fix($parse): treat falsy values as defined in assignment expressions

Closes #14990
Closes #14994

Author: m-amr

src/ng/parse.js

@@ -944,7 +944,7 @@ ASTCompiler.prototype = {
           self.if_(self.stage === 'inputs' || 's', function() {
             if (create && create !== 1) {
               self.if_(
-                self.not(self.nonComputedMember('s', ast.name)),
+                self.isNull(self.nonComputedMember('s', ast.name)),
                 self.lazyAssign(self.nonComputedMember('s', ast.name), '{}'));
             }
             self.assign(intoId, self.nonComputedMember('s', ast.name));
@@ -973,7 +973,7 @@ ASTCompiler.prototype = {
             }
           } else {
             if (create && create !== 1) {
-              self.if_(self.not(self.nonComputedMember(left, ast.property.name)), self.lazyAssign(self.nonComputedMember(left, ast.property.name), '{}'));
+              self.if_(self.isNull(self.nonComputedMember(left, ast.property.name)), self.lazyAssign(self.nonComputedMember(left, ast.property.name), '{}'));
             }
             expression = self.nonComputedMember(left, ast.property.name);
             self.assign(intoId, expression);
@@ -1155,6 +1155,10 @@ ASTCompiler.prototype = {
     return '!(' + expression + ')';
   },
 
+  isNull: function(expression) {
+    return expression + '==null';
+  },
+
   notNull: function(expression) {
     return expression + '!=null';
   },
@@ -1546,7 +1550,7 @@ ASTInterpreter.prototype = {
   identifier: function(name, context, create, expression) {
     return function(scope, locals, assign, inputs) {
       var base = locals && (name in locals) ? locals : scope;
-      if (create && create !== 1 && base && !(base[name])) {
+      if (create && create !== 1 && base && base[name] == null) {
         base[name] = {};
       }
       var value = base ? base[name] : undefined;
@@ -1583,7 +1587,7 @@ ASTInterpreter.prototype = {
     return function(scope, locals, assign, inputs) {
       var lhs = left(scope, locals, assign, inputs);
       if (create && create !== 1) {
-        if (lhs && !(lhs[right])) {
+        if (lhs && lhs[right] == null) {
           lhs[right] = {};
         }
       }

test/ng/parseSpec.js

@@ -3155,6 +3155,72 @@ describe('parser', function() {
           expect(isFunction(s.toString)).toBe(true);
           expect(l.toString).toBe(1);
         }));
+
+        it('should overwrite undefined / null scope properties when assigning', inject(function($parse) {
+          var scope;
+
+          scope = {};
+          $parse('a.b = 1')(scope);
+          $parse('c["d"] = 2')(scope);
+          expect(scope).toEqual({a: {b: 1}, c: {d: 2}});
+
+          scope = {a: {}};
+          $parse('a.b.c = 1')(scope);
+          $parse('a.c["d"] = 2')(scope);
+          expect(scope).toEqual({a: {b: {c: 1}, c: {d: 2}}});
+
+          scope = {a: undefined, c: undefined};
+          $parse('a.b = 1')(scope);
+          $parse('c["d"] = 2')(scope);
+          expect(scope).toEqual({a: {b: 1}, c: {d: 2}});
+
+          scope = {a: {b: undefined, c: undefined}};
+          $parse('a.b.c = 1')(scope);
+          $parse('a.c["d"] = 2')(scope);
+          expect(scope).toEqual({a: {b: {c: 1}, c: {d: 2}}});
+
+          scope = {a: null, c: null};
+          $parse('a.b = 1')(scope);
+          $parse('c["d"] = 2')(scope);
+          expect(scope).toEqual({a: {b: 1}, c: {d: 2}});
+
+          scope = {a: {b: null, c: null}};
+          $parse('a.b.c = 1')(scope);
+          $parse('a.c["d"] = 2')(scope);
+          expect(scope).toEqual({a: {b: {c: 1}, c: {d: 2}}});
+        }));
+
+        they('should not overwrite $prop scope properties when assigning', [0, false, '', NaN],
+          function(falsyValue) {
+            inject(function($parse) {
+              var scope;
+
+              scope = {a: falsyValue, c: falsyValue};
+              tryParseAndIgnoreException('a.b = 1');
+              tryParseAndIgnoreException('c["d"] = 2');
+              expect(scope).toEqual({a: falsyValue, c: falsyValue});
+
+              scope = {a: {b: falsyValue, c: falsyValue}};
+              tryParseAndIgnoreException('a.b.c = 1');
+              tryParseAndIgnoreException('a.c["d"] = 2');
+              expect(scope).toEqual({a: {b: falsyValue, c: falsyValue}});
+
+              // Helpers
+              //
+              // Normally assigning property on a primitive should throw exception in strict mode
+              // and silently fail in non-strict mode, IE seems to always have the non-strict-mode behavior,
+              // so if we try to use 'expect(function() {$parse('a.b=1')({a:false});).toThrow()' for testing
+              // the test will fail in case of IE because it will not throw exception, and if we just use
+              // '$parse('a.b=1')({a:false})' the test will fail because it will throw exception in case of Chrome
+              // so we use tryParseAndIgnoreException helper to catch the exception silently for all cases.
+              //
+              function tryParseAndIgnoreException(expression) {
+                try {
+                    $parse(expression)(scope);
+                } catch (error) {/* ignore exception */}
+              }
+            });
+          });
       });
 
       describe('literal', function() {