From 73f550ad2598313813731fcc2f135b5c29e3a86e Mon Sep 17 00:00:00 2001
From: Anthony Fu <anthonyfu117@hotmail.com>
Date: Fri, 10 Sep 2021 23:53:46 +0800
Subject: [PATCH] feat: support `buildStart` hook, close #14

---
 README.md            | 6 ++++--
 src/types.ts         | 1 +
 src/webpack/index.ts | 2 ++
 3 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index 0ee6af32..9830b8d6 100644
--- a/README.md
+++ b/README.md
@@ -19,13 +19,15 @@ Currently supports:
 
 | Hook | Rollup | Vite | Webpack |
 | ---- | ------ | ---- | ------- |
-| `transformInclude` | ✅ | ✅ | ✅ |
+| [`buildStart`](https://rollupjs.org/guide/en/#buildstart) | ✅ | ✅ | ✅ |
+| `transformInclude`* | ✅ | ✅ | ✅ |
 | [`transform`](https://rollupjs.org/guide/en/#transformers) | ✅ | ✅ | ✅ |
 | [`enforce`](https://rollupjs.org/guide/en/#enforce) | ❌* | ✅ | ✅ |
 | [`resolveId`](https://rollupjs.org/guide/en/#resolveid) | ✅ | ✅ | ✅ |
 | [`load`](https://rollupjs.org/guide/en/#load) | ✅ | ✅ | ✅ |
 
-- *: Rollup does not support using `enforce` to control the order of plugins. Users will need to maintain the order manually.
+- *: Webpack's id filter is outside of loader logic; an additional hook is needed for better perf on Webpack. In Rollup and Vite, this hook has been polyfilled to match the behaviors. See for following usage examples.
+- **: Rollup does not support using `enforce` to control the order of plugins. Users need to maintain the order manually.
 
 ## Usage
 
diff --git a/src/types.ts b/src/types.ts
index d248a3be..b60b9ade 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -16,6 +16,7 @@ export type TransformResult = string | { code: string; map?: SourceMap | null; }
 export interface UnpluginOptions {
   name: string;
   enforce?: 'post' | 'pre' | undefined;
+  buildStart?: () => Promise<void> | void;
   transformInclude?: (id: string) => boolean;
   transform?: (this: UnpluginContext, code: string, id: string) => Thenable<TransformResult>;
   load?: (this: UnpluginContext, id: string) => Thenable<TransformResult>
diff --git a/src/webpack/index.ts b/src/webpack/index.ts
index b325a3f3..bc36cb2f 100644
--- a/src/webpack/index.ts
+++ b/src/webpack/index.ts
@@ -137,6 +137,8 @@ export function getWebpackPlugin<UserOptions = {}> (
         if (plugin.webpack) {
           plugin.webpack(compiler)
         }
+
+        plugin.buildStart?.()
       }
     }
   }