The manifest option is not working if output.filename is not specified in webpack config

[lmichelin]

Type:

• bug
• feature
• enhancement
• question

Environment:

• OS: Ubuntu
• Browser: N/A
• Library Version: 1.1.8

I'm going to open a PR:

• yes
• no

Package options

new ExtReloader({
  reloadPage: true,
  manifest: "./src/manifest.json",
})

Description:
I was using webpack 4 and the webpack-extension-reloader package and it was working well without specifying output.filename in webpack config as the default behaviour ("[name].js") was ok for me. I decided to migrate to webpack 5 and to use this library instead of webpack-extension-reloader, but to make it work I needed to specify explicitly output.filename even if it's the default value.

If I don't specify the output.filename property, the manifest option is not working:

[webpack-cli] Error: 
    at Object.extractEntries (/home/xxxxxx/xxxxxxxxx/node_modules/webpack-ext-reloader/dist/webpack:/webpack-ext-reloader/src/utils/manifest.ts:21:11)
    at ExtensionReloaderImpl._registerPlugin (/home/xxxxxx/xxxxxxxxx/node_modules/webpack-ext-reloader/dist/webpack:/webpack-ext-reloader/src/ExtensionReloader.ts:93:9)
    at ExtensionReloaderImpl.apply (/home/xxxxxx/xxxxxxxxx/node_modules/webpack-ext-reloader/dist/webpack:/webpack-ext-reloader/src/ExtensionReloader.ts:128:12)
    at createCompiler (/home/xxxxxx/xxxxxxxxx/node_modules/webpack/lib/webpack.js:74:12)
    at /home/xxxxxx/xxxxxxxxx/node_modules/webpack/lib/webpack.js:44:48
    at Array.map (<anonymous>)
    at createMultiCompiler (/home/xxxxxx/xxxxxxxxx/node_modules/webpack/lib/webpack.js:44:33)
    at create (/home/xxxxxx/xxxxxxxxx/node_modules/webpack/lib/webpack.js:118:16)
    at webpack (/home/xxxxxx/xxxxxxxxx/node_modules/webpack/lib/webpack.js:135:47)
    at WebpackCLI.f [as webpack] (/home/xxxxxx/xxxxxxxxx/node_modules/webpack/lib/index.js:55:16)

Thanks for your support.

[rushilsrivastava]

I can't confirm whether not specifying output.filename worked in the previous versions or not, but this seems to be an intentional design choice and is not a bug. Ref: v4 vs v5.

This is an intentional design choice because we want to ensure that the output matches that of what is in the manifest. In the meantime, I've added a more helpful error message.