handlebars: support ValueResolver at module level

- fix #3513

Author: jknack

docs/asciidoc/modules/handlebars.adoc

@@ -28,7 +28,7 @@ import io.jooby.handlebars.HandlebarsModule;
   install(new HandlebarsModule());
 
   get("/", ctx -> {
-    return new ModelAndView("index.hbs")
+    return new MapModelAndView("index.hbs")
         .put("name", "Jooby");
   });
 }
@@ -43,7 +43,7 @@ import io.jooby.handlebars.HandlebarsModule
   install(HandlebarsModule())
   
   get("/") {
-    ModelAndView("index.hbs")
+    MapModelAndView("index.hbs")
         .put("name", "Jooby")
   }
 }

modules/jooby-handlebars/src/main/java/io/jooby/handlebars/HandlebarsModule.java

@@ -14,10 +14,13 @@
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
+import java.util.Deque;
+import java.util.LinkedList;
 import java.util.List;
 import java.util.Optional;
 
 import com.github.jknack.handlebars.Handlebars;
+import com.github.jknack.handlebars.ValueResolver;
 import com.github.jknack.handlebars.cache.HighConcurrencyTemplateCache;
 import com.github.jknack.handlebars.cache.NullTemplateCache;
 import com.github.jknack.handlebars.cache.TemplateCache;
@@ -199,6 +202,9 @@ protected URL getResource(String location) {
 
   private Path templatesPath;
 
+  private final Deque<ValueResolver> resolvers =
+      new LinkedList<>(ValueResolver.defaultValueResolvers());
+
   /**
    * Creates a new handlebars module.
    *
@@ -233,6 +239,17 @@ public HandlebarsModule() {
     this(TemplateEngine.PATH);
   }
 
+  /**
+   * Add custom value resolver.
+   *
+   * @param resolver Value resolver.
+   * @return This module.
+   */
+  public HandlebarsModule with(@NonNull ValueResolver resolver) {
+    resolvers.addFirst(resolver);
+    return this;
+  }
+
   @Override
   public void install(@NonNull Jooby application) throws Exception {
     if (handlebars == null) {
@@ -242,7 +259,8 @@ public void install(@NonNull Jooby application) throws Exception {
               .setTemplatesPath(templatesPath)
               .build(application.getEnvironment());
     }
-    application.encoder(new HandlebarsTemplateEngine(handlebars, EXT));
+    application.encoder(
+        new HandlebarsTemplateEngine(handlebars, resolvers.toArray(new ValueResolver[0]), EXT));
 
     ServiceRegistry services = application.getServices();
     services.put(Handlebars.class, handlebars);

modules/jooby-handlebars/src/main/java/io/jooby/handlebars/package-info.java

@@ -0,0 +1,25 @@
+/**
+ * Handlebars templates for jooby:
+ *
+ * <pre>
+ * import io.jooby.handlebars.HandlebarsModule;
+ *
+ * {
+ *   install(new HandlebarsModule());
+ *
+ *   get("/", ctx -> {
+ *     return new MapModelAndView("index.hbs")
+ *         .put("name", "Jooby");
+ *   });
+ * }
+ * </pre>
+ *
+ * <p>views/index.hbs
+ *
+ * <pre>
+ *   Hello {{name}}!
+ * </pre>
+ *
+ * @author edgar
+ */
+package io.jooby.handlebars;

modules/jooby-handlebars/src/main/java/io/jooby/internal/handlebars/HandlebarsTemplateEngine.java

@@ -5,12 +5,11 @@
  */
 package io.jooby.internal.handlebars;
 
-import static com.github.jknack.handlebars.Context.newContext;
-
 import java.util.Collections;
 import java.util.List;
 
 import com.github.jknack.handlebars.Handlebars;
+import com.github.jknack.handlebars.ValueResolver;
 import edu.umd.cs.findbugs.annotations.NonNull;
 import io.jooby.Context;
 import io.jooby.ModelAndView;
@@ -19,11 +18,14 @@
 
 public class HandlebarsTemplateEngine implements TemplateEngine {
 
-  private final List<String> extensions;
   private final Handlebars handlebars;
+  private final ValueResolver[] resolvers;
+  private final List<String> extensions;
 
-  public HandlebarsTemplateEngine(Handlebars handlebars, List<String> extensions) {
+  public HandlebarsTemplateEngine(
+      Handlebars handlebars, ValueResolver[] resolvers, List<String> extensions) {
     this.handlebars = handlebars;
+    this.resolvers = resolvers;
     this.extensions = Collections.unmodifiableList(extensions);
   }
 
@@ -35,7 +37,11 @@ public List<String> extensions() {
   @Override
   public DataBuffer render(Context ctx, ModelAndView modelAndView) throws Exception {
     var template = handlebars.compile(modelAndView.getView());
-    var engineModel = newContext(modelAndView.getModel()).data(ctx.getAttributes());
+    var engineModel =
+        com.github.jknack.handlebars.Context.newBuilder(modelAndView.getModel())
+            .resolver(resolvers)
+            .build()
+            .data(ctx.getAttributes());
     var buffer = ctx.getBufferFactory().allocateBuffer();
     template.apply(engineModel, buffer.asWriter());
     return buffer;

modules/jooby-handlebars/src/test/java/io/jooby/handlebars/HandlebarsModuleTest.java

@@ -14,6 +14,7 @@
 import org.junit.jupiter.api.Test;
 
 import com.github.jknack.handlebars.Handlebars;
+import com.github.jknack.handlebars.ValueResolver;
 import com.typesafe.config.ConfigFactory;
 import io.jooby.Environment;
 import io.jooby.ModelAndView;
@@ -46,7 +47,10 @@ public void render() throws Exception {
         HandlebarsModule.create()
             .build(new Environment(getClass().getClassLoader(), ConfigFactory.empty()));
     HandlebarsTemplateEngine engine =
-        new HandlebarsTemplateEngine(handlebars, Arrays.asList(".hbs"));
+        new HandlebarsTemplateEngine(
+            handlebars,
+            ValueResolver.defaultValueResolvers().toArray(new ValueResolver[0]),
+            Arrays.asList(".hbs"));
     MockContext ctx = new MockContext();
     ctx.getAttributes().put("local", "var");
     var output =
@@ -63,7 +67,10 @@ public void renderFileSystem() throws Exception {
             .setTemplatesPath(Paths.get("src", "test", "resources", "views").toString())
             .build(new Environment(getClass().getClassLoader(), ConfigFactory.empty()));
     HandlebarsTemplateEngine engine =
-        new HandlebarsTemplateEngine(handlebars, Arrays.asList(".hbs"));
+        new HandlebarsTemplateEngine(
+            handlebars,
+            ValueResolver.defaultValueResolvers().toArray(new ValueResolver[0]),
+            Arrays.asList(".hbs"));
     MockContext ctx = new MockContext();
     ctx.getAttributes().put("local", "var");
     var output =