feat(migration): add tsdown to vite lib migration support (#362)

- Add import rewriting: `import { defineConfig } from 'tsdown'` → `import { defineConfig } from '@voidzero-dev/vite-plus/lib'`
- Add declare module rewriting for tsdown
- Add script rewriting: `tsdown` → `vite lib`
- Add unit tests for tsdown import and declare module rewriting
- Add snap test fixture for migration-from-tsdown

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[email protected]>

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Introduces automated migration from `tsdown` to Vite+.
> 
> - Adds import/declare rewrite rules mapping `tsdown` to `@voidzero-dev/vite-plus/lib` with unit tests
> - New `merge_tsdown_config` (Rust core, NAPI binding, and JS export) imports `tsdown.config.*` into `vite.config.*` and injects `lib: tsdownConfig` (idempotent)
> - Migrator detects `tsdown.config.*`; merges JSON config content into `lib` and deletes the file, or adds an import for TS/JS; removes `tsdown` and replaces scripts via rules (`tsdown` → `vite lib`)
> - Updates CLI rules (`vite-tools.yml`) and adds snap tests for `migration-from-tsdown*`; minor scripts: adds `test:unit`
> 
> <sup>Written by [Cursor Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit f0e76cc. This will update automatically on new commits. Configure [here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: fengmk2

crates/vite_migration/src/import_rewriter.rs

@@ -22,6 +22,7 @@ use crate::{ast_grep, file_walker};
 /// - `import { ... } from '@vitest/browser-preview/{name}'` → `import { ... } from '@voidzero-dev/vite-plus/test/browser-preview/{name}'`
 /// - `import { ... } from '@vitest/browser-webdriverio'` → `import { ... } from '@voidzero-dev/vite-plus/test/browser-webdriverio'`
 /// - `import { ... } from '@vitest/browser-webdriverio/{name}'` → `import { ... } from '@voidzero-dev/vite-plus/test/browser-webdriverio/{name}'`
+/// - `import { ... } from 'tsdown'` → `import { ... } from '@voidzero-dev/vite-plus/lib'`
 ///
 /// **Declare module statements:**
 /// - `declare module 'vite' { ... }` → `declare module '@voidzero-dev/vite-plus' { ... }`
@@ -37,6 +38,7 @@ use crate::{ast_grep, file_walker};
 /// - `declare module '@vitest/browser-preview/{name}' { ... }` → `declare module '@voidzero-dev/vite-plus/test/browser-preview/{name}' { ... }`
 /// - `declare module '@vitest/browser-webdriverio' { ... }` → `declare module '@voidzero-dev/vite-plus/test/browser-webdriverio' { ... }`
 /// - `declare module '@vitest/browser-webdriverio/{name}' { ... }` → `declare module '@voidzero-dev/vite-plus/test/browser-webdriverio/{name}' { ... }`
+/// - `declare module 'tsdown' { ... }` → `declare module '@voidzero-dev/vite-plus/lib' { ... }`
 const REWRITE_IMPORT_RULES: &str = r#"---
 id: rewrite-vitest-config-import
 language: TypeScript
@@ -229,6 +231,38 @@ transform:
       replace: vitest/
       by: "@voidzero-dev/vite-plus/test/"
 fix: $NEW_IMPORT
+---
+id: rewrite-tsdown-import
+language: TypeScript
+rule:
+  pattern: $STR
+  kind: string
+  regex: ^['"]tsdown['"]$
+  inside:
+    kind: import_statement
+transform:
+  NEW_IMPORT:
+    replace:
+      source: $STR
+      replace: tsdown
+      by: "@voidzero-dev/vite-plus/lib"
+fix: $NEW_IMPORT
+---
+id: rewrite-declare-module-tsdown
+language: TypeScript
+rule:
+  pattern: $STR
+  kind: string
+  regex: ^['"]tsdown['"]$
+  inside:
+    kind: module
+transform:
+  NEW_IMPORT:
+    replace:
+      source: $STR
+      replace: tsdown
+      by: "@voidzero-dev/vite-plus/lib"
+fix: $NEW_IMPORT
 "#;
 
 /// Result of rewriting imports in a file
@@ -1393,6 +1427,86 @@ declare module '@voidzero-dev/vite-plus/test/browser' {
     name: string;
     configResolved?: (config: ResolvedConfig) => void;
   }
+}"#
+        );
+    }
+
+    #[test]
+    fn test_rewrite_import_content_tsdown() {
+        let tsdown_config = r#"import { defineConfig } from 'tsdown';
+
+export default defineConfig({
+  entry: 'src/index.ts',
+});"#;
+
+        let result = rewrite_import_content(tsdown_config).unwrap();
+        assert!(result.updated);
+        assert_eq!(
+            result.content,
+            r#"import { defineConfig } from '@voidzero-dev/vite-plus/lib';
+
+export default defineConfig({
+  entry: 'src/index.ts',
+});"#
+        );
+    }
+
+    #[test]
+    fn test_rewrite_import_content_tsdown_double_quotes() {
+        let tsdown_config = r#"import { defineConfig } from "tsdown";
+
+export default defineConfig({
+  entry: "src/index.ts",
+});"#;
+
+        let result = rewrite_import_content(tsdown_config).unwrap();
+        assert!(result.updated);
+        assert_eq!(
+            result.content,
+            r#"import { defineConfig } from "@voidzero-dev/vite-plus/lib";
+
+export default defineConfig({
+  entry: "src/index.ts",
+});"#
+        );
+    }
+
+    #[test]
+    fn test_rewrite_declare_module_tsdown() {
+        let content = r#"declare module 'tsdown' {
+  interface BuildConfig {
+    custom?: boolean;
+  }
+}"#;
+
+        let result = rewrite_import_content(content).unwrap();
+        assert!(result.updated);
+        assert_eq!(
+            result.content,
+            r#"declare module '@voidzero-dev/vite-plus/lib' {
+  interface BuildConfig {
+    custom?: boolean;
+  }
+}"#
+        );
+    }
+
+    #[test]
+    fn test_rewrite_declare_module_tsdown_double_quotes() {
+        let content = r#"declare module "tsdown" {
+  interface BuildConfig {
+    custom?: boolean;
+  }
+}"#;
+
+        let result = rewrite_import_content(content).unwrap();
+        assert!(result.updated);
+        assert_eq!(
+            result.content,
+            r#"declare module "@voidzero-dev/vite-plus/lib" {
+  interface BuildConfig {
+    custom?: boolean;
+  }
 }"#
         );
     }

crates/vite_migration/src/lib.rs

@@ -7,4 +7,4 @@ mod vite_config;
 pub use file_walker::{WalkResult, find_ts_files};
 pub use import_rewriter::{BatchRewriteResult, rewrite_imports_in_directory};
 pub use package::rewrite_scripts;
-pub use vite_config::{MergeResult, merge_json_config};
+pub use vite_config::{MergeResult, merge_json_config, merge_tsdown_config};