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Provide a minimal DI implementation for EP.
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check_api/src/main/java/com/google/errorprone/scanner/ErrorProneInjector.java
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| /* | ||
| * Copyright 2023 The Error Prone Authors. | ||
| * | ||
| * 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. | ||
| */ | ||
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| package com.google.errorprone.scanner; | ||
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| import static com.google.common.collect.Lists.reverse; | ||
| import static java.util.Arrays.stream; | ||
| import static java.util.stream.Collectors.joining; | ||
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| import com.google.common.collect.ClassToInstanceMap; | ||
| import com.google.common.collect.MutableClassToInstanceMap; | ||
| import com.google.errorprone.ErrorProneFlags; | ||
| import com.google.errorprone.annotations.CanIgnoreReturnValue; | ||
| import com.google.inject.ProvisionException; | ||
| import java.lang.reflect.Constructor; | ||
| import java.util.ArrayList; | ||
| import java.util.List; | ||
| import java.util.Optional; | ||
| import java.util.function.Predicate; | ||
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||
| /** | ||
| * An injector for ErrorProne. | ||
| * | ||
| * <p>This implements a very simplified subset of the functionality that Guice does. Specifically, | ||
| * it allows injecting only non-generic classes, and treats everything as a singleton within a given | ||
| * compilation. | ||
| */ | ||
| final class ErrorProneInjector { | ||
| private final ClassToInstanceMap<Object> instances = MutableClassToInstanceMap.create(); | ||
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| public static ErrorProneInjector create() { | ||
| return new ErrorProneInjector(); | ||
| } | ||
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| @CanIgnoreReturnValue | ||
| public <T> ErrorProneInjector addBinding(Class<T> clazz, T instance) { | ||
| instances.putInstance(clazz, instance); | ||
| return this; | ||
| } | ||
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| public synchronized <T> T getInstance(Class<T> clazz) { | ||
| return getInstance(clazz, new ArrayList<>()); | ||
| } | ||
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| private synchronized <T> T getInstance(Class<T> clazz, List<Class<?>> path) { | ||
| var instance = instances.getInstance(clazz); | ||
| if (instance != null) { | ||
| return instance; | ||
| } | ||
| path.add(clazz); | ||
| Constructor<T> constructor = | ||
| findConstructor(clazz) | ||
| .orElseThrow( | ||
| () -> | ||
| new ProvisionException( | ||
| "Failed to find an injectable constructor for " | ||
| + clazz.getCanonicalName() | ||
| + " requested by " | ||
| + printPath(path))); | ||
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| constructor.setAccessible(true); | ||
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| Object[] args = | ||
| stream(constructor.getParameterTypes()).map(c -> getInstance(c, path)).toArray(); | ||
| T newInstance; | ||
| try { | ||
| newInstance = constructor.newInstance(args); | ||
| } catch (ReflectiveOperationException e) { | ||
| throw new ProvisionException("Failed to initialize " + clazz.getCanonicalName(), e); | ||
| } | ||
| instances.putInstance(clazz, newInstance); | ||
| return newInstance; | ||
| } | ||
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| public static <T> Optional<Constructor<T>> findConstructor(Class<T> clazz) { | ||
| return findConstructorMatching( | ||
| clazz, | ||
| c -> | ||
| stream(c.getAnnotations()) | ||
| .anyMatch(a -> a.annotationType().getSimpleName().equals("Inject"))) | ||
| .or( | ||
| () -> | ||
| findConstructorMatching( | ||
| clazz, | ||
| c -> | ||
| stream(c.getParameters()) | ||
| .allMatch(p -> p.getType().equals(ErrorProneFlags.class)))); | ||
| } | ||
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| @SuppressWarnings("unchecked") | ||
| private static <T> Optional<Constructor<T>> findConstructorMatching( | ||
| Class<T> clazz, Predicate<Constructor<?>> predicate) { | ||
| return stream(clazz.getDeclaredConstructors()) | ||
| .filter(predicate) | ||
| .map(c -> (Constructor<T>) c) | ||
| .findFirst(); | ||
| } | ||
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| private static String printPath(List<Class<?>> path) { | ||
| return reverse(path).stream().map(Class::getSimpleName).collect(joining(" <- ")); | ||
| } | ||
| } |
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92
check_api/src/test/java/com/google/errorprone/scanner/ErrorProneInjectorTest.java
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| /* | ||
| * Copyright 2023 The Error Prone Authors. | ||
| * | ||
| * 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. | ||
| */ | ||
|
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| package com.google.errorprone.scanner; | ||
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| import static com.google.common.truth.Truth.assertThat; | ||
| import static org.junit.Assert.assertThrows; | ||
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| import com.google.inject.ProvisionException; | ||
| import javax.inject.Inject; | ||
| import org.junit.Test; | ||
| import org.junit.runner.RunWith; | ||
| import org.junit.runners.JUnit4; | ||
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| @RunWith(JUnit4.class) | ||
| public final class ErrorProneInjectorTest { | ||
| @Test | ||
| public void retrievesPredefinedInstance() { | ||
| var injector = ErrorProneInjector.create().addBinding(Integer.class, 2); | ||
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| assertThat(injector.getInstance(Integer.class)) | ||
| .isSameInstanceAs(injector.getInstance(Integer.class)); | ||
| } | ||
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| @Test | ||
| public void noConstructor_injectable() { | ||
| var injector = ErrorProneInjector.create(); | ||
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| var unused = injector.getInstance(NoConstructor.class); | ||
| } | ||
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| @Test | ||
| public void injectConstructor_injectable() { | ||
| var injector = ErrorProneInjector.create(); | ||
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| var unused = injector.getInstance(InjectConstructor.class); | ||
| } | ||
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| @Test | ||
| public void bothConstructors_injectable() { | ||
| var injector = ErrorProneInjector.create().addBinding(Integer.class, 2); | ||
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| var obj = injector.getInstance(InjectConstructorAndZeroArgConstructor.class); | ||
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| assertThat(obj.x).isEqualTo(2); | ||
| } | ||
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| @Test | ||
| public void pathInError() { | ||
| var injector = ErrorProneInjector.create(); | ||
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| var e = | ||
| assertThrows( | ||
| ProvisionException.class, | ||
| () -> injector.getInstance(InjectConstructorAndZeroArgConstructor.class)); | ||
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| assertThat(e).hasMessageThat().contains("Integer <- InjectConstructorAndZeroArgConstructor"); | ||
| } | ||
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| public static final class NoConstructor {} | ||
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| public static final class InjectConstructor { | ||
| @Inject | ||
| InjectConstructor() {} | ||
| } | ||
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| public static final class InjectConstructorAndZeroArgConstructor { | ||
| final int x; | ||
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| @Inject | ||
| InjectConstructorAndZeroArgConstructor(Integer x) { | ||
| this.x = x; | ||
| } | ||
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| InjectConstructorAndZeroArgConstructor() { | ||
| this.x = 0; | ||
| } | ||
| } | ||
| } |