self.__WB_MANIFEST is replaced only on the first occurrence

[ItalyPaleAle]

Library Affected:

workbox-webpack-plugin

Browser & Platform:

Webpack 5
Workbox 6.0.0-rc.0

Issue Description:

I have this code in my service worker:

if (self.__WB_MANIFEST) {
    console.log('precached', self.__WB_MANIFEST)
    precacheController.addToCacheList(self.__WB_MANIFEST)
}

And this in the webpack config:

        new InjectManifest({
            swSrc: './src/sw/sw.js',
            include: undefined,
        }),

After building this (without minification), the output files has self.__WB_MANIFEST replaced with the manifest only on the first occurrence:

// Manifest omitted
if ([{...}]) {
    console.log('precached', self.__WB_MANIFEST)
    sw_precacheController.addToCacheList(self.__WB_MANIFEST)
}

Instead, the manifest should have been replaced in all occurrences.

[jeffposnick]

This is a difference in behavior between workbox-build's version of injectManifest, and workbox-webpack-plugin's InjectManifest. In workbox-build we treat multiple instance of self.__WB_MANIFEST as a fatal error:

workbox/packages/workbox-build/src/inject-manifest.js

Lines 152 to 153 in f2ef912

	assert(injectionResults.length === 1, errors['multiple-injection-points'] +
	options.injectionPoint);

I am going to standardize things so that workbox-webpack-plugin does the same instead of just silently replacing the first instance.

The rationale behind this behavior is that the precache manifest might be lengthy, and storing multiple copies of it in the same service worker file is a waste of bytes. You can do the following if you'd like to, e.g., log it and also pass it to workbox-precaching:

const manifest = self.__WB_MANIFEST;
if (manifest) {
    console.log('precached', manifest);
    precacheController.addToCacheList(manifest);
}

[ItalyPaleAle]

Thanks. That's what I ended up doing indeed and I understand the rationale.

However, can I recommend showing an error in the console if people try to replace it more than once? Right now, it silently fails and that made me spend quite a bit of time trying to debug this.

[jeffposnick]

Yup, I'm going to treat this as a compilation error in v6.

[tangdexin]

i have the same error

[jeffposnick]

@tangdexin, please only include the symbol self.__WB_MANIFEST in your swSrc file once. If you need to refer to the manifest multiple times, assign self.__WB_MANIFEST to a variable first:

const manifest = self.__WB_MANIFEST;

// Do whatever you want with `manifest`:
if (manifest) {
    console.log('precached', manifest);
    precacheController.addToCacheList(manifest);
}

[tangdexin]

@tangdexin, please only include the symbol self.__WB_MANIFEST in your swSrc file once. If you need to refer to the manifest multiple times, assign self.__WB_MANIFEST to a variable first:

const manifest = self.__WB_MANIFEST;

// Do whatever you want with `manifest`:
if (manifest) {
    console.log('precached', manifest);
    precacheController.addToCacheList(manifest);
}

It works , thanks very much

[Alkaidd]

version: "workbox-webpack-plugin": "6.6.0"
In this version, i have the same error even if i commented out "self.__WB_MANIFEST" while run dev.
For example:

const ignored = self.__WB_MANIFEST;
// precacheAndRoute(self.__WB_MANIFEST)

This will cause same error in dev, but work well in build.
After deleting the comment, i run dev successfully.

[FleetAdmiralJakob]

Same issue here. Commented out __SW_MANIFEST counts as it is not commented out.