0dd0ef226c
This PR fixes tree-shaking for the metadata image generation module
(e.g. `opengraph-image.js` and other conventions) when the page has
`runtime = 'edge'`.
## Details
The first step of this fix is to change this from the loader:
```js
import * as exported from "./opengraph-image.js"
```
to be necessary fields only (so the `default` export can potentially be
removed):
```js
import { alt, size } from "./opengraph-image.js"
```
To know which fields are exported, we need to load the module first via
Webpack loader's `loadModule` API and check its
`HarmonyExportSpecifierDependency` dependencies.
This is the first step to make it tree-shakable. Since we have
`./opengraph-image.js` used in another entry, the actual image API route
`opengraph-image/route.js`:
```js
import * as image from "./opengraph-image.js"
```
Webpack still treats both as the same module and generates one chunk for
it. We want to "fork" it into two modules. The technique here is to add
a noop resource query and make it:
```js
import { alt, size } from "./opengraph-image.js?__next_metadata_image_meta__"
```
So it won't be shared in the chunk (as it's a different request), and
can be concatenated inline.
However that's not enough, the inlined result will still have all
imports from our `opengraph-image.js`, including `import { ImageResponse
} from 'next/server'`. Because we can't simply add `"sideEffects":
false` in Next.js' package.json, we need a way to mark this import as
side-effect free. I went through
https://github.com/webpack/webpack/blob/main/lib/optimize/SideEffectsFlagPlugin.js
and used the same method to mark that module with
`module.factoryMeta.sideEffectFree = true`.
With all these added, the page bundle will no longer contain the
`ImageResponse` instance.
## Result
The difference is quite amazing, for the new added test (an empty Edge
runtime page with an opengrah image file) here're the before/after
metrics for the `page.js` server bundle:
Edge bundle size: 892kB → 500kB.
Build time: 26.792s → 8.830s.
|
||
|---|---|---|
| .. | ||
| create-next-app | ||
| eslint-config-next | ||
| eslint-plugin-next | ||
| font | ||
| next | ||
| next-bundle-analyzer | ||
| next-codemod | ||
| next-env | ||
| next-mdx | ||
| next-plugin-storybook | ||
| next-polyfill-module | ||
| next-polyfill-nomodule | ||
| next-swc | ||
| react-dev-overlay | ||
| react-refresh-utils | ||