feat(toTypeDeclarationFile): merge imports with the same name into union

src/utils.ts

@@ -180,21 +180,41 @@ export function stripFileExtension(path: string) {
   return path.replace(/\.[a-z]+$/i, '')
 }
 
+function groupImportsByName(imports: Import[]): Map<string, Import[]> {
+  const map = new Map<string, Import[]>()
+  for (const i of imports) {
+    const name = i.as ?? i.name
+    if (!map.has(name)) {
+      map.set(name, [])
+    }
+    map.get(name)!.push(i)
+  }
+  return map
+}
+
 export function toTypeDeclarationItems(imports: Import[], options?: TypeDeclarationOptions) {
-  return imports
-    .map((i) => {
-      const from = options?.resolvePath?.(i) || stripFileExtension(i.typeFrom || i.from)
-      let typeDef = ''
-      if (i.with)
-        typeDef += `import('${from}', { with: ${stringifyWith(i.with)} })`
-      else
-        typeDef += `import('${from}')`
-
-      if (i.name !== '*' && i.name !== '=')
-        typeDef += identifierRE.test(i.name) ? `.${i.name}` : `['${i.name}']`
-
-      return `const ${i.as}: typeof ${typeDef}`
-    })
+  const groupedImports = groupImportsByName(imports)
+
+  function generateTypeDef(i: Import) {
+    const from = options?.resolvePath?.(i) || stripFileExtension(i.typeFrom || i.from)
+    let typeDef = ''
+    if (i.with)
+      typeDef += `import('${from}', { with: ${stringifyWith(i.with)} })`
+    else
+      typeDef += `import('${from}')`
+
+    if (i.name !== '*' && i.name !== '=')
+      typeDef += identifierRE.test(i.name) ? `.${i.name}` : `['${i.name}']`
+    return typeDef
+  }
+
+  const declarations: string[] = []
+  for (const [name, importGroup] of groupedImports.entries()) {
+    const typeDefs = importGroup.map(i => `typeof ${generateTypeDef(i)}`)
+    declarations.push(`const ${name}: ${typeDefs.join(' | ')}`)
+  }
+
+  return declarations
     .sort()
 }
 

test/dts.test.ts

@@ -1,5 +1,6 @@
-import { expect, it } from 'vitest'
-import { createUnimport } from '../src'
+import type { Import } from '../src'
+import { describe, expect, it } from 'vitest'
+import { createUnimport, toTypeDeclarationFile } from '../src'
 
 it('dts', async () => {
   const cwd = process.cwd().replace(/\\/g, '/')
@@ -143,3 +144,22 @@ it('should compat with `export =`', async () => {
     }"
   `)
 })
+
+describe('toTypeDeclarationFile', () => {
+  it('should merge multiple imports into union type', async () => {
+    const imports: Import[] = [
+      { name: 'a', from: 'source-1', as: 'merged' },
+      { name: 'b', from: 'source-2', as: 'merged' },
+      { name: 'c', from: 'source-3', as: 'merged' },
+      { name: 'd', from: 'source-4', as: 'other' },
+    ]
+
+    expect(toTypeDeclarationFile(imports)).toMatchInlineSnapshot(`
+      "export {}
+      declare global {
+        const merged: typeof import('source-1').a | typeof import('source-2').b | typeof import('source-3').c
+        const other: typeof import('source-4').d
+      }"
+    `)
+  })
+})