Add support for using h, s as a JSX pragmas

This change tests that `hastscript` can be used as the pragma for JSX with bublé
and babel.

Code-wise, this adds support for using `h` to generate root nodes.
This is done by omitting the tag name (like so: `h()`, `h(null, 'child')`).
Previously, omitting a `name` resulted in the default element to be created
(`div` for `h`, `g` for `s`).

This change thus is a breaking change.
The old behavior is still available when passing an empty string: `h('')`.

Another aspect of supporting JSX is supporting fragments as children.
As fragments yield root nodes, we unravel them and use only their children.
While this could be seen a change, hast prohibits roots occurring in nodes,
so the unraveling instead fixes what would otherwise be a broken tree.

Related to: syntax-tree/xastscript#3.
Related to: syntax-tree/xastscript#4.

Author: wooorm

.gitignore

@@ -3,6 +3,7 @@
 .nyc_output/
 coverage/
 node_modules/
+test/jsx-*.js
 hastscript.js
 hastscript.min.js
 yarn.lock

factory.js

@@ -17,17 +17,23 @@ function factory(schema, defaultTagName, caseSensitive) {
 
   // Hyperscript compatible DSL for creating virtual hast trees.
   function h(selector, properties) {
-    var node = parseSelector(selector, defaultTagName)
-    var name = node.tagName.toLowerCase()
+    var node =
+      selector == null
+        ? {type: 'root', children: []}
+        : parseSelector(selector, defaultTagName)
+    var name = selector == null ? null : node.tagName.toLowerCase()
     var index = 1
     var property
 
     // Normalize the name.
-    node.tagName = adjust && own.call(adjust, name) ? adjust[name] : name
+    if (name != null) {
+      node.tagName = adjust && own.call(adjust, name) ? adjust[name] : name
+    }
 
     // Handle props.
     if (properties) {
       if (
+        name == null ||
         typeof properties === 'string' ||
         'length' in properties ||
         isNode(name, properties)
@@ -134,7 +140,11 @@ function addChild(nodes, value) {
       addChild(nodes, value[index])
     }
   } else if (typeof value === 'object' && 'type' in value) {
-    nodes.push(value)
+    if (value.type === 'root') {
+      addChild(nodes, value.children)
+    } else {
+      nodes.push(value)
+    }
   } else {
     throw new Error('Expected node, nodes, or string, got `' + value + '`')
   }

package.json

@@ -45,7 +45,11 @@
     "space-separated-tokens": "^1.0.0"
   },
   "devDependencies": {
+    "@babel/core": "^7.0.0",
+    "@babel/plugin-syntax-jsx": "^7.0.0",
+    "@babel/plugin-transform-react-jsx": "^7.0.0",
     "browserify": "^17.0.0",
+    "buble": "^0.20.0",
     "dtslint": "^4.0.0",
     "nyc": "^15.0.0",
     "prettier": "^2.0.0",
@@ -54,16 +58,17 @@
     "svg-tag-names": "^2.0.0",
     "tape": "^5.0.0",
     "tinyify": "^3.0.0",
+    "unist-builder": "^2.0.0",
     "xo": "^0.34.0"
   },
   "scripts": {
-    "generate": "node build",
+    "generate": "node script/generate-jsx && node script/build",
     "format": "remark . -qfo && prettier . -w --loglevel warn && xo --fix",
     "build-bundle": "browserify . -s hastscript > hastscript.js",
     "build-mangle": "browserify . -s hastscript -p tinyify > hastscript.min.js",
     "build": "npm run build-bundle && npm run build-mangle",
     "test-api": "node test",
-    "test-coverage": "nyc --reporter lcov tape test.js",
+    "test-coverage": "nyc --reporter lcov tape test/index.js",
     "test-types": "dtslint .",
     "test": "npm run generate && npm run format && npm run build && npm run test-coverage && npm run test-types"
   },

readme.md

@@ -138,34 +138,124 @@ Yields:
 
 ## API
 
-### `h(selector?[, properties][, ...children])`
+### `h(selector?[, properties][, …children])`
 
-### `s(selector?[, properties][, ...children])`
+### `s(selector?[, properties][, …children])`
 
-DSL to create virtual [**hast**][hast] [*trees*][tree] for HTML or SVG.
+Create virtual [**hast**][hast] [*trees*][tree] for HTML or SVG.
+
+##### Signatures
+
+*   `h(): root`
+*   `h(null[, …children]): root`
+*   `h(name[, properties][, …children]): element`
+
+(and the same for `s`).
 
 ##### Parameters
 
 ###### `selector`
 
 Simple CSS selector (`string`, optional).
 Can contain a tag name (`foo`), IDs (`#bar`), and classes (`.baz`).
-If there is no tag name in the selector, `h` defaults to a `div` element,
-and `s` to a `g` element.
+If the selector is a string but there is no tag name in it, `h` defaults to
+build a `div` element, and `s` to a `g` element.
 `selector` is parsed by [`hast-util-parse-selector`][parse-selector].
+When string, builds an [`Element`][element].
+When nullish, builds a [`Root`][root] instead.
 
 ###### `properties`
 
 Map of properties (`Object.<*>`, optional).
+Keys should match either the HTML attribute name, or the DOM property name, but
+are case-insensitive.
+Cannot be given when building a [`Root`][root].
 
 ###### `children`
 
-(Lists of) child nodes (`string`, `Node`, `Array.<string|Node>`, optional).
-When strings are encountered, they are mapped to [`text`][text] nodes.
+(Lists of) children (`string`, `number`, `Node`, `Array.<children>`, optional).
+When strings or numbers are encountered, they are mapped to [`Text`][text]
+nodes.
+If [`Root`][root] nodes are given, their children are used instead.
 
 ##### Returns
 
-[`Element`][element].
+[`Element`][element] or [`Root`][root].
+
+## JSX
+
+`hastscript` can be used as a pragma for JSX.
+The example above (omitting the second) can then be written like so, using
+inline Babel pragmas, so that SVG can be used too:
+
+`example-html.jsx`:
+
+```jsx
+/** @jsx h */
+/** @jsxFrag null */
+var h = require('hastscript')
+
+console.log(
+  <div class="foo" id="some-id">
+    <span>some text</span>
+    <input type="text" value="foo" />
+    <a class="alpha bravo charlie" download>
+      deltaecho
+    </a>
+  </div>
+)
+
+console.log(
+  <form method="POST">
+    <input type="text" name="foo" />
+    <input type="text" name="bar" />
+    <input type="submit" name="send" />
+  </form>
+)
+```
+
+`example-svg.jsx`:
+
+```jsx
+/** @jsx s */
+/** @jsxFrag null */
+var s = require('hastscript/svg')
+
+console.log(
+  <svg xmlns="http://www.w3.org/2000/svg" viewbox="0 0 500 500">
+    <title>SVG `&lt;circle&gt;` element</title>
+    <circle cx={120} cy={120} r={100} />
+  </svg>
+)
+```
+
+Because JSX does not allow dots (`.`) or number signs (`#`) in tag names, you
+have to pass class names and IDs in as attributes.
+
+Note that you must still import `hastscript` yourself and configure your
+JavaScript compiler to use the identifier you assign it to as a pragma (and
+pass `null` for fragments).
+
+For [bublé][], this can be done by setting `jsx: 'h'` and `jsxFragment: 'null'`
+(note that `jsxFragment` is currently only available on the API, not the CLI).
+Bublé is less ideal because it allows a single pragma.
+
+For [Babel][], use [`@babel/plugin-transform-react-jsx`][babel-jsx] (in classic
+mode), and pass `pragma: 'h'` and `pragmaFrag: 'null'`.
+This is less ideal because it allows a single pragma.
+
+Babel also lets you configure this in a script:
+
+```jsx
+/** @jsx s */
+/** @jsxFrag null */
+var s = require('hastscript/svg')
+
+console.log(<rect />)
+```
+
+This is useful because it allows using *both* `hastscript/html` and
+`hastscript/svg`, although in different files.
 
 ## Security
 
@@ -317,10 +407,18 @@ abide by its terms.
 
 [element]: https://github.com/syntax-tree/hast#element
 
+[root]: https://github.com/syntax-tree/xast#root
+
 [text]: https://github.com/syntax-tree/hast#text
 
 [u]: https://github.com/syntax-tree/unist-builder
 
+[bublé]: https://github.com/Rich-Harris/buble
+
+[babel]: https://github.com/babel/babel
+
+[babel-jsx]: https://github.com/babel/babel/tree/main/packages/babel-plugin-transform-react-jsx
+
 [parse-selector]: https://github.com/syntax-tree/hast-util-parse-selector
 
 [xss]: https://en.wikipedia.org/wiki/Cross-site_scripting

build.js renamed to script/build.js

@@ -0,0 +1,25 @@
+'use strict'
+
+var fs = require('fs')
+var path = require('path')
+var buble = require('buble')
+var babel = require('@babel/core')
+
+var doc = String(fs.readFileSync(path.join('test', 'jsx.jsx')))
+
+fs.writeFileSync(
+  path.join('test', 'jsx-buble.js'),
+  buble.transform(doc.replace(/'name'/, "'jsx (buble)'"), {
+    jsx: 'h',
+    jsxFragment: 'null'
+  }).code
+)
+
+fs.writeFileSync(
+  path.join('test', 'jsx-babel.js'),
+  babel.transform(doc.replace(/'name'/, "'jsx (babel)'"), {
+    plugins: [
+      ['@babel/plugin-transform-react-jsx', {pragma: 'h', pragmaFrag: 'null'}]
+    ]
+  }).code
+)