Account for missing values in to_var() Fix function. (#365)

Also, test edge cases.

Author: blackwinter

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

@@ -123,16 +123,11 @@ public void apply(final Metafix metafix, final Record record, final List<String>
             metafix.getVars().putAll(options);
         }
     },
-
     to_var {
         @Override
-
         public void apply(final Metafix metafix, final Record record, final List<String> params, final Map<String, String> options) {
-            final String fieldName = params.get(0);
-            final String variableName = params.get(1);
-            final String variableValue = record.get(fieldName).toString();
-
-            metafix.getVars().put(variableName, variableValue);
+            final Value value = record.get(params.get(0));
+            metafix.getVars().put(params.get(1), Value.isNull(value) ? "" : value.toString());
         }
     },
 

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

@@ -4084,7 +4084,7 @@ public void shouldTransformStringToBase64() {
         );
     }
 
-    @Test
+    @Test // checkstyle-disable-line JavaNCSS
     public void shouldCreateVariableFromLiteralValue() {
         MetafixTestHelpers.assertFix(streamReceiver, Arrays.asList(
                 "to_var('data.title','testVar')",
@@ -4098,11 +4098,26 @@ public void shouldCreateVariableFromLiteralValue() {
                 i.endRecord();
                 i.startRecord("2");
                 i.startEntity("data");
-                i.literal("title", "second-test");
+                i.literal("title", "test1");
+                i.literal("title", "test2");
+                i.endEntity();
+                i.endRecord();
+                i.startRecord("3");
+                i.startEntity("data");
+                i.startEntity("title");
+                i.literal("key", "value");
+                i.endEntity();
+                i.endEntity();
+                i.endRecord();
+                i.startRecord("4");
+                i.endRecord();
+                i.startRecord("5");
+                i.startEntity("data");
+                i.literal("title", "final-test");
                 i.endEntity();
                 i.endRecord();
             },
-            o -> {
+            (o, f) -> {
                 o.get().startRecord("1");
                 o.get().startEntity("data");
                 o.get().literal("title", "test");
@@ -4111,9 +4126,26 @@ public void shouldCreateVariableFromLiteralValue() {
                 o.get().endRecord();
                 o.get().startRecord("2");
                 o.get().startEntity("data");
-                o.get().literal("title", "second-test");
+                o.get().literal("title", "test1");
+                o.get().literal("title", "test2");
+                o.get().endEntity();
+                o.get().literal("testResult", "This is a [test1, test2]");
+                o.get().endRecord();
+                o.get().startRecord("3");
+                o.get().startEntity("data");
+                o.get().startEntity("title");
+                o.get().literal("key", "value");
+                f.apply(2).endEntity();
+                o.get().literal("testResult", "This is a {key=value}");
+                o.get().endRecord();
+                o.get().startRecord("4");
+                o.get().literal("testResult", "This is a ");
+                o.get().endRecord();
+                o.get().startRecord("5");
+                o.get().startEntity("data");
+                o.get().literal("title", "final-test");
                 o.get().endEntity();
-                o.get().literal("testResult", "This is a second-test");
+                o.get().literal("testResult", "This is a final-test");
                 o.get().endRecord();
             }
         );