GROOVY-11578: provide default FastStringService in case of service loader failure (#2330)

Co-authored-by: Roy Teeuwen <roy.teeuwen@kbc.be>

Author: royteeuwen

subprojects/groovy-json/src/main/java/org/apache/groovy/json/internal/FastStringUtils.java

@@ -47,7 +47,7 @@ private static FastStringService loadService() {
                     }
                 }
             }
-            return found;
+            return found != null ? found : new DefaultFastStringService();
         }
     }
 

subprojects/groovy-json/src/test/groovy/org/apache/groovy/json/internal/FastStringUtilsTest.groovy

@@ -0,0 +1,58 @@
+/*
+ *  Licensed to the Apache Software Foundation (ASF) under one
+ *  or more contributor license agreements.  See the NOTICE file
+ *  distributed with this work for additional information
+ *  regarding copyright ownership.  The ASF licenses this file
+ *  to you 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 org.apache.groovy.json.internal
+
+import groovy.test.GroovyTestCase
+
+class FastStringUtilsTest extends GroovyTestCase {
+
+    static class NoServiceLoaderGroovyClassLoader extends GroovyClassLoader {
+
+        @Override
+        Enumeration<URL> getResources(String name) throws IOException {
+            if (name == "META-INF/services/org.apache.groovy.json.FastStringServiceFactory") {
+                return Collections.emptyEnumeration();
+            }
+            return super.getResources(name);
+        }
+    }
+
+    void testToCharArray() {
+        char[] expected = ["t", "e", "s", "t"]
+        assertEquals(expected, FastStringUtils.toCharArray("test"))
+    }
+
+    void testToCharArrayWithNoServiceLoaderUsedTheDefaultStringService() {
+        ClassLoader previous = Thread.currentThread().getContextClassLoader()
+        try {
+            // Making sure that our class loader is used in the ServiceLoader class
+            def loader = new NoServiceLoaderGroovyClassLoader();
+            Thread.currentThread().setContextClassLoader(loader)
+            def shell = new GroovyShell(loader)
+            def result = shell.evaluate('''
+            import org.apache.groovy.json.internal.FastStringUtils
+            FastStringUtils.toCharArray("json")
+        ''')
+            assert result == ['j', 's', 'o', 'n'] as char[]
+
+        } finally {
+            Thread.currentThread().setContextClassLoader(previous)
+        }
+    }
+}