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easejs/test/test-class-visibility.js

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/**
* Tests class member visibility (public, private, protected)
*
* Copyright (C) 2010 Mike Gerwitz
*
* This file is part of ease.js.
*
* ease.js is free software: you can redistribute it and/or modify it under the
* terms of the GNU Lesser General Public License as published by the Free
* Software Foundation, either version 3 of the License, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* @author Mike Gerwitz
* @package test
*/
var common = require( './common' ),
assert = require( 'assert' ),
Class = common.require( 'class' ),
Interface = common.require( 'interface' ),
util = common.require( 'util' ),
pub = 'foo',
prot = 'bar',
priv = 'baz',
pubf = function() { return pub; },
protf = function() { return prot; },
privf = function() { return priv; },
// new anonymous class instance
Foo = Class.extend( {
'public pub': pub,
'protected peeps': prot,
'private parts': priv,
'public pubf': pubf,
'protected protf': protf,
'private privf': privf,
'virtual public getProp': function( name )
{
// return property, allowing us to break encapsulation for
// protected/private properties (for testing purposes)
return this[ name ];
},
/**
* Does the same as the above, but we won't override this one
*/
'public nonOverrideGetProp': function( name )
{
return this[ name ];
},
/**
* Allows us to set a value from within the class
*/
'public setValue': function( name, value )
{
this[ name ] = value;
},
'public getSelf': function()
{
return this;
},
'virtual public getSelfOverride': function()
{
// override me
},
'public getPrivProp': function()
{
return this.parts;
},
'public invokePriv': function()
{
return this._priv();
},
'private _priv': function()
{
return priv;
},
}),
// instance of Foo
foo = Foo(),
// subtype
SubFoo = Foo.extend({
'private _pfoo': 'baz',
'override public getSelfOverride': function()
{
// return this from overridden method
return this;
},
/**
* We have to override this so that 'this' is not bound to the supertype
*/
'override public getProp': function( name )
{
// return property, allowing us to break encapsulation for
// protected/private properties (for testing purposes)
return this[ name ];
},
'private myOwnPrivateFoo': function() {},
}),
sub_foo = SubFoo(),
sub_sub_foo = SubFoo.extend( {} )()
;
/**
* Public members are the only members added to the instance's prototype to be
* accessible externally
*/
( function testPublicMembersAreAccessbileExternally()
{
assert.equal(
foo.pub,
pub,
"Public properties are accessible via public interface"
);
assert.equal(
foo.pubf(),
pub,
"Public methods are accessible via public interface"
);
} )();
/**
* For reasons that are discussed in the next test (writing to public
* properties), we need to make sure public members are available internally.
* Actually, we don't need to test public methods, really, but it's in there for
* good measure. Who knows what bugs may be introduced in the future.
*
* This ensures that the getter is properly proxying the value to us.
*/
( function testPublicMembersAreAccessibleInternally()
{
assert.equal(
foo.getProp( 'pub' ),
pub,
"Public properties are accessible internally"
);
assert.equal(
foo.getProp( 'pubf' )(),
pub,
"Public methods are accessible internally"
);
} )();
/**
* This may sound like an odd test, but it's actually very important. Due to how
* private/protected members are implemented, it compromises public members. In
* fact, public members would not work internally without what is essentially a
* proxy via setters.
*
* This test is to ensure that the setter is properly forwarding writes to the
* object within the prototype chain containing the public values. Otherwise,
* setting the value would simply mask it in the prototype chain. The value
* would appear to have changed internally, but when accessed externally, the
* value would still be the same. That would obviously be a problem ;)
*/
( function testPublicPropertiesAreWritableInternally()
{
var val = 'moomookittypoo';
// start by setting the value
foo.setValue( 'pub', val );
// we should see that change internally...
assert.equal(
foo.getProp( 'pub' ),
val,
"Setting the value of a public property internally should be " +
"observable /internally/"
);
// ...as well as externally
assert.equal(
foo.pub,
val,
"Setting the value of a public property internally should be " +
"observable /externally/"
);
} )();
( function testProtectedAndPrivateMembersAreNotAccessibleExternally()
{
// browsers that do not support the property proxy will not support
// encapsulating properties
if ( util.definePropertyFallback() )
{
return;
}
assert.equal(
foo.peeps,
undefined,
"Protected properties are inaccessible via public interface"
);
assert.equal(
foo.parts,
undefined,
"Private properties are inaccessible via public interface"
);
assert.equal(
foo.protf,
undefined,
"Protected methods are inaccessible via public interface"
);
assert.equal(
foo.privf,
undefined,
"Private methods are inaccessible via public interface"
);
} )();
/**
* Protected members should be accessible from within class methods
*/
( function testProtectedMembersAreAccessibleInternally()
{
assert.equal(
foo.getProp( 'peeps' ),
prot,
"Protected properties are available internally"
);
// invoke rather than checking for equality, because the method may be
// wrapped
assert.equal(
foo.getProp( 'protf' )(),
prot,
"Protected methods are available internally"
);
} )();
/**
* Private members should be accessible from within class methods
*/
( function testPrivateMembersAreAccessibleInternally()
{
assert.equal(
foo.getProp( 'parts' ),
priv,
"Private properties are available internally"
);
// invoke rather than checking for equality, because the method may be
// wrapped
assert.equal(
foo.getProp( 'privf' )(),
priv,
"Private methods are available internally"
);
} )();
/**
* Inheritance 101; protected members should be available to subtypes
*/
( function testProtectedMembersAreInheritedFromParent()
{
assert.equal(
sub_foo.getProp( 'peeps' ),
prot,
"Protected properties are available to subtypes"
);
// invoke rather than checking for equality, because the method may be
// wrapped
assert.equal(
sub_foo.getProp( 'protf' )(),
prot,
"Protected methods are available to subtypes"
);
} )();
/**
* Interface 101-2: We do not want private members to be available to subtypes.
*/
( function testPrivateMembersOfSupertypesAreInaccessibleToSubtypes()
{
// browsers that do not support the property proxy will not support
// encapsulating properties
if ( util.definePropertyFallback() )
{
return;
}
assert.equal(
sub_foo.getProp( 'parts' ),
undefined,
"Private properties of supertypes should be unavailable to subtypes"
);
// invoke rather than checking for equality, because the method may be
// wrapped
assert.equal(
sub_foo.getProp( 'privf' ),
undefined,
"Private methods of supertypes should be unavailable to subtypes"
);
} )();
/**
* For good measure, let's make sure we didn't screw anything up. To ensure that
* the same object isn't being passed around to subtypes, ensure that multiple
* class instances do not share prototypes.
*/
( function testProtectedMembersAreNotSharedBetweenClassInstances()
{
var val = 'foobar';
foo.setValue( 'prot', val );
// ensure that class instances do not share values (ensuring the same object
// isn't somehow being passed around)
assert.notEqual(
sub_foo.getProp( 'prot' ),
val,
"Class instances do not share protected values (subtype)"
);
// do the same for multiple instances of the same type
var sub_foo2 = SubFoo();
sub_foo2.setValue( 'prot', val );
assert.notEqual(
sub_foo.getProp( 'prot' ),
val,
"Class instances do not share protected values (same type)"
);
} )();
/**
* When a method is called, 'this' is bound to the property object containing
* private and protected members. Returning 'this' would therefore be a very bad
* thing. Not only would it break encapsulation, but it would likely have other
* problems down the road.
*
* Therefore, we have to check the return value of the method. If the return
* value is the property object that it was bound to, we need to replace the
* return value with the actual class instance. This allows us to transparently
* enforce encapsulation. How sweet is that?
*/
( function testReturningSelfFromMethodShouldReturnInstanceNotPropObj()
{
assert.deepEqual(
foo.getSelf(),
foo,
"Returning 'this' from a method should return instance of self"
);
// what happens in the case of inheritance?
assert.deepEqual(
sub_foo.getSelf(),
sub_foo,
"Returning 'this' from a super method should return the subtype"
);
// finally, overridden methods should still return the instance
assert.deepEqual(
sub_foo.getSelfOverride(),
sub_foo,
"Returning 'this' from a overridden method should return the subtype"
);
} )();
/**
* This one's a particularly nasty bug that snuck up on me. Private members
* should not be accessible to subtypes; that's a given. However, they need to
* be accessible to the parent methods. For example, let's say class Foo
* contains public method bar(), which invokes private method _baz(). This is
* perfectly legal. Then SubFoo extends Foo, but does not override method bar().
* Invoking method bar() should still be able to invoke private method _baz(),
* because, from the perspective of the parent class, that operation is
* perfectly legal.
*
* The resolution of this bug required a slight system redesign. The short-term
* fix was to declare any needed private members are protected, so that they
* were accessible by the subtype.
*/
( function testParentMethodsCanAccessPrivateMembersOfParent()
{
// properties
assert.equal(
sub_foo.getPrivProp(),
priv,
"Parent methods should have access to the private properties of the " +
"parent"
);
// methods
assert.equal(
sub_foo.invokePriv(),
priv,
"Parent methods should have access to the private methods of the parent"
);
// should apply to super-supertypes too
assert.equal(
sub_sub_foo.getPrivProp(),
priv,
"Parent methods should have access to the private properties of the " +
"parent (2)"
);
assert.equal(
sub_sub_foo.invokePriv(),
priv,
"Parent methods should have access to the private methods of the " +
"parent (2)"
);
} )();
/**
* When a parent method is invoked, the parent should not be given access to the
* private members of the invoking subtype. Why?
*
* This is not a matter of whether or not this is possible to do. In fact it's
* relatively simple to implement. The issue is whether or not it makes sense.
* Consider a compiled language. Let's say Foo and SubFoo (as defined in this
* test case) were written in C++. Should Foo have access to a private property
* on SubFoo when it is overridden?
*
* No - that doesn't make sense. The private member is not a member of Foo and
* therefore Foo would fail to even compile. Alright, but we don't have such a
* restriction in our case. So why not implement it?
*
* Proponents of such an implementation are likely thinking of the act of
* inheriting methods as a copy/paste type of scenario. If we inherit public
* method baz(), and it were a copy/paste type of situation, then surely baz()
* would have access to all of SubFoo's private members. But that is not the
* case. Should baz() be defined as a member of Foo, then its scope is
* restricted to Foo and its supertypes. That is not how OO works. It is /not/
* copy/paste. It is inheriting functionality.
*/
( function testParentsShouldNotHaveAccessToPrivateMembersOfSubtypes()
{
// browsers that do not support the property proxy will not support
// encapsulating properties
if ( util.definePropertyFallback() )
{
return;
}
// property
assert.equal(
sub_foo.nonOverrideGetProp( '_pfoo' ),
undefined,
"Parent should not have access to private properties of subtype when " +
"a parent method is invoked"
);
// member
assert.equal(
sub_foo.nonOverrideGetProp( '_myOwnPrivateFoo' ),
undefined,
"Parent should not have access to private methods of subtype when " +
"a parent method is invoked"
);
} )();
/**
* Visibility escalation (protected -> private) should be permitted
*/
( function testCanEscalateMemberVisibility()
{
// escalate
assert.doesNotThrow( function()
{
Class(
{
'protected foo': 'bar',
'virtual protected baz': function() {},
} ).extend( {
'public foo': 'bar',
'override public baz': function() {},
} );
}, Error, "Can escalate visibility of subtype members" );
// same level of visibility
assert.doesNotThrow( function()
{
Class(
{
'protected foo': 'bar',
'virtual protected baz': function() {},
} ).extend( {
'protected foo': 'bar',
'override protected baz': function() {},
} );
}, Error, "Can retain level of visibility for subtype members" );
} )();
/**
* We should /not/ be able to de-escalate member visibility
* (public -> {protected,private}
*/
( function testCannotDeescalateMemberVisibility()
{
// public -> protected
assert.throws( function()
{
Class(
{
'public foo': 'bar',
} ).extend( {
'protected foo': 'bar',
} );
}, Error, "Cannot de-escalate visibility of subtype props to protected" );
assert.throws( function()
{
Class(
{
'virtual public baz': function() {},
} ).extend( {
'protected baz': function() {},
} );
}, Error, "Cannot de-escalate visibility of subtype methods to protected" );
// public -> private
assert.throws( function()
{
Class(
{
'public foo': 'bar',
} ).extend( {
'private foo': 'bar',
} );
}, Error, "Cannot de-escalate visibility of subtype props to private" );
assert.throws( function()
{
Class(
{
'virtual public baz': function() {},
} ).extend( {
'private baz': function() {},
} );
}, Error, "Cannot de-escalate visibility of subtype methods to private" );
// protected -> private
assert.throws( function()
{
Class(
{
'protected foo': 'bar',
} ).extend( {
'private foo': 'bar',
} );
}, Error, "Cannot de-escalate visibility of subtype props to private2" );
assert.throws( function()
{
Class(
{
'virtual protected baz': function() {},
} ).extend( {
'private baz': function() {},
} );
}, Error, "Cannot de-escalate visibility of subtype methods to private2" );
} )();
/**
* With the visibility implementation, it's possible that __super() will not
* work properly with protected methods. This is because of the override lookup
* process (which hopefully was fixed in the commit before this test was
* originally introduced: ce736bea).
*/
( function testCallingSuperMethodWorksProperlyWithProtectedMethods()
{
var val = 'foobar',
result = Class( {
'virtual protected foo': function()
{
return val;
},
} ).extend(
{
// we override to public just so we can call it externally
'override public foo': function()
{
return this.__super();
},
} )().foo();
assert.equal( result, val,
"__super() calls work with protected overrides"
);
} )();
/**
* Concrete implementations of interfaces should have to follow the same
* visibility de-escalation rules as defined in the above tests (otherwise, that
* defeats the purpose of an interface). In other words, they must be public.
*/
( function testVisibilityDeescalationRulesApplyToInterfaces()
{
assert.throws( function()
{
Class.implement( Interface( { 'abstract public foo': [] } ) ).extend(
{
// should throw an exception; visibility de-escalation
'protected foo': function() {},
} );
}, Error, "Cannot de-escalate visibility for interface members" );
} )();
/**
* Due to the way the property object is laid atop of the public members, we
* need to ensure that protected methods' functionality can /actually/ be
* overridden, since the protected method is higher in the prototype chain and
* therefore will be accessed before the public method.
*
* We don't care about private -> protected, because that's not possible through
* inheritance.
*/
( function testCanOverrideProtectedMethodFunctionalityWithPublic()
{
// get the result of invoking overridden foo()
var result = Class(
{
'virtual protected foo': function()
{
return false;
},
} ).extend(
{
// override and escalate visibility of method foo()
'override public foo': function()
{
return true;
},
} )().foo();
// if the override was successful, we'll be able to invoke the overridden
// method
assert.equal( result, true,
"Can properly override protected methods with public"
);
} )();
/**
* There was an issue where the private property object was not proxying values
* to the true protected values. This would mean that when the parent
* initialized protected values, those values would be unavailable to the
* subtype. Instead, the value available to the subtype was the value that was
* assigned as the default value in the class definition.
*/
( function testProtectedValuesAreAvailableToSubtypesWhenSetByParentMethod()
{
var expected = 5,
result = Class(
{
'protected val': 0,
'public __construct': function()
{
this.val = expected;
},
} ).extend(
{
'public getVal': function()
{
return this.val;
},
} )().getVal();
assert.equal( result, expected,
"Subtypes should have acess to protected properties values set by " +
"super methods"
);
} )();
/**
* There was a bug introduced when we prevented protected members from
* overriding public (since in the prototype chain, protected members are laid
* atop public, and this cannot change). This bug would disallow protected
* members from being overridden by other protected members.
*
* This test is both a proof and a regression test.
*/
( function testCanProperlyOverrideProtectedWithProtected()
{
var val = 'foobar',
result = Class(
{
'virtual protected foo': function() {},
} ).extend(
{
// provide concrete implementation
'override protected foo': function()
{
return val;
},
'public doFoo': function()
{
return this.foo();
},
} )().doFoo();
;
// if everything worked as expected, the value of 'val' will have been
// returned and stored in 'result'
assert.equal( result, val,
"Protected methods can properly be overriden by another protected " +
"method"
);
} )();
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