feat(src): add support for arbitrary run order of plugin under test (#91)

Author: Xunnamius

src/__tests__/plugin-tester.js

@@ -2,7 +2,7 @@ import fs from 'fs'
 import path from 'path'
 import assert from 'assert'
 import {EOL} from 'os'
-import pluginTester from '../plugin-tester'
+import pluginTester, {runPluginUnderTestHere} from '../plugin-tester'
 import prettierFormatter from '../formatters/prettier'
 import unstringSnapshotSerializer from '../unstring-snapshot-serializer'
 import identifierReversePlugin from './helpers/identifier-reverse-plugin'
@@ -797,6 +797,46 @@ test('fixtures run plugins in the same order as tests', async () => {
   expect(runOrder2).toStrictEqual(runOrder1)
 })
 
+test('can use runPluginUnderTestHere symbol to alter plugin run order in tests', async () => {
+  const runOrder = []
+
+  await runPluginTester(
+    getOptions({
+      plugin: pluginWithOrderTracking(runOrder, 2),
+      babelOptions: {
+        plugins: [
+          pluginWithOrderTracking(runOrder, 1),
+          runPluginUnderTestHere,
+          pluginWithOrderTracking(runOrder, 3),
+        ],
+      },
+    }),
+  )
+
+  expect(runOrder).toStrictEqual([1, 2, 3])
+})
+
+test('can use runPluginUnderTestHere symbol to alter plugin run order in fixtures', async () => {
+  const runOrder = []
+
+  await runPluginTester(
+    getOptions({
+      plugin: pluginWithOrderTracking(runOrder, 2),
+      tests: null,
+      fixtures: getFixturePath('creates-output-file'),
+      babelOptions: {
+        plugins: [
+          pluginWithOrderTracking(runOrder, 1),
+          runPluginUnderTestHere,
+          pluginWithOrderTracking(runOrder, 3),
+        ],
+      },
+    }),
+  )
+
+  expect(runOrder).toStrictEqual([1, 2, 3])
+})
+
 test('endOfLine - default', async () => {
   await runPluginTester(
     getOptions({

src/index.js

@@ -1,4 +1,4 @@
-import pluginTester from './plugin-tester'
+import pluginTester, {runPluginUnderTestHere} from './plugin-tester'
 import prettierFormatter from './formatters/prettier'
 import unstringSnapshotSerializer from './unstring-snapshot-serializer'
 
@@ -7,7 +7,7 @@ if (typeof expect !== 'undefined' && expect.addSnapshotSerializer) {
   expect.addSnapshotSerializer(unstringSnapshotSerializer)
 }
 
-export {unstringSnapshotSerializer, prettierFormatter}
+export {unstringSnapshotSerializer, prettierFormatter, runPluginUnderTestHere}
 
 function defaultPluginTester(options) {
   return pluginTester({formatResult: prettierFormatter, ...options})

src/plugin-tester.js

@@ -5,6 +5,8 @@ import {EOL} from 'os'
 import mergeWith from 'lodash.mergewith'
 import stripIndent from 'strip-indent'
 
+export const runPluginUnderTestHere = Symbol('run-plugin-under-test-here')
+
 const noop = () => {}
 
 // thanks to node throwing an error if you try to use instanceof with an arrow
@@ -94,6 +96,8 @@ function pluginTester({
         'Cannot enable both skip and only on a test',
       )
 
+      finalizePluginRunOrder(babelOptions)
+
       if (skip) {
         // eslint-disable-next-line jest/no-disabled-tests
         it.skip(title, testerWrapper)
@@ -332,6 +336,8 @@ const createFixtureTests = (fixturesDir, options) => {
         mergeCustomizer,
       )
 
+      finalizePluginRunOrder(babelOptions)
+
       const input = fs.readFileSync(codePath).toString()
       let transformed, ext
       if (babel.transformAsync) {
@@ -447,6 +453,16 @@ function requiredParam(name) {
   throw new Error(`${name} is a required parameter.`)
 }
 
+function finalizePluginRunOrder(babelOptions) {
+  if (babelOptions.plugins.includes(runPluginUnderTestHere)) {
+    babelOptions.plugins.splice(
+      babelOptions.plugins.indexOf(runPluginUnderTestHere),
+      1,
+      babelOptions.plugins.pop(),
+    )
+  }
+}
+
 export default pluginTester
 
 // unfortunately the ESLint plugin for Jest thinks this is a test file