overleaf/services/web/webpack-plugins/lezer-grammar-compiler.js

const {
  compile,
  options,
} = require('../modules/source-editor/scripts/lezer-latex/generate')
const fs = require('fs')

const PLUGIN_NAME = 'lezer-grammar-compiler'

class LezerGrammarCompilerPlugin {
  apply(compiler) {
    compiler.hooks.make.tap(PLUGIN_NAME, compilation => {
      // Add the grammar file to the file paths watched by webpack
      compilation.fileDependencies.add(options.grammarPath)
    })
    compiler.hooks.beforeCompile.tapAsync(
      PLUGIN_NAME,
      (_compilation, callback) => {
        // Check timestamps on grammar and parser files, and re-compile if needed.
        // (Note: the compiled parser file is watched by webpack, and so will trigger
        //  a second compilation immediately after. This seems harmless.)
        if (
          !fs.existsSync(options.parserOutputPath) ||
          !fs.existsSync(options.termsOutputPath)
        ) {
          console.log('Parser does not exist, compiling')
          compile()
          return callback()
        }
        fs.stat(options.grammarPath, (err, grammarStat) => {
          if (err) {
            return callback(err)
          }
          fs.stat(options.parserOutputPath, (err, parserStat) => {
            if (err) {
              return callback(err)
            }
            callback()
            if (grammarStat.mtime > parserStat.mtime) {
              console.log('Grammar file newer than parser file, re-compiling')
              compile()
            }
          })
        })
      }
    )
  }
}

module.exports = { LezerGrammarCompilerPlugin }