Fix: Update Lit bundle parser regex.

Now the pattern will not fail with a StackOverflowException
as we will search from the start character accepting
any characters until we reach the caught start character with ;

flow-lit-template/src/main/java/com/vaadin/flow/component/littemplate/BundleLitParser.java

@@ -74,14 +74,14 @@ public final class BundleLitParser {
      * <p>
      * <code>render\(\)[\s]*\{</code> finds the template getter method
      * <p>
-     * <code>[\s]*return[\s]*html[\s]*`</code> finds the return statement
+     * <code>[\s]*return[\s]*html[\s]*(\`)</code> finds the return statement
      * <p>
      * </p>
-     * <code>(([^`]|\\\\.)*)</code> captures all text until we encounter the end
-     * character with <code>;}</code> e.g. <code>';}</code>
+     * <code>([\s\S]*)</code> captures all text until we encounter the end
+     * character with <code>\1;}</code> e.g. <code>';}</code>
      */
     private static final Pattern LIT_TEMPLATE_PATTERN = Pattern.compile(
-            "render\\(\\)[\\s]*\\{[\\s]*return[\\s]*html[\\s]*`(([^`]|\\\\.)*)`;[\\s]*\\}");
+            "render\\(\\)[\\s]*\\{[\\s]*return[\\s]*html[\\s]*(\\`)([\\s\\S]*?)\\1;[\\s]*\\}");
 
     private static final Pattern HASH_PATTERN = Pattern
             .compile("\"hash\"\\s*:\\s*\"([^\"]+)\"\\s*,");
@@ -144,11 +144,10 @@ public static Element parseLitTemplateElement(String fileName,
         String content = StringUtil.removeComments(source);
         Matcher templateMatcher = LIT_TEMPLATE_PATTERN.matcher(content);
 
-        // GroupCount should be 2 as the first group contains `|'|" depending
-        // on what was in template return html' and the second is the
-        // template contents.
+        // GroupCount should be 2 as the first group contains ` and the second
+        // is the template contents.
         if (templateMatcher.find() && templateMatcher.groupCount() == 2) {
-            String group = templateMatcher.group(1);
+            String group = templateMatcher.group(2);
             LOGGER.trace("Found regular Lit template content was {}", group);
 
             templateDocument = Jsoup.parse(group);

flow-lit-template/src/test/java/com/vaadin/flow/component/littemplate/BundleLitParserTest.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2000-2020 Vaadin Ltd.
+ *
+ * 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
+ *
+ * http://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 com.vaadin.flow.component.littemplate;
+
+import java.io.IOException;
+
+import org.jsoup.nodes.Element;
+import org.junit.Assert;
+import org.junit.Test;
+
+public class BundleLitParserTest {
+        private String content = "\n            var __decorate = (this && this.__decorate) || function (decorators, target, key, desc) {\n                var c = arguments.length, r = c < 3 ? target : desc === null ? desc = Object.getOwnPropertyDescriptor(target, key) : desc, d;\n                if (typeof Reflect === 'object' && typeof Reflect.decorate === 'function') r = Reflect.decorate(decorators, target, key, desc);\n                else for (var i = decorators.length - 1; i >= 0; i--) if (d = decorators[i]) r = (c < 3 ? d(r) : c > 3 ? d(target, key, r) : d(target, key)) || r;\n                return c > 3 && r && Object.defineProperty(target, key, r), r;\n            };\n            import { customElement, html, LitElement } from 'lit-element';\n            let AboutView = class AboutView extends LitElement {\n                render() {\n                    return html `<vaadin-split-layout style='width: 100%; height: 100%;'>\n                  <div style='width:400px;display:flex;flex-direction:column;'>\n                    <div style='padding:var(--lumo-space-l);flex-grow:1;'>\n                      <vaadin-form-layout>\n                        <vaadin-text-field\n                          label='First name'\n                          id='firstName'\n                        ></vaadin-text-field\n                        ><vaadin-text-field\n                          label='Last name'\n                          id='lastName'\n                        ></vaadin-text-field\n                        ><vaadin-date-picker\n                          label='Date of birth'\n                          id='dateOfBirth'\n                        ></vaadin-date-picker\n                        ><vaadin-text-field\n                          label='Occupation'\n                          id='occupation'\n                        ></vaadin-text-field\n                        ><vaadin-checkbox\n                          id='important'\n                          style='padding-top: var(--lumo-space-m);'\n                          >Important</vaadin-checkbox\n                        >\n                      </vaadin-form-layout>\n                    </div>\n                    <vaadin-horizontal-layout\n                      style='flex-wrap:wrap;width:100%;background-color:var(--lumo-contrast-5pct);padding:var(--lumo-space-s) var(--lumo-space-l);'\n                      theme='spacing'\n                    >\n                      <vaadin-button theme='primary' id='save'>Save</vaadin-button>\n                      <vaadin-button theme='tertiary' slot='' id='cancel'\n                        >Cancel</vaadin-button\n                      >\n                    </vaadin-horizontal-layout>\n                  </div>\n                </vaadin-split-layout>`;\n                }\n            };\n            AboutView = __decorate([\n                customElement('about-view')\n            ], AboutView);\n            export { AboutView };\n";
+
+        @Test
+        public void parseTemplate() throws IOException {
+            final Element element = BundleLitParser
+                .parseLitTemplateElement("in.ts", content);
+
+            Assert.assertEquals("The html should contain 12 elements making it 13 with the expected addition of a template element", 13,
+                element.getAllElements().size());
+            Assert.assertEquals("", "vaadin-split-layout", element.getElementsByTag("template").get(0).child(0).tagName());
+        }
+}