[dmitriid]

> text inside attributes being parsed as JS is no different than parsing text inside some <script> tags.

It is different. Because "text inside script tags" is Javascript. Vue's templating syntax is a weird and inconsistent mishmash of custom DSL, Javascript subsets and Javascript expressions.

And it also depends on when it's parsed.

[manigandham]

Text inside script tags is parsed as JavaScript by default. It can be other languages too, like typescript inside a .Vue file.

Again, it’s all just text in different syntax. Programming languages are just a very large and well defined syntax compared to a template language, but that’s all it is.

Vue’s directives offer just enough control to handle 99% of scenarios while remaining within HTML.

[dmitriid]

> Text inside script tags is parsed as JavaScript by default. It can be other languages too

It can be, but usually isn't.

> Again, it’s all just text in different syntax.

Again, it's not. And the reason is simple: the browser literally knows nothing about other syntaxes but Javascript [1]

So, no, "text in Vue" is literally not the same as "text in script tags". It is a mish-mash of:

- Vue's own DSL (see v-for)

- JS expressions that are wrapped in some scope (see v-if)

- JS-like DSL where function cals are not function calls, there are magic vars, but objects are also fine (see v-on)

- Maybe JS expressions in v-bind? But depends on the attribute name? Can use string concatenation, but anything else?

- Actual JS expressions in {{}} which can't be used just anywhere... but then these expressions can have pipes into filters in them? And filters once again are JS-like, but are not

None of this has any coherent specification, and we rely on Vue to properly parse and break it down into actual Javascript code that can then be included in a <script> tag.

Edit: I had the same laundry list of things for Svelte before Svelte 2, but Svelte 3 is significantly more consistent and coherent in what it expects in a template.

[1] There are ways to make it know other syntaxes, but that is rare and has largely fallen out of favor.

[manigandham]

The point is that all code starts as simple text, and is parsed and compiled into some lower layer until it finally gets to machine code. What actually does the compilation is irrelevant.

All of these JS frameworks (React+JSX, Vue+HTML, Angular, Svelte, etc) require template compilation into an actual JS render function before a browser ever runs it, but compilation is the same fundamental process regardless of language or environment: https://en.wikipedia.org/wiki/Compiler

So yes it's all just text following a different syntax, and Vue's documentation already describes exactly what you can run: https://v3.vuejs.org/api/directives.html

[dmitriid]

> The point is that all code starts as simple text, and is parsed and compiled into some lower layer

Yup

> What actually does the compilation is irrelevant.

Nope. It is relevant. For the stuff you put between script tags there's at the very least https://github.com/tc39/ecma262 that you can look at and tell exactly what's going on with your code.

With Vue (and, yes, React and Svelte and Angular): who knows? It might very well evalueate strings at runtime for all we know.

> All of these JS frameworks (React+JSX, Vue+HTML, Angular, Svelte, etc) require template compilation into an actual JS render function before a browser ever runs it,

Yup. It's an additional, different step before it can even get to the browser. The problem with this step is that for most of this code there's not even a coherent specification of what it is, and how it's compiled.

> and Vue's documentation already describes exactly what you can run

It really doesn't. For example, here's the "documentation" on v-for:

    Expects: Array | Object | number | string | Iterable

Expects where? Is this correct:

    <div v-for="{ a: 1, b: 2 }"></div>

Answer: no. Because the actual description of what is expected is written in examples. Same goes for every single other directive. I mean, v-bind expects "any (with argument)" (what does this even mean?) and v-if expects "any", and both of these are false statements.

[manigandham]

The topic is that all code is text, and everything can be parsed and understood based on specific language grammars, even if they're embedded within each other.

What are you even arguing at this point? This isn't about compilation or strings anymore. You don't like Vue's specific DSL? Or you don't understand it? Or you found a problem with the documentation? Or do you need a full grammar and syntax definition before you can do anything?

It's basically any valid `for..in/of` expression but you can always solve your mystery of "who knows" by just looking at the source code: https://github.com/vuejs/vue-next/blob/master/packages/compi...

[dmitriid]

> What are you even arguing at this point?

That Vue isn't "the same as text between script tags". Because "text between script tags" is fully specified, and known to the browser.

Vue's ad-hoc mish-mash of DSLs has to go through an unspecified series of transformations before it can even become a "text between script tags". And that's the issue not just with Vue, but with any other templating layers.

> but you can always solve your mystery of "who knows" by just looking at the source code

Ah yes. The good old "code is the source of truth" fallacy. Can you point to me where exactly in code it specifies this: `Expects: Array | Object | number | string | Iterable (since 2.6)`?

[zkldi]

> It's basically any valid `for..in/of` expression

This isn't true at all though, because `for x in y` is invalid JS.