eslint rule to prevent await in expressions

eslint-local-rules.js

/*
Should be used with "eslint-plugin-local-rules" plugin
*/

'use strict'

module.exports = {
  'no-await-in-expressions': {
    meta: {
      type: 'problem',
      docs: {
        description: 'No await in expressions',
        category: 'Stylistic Issues',
        recommended: false,
      },
      schema: [],
    },
    create: context => {
      // This rule doesn't check await before return.
      // Use "no-return-await" rule to prevent it.
      const allowedAncestors = [
        'ReturnStatement',
        'VariableDeclarator',
        'ExpressionStatement',
        'AssignmentExpression',
      ]
      return {
        AwaitExpression: node => {
          const ancestors = context.getAncestors(node)
          const last = ancestors[ancestors.length - 1]
          if (!allowedAncestors.includes(last.type)) {
            context.report({
              node,
              message: 'Using await in expressions is forbidden. Assign await result to a variable',
            })
          }
        },
      }
    },
  },
}