Add new uncamelize lambda (#18109)

Co-authored-by: Daniel Karlsson <daniel.karlsson@cinnober.com>

docs/templating.md

@@ -822,6 +822,7 @@ Many generators (*those extending DefaultCodegen*) come with a small set of lamb
 - `uppercase` - Converts all of the characters in this fragment to upper case using the rules of the `ROOT` locale.
 - `titlecase` - Converts text in a fragment to title case. For example `once upon a time` to `Once Upon A Time`.
 - `camelcase` - Converts text in a fragment to camelCase. For example `Input-text` to `inputText`.
+- `uncamelize` - Converts text in a fragment from camelCase or PascalCase to a string of words separated by whitespaces. For example `inputText` to `Input Text`.
 - `indented` - Prepends 4 spaces indention from second line of a fragment on. First line will be indented by Mustache.
 - `indented_8` - Prepends 8 spaces indention from second line of a fragment on. First line will be indented by Mustache.
 - `indented_12` - Prepends 12 spaces indention from second line of a fragment on. First line will be indented by Mustache.

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

@@ -465,6 +465,7 @@ public class DefaultCodegen implements CodegenConfig {
                 .put("kebabcase", new KebabCaseLambda())
                 .put("camelcase", new CamelCaseLambda(true).generator(this))
                 .put("pascalcase", new CamelCaseLambda(false).generator(this))
+                .put("uncamelize", new UncamelizeLambda())
                 .put("forwardslash", new ForwardSlashLambda())
                 .put("backslash", new BackSlashLambda())
                 .put("doublequote", new DoubleQuoteLambda())

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

@@ -0,0 +1,53 @@
+
+/*
+ * Copyright 2018 OpenAPI-Generator Contributors (https://openapi-generator.tech)
+ * Copyright 2018 SmartBear Software
+ *
+ * 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 org.apache.commons.lang3.StringUtils;
+
+import java.io.IOException;
+import java.io.Writer;
+
+import static org.openapitools.codegen.utils.StringUtils.camelize;
+
+/**
+ * Converts text in a fragment from camelCase or PascalCase to a space separated string
+ *
+ * Register:
+ * <pre>
+ * additionalProperties.put("uncamelize", new UncamelizeLambda());
+ * </pre>
+ *
+ * Use:
+ * <pre>
+ * {{#uncamelize}}{{name}}{{/uncamelize}}
+ * </pre>
+ */
+public class UncamelizeLambda implements Mustache.Lambda {
+
+    public UncamelizeLambda() {}
+    @Override
+    public void execute(Template.Fragment fragment, Writer writer) throws IOException {
+        String input = fragment.execute();
+        String text = StringUtils.capitalize(StringUtils.join(StringUtils.splitByCharacterTypeCamelCase(input.trim()), StringUtils.SPACE));
+        writer.write(text.trim().replaceAll(" +", " "));
+    }
+}
+

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

@@ -0,0 +1,50 @@
+package org.openapitools.codegen.templating.mustache;
+import org.mockito.MockitoAnnotations;
+import org.testng.annotations.BeforeMethod;
+import org.testng.annotations.Test;
+
+import java.util.Map;
+
+public class UncamelizeLambdaTest extends LambdaTest {
+    @BeforeMethod
+    public void setup() {
+        MockitoAnnotations.initMocks(this);
+    }
+
+    @Test
+    public void camelCaseTest() {
+        // Given
+        Map<String, Object> ctx = context("uncamelize", new UncamelizeLambda());
+
+        // When & Then
+        test("Input Text", "{{#uncamelize}}inputText{{/uncamelize}}", ctx);
+    }
+
+    @Test
+    public void pascalCaseTest() {
+        // Given
+        Map<String, Object> ctx = context("uncamelize", new UncamelizeLambda());
+
+        // When & Then
+        test("Input Text", "{{#uncamelize}}InputText{{/uncamelize}}", ctx);
+    }
+
+
+    @Test
+    public void emptyStringTest() {
+        // Given
+        Map<String, Object> ctx = context("uncamelize", new UncamelizeLambda());
+
+        // When & Then
+        test("", "{{#uncamelize}}{{/uncamelize}}", ctx);
+    }
+
+    @Test
+    public void nonCamelCaseStringTest() {
+        // Given
+        Map<String, Object> ctx = context("uncamelize", new UncamelizeLambda());
+
+        // When & Then
+        test("Input Text", "{{#uncamelize}}Input Text{{/uncamelize}}", ctx);
+    }
+}