feat($parse): add support for ternary operators to parser

Add '?' token to lexer, add ternary rule to parser at
(hopefully) proper precedence and associativity (based
on https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Operators/Operator_Precedence).
Since (exp1 && exp2 || exp3) is supported by the parser,
and (exp1 ? exp2 : exp3) works the same way, it seems
reasonable to add this minor form of control to templates
(see angular#719).

Author: zachsnow

src/ng/parse.js

@@ -58,7 +58,7 @@ function lex(text, csp){
          (token=tokens[tokens.length-1])) {
         token.json = token.text.indexOf('.') == -1;
       }
-    } else if (is('(){}[].,;:')) {
+    } else if (is('(){}[].,;:?')) {
       tokens.push({
         index:index,
         text:ch,
@@ -359,6 +359,14 @@ function parser(text, json, $filter, csp){
     });
   }
 
+  function ternaryFn(left, middle, right){
+    return extend(function(self, locals){
+      return left(self, locals) ? middle(self, locals) : right(self, locals);
+    }, {
+      constant: left.constant && middle.constant && right.constant
+    });
+  }
+  
   function binaryFn(left, fn, right) {
     return extend(function(self, locals) {
       return fn(self, locals, left, right);
@@ -427,17 +435,18 @@ function parser(text, json, $filter, csp){
   function expression() {
     return assignment();
   }
+  
 
   function _assignment() {
-    var left = logicalOR();
+    var left = ternary();
     var right;
     var token;
     if ((token = expect('='))) {
       if (!left.assign) {
         throwError("implies assignment but [" +
           text.substring(0, token.index) + "] can not be assigned to", token);
       }
-      right = logicalOR();
+      right = ternary();
       return function(self, locals){
         return left.assign(self, right(self, locals), locals);
       };
@@ -446,6 +455,25 @@ function parser(text, json, $filter, csp){
     }
   }
 
+  function ternary() {
+    var left = logicalOR();
+    var middle;
+    var right;
+    var token;
+    if((token = expect('?'))){
+      middle = ternary();
+      if((token = expect(':'))){
+        return ternaryFn(left, middle, ternary());
+      }
+      else {
+        throwError('expected :', token);
+      }
+    }
+    else {
+      return left;
+    }
+  }
+  
   function logicalOR() {
     var left = logicalAND();
     var token;

test/ng/parseSpec.js

@@ -103,6 +103,14 @@ describe('parser', function() {
       expect(tokens[7].text).toEqual('===');
       expect(tokens[8].text).toEqual('!==');
     });
+    
+    it('should tokenize logical and ternary', function() {
+      var tokens = lex("&& || ? :");
+      expect(tokens[0].text).toEqual('&&');
+      expect(tokens[1].text).toEqual('||');
+      expect(tokens[2].text).toEqual('?');
+      expect(tokens[3].text).toEqual(':');
+    });
 
     it('should tokenize statements', function() {
       var tokens = lex("a;b;");
@@ -220,6 +228,52 @@ describe('parser', function() {
         expect(scope.$eval("0||2")).toEqual(0||2);
         expect(scope.$eval("0||1&&2")).toEqual(0||1&&2);
       });
+      
+      it('should parse ternary', function(){
+        var f = scope.f = function(){ return true; };
+        var g = scope.g = function(){ return false; };
+        var h = scope.h = function(){ return 'asd'; };
+        var i = scope.i = function(){ return 123; };
+        var id = scope.id = function(x){ return x; };
+
+        // Simple.
+        expect(scope.$eval('0?0:2')).toEqual(0?0:2);
+        expect(scope.$eval('1?0:2')).toEqual(1?0:2);
+        
+        // Nested on the left.
+        expect(scope.$eval('0?0?0:0:2')).toEqual(0?0?0:0:2);
+        expect(scope.$eval('1?0?0:0:2')).toEqual(1?0?0:0:2);
+        expect(scope.$eval('0?1?0:0:2')).toEqual(0?1?0:0:2);
+        expect(scope.$eval('0?0?1:0:2')).toEqual(0?0?1:0:2);
+        expect(scope.$eval('0?0?0:2:3')).toEqual(0?0?0:2:3);
+        expect(scope.$eval('1?1?0:0:2')).toEqual(1?1?0:0:2);
+        expect(scope.$eval('1?1?1:0:2')).toEqual(1?1?1:0:2);
+        expect(scope.$eval('1?1?1:2:3')).toEqual(1?1?1:2:3);
+        expect(scope.$eval('1?1?1:2:3')).toEqual(1?1?1:2:3);
+        
+        // Nested on the right.
+        expect(scope.$eval('0?0:0?0:2')).toEqual(0?0:0?0:2);
+        expect(scope.$eval('1?0:0?0:2')).toEqual(1?0:0?0:2);
+        expect(scope.$eval('0?1:0?0:2')).toEqual(0?1:0?0:2);
+        expect(scope.$eval('0?0:1?0:2')).toEqual(0?0:1?0:2);
+        expect(scope.$eval('0?0:0?2:3')).toEqual(0?0:0?2:3);
+        expect(scope.$eval('1?1:0?0:2')).toEqual(1?1:0?0:2);
+        expect(scope.$eval('1?1:1?0:2')).toEqual(1?1:1?0:2);
+        expect(scope.$eval('1?1:1?2:3')).toEqual(1?1:1?2:3);
+        expect(scope.$eval('1?1:1?2:3')).toEqual(1?1:1?2:3);
+        
+        // Precedence with respect to logical operators.
+        expect(scope.$eval('0&&1?0:1')).toEqual(0&&1?0:1);
+        expect(scope.$eval('0&&1?0:1')).toEqual((0&&1)?0:1);
+        expect(scope.$eval('1||0?0:0')).toEqual(1||0?0:0);
+        expect(scope.$eval('1||0?0:0')).toEqual((1||0)?0:0);
+        
+        // Function calls.
+        expect(scope.$eval('f() ? h() : i()')).toEqual(f() ? h() : i());
+        expect(scope.$eval('g() ? h() : i()')).toEqual(g() ? h() : i());
+        expect(scope.$eval('f() ? h() : i()')).toEqual(f() ? h() : i());
+        expect(scope.$eval('id(g() ? h() : i())')).toEqual(id(g() ? h() : i()));
+      });
 
       it('should parse string', function() {
         expect(scope.$eval("'a' + 'b c'")).toEqual("ab c");