Webpack does not watch for block.json changes

[Jackie6]

Describe the bug
Since #14770, the block.json is introduced. However, the webpack does not watch for the json files changes.

To reproduce
Steps to reproduce the behavior:

1. npm run dev
2. modify a block.json file
   The webpack does not rebuild the package automatically.

Desktop (please complete the following information):

• OS: Mac OS
• Browser: Chrome
• Version: Gutenberg5.5

[gziolo]

Great catch @Jackie6 👍I totally missed it.

[aduth]

Implementation notes:

• I would expect this should be working by default, since the implementation in Block library: Introduce block.json metadata for all client side blocks #14770 leverages Webpack's built-in JSON import capability. As with any other dependency, Webpack should be monitoring these dependencies for changes and triggering a rebuild automatically.
• Alternatively, while JSON imports are available by default, perhaps it is an option to still specify a json-loader configuration if it is more reliable with triggering a rebuild (perhaps it's even enough to include the rules entry to test .json files, but specify no use loader)
• If none of the above works, consider some third-party plugin which would provide the ability to hook into Webpack's internal watch mechanism to extend the files monitored to include block.json files (example).

[gziolo]

I think the issue is only on Gutenberg side. We whitelist file patterns in packages to be watched for changes and we don't have json included there. I proposed a fix in #15455.

[talldan]

It seems like this issue wasn't completely solved. I've opened #16104. It is unusual that webpack doesn't pick up the changes.