[WIP] Move webpack configuration to project root

[ColinEberhardt]

As per the discussion in this issue the focus workspaces features doesn't work at the moment because webpack configuration is part of the @jpmorganchane\perspective package.

I think this configuration should be moved to the root of the project.

This PR illustrates the change for perspective-viewer only (hence it is a Work In Progress). I've simply taken the various webpack files and pasted them into scripts\webpack

With these changes, the following now works:

$ cd packages/perspective-viewer
$ yarn install --focus
$ yarn run build

If you're happy with this as an approach, I'll clean up and roll it out across the project.

[LukeSheard]

@ColinEberhardt The webpack configs need to remain part of a package that's exported so that users can consume the API through webpack. Take a look at #378 which has a base for breaking these things out into a shared directory, we can make a private development package which is symlinked in but not published.

[ColinEberhardt]

@ColinEberhardt The webpack configs need to remain part of a package that's exported so that users can consume the API through webpack.

I must admit, I'm not entirely sure what you mean! The APIs the Perspective currently exposes are the view and table via perspective, and the various 'viewer' WebComponents - are these the APIs you'd expect people to consume via Webpack?

[texodus]

@LukeSheard is correct - Perspective requires a plugin to be used via webpack due to a few features which are tricky to configure correctly without carnal knowledge of the build, namely:

• Feature detecting WASM and loading a separate WebWorker at runtime precludes use of worker-loader
• CORS restrictions on WebWorkers means we need to XHR the source when a cross-origin load is detected (again at runtime), and the Worker needs to be loaded via Blob.
• As a speed optimization - the workers take ages to compile, and can't be extended in user code, so these are pre-compiled and copied to your webpack output path.
• asm.js in particular cannot be modified by babel/uglify/etc source-to-source compilers, as none are aware of "almost asmjs" or "use asmjs" directives.
• Shadow DOM requires some non-traditional usage of CSS/HTML assets that conflict with standard webpack configs, yielding confusing errors.

The implementation is based off Microsoft's Monaco webpack plugin, which has complications. All this aside though - I am unclear why the webpack configuration is the crux of your issues with --focus. It seems this is more an issue of the way the plugin resolves paths than the specific path of the config itself.

As I don't believe this approach is going to work, I'm going to close this PR. If you feel this is in error, feel free to re-open or come over to the gitter channel where we can discuss.