Add log function

README.md

@@ -168,6 +168,21 @@ include("<path>"[, <dynamicLocalVariables>...])
 
 [Java Code](https://github.com/search?type=code&q=repo:metafacture/metafacture-fix+path:FixMethod.java+"+include+{")
 
+##### `log`
+Send a message to the logs.
+
+Parameters:
+
+- `logMessage` specifies the message that should be logged.
+
+Options:
+
+- `level` sets one of the following log levels: INFO, DEBUG, ERROR, WARN (Default: INFO).
+
+```perl
+log(“<logMessage>”,level:DEBUG)
+```
+
 ##### `nothing`
 
 Does nothing. It is used for benchmarking in Catmandu.

build.gradle

@@ -49,6 +49,7 @@ subprojects {
       'mockito':        '2.27.0',
       'requirejs':      '2.3.6',
       'slf4j':          '1.7.21',
+      'slf4j_mock':     '2.3.0',
       'wiremock':       '2.33.2',
       'xtext':          '2.26.0'
     ]

metafix/build.gradle

@@ -25,6 +25,7 @@ dependencies {
   testImplementation "org.eclipse.xtext:org.eclipse.xtext.xbase.testing:${versions.xtext}"
   testImplementation "org.junit.jupiter:junit-jupiter-api:${versions.junit_jupiter}"
   testImplementation "org.junit.platform:junit-platform-launcher:${versions.junit_platform}"
+  testImplementation "org.simplify4u:slf4j2-mock:${versions.slf4j_mock}"
 
   testRuntimeOnly "org.junit.jupiter:junit-jupiter-engine:${versions.junit_jupiter}"
 

metafix/src/main/java/org/metafacture/metafix/FixMethod.java

@@ -24,6 +24,9 @@
 import org.metafacture.metamorph.functions.URLEncode;
 import org.metafacture.metamorph.maps.FileMap;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 import java.io.File;
 import java.io.IOException;
 import java.util.Arrays;
@@ -62,6 +65,34 @@ public void apply(final Metafix metafix, final Record record, final List<String>
             metafix.getRecordTransformer(includePath).transform(record, options);
         }
     },
+    log {
+        @Override
+        public void apply(final Metafix metafix, final Record record, final List<String> params, final Map<String, String> options) {
+            // does not support Catmandu log level option FATAL
+
+            final String level = options.getOrDefault("level", "INFO");
+            final Consumer<String> consumer;
+
+            switch (level) {
+                case "DEBUG":
+                    consumer = LOG::debug;
+                    break;
+                case "ERROR":
+                    consumer = LOG::error;
+                    break;
+                case "INFO":
+                    consumer = LOG::info;
+                    break;
+                case "WARN":
+                    consumer = LOG::warn;
+                    break;
+                default:
+                    throw new IllegalArgumentException("Unsupported log level: " + level);
+            }
+
+            consumer.accept(params.get(0));
+        }
+    },
     nothing {
         @Override
         public void apply(final Metafix metafix, final Record record, final List<String> params, final Map<String, String> options) {
@@ -691,4 +722,6 @@ public void apply(final Metafix metafix, final Record record, final List<String>
 
     private static final Random RANDOM = new Random();
 
+    private static final Logger LOG = LoggerFactory.getLogger(FixMethod.class);
+
 }

metafix/src/test/java/org/metafacture/metafix/MetafixScriptTest.java

@@ -26,6 +26,7 @@
 import org.mockito.Mock;
 import org.mockito.Mockito;
 import org.mockito.junit.jupiter.MockitoExtension;
+import org.slf4j.Logger;
 
 import java.io.IOException;
 import java.util.Arrays;
@@ -45,6 +46,9 @@ public class MetafixScriptTest {
     private static final String CSV_MAP = "src/test/resources/org/metafacture/metafix/maps/test.csv";
     private static final String TSV_MAP = "src/test/resources/org/metafacture/metafix/maps/test.tsv";
 
+    @Mock(name = "org.metafacture.metafix.FixMethod")
+    private Logger fixMethodLogger;
+
     @Mock
     private StreamReceiver streamReceiver;
 
@@ -193,6 +197,29 @@ public void shouldPutExternalFileMapWithNameAndOptions() {
         assertMap("put_filemap('" + TSV_MAP + "', '" + MAP_NAME + "', sep_char: '\t')", MAP_NAME);
     }
 
+    @Test
+    public void shouldLog() {
+        assertFix("log('test')", f -> {
+            Mockito.verify(fixMethodLogger).info("test");
+            Mockito.verifyNoMoreInteractions(fixMethodLogger);
+        });
+    }
+
+    @Test
+    public void shouldLogWithLevel() {
+        assertFix("log('test', level: 'DEBUG')", f -> {
+            Mockito.verify(fixMethodLogger).debug("test");
+            Mockito.verifyNoMoreInteractions(fixMethodLogger);
+        });
+    }
+
+    @Test
+    public void shouldNotLogWithUnsupportedLevel() {
+        MetafixTestHelpers.assertProcessException(IllegalArgumentException.class, "Unsupported log level: FATAL", () ->
+            assertFix("log('test', level: 'FATAL')", f -> { })
+        );
+    }
+
     @Test
     public void shouldDoNothing() {
         assertFix("nothing()", f -> { });