babel-plugin-template-html-minifier

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Minify HTML in tagged template strings using html-minifier-terser.

Install

``bash
npm install --save-dev babel-plugin-template-html-minifier
`

Usage

In .babelrc:

`json
{
"plugins": [
["template-html-minifier", {
"modules": {
"choo/html": [null],
"hyperhtml": [{"name": "bind", "type": "factory"}],
"hyperhtml-element": [{"name": null, "member": "html"}]
},
"htmlMinifier": {
"collapseWhitespace": true
}
}]
]
}
`

Example for lit-html and lit-element:

`json
{
"plugins": [
["template-html-minifier", {
"modules": {
"lit-html": ["html"],
"lit-element": [
"html",
{"name": "css", "encapsulation": "style"}
],
},
"strictCSS": true,
"htmlMinifier": {
"collapseWhitespace": true,
"conservativeCollapse": true,
"removeComments": true,
"caseSensitive": true,
"minifyCSS": true
},
}]
]
}
`

Options

$3

The value of this property is passed unmodified to html-minifier-terser. See the
html-minifier-terser docs.

Note for usage with lit-html and lit-element:

- To preserve case sensitiveness of property binding "caseSensitive": true must be added.

- collapseBooleanAttributes should not be used when working with lit-html
or other templating systems which give special meaning to non-static boolean
attributes. Enabling collapseBooleanAttributes will cause this plugin to
throw an exception:

`js
html;
`

This exception is for two reasons. First because it means the chosen options have
caused html-minifier-terser to change the meaning of the HTML template. Second because
it deletes the point where ${readonly} goes into the final output.

- removeComments will cause the following template to throw an exception:

`js
html;
`

This exception is because ${value} inside an HTML template gets deleted. It
should be noted that an HTML template does not prevent code within ${} from
running. This means that in the following template getValue() is still executed
when processing the html template:

`js
html;
`

It is recommended to use [binding-positions] from [eslint-plugin-lit] to catch this
error. This babel transformation can only determine that a template is broken, the
eslint plugin will tell you which binding is invalid.

$3

Whether CSS should only be minified when it is valid CSS. This is necessary when using css templates which allow multiple strings of invalid CSS together to make a valid stylesheet. This is the case for example with lit-element:

`js
const unit = csspx;
const widthXL = 400;
const styleSheet = css
@media (${widthXL}px) {
.foo {
font-size: 16${unit};
}
}
;
`

Minification happens per template literal, it is only able to see the unconcatenated css literals and minify those. It will try to do the right thing, but it cannot handle every scenario. If you are using lit-element, and write these types of templates, you need to set strictCSS to true.

$3

A list of module names or import paths where tags are imported from. The values in
the arrays refers to the export names, not the import names. null refers to the
default export.

$3

Determines whether an error should be thrown when minification failed. defaults to true.

Minification can fail when using invalid syntax or comments within bindings. Especially
when using css with bindings minification can fail. When failOnError is true, this
plugin throws an error and your build will stop from proceeding. When it is false
the minification is canceled and the template is left unminified.

$3

`js
import choo from 'choo/html';
import * as lit from 'lit-html';
import {html as litHtml, css} from 'lit-element';
import HyperHTMLElement from 'hyperhtml-element';
import html from 'some-module';
import {bind} from 'hyperhtml';

choo

lit.html

litHtml

css
.sel {
background: red;
}
;

class MyHyperHTMLElement extends HyperHTMLElement {
created() {
this.render();
}

render() {
this.html

bind(document.body)

html
This
is
not
processed
;
`

Using the .babelrc shown in usage produces the following output:

`js
import choo from 'choo/html';
import * as lit from 'lit-html';
import {html as litHtml, css} from 'lit-element';
import HyperHTMLElement from 'hyperhtml-element';
import html from 'some-module';
import {bind} from 'hyperhtml';

choo

lit.html

litHtml

css.sel{background:red};

class MyHyperHTMLElement extends HyperHTMLElement {
created() {
this.render();
}

render() {
this.html

bind(document.body)

html
This
is
not
processed
;
`

* choo is processed because of "choo/html": [null] specifies that the default
export should be processed.
* lit.html is processed because "lit-html": ["html"].
* litHtml is processed because "lit-element": ["html"].
* css is processed because "lit-element": [{"name": "css", "encapsulation": "style"}].
The encapsulation argument ensures that html-minifier-terser understands that the template
contains CSS, without it the template would be processed as HTML.
* this.html in MyHyperHTMLElement is processed because
"hyperhtml-element": [{"name": null, "member": "html"}] specifies that the html member
of classes which extend the default export should be processed.
* bind is processed because of "hyperhtml": [{"name": "bind", "type": "factory"}], the
type factory specifies the bind returns a function which processes the tagged templates.
* html is not processed because it was exported from an unlisted module.

All matching is done based on the exported name, not the local/imported name.

Running tests

Tests are provided by xo and ava.

`sh
npm install
npm test
`

Attribution

This module was originally created by goto-bus-stop.

babel-plugin-template-html-minifier for enterprise

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[npm-image]: https://img.shields.io/npm/v/babel-plugin-template-html-minifier.svg
[npm-url]: https://npmjs.org/package/babel-plugin-template-html-minifier
[travis-image]: https://travis-ci.org/cfware/babel-plugin-template-html-minifier.svg?branch=master
[travis-url]: https://travis-ci.org/cfware/babel-plugin-template-html-minifier
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[downloads-image]: https://img.shields.io/npm/dm/babel-plugin-template-html-minifier.svg
[downloads-url]: https://npmjs.org/package/babel-plugin-template-html-minifier
[license-image]: https://img.shields.io/npm/l/babel-plugin-template-html-minifier.svg

[binding-positions]: https://github.com/43081j/eslint-plugin-lit/blob/master/docs/rules/binding-positions.md
[eslint-plugin-lit]: https://github.com/43081j/eslint-plugin-lit#readme