adding existence soaks for indexed-lookup property accesses: obj?['property']

lib/grammar.js

@@ -285,6 +285,8 @@
     // Indexing into an object or array.
     Index: [o("INDEX_START Expression INDEX_END", function() {
         return new IndexNode($2);
+      }), o("SOAKED_INDEX_START Expression SOAKED_INDEX_END", function() {
+        return new IndexNode($2, 'soak');
       })
     ],
     // An object literal.

lib/lexer.js

@@ -285,24 +285,30 @@
   // Multi-character operators are also literal tokens, so that Racc can assign
   // the proper order of operations.
   lex.prototype.literal_token = function literal_token() {
-    var match, tag, value;
+    var match, not_spaced, tag, value;
     match = this.chunk.match(OPERATOR);
     value = match && match[1];
     if (value && value.match(CODE)) {
       this.tag_parameters();
     }
     value = value || this.chunk.substr(0, 1);
+    not_spaced = !this.prev() || !this.prev().spaced;
     tag = value;
     if (value.match(ASSIGNMENT)) {
       tag = 'ASSIGN';
       if (JS_FORBIDDEN.indexOf(this.value()) >= 0) {
         throw new Error('SyntaxError: Reserved word "' + this.value() + '" on line ' + this.line + ' can\'t be assigned');
       }
-    }
-    if (value === ';') {
+    } else if (value === ';') {
       tag = 'TERMINATOR';
-    }
-    if (CALLABLE.indexOf(this.tag()) >= 0 && (!this.prev() || !this.prev().spaced)) {
+    } else if (value === '[' && this.tag() === '?' && not_spaced) {
+      tag = 'SOAKED_INDEX_START';
+      this.soaked_index = true;
+      this.tokens.pop();
+    } else if (value === ']' && this.soaked_index) {
+      tag = 'SOAKED_INDEX_END';
+      this.soaked_index = false;
+    } else if (CALLABLE.indexOf(this.tag()) >= 0 && not_spaced) {
       if (value === '(') {
         tag = 'CALL_START';
       }

lib/nodes.js

@@ -379,7 +379,7 @@
       for (_b = 0; _b < _a.length; _b++) {
         prop = _a[_b];
         this.source = baseline;
-        if (prop instanceof AccessorNode && prop.soak) {
+        if (prop.soak_node) {
           soaked = true;
           if (this.base instanceof CallNode && prop === props[0]) {
             temp = o.scope.free_variable();
@@ -511,7 +511,7 @@
     constructor: function constructor(name, tag) {
       this.children = [(this.name = name)];
       this.prototype = tag === 'prototype';
-      this.soak = tag === 'soak';
+      this.soak_node = tag === 'soak';
       return this;
     },
     compile_node: function compile_node(o) {
@@ -521,8 +521,9 @@
   // An indexed accessor into a part of an array or object.
   IndexNode = (exports.IndexNode = inherit(Node, {
     type: 'Index',
-    constructor: function constructor(index) {
+    constructor: function constructor(index, tag) {
       this.children = [(this.index = index)];
+      this.soak_node = tag === 'soak';
       return this;
     },
     compile_node: function compile_node(o) {

lib/rewriter.js

@@ -9,7 +9,7 @@
   // indentation, and single-line flavors of expressions.
   exports.Rewriter = (re = function re() {  });
   // Tokens that must be balanced.
-  BALANCED_PAIRS = [['(', ')'], ['[', ']'], ['{', '}'], ['INDENT', 'OUTDENT'], ['PARAM_START', 'PARAM_END'], ['CALL_START', 'CALL_END'], ['INDEX_START', 'INDEX_END']];
+  BALANCED_PAIRS = [['(', ')'], ['[', ']'], ['{', '}'], ['INDENT', 'OUTDENT'], ['PARAM_START', 'PARAM_END'], ['CALL_START', 'CALL_END'], ['INDEX_START', 'INDEX_END'], ['SOAKED_INDEX_START', 'SOAKED_INDEX_END']];
   // Tokens that signal the start of a balanced pair.
   EXPRESSION_START = (function() {
     _a = []; _b = BALANCED_PAIRS;

src/grammar.coffee

@@ -251,6 +251,7 @@ grammar: {
   # Indexing into an object or array.
   Index: [
     o "INDEX_START Expression INDEX_END",       -> new IndexNode($2)
+    o "SOAKED_INDEX_START Expression SOAKED_INDEX_END", -> new IndexNode($2, 'soak')
   ]
 
   # An object literal.

src/lexer.coffee

@@ -246,13 +246,21 @@ lex::literal_token: ->
   value: match and match[1]
   @tag_parameters() if value and value.match(CODE)
   value ||= @chunk.substr(0, 1)
+  not_spaced: not @prev() or not @prev().spaced
   tag: value
   if value.match(ASSIGNMENT)
     tag: 'ASSIGN'
     throw new Error('SyntaxError: Reserved word "' + @value() + '" on line ' + @line + ' can\'t be assigned') if JS_FORBIDDEN.indexOf(@value()) >= 0
-  tag: 'TERMINATOR' if value == ';'
-
-  if CALLABLE.indexOf(@tag()) >= 0 and (not @prev() or not @prev().spaced)
+  else if value is ';'
+    tag: 'TERMINATOR'
+  else if value is '[' and @tag() is '?' and not_spaced
+    tag: 'SOAKED_INDEX_START'
+    @soaked_index: true
+    @tokens.pop()
+  else if value is ']' and @soaked_index
+    tag: 'SOAKED_INDEX_END'
+    @soaked_index: false
+  else if CALLABLE.indexOf(@tag()) >= 0 and not_spaced
     tag: 'CALL_START'  if value is '('
     tag: 'INDEX_START' if value is '['
   @token tag, value

src/nodes.coffee

@@ -283,7 +283,7 @@ ValueNode: exports.ValueNode: inherit Node, {
 
     for prop in props
       @source: baseline
-      if prop instanceof AccessorNode and prop.soak
+      if prop.soak_node
         soaked: true
         if @base instanceof CallNode and prop is props[0]
           temp: o.scope.free_variable()
@@ -405,7 +405,7 @@ AccessorNode: exports.AccessorNode: inherit Node, {
   constructor: (name, tag) ->
     @children:  [@name: name]
     @prototype: tag is 'prototype'
-    @soak:      tag is 'soak'
+    @soak_node: tag is 'soak'
     this
 
   compile_node: (o) ->
@@ -417,8 +417,9 @@ AccessorNode: exports.AccessorNode: inherit Node, {
 IndexNode: exports.IndexNode: inherit Node, {
   type: 'Index'
 
-  constructor: (index) ->
-    @children: [@index: index]
+  constructor: (index, tag) ->
+    @children:  [@index: index]
+    @soak_node: tag is 'soak'
     this
 
   compile_node: (o) ->

src/rewriter.coffee

@@ -7,7 +7,8 @@ exports.Rewriter: re: ->
 
 # Tokens that must be balanced.
 BALANCED_PAIRS: [['(', ')'], ['[', ']'], ['{', '}'], ['INDENT', 'OUTDENT'],
-  ['PARAM_START', 'PARAM_END'], ['CALL_START', 'CALL_END'], ['INDEX_START', 'INDEX_END']]
+  ['PARAM_START', 'PARAM_END'], ['CALL_START', 'CALL_END'],
+  ['INDEX_START', 'INDEX_END'], ['SOAKED_INDEX_START', 'SOAKED_INDEX_END']]
 
 # Tokens that signal the start of a balanced pair.
 EXPRESSION_START: pair[0] for pair in BALANCED_PAIRS

test/test_existence.coffee

@@ -41,10 +41,16 @@ obj: {
 
 ok obj?.prop is "hello"
 
+ok obj?['prop'] is "hello"
+
 ok obj.prop?.length is 5
 
+ok obj?['prop']?['length'] is 5
+
 ok obj?.prop?.non?.existent?.property is undefined
 
+ok obj?['non']?['existent'].property is undefined
+
 
 # Soaks and caches method calls as well.