fix: make declaration files work with multiple entrypoints

closes #316

src/rollup.ts

@@ -1,3 +1,4 @@
+import path from 'path'
 import { parentPort } from 'worker_threads'
 import { InputOptions, OutputOptions, Plugin } from 'rollup'
 import { NormalizedOptions } from './'
@@ -19,6 +20,48 @@ type RollupConfig = {
   outputConfig: OutputOptions
 }
 
+const findLowestCommonAncestor = (filepaths: string[]) => {
+  if (filepaths.length <= 1) return ''
+  const [first, ...rest] = filepaths
+  let ancestor = first.split('/')
+  for (const filepath of rest) {
+    const directories = filepath.split('/', ancestor.length)
+    let index = 0
+    for (const directory of directories) {
+      if (directory === ancestor[index]) {
+        index += 1
+      } else {
+        ancestor = ancestor.slice(0, index)
+        break
+      }
+    }
+    ancestor = ancestor.slice(0, index)
+  }
+
+  return ancestor.length <= 1 && ancestor[0] === ''
+    ? '/' + ancestor[0]
+    : ancestor.join('/')
+}
+
+// Make sure the Rollup entry is an object
+// We use the base path (without extension) as the entry name
+// To make declaration files work with multiple entrypoints
+// See #316
+const toObjectEntry = (entry: string[]) => {
+  entry = entry.map((e) => e.replace(/\\/g, '/'))
+  const ancester = findLowestCommonAncestor(entry)
+  return entry.reduce((result, item) => {
+    const key = item
+      .replace(ancester, '')
+      .replace(/^\//, '')
+      .replace(/\.[a-z]+$/, '')
+    return {
+      ...result,
+      [key]: item,
+    }
+  }, {})
+}
+
 const getRollupConfig = async (
   options: NormalizedOptions
 ): Promise<RollupConfig> => {
@@ -37,6 +80,10 @@ const getRollupConfig = async (
       ? { entry: options.entryPoints }
       : { entry: options.entryPoints, ...options.dts }
 
+  if (Array.isArray(dtsOptions.entry)) {
+    dtsOptions.entry = toObjectEntry(dtsOptions.entry)
+  }
+
   let tsResolveOptions: TsResolveOptions | undefined
 
   if (dtsOptions.resolve) {

test/index.test.ts

@@ -21,6 +21,7 @@ async function run(
   testDir: string,
   files: { [name: string]: string },
   options: {
+    entry?: string[]
     flags?: string[]
     env?: Record<string, string>
   } = {}
@@ -34,10 +35,12 @@ async function run(
     })
   )
 
+  const entry = options.entry || ['input.ts']
+
   // Run tsup cli
   const { exitCode, stdout, stderr } = await execa(
     bin,
-    ['input.ts', ...(options.flags || [])],
+    [...entry, ...(options.flags || [])],
     {
       cwd: testDir,
       env: { ...process.env, ...options.env },
@@ -49,13 +52,14 @@ async function run(
   }
 
   // Get output
-  const output = await fs.readFile(resolve(testDir, 'dist/input.js'), 'utf8')
   const outFiles = await glob('**/*', {
     cwd: resolve(testDir, 'dist'),
   }).then((res) => res.sort())
 
   return {
-    output,
+    get output() {
+      return fs.readFileSync(resolve(testDir, 'dist/input.js'), 'utf8')
+    },
     outFiles,
     logs,
     getFileContent(filename: string) {
@@ -987,3 +991,26 @@ test('code splitting in cjs format', async () => {
     "
   `)
 })
+
+test('declaration files with multiple entrypoints #316', async () => {
+  const { getFileContent } = await run(
+    getTestName(),
+    {
+      'src/index.ts': `export const foo = 1`,
+      'src/bar/index.ts': `export const bar = 'bar'`,
+    },
+    { flags: ['--dts'], entry: ['src/index.ts', 'src/bar/index.ts'] }
+  )
+  expect(await getFileContent('dist/index.d.ts')).toMatchInlineSnapshot(`
+    "declare const foo = 1;
+
+    export { foo };
+    "
+  `)
+  expect(await getFileContent('dist/bar/index.d.ts')).toMatchInlineSnapshot(`
+    "declare const bar = \\"bar\\";
+
+    export { bar };
+    "
+  `)
+})