hyper/app/config/open.js

const {shell} = require('electron');
const {cfgPath} = require('./paths');

module.exports = () => Promise.resolve(shell.openItem(cfgPath));

if (process.platform === 'win32') {
  const Registry = require('winreg');
  const {exec} = require('child_process');

  // Windows opens .js files with  WScript.exe by default
  // If the user hasn't set up an editor for .js files, we fallback to notepad.
  const getFileExtKeys = () => new Promise((resolve, reject) => {
    Registry({
      hive: Registry.HKCU,
      key: '\\Software\\Microsoft\\Windows\\CurrentVersion\\Explorer\\FileExts\\.js'
    })
    .keys((error, keys) => {
      if (error) {
        reject(error);
      } else {
        resolve(keys || []);
      }
    });
  });

  const hasDefaultSet = async () => {
    const keys = await getFileExtKeys();

    const valueGroups = await Promise.all(keys.map(key => new Promise((resolve, reject) => {
      key.values((error, items) => {
        if (error) {
          reject(error);
        }
        resolve(items.map(item => item.value || '') || []);
      });
    })));

    const values = valueGroups
      .reduce((allValues, groupValues) => ([...allValues, ...groupValues]), [])
      .filter(value => value && typeof value === 'string');

    // No default app set
    if (values.length === 0) {
      return false;
    }

    // WScript is in default apps list
    if (values.some(value => value.includes('WScript.exe'))) {
      const userDefaults = values.filter(value => value.endsWith('.exe') && !value.includes('WScript.exe'));

      // WScript.exe is overidden
      return (userDefaults.length > 0);
    }

    return true;
  };

  // This mimics shell.openItem, true if it worked, false if not.
  const openNotepad = file => new Promise(resolve => {
    exec(`start notepad.exe ${file}`, error => {
      resolve(!error);
    });
  });

  module.exports = () => hasDefaultSet()
    .then(yes => {
      if (yes) {
        return shell.openItem(cfgPath);
      }
      console.warn('No default app set for .js files, using notepad.exe fallback');
      return openNotepad(cfgPath);
    })
    .catch(err => {
      console.error('Open config with default app error:', err);
      return openNotepad(cfgPath);
    });
}