fix(forks): wrap defines to support undefined values

packages/vitest/src/utils/config-helpers.ts

@@ -23,14 +23,20 @@ export function getOutputFile(config: PotentialConfig | undefined, reporter: Bui
  */
 export function wrapSerializableConfig(config: ResolvedConfig) {
   let testNamePattern = config.testNamePattern
+  let defines = config.defines
 
   // v8 serialize does not support regex
   if (testNamePattern && typeof testNamePattern !== 'string')
     testNamePattern = `${REGEXP_WRAP_PREFIX}${testNamePattern.toString()}` as unknown as RegExp
 
+  // v8 serialize drops properties with undefined value
+  if (defines)
+    defines = wrapDefines(defines)
+
   return {
     ...config,
     testNamePattern,
+    defines,
   } as ResolvedConfig
 }
 
@@ -45,5 +51,20 @@ export function unwrapSerializableConfig(config: ResolvedConfig) {
       config.testNamePattern = parseRegexp(testNamePattern.slice(REGEXP_WRAP_PREFIX.length))
   }
 
+  if (config.defines && Array.isArray(config.defines.keys)) {
+    const { keys, original } = config.defines as ReturnType<typeof wrapDefines>
+    const defines: ResolvedConfig['defines'] = {}
+
+    // Apply all keys from the original. Entries which had undefined value are missing from original now
+    for (const key of keys)
+      defines[key] = original[key]
+
+    config.defines = defines
+  }
+
   return config
 }
+
+function wrapDefines(input: Record<string, unknown>) {
+  return { keys: Object.keys(input), original: input }
+}

test/core/test/define-ssr.test.ts

@@ -3,6 +3,10 @@ import { afterAll, expect, test } from 'vitest'
 declare let __DEFINE__: string
 declare let __JSON__: any
 declare let __MODE__: string
+declare let __UNDEFINED__: undefined
+declare let __NULL__: null
+declare let __ZERO__: 0
+declare let __FALSE__: false
 declare let SOME: {
   VARIABLE: string
   SOME: {
@@ -64,3 +68,10 @@ test('dotted defines are processed by Vite, but cannot be reassigned', () => {
   SOME.VARIABLE = 'new variable'
   expect(SOME.VARIABLE).not.toBe('new variable')
 })
+
+test('falsy defines are passed', () => {
+  expect(__UNDEFINED__).toBe(undefined)
+  expect(__NULL__).toBe(null)
+  expect(__ZERO__).toBe(0)
+  expect(__FALSE__).toBe(false)
+})

test/core/test/define-web.test.ts

@@ -5,6 +5,10 @@ import { afterAll, expect, test } from 'vitest'
 declare let __DEFINE__: string
 declare let __JSON__: any
 declare let __MODE__: string
+declare let __UNDEFINED__: undefined
+declare let __NULL__: null
+declare let __ZERO__: 0
+declare let __FALSE__: false
 declare let SOME: {
   VARIABLE: string
   SOME: {
@@ -61,3 +65,10 @@ test('dotted defines can be reassigned', () => {
   SOME.VARIABLE = 'new variable'
   expect(SOME.VARIABLE).toBe('new variable')
 })
+
+test('falsy defines are passed', () => {
+  expect(__UNDEFINED__).toBe(undefined)
+  expect(__NULL__).toBe(null)
+  expect(__ZERO__).toBe(0)
+  expect(__FALSE__).toBe(false)
+})

test/core/vite.config.ts

@@ -32,6 +32,10 @@ export default defineConfig({
     '__MODE__': 'process.env.MODE',
     'SOME.VARIABLE': '"variable"',
     'SOME.SOME.VARIABLE': '"nested variable"',
+    '__UNDEFINED__': undefined,
+    '__NULL__': null,
+    '__ZERO__': 0,
+    '__FALSE__': false,
   },
   resolve: {
     alias: [