Add additional mustache lambda for kebab case (#17858)

* Add new kebabcase mustache lambda

* Add tests for new kebabcase lambda

* Update toLowerCase to use Locale.ROOT

modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java

@@ -461,6 +461,7 @@ public class DefaultCodegen implements CodegenConfig {
                 .put("uppercase", new UppercaseLambda())
                 .put("snakecase", new SnakecaseLambda())
                 .put("titlecase", new TitlecaseLambda())
+                .put("kebabcase", new KebabCaseLambda())
                 .put("camelcase", new CamelCaseLambda(true).generator(this))
                 .put("pascalcase", new CamelCaseLambda(false).generator(this))
                 .put("forwardslash", new ForwardSlashLambda())

modules/openapi-generator/src/main/java/org/openapitools/codegen/templating/mustache/KebabCaseLambda.java

@@ -0,0 +1,62 @@
+/*
+ * Copyright 2018 OpenAPI-Generator Contributors (https://openapi-generator.tech)
+ *
+ * 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.openapitools.codegen.templating.mustache;
+
+import com.samskivert.mustache.Mustache;
+import com.samskivert.mustache.Template;
+
+import java.io.IOException;
+import java.io.Writer;
+import java.util.Locale;
+
+import static org.openapitools.codegen.utils.StringUtils.underscore;
+
+/**
+ * Converts text in a fragment to snake case.
+ *
+ * Register:
+ * <pre>
+ * additionalProperties.put("kebabcase", new KebabCaseLambda());
+ * </pre>
+ *
+ * Use:
+ * <pre>
+ * {{#kebabcase}}{{summary}}{{/kebabcase}}
+ * </pre>
+ */
+public class KebabCaseLambda implements Mustache.Lambda {
+    @Override
+    public void execute(Template.Fragment fragment, Writer writer) throws IOException {
+        String text = fragment.execute();
+
+        String SPECIAL = "[^A-Za-z0-9_]";
+        String firstPattern = "([A-Z]+)([A-Z][a-z])";
+        String secondPattern = "([a-z\\d])([A-Z])";
+        String replacementPattern = "$1 $2";
+        // Replace package separator with slash.
+        text = text.replaceAll("\\.", "/");
+        text = text.replaceAll(SPECIAL, "");
+        // Replace capital letter with _ plus lowercase letter.
+        text = text.replaceAll(firstPattern, replacementPattern);
+        text = text.replaceAll(secondPattern, replacementPattern);
+        text = text.replace('_', '-');
+        text = text.replace(' ', '-');
+        text = text.toLowerCase(Locale.ROOT);
+
+        writer.write(text);
+    }
+}

modules/openapi-generator/src/test/java/org/openapitools/codegen/templating/mustache/KebabCaseLambdaTest.java

@@ -0,0 +1,37 @@
+package org.openapitools.codegen.templating.mustache;
+
+import org.testng.annotations.Test;
+
+import java.util.Map;
+
+public class KebabCaseLambdaTest extends LambdaTest {
+
+    @Test
+    public void CamelCaseToKebabcaseTest() {
+        // Given
+        Map<String, Object> ctx = context("kebabcase", new KebabCaseLambda());
+
+        // When & Then
+        test("access-code", "{{#kebabcase}}accessCode{{/kebabcase}}", ctx);
+    }
+
+    @Test
+    public void KebabcaseTestWithSpecialCharacters() {
+        // Given
+        Map<String, Object> ctx = context("kebabcase", new KebabCaseLambda());
+
+        // When & Then
+        test("this-is-a-test", "{{#kebabcase}}This?Is#@$%^A#@$%^Test{{/kebabcase}}", ctx);
+    }
+
+    @Test
+    public void SnakeCaseToKebabCase() {
+        // Given
+        Map<String, Object> ctx = context("kebabcase", new KebabCaseLambda());
+
+        // When & Then
+        test("this-is-another-test", "{{#kebabcase}}This_is_another_test{{/kebabcase}}", ctx);
+    }
+
+
+}