From cb51b82b8e8114aaa3e1b19c41e5c4eebf0539d5 Mon Sep 17 00:00:00 2001
From: kpdecker <kpdecker@gmail.com>
Date: Sun, 18 Jan 2015 13:23:45 -0600
Subject: [PATCH 1/4] Add support for dynamic partial names

Uses the subexpression syntax to allow for dynamic partial lookups. Ex:

```
{{> (helper) }}
```

Fixes #933
---
 docs/compiler-api.md                          | 13 ++++++++++
 lib/handlebars/compiler/ast.js                |  9 +++++++
 lib/handlebars/compiler/compiler.js           | 10 +++++--
 .../compiler/javascript-compiler.js           | 13 ++++++++--
 lib/handlebars/compiler/printer.js            |  2 +-
 lib/handlebars/compiler/visitor.js            |  5 ++++
 lib/handlebars/runtime.js                     | 15 ++++++++---
 spec/partials.js                              | 26 +++++++++++++++++++
 src/handlebars.yy                             |  8 +++++-
 9 files changed, 92 insertions(+), 9 deletions(-)

diff --git a/docs/compiler-api.md b/docs/compiler-api.md
index 74af67246..4a0ec0149 100644
--- a/docs/compiler-api.md
+++ b/docs/compiler-api.md
@@ -115,6 +115,17 @@ interface SubExpression <: Expression {
 
 `isHelper` is not required and is used to disambiguate between cases such as `{{foo}}` and `(foo)`, which have slightly different call behaviors.
 
+```java
+interface PartialExpression <: Expression {
+    type: "PartialExpression";
+    name: PathExpression | SubExpression;
+    params: [ Expression ];
+    hash: Hash;
+}
+```
+
+`path` may be a `SubExpression` when tied to a dynamic partial, i.e. `{{> (foo) }}`
+
 ##### Paths
 
 ```java
@@ -221,6 +232,8 @@ The `Handlebars.JavaScriptCompiler` object has a number of methods that may be c
   - `name` is the current path component
   - `type` is the type of name being evaluated. May be one of `context`, `data`, `helper`, or `partial`.
 
+  Note that this does not impact dynamic partials, which implementors need to be aware of. Overriding `VM.resolvePartial` may be required to support dynamic cases.
+
 - `depthedLookup(name)`
   Used to generate code that resolves parameters within any context in the stack. Is only used in `compat` mode. 
 
diff --git a/lib/handlebars/compiler/ast.js b/lib/handlebars/compiler/ast.js
index 113c03e79..c193460fc 100644
--- a/lib/handlebars/compiler/ast.js
+++ b/lib/handlebars/compiler/ast.js
@@ -63,6 +63,15 @@ var AST = {
     this.hash = hash;
   },
 
+  PartialExpression: function(name, params, hash, locInfo) {
+    this.loc = locInfo;
+
+    this.type = 'PartialExpression';
+    this.name = name;
+    this.params = params || [];
+    this.hash = hash;
+  },
+
   PathExpression: function(data, depth, parts, original, locInfo) {
     this.loc = locInfo;
     this.type = 'PathExpression';
diff --git a/lib/handlebars/compiler/compiler.js b/lib/handlebars/compiler/compiler.js
index 95fe101b8..524f9aa2f 100644
--- a/lib/handlebars/compiler/compiler.js
+++ b/lib/handlebars/compiler/compiler.js
@@ -145,7 +145,6 @@ Compiler.prototype = {
   },
 
   PartialStatement: function(partial) {
-    var partialName = partial.sexpr.path.original;
     this.usePartial = true;
 
     var params = partial.sexpr.params;
@@ -155,6 +154,12 @@ Compiler.prototype = {
       params.push({type: 'PathExpression', parts: [], depth: 0});
     }
 
+    var partialName = partial.sexpr.name.original,
+        isDynamic = partial.sexpr.name.type === 'SubExpression';
+    if (isDynamic) {
+      this.accept(partial.sexpr.name);
+    }
+
     this.setupFullMustacheParams(partial.sexpr, undefined, undefined, true);
 
     var indent = partial.indent || '';
@@ -162,7 +167,8 @@ Compiler.prototype = {
       this.opcode('appendContent', indent);
       indent = '';
     }
-    this.opcode('invokePartial', partialName, indent);
+
+    this.opcode('invokePartial', isDynamic, partialName, indent);
     this.opcode('append');
   },
 
diff --git a/lib/handlebars/compiler/javascript-compiler.js b/lib/handlebars/compiler/javascript-compiler.js
index 75f996071..a027edb91 100644
--- a/lib/handlebars/compiler/javascript-compiler.js
+++ b/lib/handlebars/compiler/javascript-compiler.js
@@ -644,17 +644,26 @@ JavaScriptCompiler.prototype = {
   //
   // This operation pops off a context, invokes a partial with that context,
   // and pushes the result of the invocation back.
-  invokePartial: function(name, indent) {
+  invokePartial: function(isDynamic, name, indent) {
     var params = [],
         options = this.setupParams(name, 1, params, false);
 
+    if (isDynamic) {
+      name = this.popStack();
+      delete options.name;
+    }
+
     if (indent) {
       options.indent = JSON.stringify(indent);
     }
     options.helpers = 'helpers';
     options.partials = 'partials';
 
-    params.unshift(this.nameLookup('partials', name, 'partial'));
+    if (!isDynamic) {
+      params.unshift(this.nameLookup('partials', name, 'partial'));
+    } else {
+      params.unshift(name);
+    }
 
     if (this.options.compat) {
       options.depths = 'depths';
diff --git a/lib/handlebars/compiler/printer.js b/lib/handlebars/compiler/printer.js
index ad276f19a..448331c03 100644
--- a/lib/handlebars/compiler/printer.js
+++ b/lib/handlebars/compiler/printer.js
@@ -75,7 +75,7 @@ PrintVisitor.prototype.BlockStatement = function(block) {
 
 PrintVisitor.prototype.PartialStatement = function(partial) {
   var sexpr = partial.sexpr,
-      content = 'PARTIAL:' + sexpr.path.original;
+      content = 'PARTIAL:' + sexpr.name.original;
   if(sexpr.params[0]) {
     content += ' ' + this.accept(sexpr.params[0]);
   }
diff --git a/lib/handlebars/compiler/visitor.js b/lib/handlebars/compiler/visitor.js
index 3fb37fbfc..03af9153e 100644
--- a/lib/handlebars/compiler/visitor.js
+++ b/lib/handlebars/compiler/visitor.js
@@ -92,6 +92,11 @@ Visitor.prototype = {
     this.acceptArray(sexpr.params);
     this.acceptKey(sexpr, 'hash');
   },
+  PartialExpression: function(partial) {
+    this.acceptRequired(partial, 'name');
+    this.acceptArray(partial.params);
+    this.acceptKey(partial, 'hash');
+  },
 
   PathExpression: function(/* path */) {},
 
diff --git a/lib/handlebars/runtime.js b/lib/handlebars/runtime.js
index 2b9f47414..4e8c33ae8 100644
--- a/lib/handlebars/runtime.js
+++ b/lib/handlebars/runtime.js
@@ -39,10 +39,8 @@ export function template(templateSpec, env) {
     if (options.hash) {
       context = Utils.extend({}, context, options.hash);
     }
-    if (!partial) {
-      partial = options.partials[options.name];
-    }
 
+    partial = env.VM.resolvePartial.call(this, partial, context, options);
     var result = env.VM.invokePartial.call(this, partial, context, options);
 
     if (result == null && env.compile) {
@@ -187,6 +185,17 @@ export function program(container, i, fn, data, declaredBlockParams, blockParams
   return prog;
 }
 
+export function resolvePartial(partial, context, options) {
+  if (!partial) {
+    partial = options.partials[options.name];
+  } else if (!partial.call && !options.name) {
+    // This is a dynamic partial that returned a string
+    options.name = partial;
+    partial = options.partials[partial];
+  }
+  return partial;
+}
+
 export function invokePartial(partial, context, options) {
   options.partial = true;
 
diff --git a/spec/partials.js b/spec/partials.js
index b1509423a..0c9e0f6dc 100644
--- a/spec/partials.js
+++ b/spec/partials.js
@@ -8,6 +8,32 @@ describe('partials', function() {
     shouldCompileToWithPartials(string, [hash, {}, {dude: partial},,false], true, 'Dudes: Yehuda (http://yehuda) Alan (http://alan) ');
   });
 
+  it('dynamic partials', function() {
+    var string = 'Dudes: {{#dudes}}{{> (partial)}}{{/dudes}}';
+    var partial = '{{name}} ({{url}}) ';
+    var hash = {dudes: [{name: 'Yehuda', url: 'http://yehuda'}, {name: 'Alan', url: 'http://alan'}]};
+    var helpers = {
+      partial: function() {
+        return 'dude';
+      }
+    };
+    shouldCompileToWithPartials(string, [hash, helpers, {dude: partial}], true, 'Dudes: Yehuda (http://yehuda) Alan (http://alan) ');
+    shouldCompileToWithPartials(string, [hash, helpers, {dude: partial},,false], true, 'Dudes: Yehuda (http://yehuda) Alan (http://alan) ');
+  });
+  it('failing dynamic partials', function() {
+    var string = 'Dudes: {{#dudes}}{{> (partial)}}{{/dudes}}';
+    var partial = '{{name}} ({{url}}) ';
+    var hash = {dudes: [{name: 'Yehuda', url: 'http://yehuda'}, {name: 'Alan', url: 'http://alan'}]};
+    var helpers = {
+      partial: function() {
+        return 'missing';
+      }
+    };
+    shouldThrow(function() {
+      shouldCompileToWithPartials(string, [hash, helpers, {dude: partial}], true, 'Dudes: Yehuda (http://yehuda) Alan (http://alan) ');
+    }, Handlebars.Exception, 'The partial missing could not be found');
+  });
+
   it("partials with context", function() {
     var string = "Dudes: {{>dude dudes}}";
     var partial = "{{#this}}{{name}} ({{url}}) {{/this}}";
diff --git a/src/handlebars.yy b/src/handlebars.yy
index 27985b8d0..6ca32d942 100644
--- a/src/handlebars.yy
+++ b/src/handlebars.yy
@@ -77,7 +77,13 @@ mustache
   ;
 
 partial
-  : OPEN_PARTIAL sexpr CLOSE -> new yy.PartialStatement($2, yy.stripFlags($1, $3), yy.locInfo(@$))
+  : OPEN_PARTIAL partial_expr CLOSE -> new yy.PartialStatement($2, yy.stripFlags($1, $3), yy.locInfo(@$))
+  ;
+
+partial_expr
+  : helperName param* hash? -> new yy.PartialExpression($1, $2, $3, yy.locInfo(@$))
+  | dataName -> new yy.PartialExpression($1, null, null, yy.locInfo(@$))
+  | OPEN_SEXPR sexpr CLOSE_SEXPR param* hash? -> new yy.PartialExpression($2, $4, $5, yy.locInfo(@$))
   ;
 
 sexpr

From d567d9c34566a6adab1eaea40ade2729fbce8144 Mon Sep 17 00:00:00 2001
From: kpdecker <kpdecker@gmail.com>
Date: Sun, 18 Jan 2015 13:29:15 -0600
Subject: [PATCH 2/4] Update PartialExpression AST docs

---
 docs/compiler-api.md | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/docs/compiler-api.md b/docs/compiler-api.md
index 4a0ec0149..7a5db380e 100644
--- a/docs/compiler-api.md
+++ b/docs/compiler-api.md
@@ -118,13 +118,13 @@ interface SubExpression <: Expression {
 ```java
 interface PartialExpression <: Expression {
     type: "PartialExpression";
-    name: PathExpression | SubExpression;
+    name: PathExpression | Literal | SubExpression;
     params: [ Expression ];
     hash: Hash;
 }
 ```
 
-`path` may be a `SubExpression` when tied to a dynamic partial, i.e. `{{> (foo) }}`
+`name` will be a `SubExpression` when tied to a dynamic partial, i.e. `{{> (foo) }}`, otherwise this is a path or literal whose `original` value is used to lookup the desired partial.
 
 ##### Paths
 

From 999da739a66199483ffc4d82426550aee5ac798f Mon Sep 17 00:00:00 2001
From: kpdecker <kpdecker@gmail.com>
Date: Sun, 18 Jan 2015 14:21:04 -0600
Subject: [PATCH 3/4] Update for proposed SubExpression dependency break

Avoids parsing against SubExpressions and instead inlines the content that a subexpression otherwise would have. This can still be based via duck typing so should not add much overhead to the compiler.
---
 docs/compiler-api.md | 36 +++++++++++++++++-------------------
 1 file changed, 17 insertions(+), 19 deletions(-)

diff --git a/docs/compiler-api.md b/docs/compiler-api.md
index 7a5db380e..39bcacdaf 100644
--- a/docs/compiler-api.md
+++ b/docs/compiler-api.md
@@ -55,15 +55,21 @@ interface Statement <: Node { }
 
 interface MustacheStatement <: Statement {
     type: "MustacheStatement";
-    sexpr: SubExpression;
-    escaped: boolean;
 
+    path: PathExpression;
+    params: [ Expression ];
+    hash: Hash;
+
+    escaped: boolean;
     strip: StripFlags | null;
 }
 
 interface BlockStatement <: Statement {
     type: "BlockStatement";
-    sexpr: SubExpression;
+    path: PathExpression;
+    params: [ Expression ];
+    hash: Hash;
+
     program: Program | null;
     inverse: Program | null;
 
@@ -74,12 +80,19 @@ interface BlockStatement <: Statement {
 
 interface PartialStatement <: Statement {
     type: "PartialStatement";
-    sexpr: SubExpression;
+    name: PathExpression | SubExpression;
+    params: [ Expression ];
+    hash: Hash;
     
     indent: string;
     strip: StripFlags | null;
 }
+```
 
+`name` will be a `SubExpression` when tied to a dynamic partial, i.e. `{{> (foo) }}`, otherwise this is a path or literal whose `original` value is used to lookup the desired partial.
+
+
+```java
 interface ContentStatement <: Statement {
     type: "ContentStatement";
     value: string;
@@ -108,24 +121,9 @@ interface SubExpression <: Expression {
     path: PathExpression;
     params: [ Expression ];
     hash: Hash;
-    
-    isHelper: true | null;
 }
 ```
 
-`isHelper` is not required and is used to disambiguate between cases such as `{{foo}}` and `(foo)`, which have slightly different call behaviors.
-
-```java
-interface PartialExpression <: Expression {
-    type: "PartialExpression";
-    name: PathExpression | Literal | SubExpression;
-    params: [ Expression ];
-    hash: Hash;
-}
-```
-
-`name` will be a `SubExpression` when tied to a dynamic partial, i.e. `{{> (foo) }}`, otherwise this is a path or literal whose `original` value is used to lookup the desired partial.
-
 ##### Paths
 
 ```java

From 884bf1553663734f22ffcd9d758c9d71d4373bf9 Mon Sep 17 00:00:00 2001
From: kpdecker <kpdecker@gmail.com>
Date: Sun, 18 Jan 2015 17:27:27 -0600
Subject: [PATCH 4/4] Avoid direct references to sexpr in statements

This allows us to avoid creating unnecessary AST nodes and avoids things like isHelper.

Side effect of these changes is that @data functions can now have data parameters passed to them.
---
 docs/compiler-api.md                |  2 +-
 lib/handlebars/compiler/ast.js      | 36 +++++++++++++---------------
 lib/handlebars/compiler/compiler.js | 30 ++++++++++-------------
 lib/handlebars/compiler/helpers.js  | 22 +++++++++--------
 lib/handlebars/compiler/printer.js  | 15 ++++++------
 lib/handlebars/compiler/visitor.js  | 13 +++++++---
 spec/ast.js                         | 10 ++++----
 spec/data.js                        | 11 +++++++++
 spec/visitor.js                     | 15 ++++++------
 src/handlebars.yy                   | 37 ++++++++++++++---------------
 10 files changed, 100 insertions(+), 91 deletions(-)

diff --git a/docs/compiler-api.md b/docs/compiler-api.md
index 39bcacdaf..3593228bc 100644
--- a/docs/compiler-api.md
+++ b/docs/compiler-api.md
@@ -204,7 +204,7 @@ function ImportScanner() {
 ImportScanner.prototype = new Visitor();
 
 ImportScanner.prototype.PartialStatement = function(partial) {
-  this.partials.push({request: partial.sexpr.original});
+  this.partials.push({request: partial.name.original});
 
   Visitor.prototype.PartialStatement.call(this, partial);
 };
diff --git a/lib/handlebars/compiler/ast.js b/lib/handlebars/compiler/ast.js
index c193460fc..45212b383 100644
--- a/lib/handlebars/compiler/ast.js
+++ b/lib/handlebars/compiler/ast.js
@@ -8,21 +8,25 @@ var AST = {
     this.strip = strip;
   },
 
-  MustacheStatement: function(sexpr, escaped, strip, locInfo) {
+  MustacheStatement: function(path, params, hash, escaped, strip, locInfo) {
     this.loc = locInfo;
     this.type = 'MustacheStatement';
 
-    this.sexpr = sexpr;
+    this.path = path;
+    this.params = params || [];
+    this.hash = hash;
     this.escaped = escaped;
 
     this.strip = strip;
   },
 
-  BlockStatement: function(sexpr, program, inverse, openStrip, inverseStrip, closeStrip, locInfo) {
+  BlockStatement: function(path, params, hash, program, inverse, openStrip, inverseStrip, closeStrip, locInfo) {
     this.loc = locInfo;
-
     this.type = 'BlockStatement';
-    this.sexpr = sexpr;
+
+    this.path = path;
+    this.params = params || [];
+    this.hash = hash;
     this.program  = program;
     this.inverse  = inverse;
 
@@ -31,12 +35,15 @@ var AST = {
     this.closeStrip = closeStrip;
   },
 
-  PartialStatement: function(sexpr, strip, locInfo) {
+  PartialStatement: function(name, params, hash, strip, locInfo) {
     this.loc = locInfo;
     this.type = 'PartialStatement';
-    this.sexpr = sexpr;
-    this.indent = '';
 
+    this.name = name;
+    this.params = params || [];
+    this.hash = hash;
+
+    this.indent = '';
     this.strip = strip;
   },
 
@@ -63,15 +70,6 @@ var AST = {
     this.hash = hash;
   },
 
-  PartialExpression: function(name, params, hash, locInfo) {
-    this.loc = locInfo;
-
-    this.type = 'PartialExpression';
-    this.name = name;
-    this.params = params || [];
-    this.hash = hash;
-  },
-
   PathExpression: function(data, depth, parts, original, locInfo) {
     this.loc = locInfo;
     this.type = 'PathExpression';
@@ -121,8 +119,8 @@ var AST = {
     // * it is an eligible helper, and
     // * it has at least one parameter or hash segment
     // TODO: Make these public utility methods
-    helperExpression: function(sexpr) {
-      return !!(sexpr.isHelper || sexpr.params.length || sexpr.hash);
+    helperExpression: function(node) {
+      return !!(node.type === 'SubExpression' || node.params.length || node.hash);
     },
 
     scopedId: function(path) {
diff --git a/lib/handlebars/compiler/compiler.js b/lib/handlebars/compiler/compiler.js
index 524f9aa2f..03bf8f430 100644
--- a/lib/handlebars/compiler/compiler.js
+++ b/lib/handlebars/compiler/compiler.js
@@ -110,28 +110,27 @@ Compiler.prototype = {
   },
 
   BlockStatement: function(block) {
-    var sexpr = block.sexpr,
-        program = block.program,
+    var program = block.program,
         inverse = block.inverse;
 
     program = program && this.compileProgram(program);
     inverse = inverse && this.compileProgram(inverse);
 
-    var type = this.classifySexpr(sexpr);
+    var type = this.classifySexpr(block);
 
     if (type === 'helper') {
-      this.helperSexpr(sexpr, program, inverse);
+      this.helperSexpr(block, program, inverse);
     } else if (type === 'simple') {
-      this.simpleSexpr(sexpr);
+      this.simpleSexpr(block);
 
       // now that the simple mustache is resolved, we need to
       // evaluate it by executing `blockHelperMissing`
       this.opcode('pushProgram', program);
       this.opcode('pushProgram', inverse);
       this.opcode('emptyHash');
-      this.opcode('blockValue', sexpr.path.original);
+      this.opcode('blockValue', block.path.original);
     } else {
-      this.ambiguousSexpr(sexpr, program, inverse);
+      this.ambiguousSexpr(block, program, inverse);
 
       // now that the simple mustache is resolved, we need to
       // evaluate it by executing `blockHelperMissing`
@@ -147,20 +146,20 @@ Compiler.prototype = {
   PartialStatement: function(partial) {
     this.usePartial = true;
 
-    var params = partial.sexpr.params;
+    var params = partial.params;
     if (params.length > 1) {
       throw new Exception('Unsupported number of partial arguments: ' + params.length, partial);
     } else if (!params.length) {
       params.push({type: 'PathExpression', parts: [], depth: 0});
     }
 
-    var partialName = partial.sexpr.name.original,
-        isDynamic = partial.sexpr.name.type === 'SubExpression';
+    var partialName = partial.name.original,
+        isDynamic = partial.name.type === 'SubExpression';
     if (isDynamic) {
-      this.accept(partial.sexpr.name);
+      this.accept(partial.name);
     }
 
-    this.setupFullMustacheParams(partial.sexpr, undefined, undefined, true);
+    this.setupFullMustacheParams(partial, undefined, undefined, true);
 
     var indent = partial.indent || '';
     if (this.options.preventIndent && indent) {
@@ -173,7 +172,7 @@ Compiler.prototype = {
   },
 
   MustacheStatement: function(mustache) {
-    this.accept(mustache.sexpr);
+    this.SubExpression(mustache);
 
     if(mustache.escaped && !this.options.noEscape) {
       this.opcode('appendEscaped');
@@ -340,11 +339,6 @@ Compiler.prototype = {
   pushParam: function(val) {
     var value = val.value != null ? val.value : val.original || '';
 
-    // Force helper evaluation
-    if (val.type === 'SubExpression') {
-      val.isHelper = true;
-    }
-
     if (this.stringParams) {
       if (value.replace) {
         value = value
diff --git a/lib/handlebars/compiler/helpers.js b/lib/handlebars/compiler/helpers.js
index 6cfc0e076..beaf98869 100644
--- a/lib/handlebars/compiler/helpers.js
+++ b/lib/handlebars/compiler/helpers.js
@@ -52,28 +52,29 @@ export function preparePath(data, parts, locInfo) {
   return new this.PathExpression(data, depth, dig, original, locInfo);
 }
 
-export function prepareMustache(sexpr, open, strip, locInfo) {
+export function prepareMustache(path, params, hash, open, strip, locInfo) {
   /*jshint -W040 */
   // Must use charAt to support IE pre-10
   var escapeFlag = open.charAt(3) || open.charAt(2),
       escaped = escapeFlag !== '{' && escapeFlag !== '&';
 
-  return new this.MustacheStatement(sexpr, escaped, strip, this.locInfo(locInfo));
+  return new this.MustacheStatement(path, params, hash, escaped, strip, this.locInfo(locInfo));
 }
 
 export function prepareRawBlock(openRawBlock, content, close, locInfo) {
   /*jshint -W040 */
-  if (openRawBlock.sexpr.path.original !== close) {
-    var errorNode = {loc: openRawBlock.sexpr.loc};
+  if (openRawBlock.path.original !== close) {
+    var errorNode = {loc: openRawBlock.path.loc};
 
-    throw new Exception(openRawBlock.sexpr.path.original + " doesn't match " + close, errorNode);
+    throw new Exception(openRawBlock.path.original + " doesn't match " + close, errorNode);
   }
 
   locInfo = this.locInfo(locInfo);
   var program = new this.Program([content], null, {}, locInfo);
 
   return new this.BlockStatement(
-      openRawBlock.sexpr, program, undefined,
+      openRawBlock.path, openRawBlock.params, openRawBlock.hash,
+      program, undefined,
       {}, {}, {},
       locInfo);
 }
@@ -81,10 +82,10 @@ export function prepareRawBlock(openRawBlock, content, close, locInfo) {
 export function prepareBlock(openBlock, program, inverseAndProgram, close, inverted, locInfo) {
   /*jshint -W040 */
   // When we are chaining inverse calls, we will not have a close path
-  if (close && close.path && openBlock.sexpr.path.original !== close.path.original) {
-    var errorNode = {loc: openBlock.sexpr.loc};
+  if (close && close.path && openBlock.path.original !== close.path.original) {
+    var errorNode = {loc: openBlock.path.loc};
 
-    throw new Exception(openBlock.sexpr.path.original + ' doesn\'t match ' + close.path.original, errorNode);
+    throw new Exception(openBlock.path.original + ' doesn\'t match ' + close.path.original, errorNode);
   }
 
   program.blockParams = openBlock.blockParams;
@@ -108,7 +109,8 @@ export function prepareBlock(openBlock, program, inverseAndProgram, close, inver
   }
 
   return new this.BlockStatement(
-      openBlock.sexpr, program, inverse,
+      openBlock.path, openBlock.params, openBlock.hash,
+      program, inverse,
       openBlock.strip, inverseStrip, close && close.strip,
       this.locInfo(locInfo));
 }
diff --git a/lib/handlebars/compiler/printer.js b/lib/handlebars/compiler/printer.js
index 448331c03..55232cc45 100644
--- a/lib/handlebars/compiler/printer.js
+++ b/lib/handlebars/compiler/printer.js
@@ -45,7 +45,7 @@ PrintVisitor.prototype.Program = function(program) {
 };
 
 PrintVisitor.prototype.MustacheStatement = function(mustache) {
-  return this.pad('{{ ' + this.accept(mustache.sexpr) + ' }}');
+  return this.pad('{{ ' + this.SubExpression(mustache) + ' }}');
 };
 
 PrintVisitor.prototype.BlockStatement = function(block) {
@@ -53,7 +53,7 @@ PrintVisitor.prototype.BlockStatement = function(block) {
 
   out = out + this.pad('BLOCK:');
   this.padding++;
-  out = out + this.pad(this.accept(block.sexpr));
+  out = out + this.pad(this.SubExpression(block));
   if (block.program) {
     out = out + this.pad('PROGRAM:');
     this.padding++;
@@ -74,13 +74,12 @@ PrintVisitor.prototype.BlockStatement = function(block) {
 };
 
 PrintVisitor.prototype.PartialStatement = function(partial) {
-  var sexpr = partial.sexpr,
-      content = 'PARTIAL:' + sexpr.name.original;
-  if(sexpr.params[0]) {
-    content += ' ' + this.accept(sexpr.params[0]);
+  var content = 'PARTIAL:' + partial.name.original;
+  if(partial.params[0]) {
+    content += ' ' + this.accept(partial.params[0]);
   }
-  if (sexpr.hash) {
-    content += ' ' + this.accept(sexpr.hash);
+  if (partial.hash) {
+    content += ' ' + this.accept(partial.hash);
   }
   return this.pad('{{> ' + content + ' }}');
 };
diff --git a/lib/handlebars/compiler/visitor.js b/lib/handlebars/compiler/visitor.js
index 03af9153e..4101a4f04 100644
--- a/lib/handlebars/compiler/visitor.js
+++ b/lib/handlebars/compiler/visitor.js
@@ -71,17 +71,24 @@ Visitor.prototype = {
   },
 
   MustacheStatement: function(mustache) {
-    this.acceptRequired(mustache, 'sexpr');
+    this.acceptRequired(mustache, 'path');
+    this.acceptArray(mustache.params);
+    this.acceptKey(mustache, 'hash');
   },
 
   BlockStatement: function(block) {
-    this.acceptRequired(block, 'sexpr');
+    this.acceptRequired(block, 'path');
+    this.acceptArray(block.params);
+    this.acceptKey(block, 'hash');
+
     this.acceptKey(block, 'program');
     this.acceptKey(block, 'inverse');
   },
 
   PartialStatement: function(partial) {
-    this.acceptRequired(partial, 'sexpr');
+    this.acceptRequired(partial, 'name');
+    this.acceptArray(partial.params);
+    this.acceptKey(partial, 'hash');
   },
 
   ContentStatement: function(/* content */) {},
diff --git a/spec/ast.js b/spec/ast.js
index d464cf110..3b2a4ae20 100644
--- a/spec/ast.js
+++ b/spec/ast.js
@@ -26,7 +26,7 @@ describe('ast', function() {
     it('should store args', function() {
       var id = {isSimple: true},
           hash = {},
-          mustache = new handlebarsEnv.AST.MustacheStatement({}, true, {}, LOCATION_INFO);
+          mustache = new handlebarsEnv.AST.MustacheStatement({}, null, null, true, {}, LOCATION_INFO);
       equals(mustache.type, 'MustacheStatement');
       equals(mustache.escaped, true);
       testLocationInfoStorage(mustache);
@@ -40,10 +40,10 @@ describe('ast', function() {
     });
 
     it('stores location info', function(){
-      var sexprNode = new handlebarsEnv.AST.SubExpression([{ original: 'foo'}], null);
-      var mustacheNode = new handlebarsEnv.AST.MustacheStatement(sexprNode, false, {});
+      var mustacheNode = new handlebarsEnv.AST.MustacheStatement([{ original: 'foo'}], null, null, false, {});
       var block = new handlebarsEnv.AST.BlockStatement(
             mustacheNode,
+            null, null,
             {body: []},
             {body: []},
             {},
@@ -104,7 +104,7 @@ describe('ast', function() {
 
   describe('PartialStatement', function(){
     it('stores location info', function(){
-      var pn = new handlebarsEnv.AST.PartialStatement('so_partial', {}, LOCATION_INFO);
+      var pn = new handlebarsEnv.AST.PartialStatement('so_partial', [], {}, {}, LOCATION_INFO);
       testLocationInfoStorage(pn);
     });
   });
@@ -200,7 +200,7 @@ describe('ast', function() {
             block = ast.body[0];
 
         equals(block.program.body[0].value, '');
-        equals(block.program.body[1].sexpr.path.original, 'foo');
+        equals(block.program.body[1].path.original, 'foo');
         equals(block.program.body[2].value, '\n');
       });
       it('marks nested block mustaches as standalone', function() {
diff --git a/spec/data.js b/spec/data.js
index bb90df5a8..1678eea85 100644
--- a/spec/data.js
+++ b/spec/data.js
@@ -93,6 +93,17 @@ describe('data', function() {
     }, Error);
   });
 
+  it('data can be functions', function() {
+    var template = CompilerContext.compile('{{@hello}}');
+    var result = template({}, { data: { hello: function() { return 'hello'; } } });
+    equals('hello', result);
+  });
+  it('data can be functions with params', function() {
+    var template = CompilerContext.compile('{{@hello "hello"}}');
+    var result = template({}, { data: { hello: function(arg) { return arg; } } });
+    equals('hello', result);
+  });
+
   it("data is inherited downstream", function() {
     var template = CompilerContext.compile("{{#let foo=1 bar=2}}{{#let foo=bar.baz}}{{@bar}}{{@foo}}{{/let}}{{@foo}}{{/let}}", { data: true });
     var helpers = {
diff --git a/spec/visitor.js b/spec/visitor.js
index 0c23c0d64..32172309c 100644
--- a/spec/visitor.js
+++ b/spec/visitor.js
@@ -24,11 +24,10 @@ describe('Visitor', function() {
     visitor.BooleanLiteral = function(bool) {
       equal(bool.value, true);
 
-      equal(this.parents.length, 4);
+      equal(this.parents.length, 3);
       equal(this.parents[0].type, 'SubExpression');
-      equal(this.parents[1].type, 'SubExpression');
-      equal(this.parents[2].type, 'BlockStatement');
-      equal(this.parents[3].type, 'Program');
+      equal(this.parents[1].type, 'BlockStatement');
+      equal(this.parents[2].type, 'Program');
     };
     visitor.PathExpression = function(id) {
       equal(/(foo\.)?bar$/.test(id.original), true);
@@ -84,26 +83,26 @@ describe('Visitor', function() {
           var visitor = new Handlebars.Visitor();
 
           visitor.mutating = true;
-          visitor.SubExpression = function() {
+          visitor.PathExpression = function() {
             return false;
           };
 
           var ast = Handlebars.parse('{{foo 42}}');
           visitor.accept(ast);
-        }, Handlebars.Exception, 'MustacheStatement requires sexpr');
+        }, Handlebars.Exception, 'MustacheStatement requires path');
       });
       it('should throw when returning non-node responses', function() {
         shouldThrow(function() {
           var visitor = new Handlebars.Visitor();
 
           visitor.mutating = true;
-          visitor.SubExpression = function() {
+          visitor.PathExpression = function() {
             return {};
           };
 
           var ast = Handlebars.parse('{{foo 42}}');
           visitor.accept(ast);
-        }, Handlebars.Exception, 'Unexpected node type "undefined" found when accepting sexpr on MustacheStatement');
+        }, Handlebars.Exception, 'Unexpected node type "undefined" found when accepting path on MustacheStatement');
       });
     });
     describe('arrays', function() {
diff --git a/src/handlebars.yy b/src/handlebars.yy
index 6ca32d942..39f802757 100644
--- a/src/handlebars.yy
+++ b/src/handlebars.yy
@@ -30,7 +30,7 @@ rawBlock
   ;
 
 openRawBlock
-  : OPEN_RAW_BLOCK sexpr CLOSE_RAW_BLOCK -> { sexpr: $2 }
+  : OPEN_RAW_BLOCK helperName param* hash? CLOSE_RAW_BLOCK -> { path: $2, params: $3, hash: $4 }
   ;
 
 block
@@ -39,15 +39,15 @@ block
   ;
 
 openBlock
-  : OPEN_BLOCK sexpr blockParams? CLOSE -> { sexpr: $2, blockParams: $3, strip: yy.stripFlags($1, $4) }
+  : OPEN_BLOCK helperName param* hash? blockParams? CLOSE -> { path: $2, params: $3, hash: $4, blockParams: $5, strip: yy.stripFlags($1, $6) }
   ;
 
 openInverse
-  : OPEN_INVERSE sexpr blockParams? CLOSE -> { sexpr: $2, blockParams: $3, strip: yy.stripFlags($1, $4) }
+  : OPEN_INVERSE helperName param* hash? blockParams? CLOSE -> { path: $2, params: $3, hash: $4, blockParams: $5, strip: yy.stripFlags($1, $6) }
   ;
 
 openInverseChain
-  : OPEN_INVERSE_CHAIN sexpr blockParams? CLOSE -> { sexpr: $2, blockParams: $3, strip: yy.stripFlags($1, $4) }
+  : OPEN_INVERSE_CHAIN helperName param* hash? blockParams? CLOSE -> { path: $2, params: $3, hash: $4, blockParams: $5, strip: yy.stripFlags($1, $6) }
   ;
 
 inverseAndProgram
@@ -72,23 +72,12 @@ closeBlock
 mustache
   // Parsing out the '&' escape token at AST level saves ~500 bytes after min due to the removal of one parser node.
   // This also allows for handler unification as all mustache node instances can utilize the same handler
-  : OPEN sexpr CLOSE -> yy.prepareMustache($2, $1, yy.stripFlags($1, $3), @$)
-  | OPEN_UNESCAPED sexpr CLOSE_UNESCAPED -> yy.prepareMustache($2, $1, yy.stripFlags($1, $3), @$)
+  : OPEN helperName param* hash? CLOSE -> yy.prepareMustache($2, $3, $4, $1, yy.stripFlags($1, $5), @$)
+  | OPEN_UNESCAPED helperName param* hash? CLOSE_UNESCAPED -> yy.prepareMustache($2, $3, $4, $1, yy.stripFlags($1, $5), @$)
   ;
 
 partial
-  : OPEN_PARTIAL partial_expr CLOSE -> new yy.PartialStatement($2, yy.stripFlags($1, $3), yy.locInfo(@$))
-  ;
-
-partial_expr
-  : helperName param* hash? -> new yy.PartialExpression($1, $2, $3, yy.locInfo(@$))
-  | dataName -> new yy.PartialExpression($1, null, null, yy.locInfo(@$))
-  | OPEN_SEXPR sexpr CLOSE_SEXPR param* hash? -> new yy.PartialExpression($2, $4, $5, yy.locInfo(@$))
-  ;
-
-sexpr
-  : helperName param* hash? -> new yy.SubExpression($1, $2, $3, yy.locInfo(@$))
-  | dataName -> new yy.SubExpression($1, null, null, yy.locInfo(@$))
+  : OPEN_PARTIAL partialName param* hash? CLOSE -> new yy.PartialStatement($2, $3, $4, yy.stripFlags($1, $5), yy.locInfo(@$))
   ;
 
 param
@@ -97,7 +86,11 @@ param
   | NUMBER -> new yy.NumberLiteral($1, yy.locInfo(@$))
   | BOOLEAN -> new yy.BooleanLiteral($1, yy.locInfo(@$))
   | dataName -> $1
-  | OPEN_SEXPR sexpr CLOSE_SEXPR -> $2
+  | sexpr -> $1
+  ;
+
+sexpr
+  : OPEN_SEXPR helperName param* hash? CLOSE_SEXPR -> new yy.SubExpression($2, $3, $4, yy.locInfo(@$))
   ;
 
 hash
@@ -114,10 +107,16 @@ blockParams
 
 helperName
   : path -> $1
+  | dataName -> $1
   | STRING -> new yy.StringLiteral($1, yy.locInfo(@$)), yy.locInfo(@$)
   | NUMBER -> new yy.NumberLiteral($1, yy.locInfo(@$))
   ;
 
+partialName
+  : helperName -> $1
+  | sexpr -> $1
+  ;
+
 dataName
   : DATA pathSegments -> yy.preparePath(true, $2, @$)
   ;