Added support for logging when template not found

Author: danielbodart

src/com/googlecode/totallylazy/template/Templates.java

@@ -4,7 +4,6 @@
 import com.googlecode.totallylazy.functions.Function2;
 import com.googlecode.totallylazy.io.Uri;
 import com.googlecode.totallylazy.predicates.Predicate;
-import com.googlecode.totallylazy.predicates.Predicates;
 import com.googlecode.totallylazy.xml.Xml;
 
 import java.io.IOException;
@@ -16,6 +15,7 @@
 import static com.googlecode.totallylazy.Unchecked.cast;
 import static com.googlecode.totallylazy.predicates.Predicates.always;
 import static com.googlecode.totallylazy.template.CompositeRenderer.compositeRenderer;
+import static java.lang.String.format;
 
 public class Templates implements Renderers {
     private final Function2<? super String, ? super Renderers, ? extends Renderer<?>> missing;
@@ -84,4 +84,15 @@ public Renderer<Object> get(String name) {
     public Templates extension(String value) {
         return new Templates((s, r) -> missing.apply(s + "." + value, r));
     }
+
+    public Templates logger(Appendable logger) {
+        return new Templates((s, r) -> {
+            try {
+                return missing.apply(s, r);
+            } catch (Exception e) {
+                logger.append(format("Unable to load template '%s' because: %s", s, e.getMessage()));
+                return (instance, appendable) -> appendable;
+            }
+        });
+    }
 }

test/com/googlecode/totallylazy/template/TemplatesTest.java

@@ -3,8 +3,12 @@
 import com.googlecode.totallylazy.Strings;
 import org.junit.Test;
 
+import java.io.PrintWriter;
+
 import static com.googlecode.totallylazy.Assert.assertThat;
 import static com.googlecode.totallylazy.Maps.map;
+import static com.googlecode.totallylazy.Strings.startsWith;
+import static com.googlecode.totallylazy.predicates.Predicates.contains;
 import static com.googlecode.totallylazy.predicates.Predicates.instanceOf;
 import static com.googlecode.totallylazy.predicates.Predicates.is;
 import static com.googlecode.totallylazy.template.Templates.templates;
@@ -50,4 +54,13 @@ public void canUseTemplatesFromClassPathAndDefaultTemplates() throws Exception {
         String result = template.render(map("name", "Dan"));
         assertThat(result, is("Say Hello Dan"));
     }
+
+    @Test
+    public void doesNotThrowWhenASubTemplateIsNotFoundButReturnsEmptyStringAndLogs() throws Exception {
+        StringBuilder log = new StringBuilder();
+        Templates templates = templates(getClass()).logger(log).extension("st");
+        String result = templates.get("error").render(map());
+        assertThat(result, is("Sub template returned ''"));
+        assertThat(log.toString(), startsWith("Unable to load template 'foo.st' because: "));
+    }
 }

test/com/googlecode/totallylazy/template/error.st

@@ -0,0 +1 @@
+Sub template returned '$foo()$'