transform-unnecessary-arrow-functions.js

export default function(file, api) {
  const j = api.jscodeshift;

  const f = j(file.source);

  f.find(j.ClassDeclaration).forEach((c) => {
    j(c).find(j.ClassProperty, {
      value: { type: 'ArrowFunctionExpression' },
    }).forEach((cp) => {
      let canReplace = true;

      j(c).find(j.MemberExpression, {
        object: { type: 'ThisExpression' },
        property: { type: 'Identifier', name: cp.value.key.name },
      }).forEach((me) => {
        switch (me.parentPath.value.type) {
        case 'CallExpression':
        case 'MemberExpression':
          canReplace = false;
          break;
        default: // nothing
        }
      });

      if (canReplace) {
        j(c).find(j.MemberExpression, {
          object: { type: 'ThisExpression' },
          property: { type: 'Identifier', name: cp.value.key.name },
        }).forEach((me) => {
          switch (me.parentPath.value.type) {
          case 'CallExpression':
          case 'MemberExpression':
            break;
          default:
            j(me).replaceWith((e) => j.bindExpression(null, e.value));
          }
        });

        j(cp).replaceWith(j.methodDefinition(
          'method',
          cp.value.key,
          j.functionExpression(null, cp.value.value.params, cp.value.value.body),
        ));
      }
    });
  });

  return f.toSource();
}