fix: ensure bundle fallback wont go to types

src/constants.ts

@@ -35,15 +35,16 @@ export const runtimeExportConventionsFallback = new Map<string, string[]>([
   // ESM only runtime
   ['workerd', ['import', 'default']],
   ['edge-light', ['import', 'default']],
-  ['browser', ['import', 'default']],
-
-  // it could be CJS or ESM
+  // Fallback to default when unsure
   ['electron', ['default']],
   ['react-server', ['default']],
   ['react-native', ['default']],
   ['node', ['default']],
   ['deno', ['default']],
   ['bun', ['default']],
+  ['development', ['default']],
+  ['production', ['default']],
+  ['browser', ['import', 'require', 'default']],
 ])
 export const optimizeConventions = new Set(['development', 'production'])
 export const specialExportConventions = new Set([

src/plugins/alias-plugin.ts

@@ -26,14 +26,17 @@ function findJsBundlePathCallback(
     conditionNames: Set<string>
   },
   specialCondition: string,
-) {
+): boolean {
   const hasBundle = bundlePath != null
   const formatCond = format === 'cjs' ? 'require' : 'import'
 
   const isTypesCondName = conditionNames.has('types')
   const hasFormatCond =
     conditionNames.has('import') || conditionNames.has('require')
 
+  // Check if the format condition is matched:
+  // if there's condition existed, check if the format condition is matched;
+  // if there's no condition, just return true, assuming format doesn't matter;
   const isMatchedFormat = hasFormatCond ? conditionNames.has(formatCond) : true
 
   const isMatchedConditionWithFormat =
@@ -50,7 +53,16 @@ function findJsBundlePathCallback(
     if (!fallback) {
       return false
     } else {
-      return fallback.some((name) => conditionNames.has(name))
+      // Match its own condition first,
+      // e.g. when import utils.js in index.js
+      // In output: index.browser.js should match util.browser.js, fallback to util.js
+      // The last guard condition is to ensure bundle condition but not types file.
+      return (
+        isMatchedFormat &&
+        (conditionNames.has(specialCondition) ||
+          fallback.some((name) => conditionNames.has(name))) &&
+        !conditionNames.has('types')
+      )
     }
   } else {
     return match

test/fixtures/integration-test-template/src/index.js

@@ -1,3 +1,3 @@
-export function Foo() {
-  return <p>Foo</p>
+export function foo() {
+  return 'foo'
 }

test/integration/shared-module-special-condition/package.json

@@ -0,0 +1,13 @@
+{
+  "name": "shared-module-special-condition",
+  "main": "./dist/index.js",
+  "type": "module",
+  "exports": {
+    ".": {
+      "import": "./dist/index.js",
+      "development": "./dist/index.development.js",
+      "production": "./dist/index.production.js",
+      "browser": "./dist/index.browser.js"
+    }
+  }
+}

test/integration/shared-module-special-condition/shared-module-special-condition.test.ts

@@ -0,0 +1,19 @@
+import { createJob, getFileContents } from '../../testing-utils'
+
+describe('integration - shared-module-special-condition', () => {
+  const { distDir } = createJob({
+    directory: __dirname,
+  })
+  it('should work', async () => {
+    const contents = await getFileContents(distDir)
+    const files = [
+      'index.development.js',
+      'index.production.js',
+      'index.browser.js',
+    ]
+    files.forEach((file) => {
+      expect(contents[file]).toContain('./_util.js')
+      expect(contents[file]).not.toContain('./_util.ts')
+    })
+  })
+})

test/integration/shared-module-special-condition/src/_util.ts

@@ -0,0 +1 @@
+export const sharedValue = 'shared-value-text'

test/integration/shared-module-special-condition/src/index.ts

@@ -0,0 +1,5 @@
+import { sharedValue } from './_util'
+
+export function index() {
+  return process.env.NODE_ENV + sharedValue
+}

test/testing-utils/helpers.ts

@@ -44,7 +44,7 @@ type FunctionCondition = (content: string) => Boolean
 
 export async function getFileContents(dir: string, filePaths?: string[]) {
   const results: Record<string, string> = {}
-  const files = filePaths || (await fsp.readdir(dir))
+  const files = filePaths || (await fsp.readdir(dir, { recursive: true }))
   for (const file of files) {
     const fullPath = path.resolve(dir, file)
     const content = await fsp.readFile(fullPath, { encoding: 'utf-8' })