Skip lambda checks in switch expressions

Update `SpringLambdaCheck` to skip switch statement "arrow case"
labels.

Fixes gh-300

Author: philwebb

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

@@ -20,9 +20,9 @@
 import com.puppycrawl.tools.checkstyle.api.TokenTypes;
 
 /**
- * Checks that lambda definitions follow Spring conventions. Single argument lambda
- * parameters should have parentheses. Single statement implementations should not use
- * curly braces.
+ * Checks that lambda definitions follow Spring conventions. Single argument
+ * lambda parameters should have parentheses. Single statement implementations
+ * should not use curly braces.
  *
  * @author Phillip Webb
  */
@@ -38,7 +38,8 @@ public int[] getAcceptableTokens() {
 
 	@Override
 	public void visitToken(DetailAST ast) {
-		if (ast.getType() == TokenTypes.LAMBDA) {
+		if (ast.getType() == TokenTypes.LAMBDA && ast.getParent() != null
+				&& ast.getParent().getType() != TokenTypes.SWITCH_RULE) {
 			visitLambda(ast);
 		}
 	}
@@ -48,8 +49,7 @@ private void visitLambda(DetailAST lambda) {
 			boolean hasParentheses = hasToken(lambda, TokenTypes.LPAREN);
 			if (this.singleArgumentParentheses && !hasParentheses) {
 				log(lambda.getLineNo(), lambda.getColumnNo(), "lambda.missingParen");
-			}
-			else if (!this.singleArgumentParentheses && hasParentheses) {
+			} else if (!this.singleArgumentParentheses && hasParentheses) {
 				if (!isUsingParametersToDefineType(lambda)) {
 					log(lambda.getLineNo(), lambda.getColumnNo(), "lambda.unnecessaryParen");
 				}

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

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

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

@@ -0,0 +1,35 @@
+/*
+ * 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.
+ */
+
+import java.util.function.Function;
+
+/**
+ * Lambda in a switch statement.
+ *
+ * @author Josef Reichardt
+ */
+public class LambdaSwitch {
+
+	private void sayHello(String[] args) {
+		Function<Integer, String> getText = (cnt) -> "Number of args: " + cnt;
+		String message = switch (args.length) {
+		case 0 -> "No arg";
+		case 1 -> "One arg";
+		default -> getText.apply(args.length);
+		};
+		System.out.println(message);
+	}
+}