feat: custom import rewriter

closes #25

src/core/ast.ts

@@ -70,7 +70,7 @@ export function rewriteImports(
       )
     }
 
-    if (final) {
+    if (final && final !== source.value) {
       final = final.replaceAll('\\', '/')
       if (!/^\.\.?\//.test(final)) {
         final = `./${final}`

src/core/options.ts

@@ -15,6 +15,10 @@ export type Options = {
   autoAddExts?: boolean
   /** Patch `export default` in `.d.cts` to `export = ` */
   patchCjsDefaultExport?: boolean
+  rewriteImports?: (
+    id: string,
+    importer: string,
+  ) => string | void | null | undefined
 } & (
   | {
       /**
@@ -38,7 +42,7 @@ type Overwrite<T, U> = Pick<T, Exclude<keyof T, keyof U>> & U
 
 export type OptionsResolved = Overwrite<
   Required<Options>,
-  Pick<Options, 'enforce' | 'extraOutdir'>
+  Pick<Options, 'enforce' | 'extraOutdir' | 'rewriteImports'>
 >
 
 export function resolveOptions(options: Options): OptionsResolved {
@@ -51,5 +55,6 @@ export function resolveOptions(options: Options): OptionsResolved {
     extraOutdir: options.extraOutdir,
     autoAddExts: options.autoAddExts || false,
     patchCjsDefaultExport: options.patchCjsDefaultExport || false,
+    rewriteImports: options.rewriteImports,
   }
 }

src/index.ts

@@ -139,17 +139,34 @@ export const IsolatedDecl: UnpluginInstance<Options | undefined, false> =
       const imports = filterImports(program)
 
       const s = new MagicString(dts)
-      if (options.autoAddExts) {
+      if (options.autoAddExts || options.rewriteImports) {
         for (const i of imports) {
           const { source } = i
-          if (path.basename(source.value).includes('.')) continue
-
-          const resolved = await resolve(context, source.value, id)
-          if (!resolved || resolved.external) continue
-          if (resolved.id.endsWith('.ts') || resolved.id.endsWith('.tsx')) {
-            i.suffix = '.js'
-            source.value = (source.originalValue = source.value) + i.suffix
-            s.overwrite(source.start + 1, source.end - 1, source.value)
+          let { value } = source
+
+          if (options.rewriteImports) {
+            const result = options.rewriteImports(value, id)
+            if (typeof result === 'string') {
+              value = result
+            }
+          }
+
+          if (
+            options.autoAddExts &&
+            (path.isAbsolute(value) || value[0] === '.') &&
+            !path.basename(value).includes('.')
+          ) {
+            const resolved = await resolve(context, value, id)
+            if (!resolved || resolved.external) continue
+            if (resolved.id.endsWith('.ts') || resolved.id.endsWith('.tsx')) {
+              value = value + (i.suffix = '.js')
+            }
+          }
+
+          if (source.value !== value) {
+            source.originalValue = source.value
+            source.value = value
+            s.overwrite(source.start + 1, source.end - 1, value)
           }
         }
       }
@@ -339,16 +356,18 @@ export const IsolatedDecl: UnpluginInstance<Options | undefined, false> =
 
         const textEncoder = new TextEncoder()
         for (const [filename, { s }] of Object.entries(outputFiles)) {
-          let source = s.toString()
           const outDir = build.initialOptions.outdir
           let outFile = `${path.relative(inputBase, filename)}.d.${outExt}`
           if (options.extraOutdir) {
             outFile = path.join(options.extraOutdir, outFile)
           }
           const filePath = outDir ? path.resolve(outDir, outFile) : outFile
+
+          let source = s.toString()
           if (options.patchCjsDefaultExport && filePath.endsWith('.d.cts')) {
             source = patchCjsDefaultExport(source)
           }
+
           if (write) {
             await mkdir(path.dirname(filePath), { recursive: true })
             await writeFile(filePath, source)

tests/__snapshots__/rollup.test.ts.snap

@@ -1,5 +1,17 @@
 // Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
 
+exports[`rollup > custom rewriter 1`] = `
+"// index.d.ts
+export type * from './test.ts';
+
+// index.js
+
+
+// test.d.ts
+export type Str = string;
+"
+`;
+
 exports[`rollup > generate basic 1`] = `
 "// main.js
 function Component() {

tests/fixtures/import-rewriter/index.ts

@@ -0,0 +1,2 @@
+// @ts-ignore
+export type * from '~/test.ts'

tests/fixtures/import-rewriter/test.ts

@@ -0,0 +1 @@
+export type Str = string

tests/rollup.test.ts

@@ -11,8 +11,8 @@ describe('rollup', () => {
   const TEST_SANDBOX_FOLDER = path.resolve(__dirname, 'temp/rollup')
 
   test('generate basic', async () => {
-    const input = path.resolve(__dirname, 'fixtures/basic/main.ts')
-    const dist = path.resolve(__dirname, `${TEST_SANDBOX_FOLDER}/basic`)
+    const dir = 'basic'
+    const input = path.resolve(fixtures, dir, 'main.ts')
 
     const bundle = await rollup({
       input,
@@ -25,10 +25,7 @@ describe('rollup', () => {
       ],
       logLevel: 'silent',
     })
-
-    const result = await bundle.generate({
-      dir: dist,
-    })
+    const result = await bundle.generate({})
 
     expect(outputToSnapshot(result.output)).toMatchSnapshot()
   })
@@ -80,6 +77,42 @@ describe('rollup', () => {
 
     expect(await getFileSnapshot(dist)).toMatchSnapshot()
   })
+
+  test('custom rewriter', async () => {
+    const dir = 'import-rewriter'
+    const input = path.resolve(fixtures, dir, 'index.ts')
+
+    let importer
+    const bundle = await rollup({
+      input,
+      plugins: [
+        {
+          name: 'resolver',
+          resolveId(id, importer, opt) {
+            if (id[0] === '~') {
+              id = `.${id.slice(1)}`
+              return this.resolve(id, importer, opt)
+            }
+          },
+        },
+        UnpluginIsolatedDecl({
+          autoAddExts: true,
+          rewriteImports(id, _importer) {
+            if (id[0] === '~') {
+              importer = _importer
+              return `.${id.slice(1)}`
+            }
+          },
+        }),
+        esbuild(),
+      ],
+      logLevel: 'silent',
+    })
+    const result = await bundle.generate({})
+
+    expect(outputToSnapshot(result.output)).toMatchSnapshot()
+    expect(importer).toBe(path.resolve(fixtures, dir, 'index.ts'))
+  })
 })
 
 async function getFileSnapshot(dir: string) {