NullPointerException when partial is empty fix #835

- Added tests and safe-guard

Author: jknack

handlebars/src/main/java/com/github/jknack/handlebars/internal/HbsParserFactory.java

@@ -18,6 +18,7 @@
 package com.github.jknack.handlebars.internal;
 
 import java.io.IOException;
+import java.util.Optional;
 
 import org.antlr.v4.runtime.ANTLRErrorListener;
 import org.antlr.v4.runtime.CharStream;
@@ -73,7 +74,8 @@ public Template parse(final TemplateSource source) throws IOException {
         final ANTLRErrorListener errorReporter = new HbsErrorReporter(sourceName);
 
         // 1. Lexer
-        String content = source.content(handlebars.getCharset());
+        String content = Optional.ofNullable(source.content(handlebars.getCharset()))
+            .orElse("");
         final HbsLexer lexer = newLexer(CharStreams.fromString(content, sourceName), startDelimiter, endDelimiter);
         configure(lexer, errorReporter);
 

handlebars/src/test/java/com/github/jknack/handlebars/i835/Issue835.java

@@ -0,0 +1,35 @@
+package com.github.jknack.handlebars.i835;
+
+import static org.junit.Assert.assertEquals;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+
+import org.junit.Test;
+
+import com.github.jknack.handlebars.Handlebars;
+import com.github.jknack.handlebars.io.ClassPathTemplateLoader;
+import com.github.jknack.handlebars.v4Test;
+
+public class Issue835 extends v4Test {
+
+  @Override protected void configure(Handlebars handlebars) {
+    handlebars.with(
+        new ClassPathTemplateLoader("/" + getClass().getPackage().getName().replace(".", "/")));
+  }
+
+  @Test
+  public void shouldIgnoreZeroSizeFileTemplate() throws IOException {
+    assertEquals(0, Files.size(
+        Paths.get("src", "test", "resources", "com", "github", "jknack", "handlebars", "i835",
+            "i835.hbs")));
+    shouldCompileTo("-{{> i835}}-", $(), "--");
+  }
+
+  @Test
+  public void shouldIgnoreEmptyTemplate() throws IOException {
+    shouldCompileTo("", $(), "");
+  }
+
+}