notes/node_modules/stylelint/lib/testUtils/createRuleTester.js

"use strict"

const _ = require("lodash")
const assignDisabledRanges = require("../assignDisabledRanges")
const basicChecks = require("./basicChecks")
const lessSyntax = require("postcss-less")
const normalizeRuleSettings = require("../normalizeRuleSettings")
const postcss = require("postcss")
const scssSyntax = require("postcss-scss")
const sugarss = require("sugarss")

/**
 * Create a stylelint rule testing function.
 *
 * Pass in an `equalityCheck` function. Given some information,
 * this checker should use Whatever Test Runner to perform
 * equality checks.
 *
 * `equalityCheck` should accept two arguments:
 * - `processCss` {Promise}: A Promise that resolves with an array of
 *   comparisons that you need to check (documented below).
 * - `context` {object}: An object that contains additional information
 *   you may need:
 *   - `caseDescription` {string}: A description of the test case as a whole.
 *   	 Will look like this:
 *   	   > rule: value-list-comma-space-before
 *   	   > config: "always-single-line"
 *   	   > code: "a { background-size: 0 ,0;\n}"
 *   - `comparisonCount` {number}: The number of comparisons that
 *     will need to be performed (e.g. useful for tape).
 *   - `completeAssertionDescription` {string}: While each individual
 *   	 comparison may have its own description, this is a description
 *   	 of the whole assertion (e.g. useful for Mocha).
 *   - `only` {boolean}: If `true`, the test runner should only run this
 *     test case (e.g. `test.only` in tape, `describe.only` in Mocha).
 *
 * `processCss` is a Promsie that resolves with an array of comparisons.
 * Each comparison has the following properties:
 * - `actual` {any}: Some actual value.
 * - `expected` {any}: Some expected value.
 * - `description` {string}: A (possibly empty) description of the comparison.
 *
 * Within `equalityCheck`, you need to ensure that you:
 * - Set up the test case.
 * - When `processCss` resolves, loop through every comparison.
 * - For each comparison, make an assertion checking that `actual === expected`.
 *
 * The `testRule` function that you get has a simple signature:
 * `testRule(rule, testGroupDescription)`.
 *
 * `rule` is just the rule that you are testing (a function).
 *
 * `testGroupDescription` is an object fitting the following schema.
 *
 * Required properties:
 * - `ruleName` {string}: The name of the rule. Used in descriptions.
 * - `config` {any}: The rule's configuration for this test group.
 *   Should match the format you'd use in `.stylelintrc`.
 * - `accept` {array}: An array of objects describing test cases that
 *   should not violate the rule. Each object has these properties:
 *   - `code` {string}: The source CSS to check.
 *   - `description` {[string]}: An optional description of the case.
 * - `reject` {array}: An array of objects describing test cases that
 *   should violate the rule once. Each object has these properties:
 *   - `code` {string}: The source CSS to check.
 *   - `message` {string}: The message of the expected violation.
 *   - `line` {[number]}: The expected line number of the violation.
 *     If this is left out, the line won't be checked.
 *   - `column` {[number]}: The expected column number of the violation.
 *     If this is left out, the column won't be checked.
 *   - `description` {[string]}: An optional description of the case.
 *
 * Optional properties:
 * - `syntax` {"css"|"scss"|"less"|"sugarss"}: Defaults to `"css"`.
 * - `skipBasicChecks` {boolean}: Defaults to `false`. If `true`, a
 *   few rudimentary checks (that should almost always be included)
 *   will not be performed.
 * - `preceedingPlugins` {array}: An array of PostCSS plugins that
 *   should be run before the CSS is tested.
 *
 * @param {function} equalityCheck - Described above
 * @return {function} testRule - Decsribed above
 */
let onlyTest

function checkCaseForOnly(caseType, testCase) {
  if (!testCase.only) {
    return
  }
  /* istanbul ignore next */
  if (onlyTest) {
    throw new Error("Cannot use `only` on multiple test cases")
  }
  onlyTest = { case: testCase, type: caseType }
}

module.exports = function (equalityCheck) {
  return function (rule, schema) {
    const alreadyHadOnlyTest = !!onlyTest
    if (schema.accept) {
      schema.accept.forEach(_.partial(checkCaseForOnly, "accept"))
    }

    if (schema.reject) {
      schema.reject.forEach(_.partial(checkCaseForOnly, "reject"))
    }

    if (onlyTest) {
      schema = _.assign(_.omit(schema, [ "accept", "reject" ]), {
        skipBasicChecks: true,
        [onlyTest.type]: [onlyTest.case],
      })
    }

    if (!alreadyHadOnlyTest) {
      process.nextTick(() => {
        processGroup(rule, schema, equalityCheck)
      })
    }
  }
}

function processGroup(rule, schema, equalityCheck) {
  const ruleName = schema.ruleName

  const ruleOptions = normalizeRuleSettings(schema.config, ruleName)
  const rulePrimaryOptions = ruleOptions[0]
  const ruleSecondaryOptions = ruleOptions[1]

  let printableConfig = rulePrimaryOptions ? JSON.stringify(rulePrimaryOptions) : ""
  if (printableConfig && ruleSecondaryOptions) {
    printableConfig += ", " + JSON.stringify(ruleSecondaryOptions)
  }

  function createCaseDescription(code) {
    let text = `\n> rule: ${ruleName}\n`
    text += `> config: ${printableConfig}\n`
    text += `> code: ${JSON.stringify(code)}\n`
    return text
  }

  // Process the code through the rule and return
  // the PostCSS LazyResult promise
  function postcssProcess(code) {
    const postcssProcessOptions = {}

    switch (schema.syntax) {
      case "scss":
        postcssProcessOptions.syntax = scssSyntax
        break
      case "less":
        postcssProcessOptions.syntax = lessSyntax
        break
      case "sugarss":
        postcssProcessOptions.syntax = sugarss
        break
    }

    const processor = postcss()
    processor.use(assignDisabledRanges)

    if (schema.preceedingPlugins) {
      schema.preceedingPlugins.forEach(processor.use)
    }

    return processor.use(rule(rulePrimaryOptions, ruleSecondaryOptions)).process(code, postcssProcessOptions)
  }

  // Apply the basic positive checks unless
  // explicitly told not to
  const passingTestCases = schema.skipBasicChecks ? schema.accept : basicChecks.concat(schema.accept)

  if (passingTestCases && passingTestCases.length) {
    passingTestCases.forEach(acceptedCase => {
      if (!acceptedCase) {
        return
      }
      const assertionDescription = spaceJoin(acceptedCase.description, "should be accepted")
      const resultPromise = postcssProcess(acceptedCase.code).then(postcssResult => {
        const warnings = postcssResult.warnings()
        return [{
          expected: 0,
          actual: warnings.length,
          description: assertionDescription,
        }]
      }).catch(err => console.log(err.stack)) // eslint-disable-line no-console

      equalityCheck(resultPromise, {
        comparisonCount: 1,
        caseDescription: createCaseDescription(acceptedCase.code),
        completeAssertionDescription: assertionDescription,
      })
    })
  }

  if (schema.reject && schema.reject.length) {
    schema.reject.forEach(rejectedCase => {
      let completeAssertionDescription = "should register one warning"
      let comparisonCount = 1
      if (rejectedCase.line) {
        comparisonCount++
        completeAssertionDescription += ` on line ${rejectedCase.line}`
      }
      if (rejectedCase.column !== undefined) {
        comparisonCount++
        completeAssertionDescription += ` on column ${rejectedCase.column}`
      }
      if (rejectedCase.message) {
        comparisonCount++
        completeAssertionDescription += ` with message "${rejectedCase.message}"`
      }

      const resultPromise = postcssProcess(rejectedCase.code).then(postcssResult => {
        const warnings = postcssResult.warnings()
        const warning = warnings[0]

        const comparisons = [{
          expected: 1,
          actual: warnings.length,
          description: spaceJoin(rejectedCase.description, "should register one warning"),
        }]

        if (rejectedCase.line) {
          comparisons.push({
            expected: rejectedCase.line,
            actual: _.get(warning, "line"),
            description: spaceJoin(rejectedCase.description, `should warn on line ${rejectedCase.line}`),
          })
        }
        if (rejectedCase.column !== undefined) {
          comparisons.push({
            expected: rejectedCase.column,
            actual: _.get(warning, "column"),
            description: spaceJoin(rejectedCase.description, `should warn on column ${rejectedCase.column}`),
          })
        }
        if (rejectedCase.message) {
          comparisons.push({
            expected: rejectedCase.message,
            actual: _.get(warning, "text"),
            description: spaceJoin(rejectedCase.description, `should warn with message ${rejectedCase.message}`),
          })
        }
        return comparisons
      }).catch(err => console.log(err.stack)) // eslint-disable-line no-console

      equalityCheck(resultPromise, {
        comparisonCount,
        completeAssertionDescription,
        caseDescription: createCaseDescription(rejectedCase.code),
        only: rejectedCase.only,
      })
    })
  }
}

function spaceJoin() {
  return _.compact(Array.from(arguments)).join(" ")
}