Before this change, __super was set to undefined. However, consider that we have two
method overrides---foo and bar---and the code for bar is:
this.foo();
this.__super();
foo() would set __super to undefined and so bar cannot invoke its super method
unless it stores a reference to __super before invoking foo(). This patch fixes
this issue.
Getters/setters did not get much attention during the initial development of
ease.js, simply because there was such a strong focus on pre-ES5
compatibility---ease.js was created for a project that strongly required it.
Given that, getters/setters were not used, since those are ES5 features. As
such, I find that two things have happened:
1. There was little incentive to provide a proper implementation; even though
I noticed the issues during the initial development, they were left
unresolved and were then forgotten about as the project lay dormant for a
while.
2. The project was dormant because it was working as intended (sure, there
are still things on the TODO-list feature-wise). Since getters/setters were
unused in the project for which ease.js was created, the bug was never
found and so never addressed.
That said, I now am using getters/setters in a project with ease.js and noticed
a very odd bug that could not be explained by that project's implementation.
Sure enough, it was an ease.js issue and this commit resolves it.
Now, there is more to be said about this commit. Mainly, it should be noted that
MemberBuilder.buildGetterSetter, when compared with its method counterpart
(buildMethod) is incomplete---it does not properly address overrides, the
abstract keyword, proxies or the possibility of method hiding. This is certainly
something that I will get to, but I want to get this fix out as soon as I can.
Since overriding ES5 getters/setters (rather than explicit methods) is more
likely to be a rarity, and since a partial fix is better than no fix, this will
likely be tagged immediately and a further fix will follow in the (hopefully
near) future.
(This is an interesting example of how glaring bugs manage to slip through the
cracks, even when the developer is initially aware of them.)
The concept of proxy methods will become an important, core concept in ease.js
that will provide strong benefits for creating decorators and proxies, removing
boilerplate code and providing useful metadata to the system. Consider the
following example:
Class( 'Foo',
{
// ...
'public performOperation': function( bar )
{
this._doSomethingWith( bar );
return this;
},
} );
Class( 'FooDecorator',
{
'private _foo': null,
// ...
'public performOperation': function( bar )
{
return this._foo.performOperation( bar );
},
} );
In the above example, `FooDecorator` is a decorator for `Foo`. Assume that the
`getValueOf()` method is undecorated and simply needs to be proxied to its
component --- an instance of `Foo`. (It is not uncommon that a decorator, proxy,
or related class will alter certain functionality while leaving much of it
unchanged.) In order to do so, we can use this generic, boilerplate code
return this.obj.func.apply( this.obj, arguments );
which would need to be repeated again and again for *each method that needs to
be proxied*. We also have another problem --- `Foo.getValueOf()` returns
*itself*, which `FooDecorator` *also* returns. This breaks encapsulation, so we
instead need to return ourself:
'public performOperation': function( bar )
{
this._foo.performOperation( bar );
return this;
},
Our boilerplate code then becomes:
var ret = this.obj.func.apply( this.obj, arguments );
return ( ret === this.obj )
? this
: ret;
Alternatively, we could use the `proxy' keyword:
Class( 'FooDecorator2',
{
'private _foo': null,
// ...
'public proxy performOperation': '_foo',
} );
`FooDecorator2.getValueOf()` and `FooDecorator.getValueOf()` both perform the
exact same task --- proxy the entire call to another object and return its
result, unless the result is the component, in which case the decorator itself
is returned.
Proxies, as of this commit, accomplish the following:
- All arguments are forwarded to the destination
- The return value is forwarded to the caller
- If the destination returns a reference to itself, it will be replaced with
a reference to the caller's context (`this`).
- If the call is expected to fail, either because the destination is not an
object or because the requested method is not a function, a useful error
will be immediately thrown (rather than the potentially cryptic one that
would otherwise result, requiring analysis of the stack trace).
N.B. As of this commit, static proxies do not yet function properly.
- Perhaps in future versions. The implementation details will not be ironed out before v0.1.0 and we can easily add it in the future without breaking BC. Getters/setters have not had too much attention thusfar in ease.js due to testing with systems that must work across many environments, including pre-ES5.
- This is a bug fix. The resulting class was not declared abstract, which is a problem if the resulting class chose not to provide a concrete implementation for each of the abstract members.
Getting ready for release means that we need to rest assured that everything is
operating as it should. Tests do an excellent job at aiding in this, but they
cannot cover everything. For example, a simple missing comma in a variable
declaration list could have terrible, global consequences.
I'm unsure as to why I originally placed them in separate methods. propParse() will
always find a getter at the same time it finds a setter, and vice versa, should they
both have been defined on the object.
Finally feels like things are starting to come together.
It's rather interesting looking back. Each time I begin writing a piece of
software, I think to myself, "This is the best way to do it." Well, generally.
Perhaps the implementation could have been better, but I may not have had the
time. However, the general concept remains.
Each time I look back months later and find that I disagree with certain
decisions. I find certain implementations to be messy or poorly constructed. Or
perhaps I was just being lazy to begin with. Whatever the case, it is
comforting. It shows that one is continuing to learn and evolve.
Now, in the case of ease.js, we're working with a number of different factors in
regards to my perception of prior code quality. Primarily, I'm looking at a
basic implementation (in this case, I'm referring to test cases) that served as
a foundation that could be later evolved. I didn't have the time to devote to a
stronger solution. However, since the project has evolved so far past my
original expectations, a more sophisticated solution is needed in order to
simplify the overall design. That is what happened here.
Of course, we're also looking at a year's worth of additional, intimate
experience with a language.
Regardless of the reason, I love to see software evolve. Especially my own. It's
as if I'm watching my child grow. From that, I can get a great deal of
satisfaction.
One shouldn't expect perfection. But one should certainly aim for it.
Ironic, considering the current refactoring (not yet committed) of MemberBuilder to split validation logic into MemberBuilderValidator was partially to be able to easily override the fallback logic. It's a useful refactoring nonetheless, but it could have waited.
As mentioned in a prior commit blog-like entry, many of the tests evolved into more of an integration or system-level type of test. Let's get away from that.
This is the first test case to use the new basic xUnit-style system. This
system is likely to evolve over time. Right now it's purely for
setUp, organizational and output purposes.
The one year anniversary of the beginning of the ease.js project is quickly
approaching. I find myself to be not quite where I had expected many months ago,
but find that the project has evolved so much further than I had event
originally anticipated. My main motivation behind the project continues to be
making my life at work easier, while providing an excellent library that others
can hopefully benefit from. If anything, it's a fascinating experiment and
clever hack around JavaScript.
Now I find myself with a newborn child (nearly four weeks old), who demands my
constant attention (and indeed, it is difficult to find the desire to put my
attention elsewhere). Still - I am a hacker. Software is my passion. So the
project must move forward.
I also find myself unwilling to create a blog for ease.js. I feel it's
inappropriate for a project that's in its (relative) infancy and does not have
much popularity (it has never been announced to anyone). As such, I feel that
commit messages will serve my purpose as useful journal entries regarding the
status of the project. They will also be interesting easter eggs for those who
would wish to seek them out for additional perspective on the project. (Granted,
one could easy script the discovery of such entries by examining the absurd
length of the commit message...perhaps the git log manpages would be useful).
So. Let's get back to the project.
ease.js is currently going through a strong refactoring in order to address
design issues that have begun to creep up as the project grew. The initial
design was a very simple one - a "series of modules", as it was originally
described in a CommonJS sense, that would provide features of a classical
Object-Oriented system. It would seem ironic that, having a focus on
classical Object-Oriented development, one would avoid developing the project in
such a paradigm. Instead, I wished to keep the design simple (because the
project seemed simple), more natural to JS developers (prototypal) and
performant (object literals do not have the overhead of instantiation). Well,
unfortunately, the project scope has increased drastically due to the success of
the implementation (and my playfulness), the chosen paradigm has become awkward
in itself and the performance benefit is indeed a micro-optimization when
compared with the performance of both the rest of the system and the system that
will implement ease.js as a framework.
You can only put off refactoring for so long before the system begins to trip
over itself and stop being a pleasure to work with. In fact, it's a slap in the
face. You develop this intricate and beautiful system (speaking collectively and
generally, of course) and it begins to feel tainted. In order to prevent it from
developing into a ball of mud - a truly unmaintainable mess - the act of
refactoring is inevitable, especially if we want to ensure that the project
survives and is actively developed for any length of time.
In this case, the glaring problem is that each of the modules are terribly,
tightly coupled. This reduces the flexibility of the system and forces us to
resort to a system riddled with conditionals. This becomes increasingly apparent
when we need to provide slightly different implementations between environments
(e.g. ES5/pre-ES5, production/development, etc and every combination).
Therefore, we need to decouple the modules in order to take advantage of
composition in order to provide more flexible feature sets depending on
environment.
What does this mean?
We need to move from object literals for the modules to prototypes (class-like,
but remember that ease.js exists because JS does not have "classes"). A number
of other prototypes can be extracted from the existing modules and abstracted to
the point where they can be appropriately injected where necessary. Rather than
using conditions for features such as fallbacks, we can encapsulate the entire
system in a facade that contains the features relevant to that particular
environment. This will also have the consequence that we can once again test
individual units rather than systems.
At the point of this commit (this entry was written before any work was done),
the major hurdle is refactoring the test cases so that they do not depend on
fallback logic and instead simply test specific units and skip the test if the
unit (the prototype) is not supported by the environment (e.g. proxies in a
pre-ES5 environment). This will allow us to finish refactoring the fallback and
environment-specific logic. It will also allow us to cleanly specify a fallback
implementation (through composition) in an ES5 environment while keeping ES5
detection mechanisms separate.
The remaining refactorings will likely be progressive. This all stemmed out of
the desire to add the method hiding feature, whose implementation varies
depending on environment. I want to get back to developing that feature so I can
get the first release (v0.1.0) out. Refactoring can continue after that point.
This project needs a version number so it can be used reliably.
- This commit was originally many. Unfortunately, certain Git objects became
corrupt shortly after my 500th commit due to HDD issues. Due to the scope, I
was unable to recover the set of commits I needed (after an hour of trying
every method).
- Fortunately, vim's swap files came to the rescue. Had I been able to
properly shut down my PC, I would have been rather frustrated.
- The ctor must be instantiated for use in the prototype chain
- This was working in the past, but apparently no test existed for it and
refactoring broke it
Mike Gerwitz