Implement LocationAware requiresLocation method in FileLocationPatternConverter (#2781)

Author: Benjamin Peter

log4j-core-test/src/test/java/org/apache/logging/log4j/core/pattern/LocationPatternConvertersRequireLocationText.java

@@ -0,0 +1,50 @@
+/*
+ * 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.logging.log4j.core.pattern;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertInstanceOf;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.List;
+import org.apache.logging.log4j.core.impl.LocationAware;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+
+public class LocationPatternConvertersRequireLocationText {
+
+    /**
+     * Reproduces <a href="https://github.com/apache/logging-log4j2/issues/2781">github issue #2781</a>.
+     */
+    @ParameterizedTest
+    @CsvSource({"%L", "%l", "%F", "%C", "%M"})
+    void testThatLocationDependentPatternConvertersIndicateLocationRequirement(final String converterKey)
+            throws Exception {
+        final PatternFormatter formatter = createSinglePatternFormatterFromConverterKey(converterKey);
+
+        final LocationAware locationAwareFormatter = assertInstanceOf(LocationAware.class, formatter.getConverter());
+        assertTrue(locationAwareFormatter.requiresLocation());
+    }
+
+    private static PatternFormatter createSinglePatternFormatterFromConverterKey(final String converterKey) {
+        final PatternParser parser = new PatternParser("Converter");
+        final List<PatternFormatter> formatters = parser.parse(converterKey);
+        assertThat(formatters).hasSize(1);
+        final PatternFormatter formatter = formatters.get(0);
+        return formatter;
+    }
+}

log4j-core/src/main/java/org/apache/logging/log4j/core/pattern/FileLocationPatternConverter.java

@@ -18,13 +18,14 @@
 
 import org.apache.logging.log4j.core.LogEvent;
 import org.apache.logging.log4j.core.config.plugins.Plugin;
+import org.apache.logging.log4j.core.impl.LocationAware;
 
 /**
  * Returns the event's line location information in a StringBuilder.
  */
 @Plugin(name = "FileLocationPatternConverter", category = PatternConverter.CATEGORY)
 @ConverterKeys({"F", "file"})
-public final class FileLocationPatternConverter extends LogEventPatternConverter {
+public final class FileLocationPatternConverter extends LogEventPatternConverter implements LocationAware {
     /**
      * Singleton.
      */
@@ -58,4 +59,9 @@ public void format(final LogEvent event, final StringBuilder output) {
             output.append(element.getFileName());
         }
     }
+
+    @Override
+    public boolean requiresLocation() {
+        return true;
+    }
 }

src/changelog/.2.x.x/2781_fix_file_location_pattern_converter_location_requirement.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<entry xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+       xmlns="https://logging.apache.org/xml/ns"
+       xsi:schemaLocation="https://logging.apache.org/xml/ns https://logging.apache.org/xml/ns/log4j-changelog-0.xsd"
+       type="fixed">
+  <issue id="2781" link="https://github.com/apache/logging-log4j2/issues/2781"/>
+  <description format="asciidoc">Fix handling of location requirement for pattern key `%F` / `%file`.</description>
+</entry>