Exclude assets from other plugin instances

[jeffposnick]

R: @philipwalton

Fixes #2181

The one thing that makes me a little uneasy about this is that it relies on static, module-scoped state to keep track of the assets output by other instances of the exported class. I think it's appropriate for this use case, but at the same time, I kind of wish there were another viable approach—like a sanctioned way of adding state to the webpack compilation object, but I can't find references to anyone doing that, so I assume it would be even hacky-er.

[workbox-pr-bot]

PR-Bot Size Plugin

Changed File Sizes

File	Before	After	Change	GZipped
packages/workbox-webpack-plugin/build/generate-sw.js	3.82 KB	4.24 KB	+11%	1.62 KB	☠️
packages/workbox-webpack-plugin/build/inject-manifest.js	4.68 KB	5.12 KB	+9%	1.77 KB

New Files

No new files have been added.

All File Sizes

View Table

File	Before	After	Change	GZipped
packages/workbox-background-sync/build/workbox-background-sync.prod.js	3.86 KB	3.86 KB	0%	1.60 KB
packages/workbox-broadcast-update/build/workbox-broadcast-update.prod.js	1.92 KB	1.92 KB	0%	959 B
packages/workbox-build/build/_types.js	41 B	41 B	0%	61 B
packages/workbox-build/build/index.js	3.30 KB	3.30 KB	0%	1.31 KB
packages/workbox-cacheable-response/build/workbox-cacheable-response.prod.js	594 B	594 B	0%	354 B
packages/workbox-cli/build/app.js	4.16 KB	4.16 KB	0%	1.64 KB
packages/workbox-cli/build/bin.js	940 B	940 B	0%	502 B
packages/workbox-core/build/workbox-core.prod.js	5.94 KB	5.94 KB	0%	2.46 KB
packages/workbox-expiration/build/workbox-expiration.prod.js	2.94 KB	2.94 KB	0%	1.27 KB
packages/workbox-google-analytics/build/workbox-offline-ga.prod.js	1.95 KB	1.95 KB	0%	912 B
packages/workbox-navigation-preload/build/workbox-navigation-preload.prod.js	660 B	660 B	0%	323 B
packages/workbox-precaching/build/workbox-precaching.prod.js	4.99 KB	4.99 KB	0%	1.94 KB
packages/workbox-range-requests/build/workbox-range-requests.prod.js	1.57 KB	1.57 KB	0%	797 B
packages/workbox-routing/build/workbox-routing.prod.js	3.09 KB	3.09 KB	0%	1.36 KB
packages/workbox-strategies/build/workbox-strategies.prod.js	4.10 KB	4.10 KB	0%	1.13 KB
packages/workbox-streams/build/workbox-streams.prod.js	1.46 KB	1.46 KB	0%	721 B
packages/workbox-sw/build/workbox-sw.js	1.34 KB	1.34 KB	0%	748 B
packages/workbox-webpack-plugin/build/generate-sw.js	3.82 KB	4.24 KB	+11%	1.62 KB	☠️
packages/workbox-webpack-plugin/build/index.js	349 B	349 B	0%	255 B
packages/workbox-webpack-plugin/build/inject-manifest.js	4.68 KB	5.12 KB	+9%	1.77 KB
packages/workbox-window/build/workbox-window.dev.umd.js	41.34 KB	41.34 KB	0%	9.09 KB
packages/workbox-window/build/workbox-window.prod.umd.js	4.65 KB	4.65 KB	0%	1.91 KB

Workbox Aggregate Size Plugin

3.5KB gzip'ed (23% of limit)
7.79KB uncompressed

[philipwalton]

This approach seems fine to me. I don't think it's hacky to have the plugin logic itself keep track of all usage of the plugin.