fix: rewrite emitted declaration specifiers

Author: chrisbbreuer

packages/dtsx/src/generator.ts

@@ -684,6 +684,44 @@ function getOutputPath(inputPath: string, config: DtsGenerationConfig): string {
   }
 }
 
+function getDeclarationSpecifier(fromOutputPath: string, toOutputPath: string): string {
+  let specifier = relative(dirname(fromOutputPath), toOutputPath).replace(/\\/g, '/')
+  specifier = specifier
+    .replace(/\.d\.mts$/, '')
+    .replace(/\.d\.cts$/, '')
+    .replace(/\.d\.ts$/, '')
+
+  if (!specifier.startsWith('.')) {
+    specifier = `./${specifier}`
+  }
+
+  return specifier
+}
+
+function rewriteRelativeDeclarationSpecifiers(content: string, filePath: string, config: DtsGenerationConfig): string {
+  const outputPath = getOutputPath(filePath, config)
+
+  const rewriteSpecifier = (specifier: string): string => {
+    const resolved = resolveRelativeSpecifier(specifier, filePath)
+    if (!resolved.isRelative || !resolved.resolved) {
+      return specifier
+    }
+
+    return getDeclarationSpecifier(outputPath, getOutputPath(resolved.resolved, config))
+  }
+
+  return content
+    .replace(/\b(from\s*)(['"])(\.{1,2}\/[^'"]+)\2/g, (_match, prefix: string, quote: string, specifier: string) => {
+      return `${prefix}${quote}${rewriteSpecifier(specifier)}${quote}`
+    })
+    .replace(/\b(import\s*)(['"])(\.{1,2}\/[^'"]+)\2/g, (_match, prefix: string, quote: string, specifier: string) => {
+      return `${prefix}${quote}${rewriteSpecifier(specifier)}${quote}`
+    })
+    .replace(/\b(import\s*\(\s*)(['"])(\.{1,2}\/[^'"]+)\2/g, (_match, prefix: string, quote: string, specifier: string) => {
+      return `${prefix}${quote}${rewriteSpecifier(specifier)}${quote}`
+    })
+}
+
 /**
  * Process a single TypeScript file and generate its DTS
  */
@@ -755,6 +793,7 @@ async function processFileWithStatsFromSource(
 
   // Process declarations to generate DTS
   let dtsContent = processDeclarations(declarations, context, config.keepComments, config.importOrder)
+  dtsContent = rewriteRelativeDeclarationSpecifiers(dtsContent, filePath, config)
 
   // Run onAfterFile hooks (may modify output)
   if (pluginManager) {

packages/dtsx/test/generator.test.ts

@@ -1,11 +1,24 @@
 import type { DtsGenerationConfig } from '../src/types'
 import { afterEach, describe, expect, it } from 'bun:test'
-import { mkdir, rm, writeFile } from 'node:fs/promises'
+import { mkdir, mkdtemp, readFile, rm, writeFile } from 'node:fs/promises'
+import { tmpdir } from 'node:os'
 import { join } from 'node:path'
 import { generate, processSource } from '../src/generator'
 import { extractDeclarations } from '../src/extractor'
 import { processCode } from './test-utils'
 
+const tempDirs: string[] = []
+
+async function createTempDir(): Promise<string> {
+  const tempDir = await mkdtemp(join(tmpdir(), 'dtsx-generator-'))
+  tempDirs.push(tempDir)
+  return tempDir
+}
+
+afterEach(async () => {
+  await Promise.all(tempDirs.splice(0).map(dir => rm(dir, { recursive: true, force: true })))
+})
+
 describe('processSource (stdin support)', () => {
   it('should process simple variable declaration', () => {
     const source = `export const foo: string = 'bar';`
@@ -97,6 +110,40 @@ describe('processSource (stdin support)', () => {
   })
 })
 
+describe('generate relative declaration specifiers', () => {
+  it('rewrites relative imports and exports from the emitted declaration path', async () => {
+    const tempDir = await createTempDir()
+    const srcDir = join(tempDir, 'src')
+    const outDir = join(tempDir, 'dist')
+
+    await mkdir(join(srcDir, 'nested'), { recursive: true })
+    await writeFile(join(tempDir, 'index.ts'), [
+      `export * from './src/request'`,
+      `export { Thing } from './src/nested/thing'`,
+      `export interface Wrapper { request: import('./src/request').RequestInstance }`,
+    ].join('\n'))
+    await writeFile(join(srcDir, 'request.ts'), `export interface RequestInstance { id: string }\n`)
+    await writeFile(join(srcDir, 'nested', 'thing.ts'), `export interface Thing { name: string }\n`)
+
+    await generate({
+      cwd: tempDir,
+      root: '.',
+      outdir: outDir,
+      entrypoints: ['index.ts'],
+      outputStructure: 'mirror',
+      clean: false,
+      keepComments: true,
+      logLevel: 'error',
+    })
+
+    const output = await readFile(join(outDir, 'index.d.ts'), 'utf8')
+
+    expect(output).toContain(`export * from './src/request';`)
+    expect(output).toContain(`export { Thing } from './src/nested/thing';`)
+    expect(output).toContain(`import('./src/request').RequestInstance`)
+  })
+})
+
 describe('generate with parallel processing', () => {
   const tempDir = join(__dirname, 'temp-parallel-test')
   const inputDir = join(tempDir, 'input')