fix(config): support async function configuration

Closes #10

lib/__tests__/getData.test.js

@@ -3,7 +3,14 @@ const fs = require('fs')
 const getData = require('../getData')
 
 const configPath = './jest.config.js'
-
+const coverageThreshold = {
+  global: {
+    branches: 10,
+    functions: 20,
+    lines: 30,
+    statements: 40,
+  },
+}
 const reportContents = JSON.stringify({
   total: {
     branches: { pct: 80 },
@@ -16,27 +23,43 @@ const reportContents = JSON.stringify({
 jest.mock('fs')
 jest.spyOn(process, 'cwd').mockImplementation(() => '/workingDir')
 
-jest.mock(
-  '../jest.config.js',
-  () => ({
-    coverageThreshold: {
-      global: {
-        branches: 10,
-        functions: 20,
-        lines: 30,
-        statements: 40,
-      },
-    },
-  }),
-  { virtual: true },
-)
+beforeAll(() => fs.readFileSync.mockReturnValue(reportContents))
+beforeEach(() => jest.resetModules())
+
+it('returns parsed config and report contents', async () => {
+  jest.mock('../jest.config.js', () => ({ coverageThreshold }), {
+    virtual: true,
+  })
+
+  const data = await getData(configPath)
 
-beforeAll(() => {
-  fs.readFileSync.mockReturnValue(reportContents)
+  expect(fs.readFileSync).toHaveBeenCalledTimes(1)
+  expect(fs.readFileSync).toHaveBeenCalledWith(
+    '/workingDir/coverage/coverage-summary.json',
+    'utf8',
+  )
+  expect(data).toStrictEqual({
+    coverages: {
+      branches: { pct: 80 },
+      functions: { pct: 70 },
+      lines: { pct: 60 },
+      statements: { pct: 50 },
+    },
+    thresholds: {
+      branches: 10,
+      functions: 20,
+      lines: 30,
+      statements: 40,
+    },
+  })
 })
 
-it('returns parsed config and report contents when no coverage directory is specified in the jest config', () => {
-  const data = getData(configPath)
+it('returns parsed async config and report contents', async () => {
+  jest.mock('../jest.config.js', () => async () => ({ coverageThreshold }), {
+    virtual: true,
+  })
+
+  const data = await getData(configPath)
 
   expect(fs.readFileSync).toHaveBeenCalledTimes(1)
   expect(fs.readFileSync).toHaveBeenCalledWith(
@@ -59,11 +82,17 @@ it('returns parsed config and report contents when no coverage directory is spec
   })
 })
 
-it('returns parsed config and report contents when a custom coverage directory is specified in the jest config', () => {
-  const config = require('../jest.config.js')
-  const { coverageDirectory: defaultCovergeDirectory } = config
-  config.coverageDirectory = 'custom/coverage/directory'
-  const data = getData(configPath)
+it('returns parsed config and report contents when a custom coverage directory is specified in the jest config', async () => {
+  jest.mock(
+    '../jest.config.js',
+    () => ({
+      coverageThreshold,
+      coverageDirectory: 'custom/coverage/directory',
+    }),
+    { virtual: true },
+  )
+
+  const data = await getData(configPath)
 
   expect(fs.readFileSync).toHaveBeenCalledTimes(1)
   expect(fs.readFileSync).toHaveBeenCalledWith(
@@ -84,5 +113,4 @@ it('returns parsed config and report contents when a custom coverage directory i
       statements: 40,
     },
   })
-  config.coverageDirectory = defaultCovergeDirectory
 })

lib/getData.js

@@ -1,11 +1,12 @@
 const fs = require('fs')
 const path = require('path')
 
-const getData = configPath => {
+const getData = async configPath => {
+  const config = require(configPath)
   const {
     coverageThreshold: { global: thresholds },
     coverageDirectory = 'coverage',
-  } = require(configPath)
+  } = typeof config === 'function' ? await config() : config
   const reportPath = path.resolve(
     process.cwd(),
     coverageDirectory,

lib/index.js

@@ -17,7 +17,7 @@ module.exports = async ({
 } = {}) => {
   const configPath = path.resolve(process.cwd(), 'jest.config.js')
 
-  const { thresholds, coverages } = getData(configPath)
+  const { thresholds, coverages } = await getData(configPath)
   const newThresholds = getNewThresholds(thresholds, coverages, margin)
   const { changes, data } = getChanges(configPath, newThresholds)