and now with if/else statements, CoffeeScript-in-CoffeeScript is language-complete -- now for the shakedown cruise

lib/coffee_script/nodes.js

@@ -1,5 +1,5 @@
 (function(){
-  var AccessorNode, ArrayNode, AssignNode, CallNode, ClosureNode, CodeNode, CommentNode, ExistenceNode, Expressions, ExtendsNode, ForNode, IDENTIFIER, IndexNode, LiteralNode, Node, ObjectNode, OpNode, ParentheticalNode, PushNode, RangeNode, ReturnNode, SliceNode, SplatNode, TAB, TRAILING_WHITESPACE, ThisNode, ThrowNode, TryNode, ValueNode, WhileNode, any, compact, del, dup, flatten, inherit, merge, statement;
+  var AccessorNode, ArrayNode, AssignNode, CallNode, ClosureNode, CodeNode, CommentNode, ExistenceNode, Expressions, ExtendsNode, ForNode, IDENTIFIER, IfNode, IndexNode, LiteralNode, Node, ObjectNode, OpNode, ParentheticalNode, PushNode, RangeNode, ReturnNode, SliceNode, SplatNode, TAB, TRAILING_WHITESPACE, ThisNode, ThrowNode, TryNode, ValueNode, WhileNode, any, compact, del, dup, flatten, inherit, merge, statement;
   var __hasProp = Object.prototype.hasOwnProperty;
   process.mixin(require('./scope'));
   // The abstract base class for all CoffeeScript nodes.
@@ -1290,4 +1290,113 @@
     }
   }));
   statement(ForNode);
+  // If/else statements. Switch/whens get compiled into these. Acts as an
+  // expression by pushing down requested returns to the expression bodies.
+  // Single-expression IfNodes are compiled into ternary operators if possible,
+  // because ternaries are first-class returnable assignable expressions.
+  IfNode = (exports.IfNode = inherit(Node, {
+    constructor: function constructor(condition, body, else_body, tags) {
+      this.condition = condition;
+      this.body = body && body.unwrap();
+      this.else_body = else_body && else_body.unwrap();
+      this.children = [this.condition, this.body, this.else_body];
+      this.tags = tags || {
+      };
+      if (this.condition instanceof Array) {
+        this.multiple = true;
+      }
+      if (this.tags.invert) {
+        this.condition = new OpNode('!', new ParentheticalNode(this.condition));
+      }
+      return this;
+    },
+    push: function push(else_body) {
+      var eb;
+      eb = else_body.unwrap();
+      this.else_body ? this.else_body.push(eb) : (this.else_body = eb);
+      return this;
+    },
+    force_statement: function force_statement() {
+      this.tags.statement = true;
+      return this;
+    },
+    // Rewrite a chain of IfNodes with their switch condition for equality.
+    rewrite_condition: function rewrite_condition(expression) {
+      var __a, __b, __c, cond;
+      this.condition = (function() {
+        if (this.multiple) {
+          __a = []; __b = this.condition;
+          for (__c = 0; __c < __b.length; __c++) {
+            cond = __b[__c];
+            __a.push(new OpNode('is', expression, cond));
+          }
+          return __a;
+        } else {
+          return new OpNode('is', expression, this.condition);
+        }
+      }).call(this);
+      if (this.is_chain()) {
+        this.else_body.rewrite_condition(expression);
+      }
+      return this;
+    },
+    // Rewrite a chain of IfNodes to add a default case as the final else.
+    add_else: function add_else(exprs) {
+      this.is_chain() ? this.else_body.add_else(exprs) : (this.else_body = exprs && exprs.unwrap());
+      return this;
+    },
+    // If the else_body is an IfNode itself, then we've got an if-else chain.
+    is_chain: function is_chain() {
+      return this.chain = this.chain || this.else_body && this.else_body instanceof IfNode;
+    },
+    // The IfNode only compiles into a statement if either of the bodies needs
+    // to be a statement.
+    is_statement: function is_statement() {
+      return this.statement = this.statement || !!(this.comment || this.tags.statement || this.body.is_statement() || (this.else_body && this.else_body.is_statement()));
+    },
+    compile_condition: function compile_condition(o) {
+      var __a, __b, __c, cond;
+      return ((function() {
+        __a = []; __b = flatten(this.condition);
+        for (__c = 0; __c < __b.length; __c++) {
+          cond = __b[__c];
+          __a.push(cond.compile(o));
+        }
+        return __a;
+      }).call(this)).join(' || ');
+    },
+    compile_node: function compile_node(o) {
+      return this.is_statement() ? this.compile_statement(o) : this.compile_ternary(o);
+    },
+    // Compile the IfNode as a regular if-else statement. Flattened chains
+    // force sub-else bodies into statement form.
+    compile_statement: function compile_statement(o) {
+      var body, child, com_dent, cond_o, else_part, if_dent, if_part, prefix;
+      child = del(o, 'chain_child');
+      cond_o = dup(o);
+      del(cond_o, 'returns');
+      o.indent = this.idt(1);
+      o.top = true;
+      if_dent = child ? '' : this.idt();
+      com_dent = child ? this.idt() : '';
+      prefix = this.comment ? this.comment.compile(cond_o) + '\n' + com_dent : '';
+      body = Expressions.wrap([body]).compile(o);
+      if_part = prefix + if_dent + 'if (' + compile_condition(cond_o) + ') {\n' + body + '\n' + this.idt() + '}';
+      if (!(this.else_body)) {
+        return if_part;
+      }
+      else_part = this.is_chain() ? ' else ' + this.else_body.compile(merge(o, {
+        indent: this.idt(),
+        chain_child: true
+      })) : ' else {\n' + Expressions.wrap(this.else_body).compile(o) + '\n' + this.idt() + '}';
+      return if_part + else_part;
+    },
+    // Compile the IfNode into a ternary operator.
+    compile_ternary: function compile_ternary(o) {
+      var else_part, if_part;
+      if_part = this.condition.compile(o) + ' ? ' + this.body.compile(o);
+      else_part = this.else_body ? this.else_body.compile(o) : 'null';
+      return if_part + ' : ' + else_part;
+    }
+  }));
 })();

lib/coffee_script/nodes.rb

@@ -1029,7 +1029,7 @@ module CoffeeScript
     # Compile the IfNode into a ternary operator.
     def compile_ternary(o)
       if_part   = "#{@condition.compile(o)} ? #{@body.compile(o)}"
-      else_part = @else_body ? "#{@else_body.compile(o)}" : 'null'
+      else_part = @else_body ? @else_body.compile(o) : 'null'
       "#{if_part} : #{else_part}"
     end
   end

lib/coffee_script/parser.js

@@ -462,7 +462,7 @@
           statement: true
         });
       }), o("Comment TERMINATOR When", function() {
-        return $3.add_comment($1);
+        return $3.comment = $1;
       })
     ],
     // The most basic form of "if".

src/nodes.coffee

@@ -945,7 +945,87 @@ ForNode: exports.ForNode: inherit Node, {
 
 statement ForNode
 
-
+# If/else statements. Switch/whens get compiled into these. Acts as an
+# expression by pushing down requested returns to the expression bodies.
+# Single-expression IfNodes are compiled into ternary operators if possible,
+# because ternaries are first-class returnable assignable expressions.
+IfNode: exports.IfNode: inherit Node, {
+
+  constructor: (condition, body, else_body, tags) ->
+    @condition: condition
+    @body:      body and body.unwrap()
+    @else_body: else_body and else_body.unwrap()
+    @children:  [@condition, @body, @else_body]
+    @tags:      tags or {}
+    @multiple:  true if @condition instanceof Array
+    @condition: new OpNode('!', new ParentheticalNode(@condition)) if @tags.invert
+    this
+
+  push: (else_body) ->
+    eb: else_body.unwrap()
+    if @else_body then @else_body.push(eb) else @else_body: eb
+    this
+
+  force_statement: ->
+    @tags.statement: true
+    this
+
+  # Rewrite a chain of IfNodes with their switch condition for equality.
+  rewrite_condition: (expression) ->
+    @condition: if @multiple
+      new OpNode('is', expression, cond) for cond in @condition
+    else
+      new OpNode('is', expression, @condition)
+    @else_body.rewrite_condition(expression) if @is_chain()
+    this
+
+  # Rewrite a chain of IfNodes to add a default case as the final else.
+  add_else: (exprs) ->
+    if @is_chain() then @else_body.add_else(exprs) else @else_body: exprs and exprs.unwrap()
+    this
+
+  # If the else_body is an IfNode itself, then we've got an if-else chain.
+  is_chain: ->
+    @chain ||= @else_body and @else_body instanceof IfNode
+
+  # The IfNode only compiles into a statement if either of the bodies needs
+  # to be a statement.
+  is_statement: ->
+    @statement ||= !!(@comment or @tags.statement or @body.is_statement() or (@else_body and @else_body.is_statement()))
+
+  compile_condition: (o) ->
+    (cond.compile(o) for cond in flatten(@condition)).join(' || ')
+
+  compile_node: (o) ->
+    if @is_statement() then @compile_statement(o) else @compile_ternary(o)
+
+  # Compile the IfNode as a regular if-else statement. Flattened chains
+  # force sub-else bodies into statement form.
+  compile_statement: (o) ->
+    child:        del o, 'chain_child'
+    cond_o:       dup o
+    del cond_o, 'returns'
+    o.indent:     @idt(1)
+    o.top:        true
+    if_dent:      if child then '' else @idt()
+    com_dent:     if child then @idt() else ''
+    prefix:       if @comment then @comment.compile(cond_o) + '\n' + com_dent else ''
+    body:         Expressions.wrap([body]).compile(o)
+    if_part:      prefix + if_dent + 'if (' + compile_condition(cond_o) + ') {\n' + body + '\n' + @idt() + '}'
+    return if_part unless @else_body
+    else_part: if @is_chain()
+      ' else ' + @else_body.compile(merge(o, {indent: @idt(), chain_child: true}))
+    else
+      ' else {\n' + Expressions.wrap(@else_body).compile(o) + '\n' + @idt() + '}'
+    if_part + else_part
+
+  # Compile the IfNode into a ternary operator.
+  compile_ternary: (o) ->
+    if_part:    @condition.compile(o) + ' ? ' + @body.compile(o)
+    else_part:  if @else_body then @else_body.compile(o) else 'null'
+    if_part + ' : ' + else_part
+
+}
 
 
 

src/parser.coffee

@@ -405,7 +405,7 @@ grammar: {
   When: [
     o "LEADING_WHEN SimpleArgs Block",          -> new IfNode($2, $3, null, {statement: true})
     o "LEADING_WHEN SimpleArgs Block TERMINATOR", -> new IfNode($2, $3, null, {statement: true})
-    o "Comment TERMINATOR When",                -> $3.add_comment($1)
+    o "Comment TERMINATOR When",                -> $3.comment: $1
   ]
 
   # The most basic form of "if".