Add coalesce function

main/src/com/google/refine/expr/functions/Coalesce.java

@@ -0,0 +1,72 @@
+/*
+
+Copyright 2018, Owen Stephens
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+    * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+    * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+    * Neither the name of the copyright holder nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,           
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY           
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+*/
+
+package com.google.refine.expr.functions;
+
+import java.util.Properties;
+
+import org.json.JSONException;
+import org.json.JSONWriter;
+
+import com.google.refine.expr.EvalError;
+import com.google.refine.grel.ControlFunctionRegistry;
+import com.google.refine.grel.Function;
+
+public class Coalesce implements Function {
+
+    @Override
+    public Object call(Properties bindings, Object[] args) {
+        if (args.length> 0) {
+            for (int i = 0; i < args.length; i++){
+                if (args[i] == null) {
+                    continue;
+                } else {
+                    return args[i];
+                }
+            }
+            return null;
+        }
+        return new EvalError(ControlFunctionRegistry.getFunctionName(this) + " expects at least one argument");
+    }
+
+    @Override
+    public void write(JSONWriter writer, Properties options)
+        throws JSONException {
+    
+        writer.object();
+        writer.key("description"); writer.value("Returns the first non-null from a series of values");
+        writer.key("params"); writer.value("one or more objects");
+        writer.key("returns"); writer.value("object");
+        writer.endObject();
+    }
+}

main/src/com/google/refine/grel/ControlFunctionRegistry.java

@@ -38,6 +38,7 @@ import java.util.Map;
 import java.util.Map.Entry;
 import java.util.Set;
 
+import com.google.refine.expr.functions.Coalesce;
 import com.google.refine.expr.functions.Cross;
 import com.google.refine.expr.functions.FacetCount;
 import com.google.refine.expr.functions.Get;
@@ -186,6 +187,7 @@ public class ControlFunctionRegistry {
     }
 
     static {
+        registerFunction("coalesce", new Coalesce());
         registerFunction("type", new Type());
 
         registerFunction("toString", new ToString());

main/tests/server/src/com/google/refine/tests/expr/functions/CoalesceTests.java

@@ -0,0 +1,104 @@
+/*
+
+Copyright 2011, Owen Stephens
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+ * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+ * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+ * Neither the name of the copyright holder nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,           
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY           
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+ */
+
+package com.google.refine.tests.expr.functions.strings;
+
+import java.util.Properties;
+
+import org.slf4j.LoggerFactory;
+import org.testng.Assert;
+import org.testng.annotations.AfterMethod;
+import org.testng.annotations.BeforeMethod;
+import org.testng.annotations.BeforeTest;
+import org.testng.annotations.Test;
+
+import com.google.refine.expr.EvalError;
+import com.google.refine.grel.ControlFunctionRegistry;
+import com.google.refine.grel.Function;
+import com.google.refine.tests.RefineTest;
+
+
+public class CoalesceTests extends RefineTest {
+
+    static Properties bindings;
+    private static final Integer[] ZERO_TO_TWO = new Integer[] {0, 1, 2};
+
+    @Override
+    @BeforeTest
+    public void init() {
+        logger = LoggerFactory.getLogger(this.getClass());
+    }
+    
+    @BeforeMethod
+    public void SetUp() {
+        bindings = new Properties();
+    }
+
+    @AfterMethod
+    public void TearDown() {
+        bindings = null;
+    }
+    
+    /**
+     * Lookup a control function by name and invoke it with a variable number of args
+     */
+    private static Object invoke(String name,Object... args) {
+        // registry uses static initializer, so no need to set it up
+        Function function = ControlFunctionRegistry.getFunction(name);
+        if (function == null) {
+            throw new IllegalArgumentException("Unknown function "+name);
+        }
+        if (args == null) {
+            return function.call(bindings,new Object[0]);
+        } else {
+            return function.call(bindings,args);
+        }
+    }
+    
+    @Test
+    public void testCoalesceInvalidParams() {        
+        Assert.assertTrue(invoke("coalesce") instanceof EvalError);
+    }
+    
+    @Test
+    public void testCoalesce() {        
+        Assert.assertNull(invoke("coalesce", (Object) null));
+        Assert.assertEquals(invoke("coalesce", "string"),"string");
+        Assert.assertEquals(invoke("coalesce", 1),1);
+        Assert.assertEquals(invoke("coalesce", (Object) null, "string"),"string");
+        Assert.assertEquals(invoke("coalesce", (Object) null, (Object) null, "string"),"string");
+        Assert.assertEquals(invoke("coalesce", (Object) null, 1),1);
+        Assert.assertEquals(invoke("coalesce", (Object) null, ZERO_TO_TWO),ZERO_TO_TWO);
+    }
+    
+}