to-have-form-values.js

import isEqualWith from 'lodash/isEqualWith.js'
import escape from 'css.escape'
import {
  checkHtmlElement,
  getSingleElementValue,
  compareArraysAsSet,
} from './utils'

// Returns the combined value of several elements that have the same name
// e.g. radio buttons or groups of checkboxes
function getMultiElementValue(elements) {
  const types = [...new Set(elements.map(element => element.type))]
  if (types.length !== 1) {
    if (
      types.length === 2 &&
      types[0] === 'hidden' &&
      types[1] === 'checkbox'
    ) {
      // Allow the special case where there's a 'checkbox' input, and a matching 'hidden' input
      // before it, which works around browser forms so a 'false' value is submitted.
    } else {
      throw new Error(
        'Multiple form elements with the same name must be of the same type',
      )
    }
  }
  switch (types[0]) {
    case 'radio': {
      const theChosenOne = elements.find(radio => radio.checked)
      return theChosenOne ? theChosenOne.value : undefined
    }
    case 'checkbox':
      return elements
        .filter(checkbox => checkbox.checked)
        .map(checkbox => checkbox.value)
    default:
      // NOTE: Not even sure this is a valid use case, but just in case...
      return elements.map(element => element.value)
  }
}

function getFormValue(container, name) {
  const elements = [...container.querySelectorAll(`[name="${escape(name)}"]`)]
  /* istanbul ignore if */
  if (elements.length === 0) {
    return undefined // shouldn't happen, but just in case
  }
  switch (elements.length) {
    case 1:
      return getSingleElementValue(elements[0])
    default:
      return getMultiElementValue(elements)
  }
}

// Strips the `[]` suffix off a form value name
function getPureName(name) {
  return /\[\]$/.test(name) ? name.slice(0, -2) : name
}

function getAllFormValues(container) {
  const names = Array.from(container.elements).map(element => element.name)
  return names.reduce(
    (obj, name) => ({
      ...obj,
      [getPureName(name)]: getFormValue(container, name),
    }),
    {},
  )
}

export function toHaveFormValues(formElement, expectedValues) {
  checkHtmlElement(formElement, toHaveFormValues, this)
  if (!formElement.elements) {
    // TODO: Change condition to use instanceof against the appropriate element classes instead
    throw new Error('toHaveFormValues must be called on a form or a fieldset')
  }
  const formValues = getAllFormValues(formElement)
  return {
    pass: Object.entries(expectedValues).every(([name, expectedValue]) =>
      isEqualWith(formValues[name], expectedValue, compareArraysAsSet),
    ),
    message: () => {
      const to = this.isNot ? 'not to' : 'to'
      const matcher = `${this.isNot ? '.not' : ''}.toHaveFormValues`
      const commonKeyValues = Object.keys(formValues)
        .filter(key => expectedValues.hasOwnProperty(key))
        .reduce((obj, key) => ({...obj, [key]: formValues[key]}), {})
      return [
        this.utils.matcherHint(matcher, 'element', ''),
        `Expected the element ${to} have form values`,
        this.utils.diff(expectedValues, commonKeyValues),
      ].join('\n\n')
    },
  }
}