dynamic partials fix #375

+ dynamic partials
+ lookup helper

Author: jknack

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

@@ -179,7 +179,7 @@ START_DELIM
  ;
 
 START_PARTIAL
- : {startToken(start, ">")}? . -> pushMode(PARTIAL)
+ : {startToken(start, ">")}? . -> pushMode(VAR)
  ;
 
 END_BLOCK
@@ -213,25 +213,6 @@ WS_DELIM
 
 DELIM: .;
 
-mode PARTIAL;
-
-PATH
-  :
-  (
-    '[' PATH_SEGMENT ']'
-  | PATH_SEGMENT
-  ) -> mode(VAR)
-  ;
-
-fragment
-PATH_SEGMENT
-  : [a-zA-Z0-9_$'/.:\-]+
-  ;
-
-WS_PATH
-  : [ \t\r\n] -> skip
-  ;
-
 mode VAR;
 
 END_T
@@ -283,6 +264,17 @@ QID
  | ID
  ;
 
+PATH
+  :
+    '[' PATH_SEGMENT ']'
+  | PATH_SEGMENT
+  ;
+
+fragment
+PATH_SEGMENT
+  : [a-zA-Z0-9_$'/.:\-]+
+  ;
+
 fragment
 ID_SEPARATOR
   : ('.'|'/'|'-');

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

@@ -132,7 +132,13 @@ delimiters
 
 partial
   :
-    START_PARTIAL PATH QID? hash* END
+    START_PARTIAL pexpr END
+  ;
+
+pexpr
+  :
+    LP sexpr RP hash*             #dynamicPath
+  | path = (QID|PATH) QID? hash*  #staticPath
   ;
 
 param

handlebars/src/main/java/com/github/jknack/handlebars/Handlebars.java

@@ -1093,7 +1093,7 @@ public String handlebarsJsFile() {
   /**
    * Return a parser factory.
    *
-   * @return A parsert factory.
+   * @return A parser factory.
    */
   public ParserFactory getParserFactory() {
     return parserFactory;

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

@@ -221,6 +221,7 @@ private static void registerBuiltinsHelpers(final HelperRegistry registry) {
     registry.registerHelper(PrecompileHelper.NAME, PrecompileHelper.INSTANCE);
     registry.registerHelper("i18n", I18nHelper.i18n);
     registry.registerHelper("i18nJs", I18nHelper.i18nJs);
+    registry.registerHelper(LookupHelper.NAME, LookupHelper.INSTANCE);
   }
 
 }

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

@@ -0,0 +1,80 @@
+/**
+ * Copyright (c) 2012-2013 Edgar Espina
+ *
+ * This file is part of Handlebars.java.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.github.jknack.handlebars.helper;
+
+import java.io.IOException;
+
+import com.github.jknack.handlebars.Context;
+import com.github.jknack.handlebars.Helper;
+import com.github.jknack.handlebars.Options;
+
+/**
+ * Lookup helper, which allows to get a context variable... It is kind of useless, but it it present
+ * to keep better integration with handlebars.js.
+ *
+ * It was introduced with dynamic partials:
+ *
+ * <pre>
+ * {{> (lookup '.' 'myVariable') }}
+ * </pre>
+ *
+ * This helper is useless bc it shouldn't be required to get a variable via a helper, like:
+ *
+ * <pre>
+ * {{> (myVariable) }}
+ * </pre>
+ *
+ * For now, previous expression isn't supported in Handlebars.java... but the only reason of that is
+ * handlebars.js
+ *
+ * @author edgar
+ * @since 2.2.0
+ */
+public class LookupHelper implements Helper<Object> {
+
+  /**
+   * A singleton instance of this helper.
+   */
+  public static final Helper<Object> INSTANCE = new LookupHelper();
+
+  /**
+   * The helper's name.
+   */
+  public static final String NAME = "lookup";
+
+  @Override
+  public CharSequence apply(final Object context, final Options options)
+      throws IOException {
+    if (options.params.length <= 0) {
+      return context.toString();
+    }
+    Context ctx = options.context;
+    while (ctx != null && context != ctx.model()) {
+      ctx = ctx.parent();
+    }
+    if (ctx == null) {
+      return null;
+    }
+    Object lookup = ctx.get(options.param(0).toString());
+    if (lookup == null) {
+      return null;
+    }
+    return lookup.toString();
+  }
+
+}

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

@@ -19,7 +19,7 @@
 
 import static org.apache.commons.lang3.StringUtils.isEmpty;
 import static org.apache.commons.lang3.StringUtils.join;
-import static org.apache.commons.lang3.Validate.notEmpty;
+import static org.apache.commons.lang3.Validate.notNull;
 
 import java.io.IOException;
 import java.io.Writer;
@@ -50,7 +50,7 @@ class Partial extends HelperResolver {
   /**
    * The partial path.
    */
-  private String path;
+  private Template path;
 
   /**
    * A partial context. Optional.
@@ -80,10 +80,10 @@ class Partial extends HelperResolver {
    * @param context The template context.
    * @param hash Template params
    */
-  public Partial(final Handlebars handlebars, final String path, final String context,
+  public Partial(final Handlebars handlebars, final Template path, final String context,
       final Map<String, Object> hash) {
     super(handlebars);
-    this.path = notEmpty(path, "The path is required.");
+    this.path = notNull(path, "The path is required.");
     this.context = context;
     this.hash(hash);
   }
@@ -95,6 +95,8 @@ public void merge(final Context context, final Writer writer)
     try {
       LinkedList<TemplateSource> invocationStack = context.data(Context.INVOCATION_STACK);
 
+      String path = this.path.apply(context);
+
       TemplateSource source = loader.sourceAt(path);
 
       if (exists(invocationStack, source.filename())) {
@@ -129,7 +131,7 @@ public void merge(final Context context, final Writer writer)
       template.apply(Context.newContext(context, context.get(key)).data(hash(context)), writer);
     } catch (IOException ex) {
       String reason = String.format("The partial '%s' could not be found",
-          loader.resolve(path));
+          loader.resolve(path.text()));
       String message = String.format("%s:%s:%s: %s", filename, line, column, reason);
       HandlebarsError error = new HandlebarsError(filename, line,
           column, reason, text(), message);
@@ -222,7 +224,7 @@ private String partialInput(final String input, final String indent) {
   public String text() {
     StringBuilder buffer = new StringBuilder(startDelimiter)
         .append('>')
-        .append(path);
+        .append(path.text());
 
     if (context != null) {
       buffer.append(' ').append(context);

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

@@ -48,6 +48,7 @@
 import com.github.jknack.handlebars.internal.HbsParser.BoolParamContext;
 import com.github.jknack.handlebars.internal.HbsParser.CharParamContext;
 import com.github.jknack.handlebars.internal.HbsParser.CommentContext;
+import com.github.jknack.handlebars.internal.HbsParser.DynamicPathContext;
 import com.github.jknack.handlebars.internal.HbsParser.ElseBlockContext;
 import com.github.jknack.handlebars.internal.HbsParser.EscapeContext;
 import com.github.jknack.handlebars.internal.HbsParser.HashContext;
@@ -59,6 +60,7 @@
 import com.github.jknack.handlebars.internal.HbsParser.SexprContext;
 import com.github.jknack.handlebars.internal.HbsParser.SpacesContext;
 import com.github.jknack.handlebars.internal.HbsParser.StatementContext;
+import com.github.jknack.handlebars.internal.HbsParser.StaticPathContext;
 import com.github.jknack.handlebars.internal.HbsParser.StringParamContext;
 import com.github.jknack.handlebars.internal.HbsParser.SubParamExprContext;
 import com.github.jknack.handlebars.internal.HbsParser.TemplateContext;
@@ -76,6 +78,28 @@
  */
 abstract class TemplateBuilder extends HbsParserBaseVisitor<Object> {
 
+  /**
+   * Get partial info: static vs dynamic.
+   *
+   * @author edgar
+   * @since 2.2.0
+   */
+  private static class PartialInfo {
+
+    /** Token to report errors. */
+    private Token token;
+
+    /** Partial params. */
+    private Map<String, Object> hash;
+
+    /** Partial path: static vs subexpression. */
+    private Template path;
+
+    /** Template context. */
+    private String context;
+
+  }
+
   /**
    * A handlebars object. required.
    */
@@ -384,16 +408,6 @@ protected void afterApply(final Context context) {
   @Override
   public Template visitPartial(final PartialContext ctx) {
     hasTag(true);
-    Token pathToken = ctx.PATH().getSymbol();
-    String uri = pathToken.getText();
-    if (uri.startsWith("[") && uri.endsWith("]")) {
-      uri = uri.substring(1, uri.length() - 1);
-    }
-
-    if (uri.startsWith("/")) {
-      String message = "found: '/', partial shouldn't start with '/'";
-      reportError(null, pathToken.getLine(), pathToken.getCharPositionInLine(), message);
-    }
 
     String indent = line.toString();
     if (hasTag()) {
@@ -404,16 +418,54 @@ public Template visitPartial(final PartialContext ctx) {
       indent = null;
     }
 
-    TerminalNode partialContext = ctx.QID();
+    PartialInfo info = (PartialInfo) super.visit(ctx.pexpr());
+
     String startDelim = ctx.start.getText();
-    Template partial = new Partial(handlebars, uri,
-        partialContext != null ? partialContext.getText() : null, hash(ctx.hash()))
+    Template partial = new Partial(handlebars, info.path, info.context, info.hash)
         .startDelimiter(startDelim.substring(0, startDelim.length() - 1))
         .endDelimiter(ctx.stop.getText())
         .indent(indent)
         .filename(source.filename())
-        .position(pathToken.getLine(), pathToken.getCharPositionInLine());
+        .position(info.token.getLine(), info.token.getCharPositionInLine());
+
+    return partial;
+  }
+
+  @Override
+  public PartialInfo visitStaticPath(final StaticPathContext ctx) {
+    Token pathToken = ctx.path;
+    String uri = pathToken.getText();
+    if (uri.startsWith("[") && uri.endsWith("]")) {
+      uri = uri.substring(1, uri.length() - 1);
+    }
+
+    if (uri.startsWith("/")) {
+      String message = "found: '/', partial shouldn't start with '/'";
+      reportError(null, pathToken.getLine(), pathToken.getCharPositionInLine(), message);
+    }
+
+    TerminalNode partialContext = ctx.QID(1);
+
+    PartialInfo partial = new PartialInfo();
+    partial.token = pathToken;
+    partial.path = new Text(handlebars, uri);
+    partial.hash = hash(ctx.hash());
+    partial.context = partialContext != null ? partialContext.getText() : null;
+    return partial;
+  }
+
+  @Override
+  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());
 
+    PartialInfo partial = new PartialInfo();
+    partial.path = expression;
+    partial.hash = hash(ctx.hash());
+    partial.context = null;
+    partial.token = qid.getSymbol();
     return partial;
   }
 

handlebars/src/test/java/com/github/jknack/handlebars/MapTemplateLoader.java

@@ -17,9 +17,6 @@
  */
 package com.github.jknack.handlebars;
 
-import static org.apache.commons.lang3.Validate.notEmpty;
-import static org.apache.commons.lang3.Validate.notNull;
-
 import java.io.FileNotFoundException;
 import java.net.URL;
 import java.util.HashMap;
@@ -54,8 +51,6 @@ public MapTemplateLoader define(final String name, final String content) {
 
   @Override
   public TemplateSource sourceAt(final String uri) throws FileNotFoundException {
-    notNull(uri, "The uri is required.");
-    notEmpty(uri.toString(), "The uri is required.");
     String location = resolve(normalize(uri));
     String text = map.get(location);
     if (text == null) {