Modules can be included twice resulting in subtle hard-to-debug bugs

[matrixbot]

Created by @ kegan:matrix.org.

This happens because webpack isn't smart enough to work out the absolute path of files when symlinks are involved. Therefore it sees vector-web/node_modules/matrix-react-sdk/foo as different to matrix-react-sdk/foo

[dbkr]

Hopefully this only impacts us in development because of npm link symlinks, but if not it would be inflating the js size too which is annoying.

[kegsay]

This can result in all sorts of fun. This bug was made because it turns out I managed to break the X on the desktop notifications toolbar because one require() was setting "hide the toolbar" and another require() was checking "is the toolbar hidden", and they were not hitting the same singleton.

[dbkr]

Relevant webpack bug (implies it should now "support symlinks" although I think this means it doesn't include the file twice but does make them two separate instances of the class) webpack/webpack#554

[kegsay]

Stopgap for now is to assign module.exports to a known singleton via globals.. I don't like this because it's very easy to forget to do this and it pollutes the window. namespace. I would prefer to do this exactly once if we have to, and then tie all the other singletons off that (which then come to think of it is starting to look and smell a lot like the Context singleton object I was proposing to inject into components, which also allows multiple instances in the same window to work).

[t3chguy]

This looks to be fixed with modern Webpack, analysing our bundles it looks sane