uber Technologies, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License 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 testcases.T068_scope_factory;
+
+import motif.Creatable;
+
+@motif.Scope
+public interface Scope extends Creatable<Scope.Dependencies> {
+
+    String string();
+
+    interface Dependencies {
+
+        String s();
+    }
+}

tests/src/main/java/testcases/T068_scope_factory/Test.java

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2018-2019 Uber Technologies, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License 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 testcases.T068_scope_factory;
+
+import motif.ScopeFactory;
+
+import static com.google.common.truth.Truth.assertThat;
+
+public class Test {
+
+    public static void run() {
+        Scope scope = ScopeFactory.create(Scope.class, new Scope.Dependencies() {
+            @Override
+            public String s() {
+                return "s";
+            }
+        });
+        assertThat(scope.string()).isEqualTo("s");
+    }
+}

tests/src/main/java/testcases/T068_scope_factory/config.pro

@@ -0,0 +1,9 @@
+-dontshrink
+-keep class **Test {
+    public static void run();
+}
+
+-keepnames @motif.Scope interface *
+-keepnames @motif.ScopeImpl class * {
+    <init>(...);
+}