other plugin invoke twice

const postcss = require( 'postcss' )
const modules = require( 'postcss-modules' )

let testPlugin = postcss.plugin( 'test-plugin-1', () => {
    return () => {
        console.log( 'test-plugin-1 running' )
    }
} )

let testPlugin2 = postcss.plugin( 'test-plugin-2', () => {
    return () => {
        console.log( 'test-plugin-2 running' )
    }
} )

postcss( [
    modules( {
        getJSON( _, json ) {
        }
    } ),
    testPlugin(),
    testPlugin2()
] )
    .process( `
    .title {
        color: green;
    }` )
    .then( () => {
    } )

if you run this code, that two plugins were running twice. Did i use this plugin in a wrong way?

[EECOLOR]

@peter-mouland I recommend you move away from this module as it is not properly maintained. I have opened several pull requests and issues (to upgrade the postcss dependency) in October, but they are still open.

Both our our webpack css loader and the defaul css loader have adopted another strategy of supporting css modules.

Incidentally, this other approach does not involve the composition plugin.

[EECOLOR]

No you did not. I don’t know why, but this plugin executes postcss with all other plugins: https://github.com/css-modules/postcss-modules/blob/master/src/index.js#L75

The simple fix is:

const plugins = [
  require('postcss-plugin-composition', [
      // plugins that need to run on each individual file (import, modules, etc.)
  ]),
  // plugins that need to run on the result (once)
]

Please be aware of: https://github.com/btd/postcss-plugin-composition/issues/1

A copy without this problem:

const postcss = require('postcss')

module.exports = postcss.plugin('postcss-plugin-composition', plugins => {
  if(!Array.isArray(plugins)) throw new Error('`options` for postcss-plugin-composition must be array of plugins')

  return (root, { opts, messages }) => 
    postcss(plugins)
      .process(root, opts)
      .then(({ messages: m }) => { messages.push.apply(messages, m) })
})