reflect-metadata VS proposal-decorators

Counter to this post, as soon as I read the title I knew what this was, & I knew it was speaking exactly to something we've wanted for a long time. This is asking for more official & better supported https://github.com/rbuckton/reflect-metadata .

TypeScript is a compiler. It has a lot of type information during compilation. We could write that type information out into a file. Instead what we do is throw that information out when the compile ends. Taking all that typing information & throwing it away at the end of compile time is a bad dumb & silly limitation. Especially for a language like JavaScript, which historically could be semi-proud it had such a strong Everything Is An Object philosophy running through it (such as the malleable prototype-based inheritance system); so much type information should be on that Class object. Reflect-metadata for example defined new methods on Reflect to store this metadata.

I could not be more delighted to see the pennon of this website go up. We needed a rallying point for this. We needed a rallying point for keeping class data around. A rallying point for enriching the runtime with good actionable data is a good rallying point.

It's not what's afoot here, but I think you're a bit off-base about the impossibility of adding even some type-safety. We might not be able to get exact TS type safety. But we can definitely build some safety in. Owing to the malleable prototype-based type system in JS, we can add getters/setters to objects to do a lot of type checking. This doesn't even begin to explore the possibility of what we might do with es2015's proxies, which could allow even more interesting checks to be layered in. I also wish JS had an official AST (and renderer), so had more official options for code-rewriting that might let us weave in type checks.

What we can do as programmers is limited by what we have at our disposal. Not throwing out all the typing information, keeping it around at runtime, opens a lot of interesting doors.

Second, TypeScript 5.0 cannot emit decorator metadata. Subsequently, it doesn’t integrate with the Reflect API and won’t work with the reflect-metadata npm package.

Database columns will be mapped to domain object properties using decorators. This will include relationships and enum types. reflect-metadata stores metadata about the classes and properties. Most of the work is a simple map for each class, renaming db column properties to domain model properties and vice versa. Reflect.defineProperty holds a list of field metadata on the target class. This is where more database ORM logic could live in the future such as column type, length, etc. A base domain model entity will use this metadata to map the models appropriately.

Because many rules are common to many attributes (the coerceType operation is defined by WebIDL, or using similar rules, and the HTML specification defines a handful of microsyntaxes for the parseValue and stringifyValue operations), those could be packaged up in a helper library. And with decorators coming to ECMAScript (and already available in TypeScript), those could be greatly simplified:

Decorators are currently not a part of the standard JavaScript language. They are still being discussed in tc39 and have reached proposal stage 3. This means the spec has more or less stabilized and we can use them but they would be transplied before being run in the browser. This would be done via babel or tsc for most users

JavaScript was created a long time ago, and at the time of its inception, the authors decided not to use affirmative prefixes for boolean names. Now, they do their best by continuing to follow their convention, even if it goes against the community's opinion. Even if the authors wanted to introduce new naming conventions in the specification, they could not do it, at least not coherently. Old code cannot be renamed because JavaScript must remain backward-compatible. And starting to write new code using new approaches is not a great idea either, as there would be two ways to do the same thing, which is also undesirable.

2016-07 – Stage 2. After the decorators proposal reached stage 2, its API began to undergo significant changes. Furthermore, at one point the proposal was referred to as "ESnext class features for JavaScript." During its development, there were numerous ideas about how decorators could be structured. To get a comprehensive view of the entire history of changes, I recommend reviewing the commits in the proposal's repository. Here is an example of what the decorators API used to look like:

The example you've given isn't valid JavaScript, JS doesn't have decorators. (Although there is a stage 3 tc39 for it, afaik no browser has implemented it)

There was a decorators issue brought up in the meeting (issue 508) and decorators metadata, as noted in the article, is now at stage 3. So there's still active work being done on decorators. If I had to guess, I'd say they'd be a likely candidate for ES2024.

As per the proposal, decorators can be used with Classes and their elements such as fields, methods, and accessors. To leverage this feature, we need to ensure that our resolvers provider is an instance of a Class. Therefore, we will modify the code in src/api/users/users-resolvers.js to the following:

The modern version of decorators, which will be officially rolled out in TypeScript 5.0, no longer requires a compiler flag and follows the official ECMAScript Stage-3 proposal. Alongside a stable implementation that follows ECMAScript standards, decorators now work seamlessly with the TypeScript type system, enabling more enhanced functionality than the original version.

100% this. Going in depth of libraries will make you so much better developer than learning newest and coolest frameworks in JS ecosystem. Learn to create your own React, Promises, or anything you like in JS. It will give you immense perspective about these libraries. Once you start understanding them you will feel like they are not that complex and you can do it too. Go read TC39 proposals and issues people point out in them. You will see how JS is borrowing features from other languages.

The actual proposal gives the "@reactive" decorator as the first example, which just so happens is the only decorator that I use in my library with TypeScript's legacy decorator option. Was so happy to see they recognize this use case! https://github.com/tc39/proposal-decorators