Added support for subexpressions

Handlebars now supports subexpressions.

    {{foo (bar 3)}}

Subexpressions are always evaluated as helpers; if
`3` were omitted from the above example, `bar`
would be invoked as a param-less helper, even
though a top-levell `{{bar}}` would be considered
ambiguous.

The return value of a subexpression helper is
passed in as a parameter of a parent subexpression
helper, even in string params mode. Their type,
as listed in `options.types` or `options.hashTypes`
in string params mode, is "sexpr".

The main conceptual change in the Handlebars code
is that there is a new AST.SexprNode that manages
the params/hash passed into a mustache, as well
as the logic that governs whether that mustache
is a helper invocation, property lookup, etc.
MustacheNode, which used to manage this stuff,
still exists, but only manages things like
white-space stripping and whether the mustache
is escaped or not. So, a MustacheNode _has_
a SexprNode.

The introduction of subexpressions is fully
backwards compatible, but a few things needed
to change about the compiled output of a template
in order to support subexpressions. The main one
is that the options hash is no longer stashed in
a local `options` var before being passed to
either the helper being invoked or the
`helperMissing` fallback. Rather, the options
object is inlined in these cases. This does
mean compiled template sizes will be a little
bit larger, even those that don't make use of
subexpressions, but shouldn't have any noticeable
impact on performance when actually rendering
templates as only one of these inlined objects
will actually get evaluated.

1 files changed, 46 insertions, 44 deletions

diff --git a/lib/handlebars/compiler/compiler.js b/lib/handlebars/compiler/compiler.js
index 259c543..00353a8 100644
--- a/lib/handlebars/compiler/compiler.js
+++ b/lib/handlebars/compiler/compiler.js
@@ -156,12 +156,13 @@ Compiler.prototype = {
       inverse = this.compileProgram(inverse);
     }
 
-    var type = this.classifyMustache(mustache);
+    var sexpr = mustache.sexpr;
+    var type = this.classifySexpr(sexpr);
 
     if (type === "helper") {
-      this.helperMustache(mustache, program, inverse);
+      this.helperSexpr(sexpr, program, inverse);
     } else if (type === "simple") {
-      this.simpleMustache(mustache);
+      this.simpleSexpr(sexpr);
 
       // now that the simple mustache is resolved, we need to
       // evaluate it by executing `blockHelperMissing`
@@ -170,7 +171,7 @@ Compiler.prototype = {
       this.opcode('emptyHash');
       this.opcode('blockValue');
     } else {
-      this.ambiguousMustache(mustache, program, inverse);
+      this.ambiguousSexpr(sexpr, program, inverse);
 
       // now that the simple mustache is resolved, we need to
       // evaluate it by executing `blockHelperMissing`
@@ -198,6 +199,12 @@ Compiler.prototype = {
         }
         this.opcode('getContext', val.depth || 0);
         this.opcode('pushStringParam', val.stringModeValue, val.type);
+
+        if (val.type === 'sexpr') {
+          // Subexpressions get evaluated and passed in
+          // in string params mode.
+          this.sexpr(val);
+        }
       } else {
         this.accept(val);
       }
@@ -226,26 +233,17 @@ Compiler.prototype = {
   },
 
   mustache: function(mustache) {
-    var options = this.options;
-    var type = this.classifyMustache(mustache);
-
-    if (type === "simple") {
-      this.simpleMustache(mustache);
-    } else if (type === "helper") {
-      this.helperMustache(mustache);
-    } else {
-      this.ambiguousMustache(mustache);
-    }
+    this.sexpr(mustache.sexpr);
 
-    if(mustache.escaped && !options.noEscape) {
+    if(mustache.escaped && !this.options.noEscape) {
       this.opcode('appendEscaped');
     } else {
       this.opcode('append');
     }
   },
 
-  ambiguousMustache: function(mustache, program, inverse) {
-    var id = mustache.id,
+  ambiguousSexpr: function(sexpr, program, inverse) {
+    var id = sexpr.id,
         name = id.parts[0],
         isBlock = program != null || inverse != null;
 
@@ -257,8 +255,8 @@ Compiler.prototype = {
     this.opcode('invokeAmbiguous', name, isBlock);
   },
 
-  simpleMustache: function(mustache) {
-    var id = mustache.id;
+  simpleSexpr: function(sexpr) {
+    var id = sexpr.id;
 
     if (id.type === 'DATA') {
       this.DATA(id);
@@ -274,9 +272,9 @@ Compiler.prototype = {
     this.opcode('resolvePossibleLambda');
   },
 
-  helperMustache: function(mustache, program, inverse) {
-    var params = this.setupFullMustacheParams(mustache, program, inverse),
-        name = mustache.id.parts[0];
+  helperSexpr: function(sexpr, program, inverse) {
+    var params = this.setupFullMustacheParams(sexpr, program, inverse),
+        name = sexpr.id.parts[0];
 
     if (this.options.knownHelpers[name]) {
       this.opcode('invokeKnownHelper', params.length, name);
@@ -287,6 +285,18 @@ Compiler.prototype = {
     }
   },
 
+  sexpr: function(sexpr) {
+    var type = this.classifySexpr(sexpr);
+
+    if (type === "simple") {
+      this.simpleSexpr(sexpr);
+    } else if (type === "helper") {
+      this.helperSexpr(sexpr);
+    } else {
+      this.ambiguousSexpr(sexpr);
+    }
+  },
+
   ID: function(id) {
     this.addDepth(id.depth);
     this.opcode('getContext', id.depth);
@@ -349,14 +359,14 @@ Compiler.prototype = {
     }
   },
 
-  classifyMustache: function(mustache) {
-    var isHelper   = mustache.isHelper;
-    var isEligible = mustache.eligibleHelper;
+  classifySexpr: function(sexpr) {
+    var isHelper   = sexpr.isHelper;
+    var isEligible = sexpr.eligibleHelper;
     var options    = this.options;
 
     // if ambiguous, we can possibly resolve the ambiguity now
     if (isEligible && !isHelper) {
-      var name = mustache.id.parts[0];
+      var name = sexpr.id.parts[0];
 
       if (options.knownHelpers[name]) {
         isHelper = true;
@@ -383,35 +393,27 @@ Compiler.prototype = {
 
         this.opcode('getContext', param.depth || 0);
         this.opcode('pushStringParam', param.stringModeValue, param.type);
+
+        if (param.type === 'sexpr') {
+          // Subexpressions get evaluated and passed in
+          // in string params mode.
+          this.sexpr(param);
+        }
       } else {
         this[param.type](param);
       }
     }
   },
 
-  setupMustacheParams: function(mustache) {
-    var params = mustache.params;
-    this.pushParams(params);
-
-    if(mustache.hash) {
-      this.hash(mustache.hash);
-    } else {
-      this.opcode('emptyHash');
-    }
-
-    return params;
-  },
-
-  // this will replace setupMustacheParams when we're done
-  setupFullMustacheParams: function(mustache, program, inverse) {
-    var params = mustache.params;
+  setupFullMustacheParams: function(sexpr, program, inverse) {
+    var params = sexpr.params;
     this.pushParams(params);
 
     this.opcode('pushProgram', program);
     this.opcode('pushProgram', inverse);
 
-    if(mustache.hash) {
-      this.hash(mustache.hash);
+    if (sexpr.hash) {
+      this.hash(sexpr.hash);
     } else {
       this.opcode('emptyHash');
     }