Issue checkstyle#6232: Load resources relative to resources root

.ci/jsoref-spellchecker/whitelist.words

@@ -250,6 +250,7 @@ columnlimit
 Combobox
 commentsindentation
 commerical
+commonutil
 Compat
 Compiletime
 Comspace

.ci/pitest.sh

@@ -282,9 +282,7 @@ pitest-tree-walker)
 pitest-utils)
   mvn -e -P$1 clean test org.pitest:pitest-maven:mutationCoverage;
   declare -a ignoredItems=(
-  "CommonUtil.java.html:<td class='uncovered'><pre><span  class=''>                    uri = configUrl.toURI();</span></pre></td></tr>"
   "CommonUtil.java.html:<td class='uncovered'><pre><span  class=''>                catch (final URISyntaxException ex) {</span></pre></td></tr>"
-  "CommonUtil.java.html:<td class='uncovered'><pre><span  class=''>                }</span></pre></td></tr>"
   "CommonUtil.java.html:<td class='uncovered'><pre><span  class='survived'>                    throw new CheckstyleException(UNABLE_TO_FIND_EXCEPTION_PREFIX + filename, ex);</span></pre></td></tr>"
   );
   checkPitestReport "${ignoredItems[@]}"

src/main/java/com/puppycrawl/tools/checkstyle/utils/CommonUtil.java

@@ -507,8 +507,13 @@ public static URI getUriByFilename(String filename) throws CheckstyleException {
             else {
                 // check to see if the file is in the classpath
                 try {
-                    final URL configUrl = CommonUtil.class
-                            .getResource(filename);
+                    final URL configUrl;
+                    if (filename.charAt(0) == '/') {
+                        configUrl = CommonUtil.class.getResource(filename);
+                    }
+                    else {
+                        configUrl = ClassLoader.getSystemResource(filename);
+                    }
                     if (configUrl == null) {
                         throw new CheckstyleException(UNABLE_TO_FIND_EXCEPTION_PREFIX + filename);
                     }

src/test/java/com/puppycrawl/tools/checkstyle/internal/powermock/CommonUtilPowerTest.java

@@ -49,7 +49,7 @@ public void testLoadSuppressionsUriSyntaxException() throws Exception {
 
         when(configUrl.toURI()).thenThrow(URISyntaxException.class);
         mockStatic(CommonUtil.class, Mockito.CALLS_REAL_METHODS);
-        final String fileName = "suppressions_none.xml";
+        final String fileName = "/suppressions_none.xml";
         when(CommonUtil.class.getResource(fileName)).thenReturn(configUrl);
 
         try {

src/test/java/com/puppycrawl/tools/checkstyle/utils/CommonUtilTest.java

@@ -20,25 +20,37 @@
 package com.puppycrawl.tools.checkstyle.utils;
 
 import static com.puppycrawl.tools.checkstyle.internal.utils.TestUtil.isUtilsClassHasPrivateConstructor;
+import static org.hamcrest.CoreMatchers.containsString;
+import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.CoreMatchers.not;
+import static org.hamcrest.CoreMatchers.nullValue;
+import static org.hamcrest.CoreMatchers.startsWith;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 
+import java.io.ByteArrayOutputStream;
 import java.io.Closeable;
 import java.io.File;
 import java.io.IOException;
+import java.io.InputStream;
 import java.lang.reflect.Constructor;
+import java.net.URI;
+import java.nio.charset.StandardCharsets;
 import java.util.Dictionary;
 import java.util.regex.Pattern;
 
+import org.apache.commons.io.IOUtils;
 import org.junit.Test;
 
+import com.puppycrawl.tools.checkstyle.AbstractPathTestSupport;
 import com.puppycrawl.tools.checkstyle.api.DetailAST;
 import com.puppycrawl.tools.checkstyle.api.TokenTypes;
 
-public class CommonUtilTest {
+public class CommonUtilTest extends AbstractPathTestSupport {
 
     /** After appending to path produces equivalent, but denormalized path. */
     private static final String PATH_DENORMALIZER = "/levelDown/.././";
@@ -440,6 +452,42 @@ public void testIsIntNull() {
             CommonUtil.isInt(null));
     }
 
+    @Test
+    public void testGetUriByFilenameFindsAbsoluteResourceOnClasspath() throws Exception {
+        final String filename =
+            "/" + getPackageLocation() + "/InputCommonUtilTest_empty_checks.xml";
+        final URI uri = CommonUtil.getUriByFilename(filename);
+        assertThat("URI is null for: " + filename, uri, is(not(nullValue())));
+    }
+
+    @Test
+    public void testGetUriByFilenameFindsRelativeResourceOnClasspath() throws Exception {
+        final String filename =
+            getPackageLocation() + "/InputCommonUtilTest_empty_checks.xml";
+        final URI uri = CommonUtil.getUriByFilename(filename);
+        assertThat("URI is null for: " + filename, uri, is(not(nullValue())));
+    }
+
+    @Test
+    public void testGetUriByFilenameFindsResourceRelativeToRootClasspath() throws Exception {
+        final String filename = "commonutil/InputCommonUtilTest_resource.txt";
+        final URI uri = CommonUtil.getUriByFilename(filename);
+        assertThat("URI is null for: " + filename, uri, is(not(nullValue())));
+        assertThat("URI contains com/puppycrawl/tools/checkstyle/utils",
+            uri.toString(), not(containsString("com/puppycrawl/tools/checkstyle/utils")));
+        final ByteArrayOutputStream out = new ByteArrayOutputStream();
+        try (InputStream in = uri.toURL().openStream()) {
+            IOUtils.copy(in, out);
+        }
+        assertThat("Content mismatches for: " + uri,
+            new String(out.toByteArray(), StandardCharsets.UTF_8), startsWith("good"));
+    }
+
+    @Override
+    protected String getPackageLocation() {
+        return "com/puppycrawl/tools/checkstyle/utils/commonutil";
+    }
+
     private static class TestCloseable implements Closeable {
 
         private boolean closed;

src/test/resources/com/puppycrawl/tools/checkstyle/utils/commonutil/InputCommonUtilTest_empty_checks.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0"?>
+<!DOCTYPE module PUBLIC
+        "-//Puppy Crawl//DTD Check Configuration 1.3//EN"
+        "http://checkstyle.sourceforge.net/dtds/configuration_1_3.dtd">
+<module name="Checker"/>

src/test/resources/com/puppycrawl/tools/checkstyle/utils/commonutil/InputCommonUtilTest_resource.txt

@@ -0,0 +1 @@
+bad

src/test/resources/commonutil/InputCommonUtilTest_resource.txt

@@ -0,0 +1 @@
+good