typescript-node-scripts/lib/formatWebpackMessages.js

const chalk = require('chalk')

const friendlyModuleParseErrorLabel = 'Module parse failed:'
const friendlyRedundantModuleWarningLabel = 'Module Warning'

const filterWithLabel = (message, label) => message.indexOf(label) === -1

const formatMessage = message => {
    let lines = message.split('\n')

    // Remove full path if relative path exists.
    // This weird behavior happens when
    // ts-loader and webpack tries to print both paths.
    if (lines[0].includes(lines[1].slice(2))) {
        lines.splice(0, 1)
    }
    if (lines[1].includes(lines[0])) {
        lines.splice(0, 1)
    }

    // Remove excessive warning label
    lines = lines.filter(message =>
        filterWithLabel(message, friendlyRedundantModuleWarningLabel)
    )

    if (lines.length > 2 && lines[1] === '') {
        // Remove extra newline.
        lines.splice(1, 1)
    }

    // webpack adds a list of entry points to warning messages
    // @ src/...
    // we don't need this since we already have the path printed out
    lines = lines.filter(line => line.indexOf(' @ ') !== 0)

    // line #0 is filename
    // line #1 is the main error message
    if (!lines[0] || !lines[1]) {
        return lines.join('\n')
    }

    lines[0] = chalk.underline.bold(lines[0])

    // Reassemble the message.
    message = lines.join('\n')

    return message.trim()
}

const formatWebpackMessages = json => {
    const errors = json.errors
        .map(message => formatMessage(message))
        .filter(message =>
            filterWithLabel(message, friendlyModuleParseErrorLabel)
        )
    const warnings = json.warnings.map(message => formatMessage(message))

    return {
        errors,
        warnings,
    }
}

module.exports = formatWebpackMessages