Dynamic Partial (lookup) with a default parameter doesn't work fix #531

Author: jknack

handlebars/src/main/antlr4/com/github/jknack/handlebars/internal/HbsParser.g4

@@ -170,8 +170,8 @@ partialBlock
 
 pexpr
   :
-    LP sexpr RP hash*             #dynamicPath
-  | path = (QID|PATH) QID? hash*  #staticPath
+    LP sexpr RP QID? hash*                            #dynamicPath
+  | path = (QID|PATH) QID? hash*                      #staticPath
   | path = (DOUBLE_STRING | SINGLE_STRING) QID? hash* #literalPath
   ;
 

handlebars/src/main/java/com/github/jknack/handlebars/helper/LookupHelper.java

@@ -59,7 +59,7 @@ public Object apply(final Object context, final Options options)
     Context ctx = Context.newBuilder(options.context, context).build();
     Object lookup = ctx.get(options.param(0).toString());
     if (lookup == null) {
-      return null;
+      return context;
     }
     return lookup;
   }

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

@@ -482,7 +482,7 @@ public Object visitSubParamExpr(final SubParamExprContext ctx) {
     SexprContext sexpr = ctx.sexpr();
     return new VarParam(
         newVar(sexpr.QID().getSymbol(), TagType.SUB_EXPRESSION, params(sexpr.param()),
-            hash(sexpr.hash()), ctx.start.getText(), ctx.stop.getText(), false));
+            hash(sexpr.hash()), "(", ")", false));
   }
 
   @Override
@@ -638,12 +638,13 @@ public PartialInfo visitDynamicPath(final DynamicPathContext ctx) {
     SexprContext sexpr = ctx.sexpr();
     TerminalNode qid = sexpr.QID();
     Template expression = newVar(qid.getSymbol(), TagType.SUB_EXPRESSION, params(sexpr.param()),
-        hash(sexpr.hash()), ctx.start.getText(), ctx.stop.getText(), false);
+        hash(sexpr.hash()), "(", ")", false);
 
     PartialInfo partial = new PartialInfo();
     partial.path = expression;
     partial.hash = hash(ctx.hash());
-    partial.context = null;
+    TerminalNode scope = ctx.QID();
+    partial.context = scope != null ? scope.getText() : null;
     partial.token = qid.getSymbol();
     return partial;
   }

handlebars/src/test/java/com/github/jknack/handlebars/issues/Hbs531.java

@@ -0,0 +1,30 @@
+package com.github.jknack.handlebars.issues;
+
+import static org.junit.Assert.assertEquals;
+
+import java.io.IOException;
+import java.util.Arrays;
+
+import org.junit.Test;
+
+import com.github.jknack.handlebars.v4Test;
+
+public class Hbs531 extends v4Test {
+
+  @Test
+  public void dynamicPartialLookupWithADefaultParameterDoesn_tWork() throws IOException {
+    shouldCompileTo("{{#each this}} {{> (lookup profession 'name') this.person}}<br /> {{/each}}",
+        $("hash", Arrays.asList(
+            $("firstName", "John", "lastName", "Foe", "profession", "developer"),
+            $("firstName", "James", "lastName", "Doe", "profession", "analyst")),
+            "partials",
+            $("analyst", "Analyst - {{firstName}} {{lastName}}",
+                "developer", "Developer - {{firstName}} {{lastName}}")),
+        " Developer - John Foe<br />  Analyst - James Doe<br /> ");
+
+    assertEquals("{{#each this}} {{>(lookup profession 'name') this.person}}<br /> {{/each}}",
+        compile("{{#each this}} {{> (lookup profession 'name') this.person}}<br /> {{/each}}")
+            .text());
+  }
+
+}