Add support for generating methods

Add `GeneratedMethods` and `GeneratedMethod` support classes which
can be used during code generation to generation additional methods
that will ultimately be included in a `JavaFile`.

See gh-28414

spring-core/src/test/java/org/springframework/aot/generate/GeneratedMethodTests.java

@@ -0,0 +1,72 @@
+/*
+ * Copyright 2002-2022 the original author or 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
+ *
+ *      https://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 org.springframework.aot.generate;
+
+import javax.lang.model.element.Modifier;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
+import static org.assertj.core.api.Assertions.assertThatIllegalStateException;
+
+/**
+ * Tests for {@link GeneratedMethod}.
+ *
+ * @author Phillip Webb
+ */
+class GeneratedMethodTests {
+
+	private static final String NAME = "spring";
+
+	@Test
+	void getNameReturnsName() {
+		GeneratedMethod method = new GeneratedMethod(NAME);
+		assertThat(method.getName()).isSameAs(NAME);
+	}
+
+	@Test
+	void getSpecReturnsSpec() {
+		GeneratedMethod method = new GeneratedMethod(NAME);
+		method.using(builder -> builder.addJavadoc("Test"));
+		assertThat(method.getSpec().javadoc.toString()).contains("Test");
+	}
+
+	@Test
+	void getSpecReturnsSpecWhenNoSpecDefinedThrowsException() {
+		GeneratedMethod method = new GeneratedMethod(NAME);
+		assertThatIllegalStateException().isThrownBy(() -> method.getSpec())
+				.withMessage("Method 'spring' has no method spec defined");
+	}
+
+	@Test
+	void usingAddsSpec() {
+		GeneratedMethod method = new GeneratedMethod(NAME);
+		method.using(builder -> builder.addModifiers(Modifier.PUBLIC));
+		assertThat(method.getSpec().toString())
+				.isEqualToIgnoringNewLines("public void spring() {}");
+	}
+
+	@Test
+	void usingWhenBuilderChanagesNameThrowsException() {
+		GeneratedMethod method = new GeneratedMethod(NAME);
+		assertThatIllegalArgumentException()
+				.isThrownBy(() -> method.using(builder -> builder.setName("badname")))
+				.withMessage("'spec' must use the generated name \"spring\"");
+	}
+
+}

spring-core/src/test/java/org/springframework/aot/generate/GeneratedMethodsTests.java

@@ -0,0 +1,100 @@
+/*
+ * Copyright 2002-2022 the original author or 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
+ *
+ *      https://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 org.springframework.aot.generate;
+
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.javapoet.MethodSpec;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
+import static org.assertj.core.api.Assertions.assertThatIllegalStateException;
+
+/**
+ * Tests for {@link GeneratedMethods}.
+ *
+ * @author Phillip Webb
+ */
+class GeneratedMethodsTests {
+
+	private final GeneratedMethods methods = new GeneratedMethods();
+
+	@Test
+	void createWhenMethodNameGeneratorIsNullThrowsException() {
+		assertThatIllegalArgumentException().isThrownBy(() -> new GeneratedMethods(null))
+				.withMessage("'methodNameGenerator' must not be null");
+	}
+
+	@Test
+	void createWithExistingGeneratorUsesGenerator() {
+		MethodNameGenerator generator = new MethodNameGenerator();
+		generator.generateMethodName("test");
+		GeneratedMethods methods = new GeneratedMethods(generator);
+		assertThat(methods.add("test").getName()).hasToString("test1");
+	}
+
+	@Test
+	void addAddsMethod() {
+		this.methods.add("spring", "beans").using(this::build);
+		this.methods.add("spring", "context").using(this::build);
+		assertThat(
+				this.methods.stream().map(GeneratedMethod::getName).map(Object::toString))
+						.containsExactly("springBeans", "springContext");
+	}
+
+	@Test
+	void doWithMethodSpecsAcceptsMethodSpecs() {
+		this.methods.add("spring", "beans").using(this::build);
+		this.methods.add("spring", "context").using(this::build);
+		List<String> names = new ArrayList<>();
+		this.methods.doWithMethodSpecs(spec -> names.add(spec.name));
+		assertThat(names).containsExactly("springBeans", "springContext");
+	}
+
+	@Test
+	void doWithMethodSpecsWhenMethodHasNotHadSpecDefinedThrowsException() {
+		this.methods.add("spring");
+		assertThatIllegalStateException()
+				.isThrownBy(() -> this.methods.doWithMethodSpecs(spec -> {
+				})).withMessage("Method 'spring' has no method spec defined");
+	}
+
+	@Test
+	void iteratorIteratesMethods() {
+		this.methods.add("spring", "beans").using(this::build);
+		this.methods.add("spring", "context").using(this::build);
+		Iterator<GeneratedMethod> iterator = this.methods.iterator();
+		assertThat(iterator.next().getName()).hasToString("springBeans");
+		assertThat(iterator.next().getName()).hasToString("springContext");
+		assertThat(iterator.hasNext()).isFalse();
+	}
+
+	@Test
+	void streamStreamsMethods() {
+		this.methods.add("spring", "beans").using(this::build);
+		this.methods.add("spring", "context").using(this::build);
+		assertThat(this.methods.stream()).hasSize(2);
+	}
+
+	private void build(MethodSpec.Builder builder) {
+	}
+
+}

spring-core/src/test/java/org/springframework/aot/generate/MethodGeneratorWithNameTests.java

@@ -0,0 +1,61 @@
+/*
+ * Copyright 2002-2022 the original author or 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
+ *
+ *      https://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 org.springframework.aot.generate;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests {@link MethodGeneratorWithName}.
+ *
+ * @author Phillip Webb
+ * @since 6.0
+ */
+class MethodGeneratorWithNameTests {
+
+	private final GeneratedMethods generatedMethods = new GeneratedMethods();
+
+	@Test
+	void withNameWhenGeneratingGetMethod() {
+		GeneratedMethod generateMethod = generatedMethods.withName("my", "bean")
+				.generateMethod("get", "test");
+		assertThat(generateMethod.getName()).hasToString("getMyBeanTest");
+	}
+
+	@Test
+	void withNameWhenGeneratingSetMethod() {
+		GeneratedMethod generateMethod = generatedMethods.withName("my", "bean")
+				.generateMethod("set", "test");
+		assertThat(generateMethod.getName()).hasToString("setMyBeanTest");
+	}
+
+	@Test
+	void withNameWhenGeneratingIsMethod() {
+		GeneratedMethod generateMethod = generatedMethods.withName("my", "bean")
+				.generateMethod("is", "test");
+		assertThat(generateMethod.getName()).hasToString("isMyBeanTest");
+	}
+
+	@Test
+	void withNameWhenGeneratingOtherMethod() {
+		GeneratedMethod generateMethod = generatedMethods.withName("my", "bean")
+				.generateMethod("test");
+		assertThat(generateMethod.getName()).hasToString("myBeanTest");
+	}
+
+}