Typed DSL in TypeScript of JSX

 3r33430. 3r3-31. 3r33417. Typed DSL in TypeScript of JSX 3r33418. 3r3155.  3r33430. 3r33417. TypeScript has built-in support for JSX syntax and TypeScript compiler provides useful tools for customizing the JSX compilation process. In essence, this creates the ability to write typed DSL using JSX. This article is about this - how to write DSL
from r3r39. using jsx. Interested please under the cat. 3r33418. 3r311. 3r3409. 3r3155.  3r33430. 3r33417. 3r3406. →
3r3408. A repository with a ready-made example. 3r3409. 3r33418. 3r3155.  3r33430. 3r33417. In this article I will not show the possibilities with examples related to the web, React'u and similar. An example not from the web will allow you to demonstrate that the capabilities of JSX are not limited to React, its components and html generation in general. In this article, I will show how to implement DSL to generate 3r324. message objects for Slack
. 3r33418. 3r3155.  3r33430. 3r33417. Here is the code that we take as a basis. This is a small message factory of the same type: 3r3343418. 3r3155.  3r33430.
interface Story {
title: string
link: string
publishedAt: Date
author: {name: string, avatarURL: string}
}
3r33430. const template = (username: string, stories: Story[]) => ({
text: `: wave: Hi $ {username}, check out our latest articles.,
attachments: stories.map (s => ({
Title,
Color: '# 000000',
Title_link: s.link,
Author_name: s.author.name,
Author_icon: s.author.avatarURL,
Text: `Published in _ $ {s.publishedAt} _. `
})
})

 3r33430. 3r33417. It seems to be looking good, but there is one thing that can be significantly improved - 3r3406. readability 3r3407. . For example, pay attention to what the related property is incomprehensible to. color , into two fields for the title (3r3308. title 3r3333399 and 3r3308. title_link ) or underscores in 3r3308. text (text inside 3r3308. _ 3r33399. will be 3r3-369. italic 3r370.). All this prevents us from separating content from stylistic details, complicating the search for what is important. And with such problems DSL should help. 3r33418. 3r3155.  3r33430. 3r33417. Here is the same example only already written in JSX: 3r3155.  3r33430.
    const template = (username: string, stories: Story[]) =>
3r33430. : wave: Hello $ {username}, check out our latest articles. 3r33430. 3r33430. {stories.map (s => 3r33430. 3r3-3303. {s.author.name} 3r33030. 3r3388. 3r33430.)} 3r33430. 3r33399. 3r33400. 3r3155.  3r33430. 3r33417. Much better! All that should live together is united, the stylistic details and content are clearly separated - beauty in one word. 3r33418. 3r3155.  3r33430. 3r31-10. We write DSL 3r3155.  3r33430. 3r3114. Customized project 3r3155.  3r33430. 3r33417. First you need to enable JSX in the project and tell the compiler that we do not use React, that our JSX needs to be compiled otherwise. 3r33418. 3r3155.  3r33430.
    //tsconfig.json
{
"compilerOptions": {
"jsx": "react",
"jsxFactory": "Template.create"
}
}
3r33400. 3r3155.  3r33430. 3r33417. 3r3308. "jsx": "react"
includes JSX support in the project and the compiler compiles all JSX elements into calls 3r3308. React.createElement . And option 3r3308. "jsxFactory" configures the compiler to use our JSX element factory. 3r33418. 3r3155.  3r33430. 3r33417. After these simple settings, the view code: 3r33418. 3r3155.  3r33430.
    import * as Template from './template'
3r33430. const JSX = Text with italic . 3r33399. 3r33400. 3r3155.  3r33430. 3r33417. will be compiled into 3r3155.  3r33430.
    const Template = require ('./template'); 3r33430. 3r33430. const JSX = Template.create ('message', null,
'Text with',
Template.create ('i', null, 'italic'),
'.'); 3r33399. 3r33400. 3r3155.  3r33430. 3r? 3175. We describe the JSX tags 3r3155.  3r33430. 3r33417. Now that the compiler knows what to compile JSX for, we need to declare the tags themselves. To do this, we will use one of TypeScript's cool features — namely, local namespace declarations. For the case of JSX, TypeScript expects the project to have a namespace of 3r3308. JSX
(the specific location of the file does not matter) with the interface 3r3308. IntrinsicElements
in which the tags themselves are described. The compiler catches them and uses them for type checking and for hints. 3r33418. 3r3155.  3r33430.
    //jsx.d.ts
declare namespace JSX {
interface IntrinsicElements {
i: {}
message: {}
author: {icon: string}
title: {link ?: string}
attachment: {
color ?: string
}
}
}
3r33400. 3r3155.  3r33430. 3r33417. Here we declared all JSX tags for our DSL and all their attributes. In essence, the name of the key in the interface is the name of the tag itself, which will be available in the code. Value is a description of the available attributes. Some tags (3r3308. I 3r-3399. In our case) may not have any attributes, others have optional or even necessary attributes. 3r33418. 3r3155.  3r33430.

Actually factory - 3r3308. Template.create

3r3155.  3r33430. 3r33417. Our factory is from 3r3308. tsconfig.json and there is a subject of conversation. It will be used in runtime to create objects. 3r33418. 3r3155.  3r33430. 3r33417. In the simplest case, it might look something like this: 3r3155.  3r33430.
    type Kinds = keyof JSX.IntrinsicElements //Names of all tags
type Attrubute = JSX.IntrinsicElements[K]//and their attributes
3r33430. export const create = (kind: K, attributes: Attrubute , children) => {
switch (kind) {
case 'i': return `_ $ {chidlren.join ('')} _`
default: //3r33430.}
}
3r33400. 3r3155.  3r33430. 3r33417. Tags that add only styles to the text inside are easy to write (3r3308. I 3r33399. In our case): our factory simply wraps the contents of the tag in a line from 3r3308. _ 3r33333. at both sides. Problems begin with complex tags. Most of the time I was busy with them, looking for a cleaner solution. What is the actual problem? 3r33418. 3r3155.  3r33430. 3r33417. And it is that the compiler prints the type Text 3r33399. in 3r3308. any . That didn’t come close to a typed DSL, well, well, the second part of the problem is that all tags will have one type after passing through the factory - this is a limitation of JSX itself (React has all tags converted to ReactElement). 3r33418. 3r3155.  3r33430. 3r33417. Generics go to the rescue! 3r33418. 3r3155.  3r33430.
    //jsx.d.ts
declare namespace JSX {
interface element {
toMessage (): {
text ?: string
attachments ?: {
text ?: string
author_name ?: string
author_icon ?: string
title_link ?: string
color ?: string
}[]3r33430.}
}
3r33430. interface IntrinsicElements {
i: {}
message: {}
author: {icon: string}
title: {link ?: string}
attachment: {
color ?: string
}
}
}
3r33400. 3r3155.  3r33430. 3r33417. Added only 3r3308. Element and now the compiler will output all JSX tags to type 3r3308. Element . This is also the standard behavior of the compiler - use 3r3308. JSX.Element as type for all tags. 3r33418. 3r3155.  3r33430. 3r33417. Our 3r3308. Element there is only one common method - casting it to the type of the message object. Unfortunately, it will not always work, only on the top-level tag 3r3308. 3r33399. and it will be in raintime. 3r33418. 3r3155.  3r33430. 3r33417. And under the spoiler, the full version of our factory. 3r33418. 3r3155.  3r33430. 3r33333. 3r33333. Actually factory code [/b]
    import {flatten} from 'lodash'
3r33430. type Kinds = keyof JSX.IntrinsicElements //Names of all tags
type Attrubute = JSX.IntrinsicElements[K]//and their attributes
3r33430. const isElement = (e: any): e is Element => 3r33030. e && e.kind
3r33430. const is = 3r3r92. (k: K, e: string | Element ): e is Element => 3r33030. isElement (e) && e.kind === k
3r33430. /* Concatenation of all direct descendants that are not elements (strings) * /
const buildText = (e: Element ) =>
e.children.filter (i =>! isElement (i)). join ('')
3r33430. const buildTitle = (e: Element <'title'> ) => ({
title: buildText (e),
title_link: e.attributes.link 3r33034.})
3r33430. const buildAuthor = (e: Element <'author'> ) => ({
author_name: buildText (e),
author_icon: e.attributes.icon
})
3r33430. const buildAttachment = (e: Element <'attachment'> ) => {
const authorNode = e.children.find (i => is ('author', i))
const author = authorNode? buildAuthor ( is ('title', i))
const title = titleNode? buildTitle ( {
children: Array ,
Children: Array is ('attachment', i)). map (buildAttachment)
return {attachments, text: buildText (this)}
}
} 3r3 r3430.
export const create = (kind: K, attributes: Attrubute , children) => {
switch (kind) {
case 'i': return `_ $ {children.join ('')} _`
default: return new Element (kind, attributes, children)
}
}
3r33400. 3r33434. 3r33434. 3r3155.  3r33430. 3r33417. 3r3406. →
3r3408. A repository with a ready-made example. 3r3409. 3r33418. 3r3155.  3r33430.
Instead of concluding
3r3155.  3r33430. 3r33417. When I did these experiences, TypeScript’s team only had an understanding of the power and limitations of what they did with JSX. Now its capabilities are even greater and the factory can be written cleaner. If there is a desire to delve and improve the repository with an example - Wellcome with pull requests. 3r33418. 3r33434. 3r33430. 3r33430. 3r33430. 3r33434. ! function (e) {function t (t, n) {if (! (n in e)) {for (var r, a = e.document, i = a.scripts, o = i.length; o-- ;) if (-1! == i[o].src.indexOf (t)) {r = i[o]; break} if (! r) {r = a.createElement ("script"), r.type = "text /jаvascript", r.async =! ? r.defer =! ? r.src = t, r.charset = "UTF-8"; var d = function () {var e = a.getElementsByTagName ("script")[0]; e.parentNode.insertBefore (r, e)}; "[object Opera]" == e.opera? a.addEventListener? a.addEventListener ("DOMContentLoaded", d,! 1): e.attachEvent ("onload", d ): d ()}}} t ("//mediator.mail.ru/script/2820404/"""_mediator") () (); 3r33424. 3r33430. 3r33434. 3r33430. 3r33430. 3r33430. 3r33430.
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