Allow @SInCE tag inside interface types

Update `SpringJavadocCheck` so that `@Since` tags can be used on types
nested inside a public interface.

Closes gh-132

Author: philwebb

spring-javaformat/spring-javaformat-checkstyle/src/main/java/io/spring/javaformat/checkstyle/check/SpringJavadocCheck.java

@@ -95,9 +95,8 @@ private void checkSinceTag(DetailAST ast, TextBlock javadoc) {
 			return;
 		}
 		String[] text = javadoc.getText();
-		DetailAST modifiers = ast.findFirstToken(TokenTypes.MODIFIERS);
-		boolean privateType = modifiers.findFirstToken(TokenTypes.LITERAL_PUBLIC) == null
-				&& modifiers.findFirstToken(TokenTypes.LITERAL_PROTECTED) == null;
+		DetailAST interfaceDef = getInterfaceDef(ast);
+		boolean privateType = !isPublicOrProtected(ast) && (interfaceDef == null || !isPublicOrProtected(interfaceDef));
 		boolean innerType = ast.getParent() != null;
 		boolean found = false;
 		for (int i = 0; i < text.length; i++) {
@@ -127,4 +126,27 @@ public void setPublicOnlySinceTags(boolean publicOnlySinceTags) {
 		this.publicOnlySinceTags = publicOnlySinceTags;
 	}
 
+	private DetailAST getInterfaceDef(DetailAST ast) {
+		return findParent(ast, TokenTypes.INTERFACE_DEF);
+	}
+
+	private DetailAST findParent(DetailAST ast, int classDef) {
+		while (ast != null) {
+			if (ast.getType() == classDef) {
+				return ast;
+			}
+			ast = ast.getParent();
+		}
+		return null;
+	}
+
+	private boolean isPublicOrProtected(DetailAST ast) {
+		DetailAST modifiers = ast.findFirstToken(TokenTypes.MODIFIERS);
+		if (modifiers == null) {
+			return false;
+		}
+		return modifiers.findFirstToken(TokenTypes.LITERAL_PUBLIC) != null
+				|| modifiers.findFirstToken(TokenTypes.LITERAL_PROTECTED) != null;
+	}
+
 }

spring-javaformat/spring-javaformat-checkstyle/src/test/resources/check/JavadocNonPublicSinceInsideInterface.txt

@@ -0,0 +1 @@
++0 errors

spring-javaformat/spring-javaformat-checkstyle/src/test/resources/config/JavadocNonPublicSinceInsideInterface.xml

@@ -0,0 +1,11 @@
+<?xml version="1.0"?>
+<!DOCTYPE module PUBLIC
+		"-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
+		"https://checkstyle.org/dtds/configuration_1_3.dtd">
+<module name="com.puppycrawl.tools.checkstyle.Checker">
+	<module name="com.puppycrawl.tools.checkstyle.TreeWalker">
+		<module name="io.spring.javaformat.checkstyle.check.SpringJavadocCheck">
+			<property name="publicOnlySinceTags" value="true"/>
+		</module>
+	</module>
+</module>

spring-javaformat/spring-javaformat-checkstyle/src/test/resources/source/JavadocNonPublicSinceInsideInterface.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2017-2019 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.
+ */
+
+/**
+ * Javadoc with a good since tag.
+ *
+ * @author Phillip Webb
+ * @since 1.2.3
+ */
+public interface JavadocNonPublicSinceInsideInterface {
+
+	/**
+	 * Inner enum.
+	 *
+	 * @since 1.2.3
+	 */
+	enum Inner {
+
+		FOO
+
+	}
+
+}