Optimize webpack production builds and asset compilation

app/assets/config/manifest.js

@@ -1,6 +1,13 @@
 //= link_tree ../images
-//= link_directory ../javascripts .js
-//= link_directory ../stylesheets .css
+
+// Only the bundles we actually reference from a layout get their own compiled
+// output. app/assets/javascripts/application.js and app/assets/stylesheets/application.css
+// already `require_tree .` everything beside them, so the `link_directory`
+// directives that used to live here compiled every one of those ~85 files a
+// second time as a standalone (fingerprinted, gzipped) asset that no view links to.
+// Add an explicit `//= link` here if a file ever needs to be served on its own.
+//= link application.js
+//= link application.css
 //= link preload/jquery-3.1.1.min.js
 //= link Chart.bundle.js
 //= link chartkick.js

config/webpack/environment.js

@@ -89,4 +89,26 @@ if (environment.plugins.getIndex('OptimizeCSSAssets') >= 0) {
   environment.plugins.delete('OptimizeCSSAssets')
 }
 
+// This file is shared by all three environments, so guard production-only tweaks
+// on NODE_ENV (config/webpack/production.js sets it before requiring us).
+if (process.env.NODE_ENV === 'production') {
+  // Webpacker defaults to `devtool: 'source-map'`, which appends a
+  // `//# sourceMappingURL=` comment to every shipped bundle. Nothing consumes those
+  // maps automatically (there is no browser-side Sentry SDK), but every visitor who
+  // opens devtools pulls down a multi-megabyte map. `hidden-source-map` still writes
+  // the maps into public/packs for manual debugging, just without the comment.
+  environment.config.merge({ devtool: 'hidden-source-map' })
+
+  // Webpacker gzips and brotlis `.map` files too, which is where most of the
+  // "asset size limit" warnings in the precompile output come from. Maps are never
+  // fetched with content-encoding negotiation, so drop them from both passes.
+  const COMPRESSED_TYPES = /\.(js|css|html|json|ico|svg|eot|otf|ttf)$/
+  const compressionPlugins = ['Compression', 'Compression Brotli']
+  compressionPlugins.forEach((name) => {
+    if (environment.plugins.getIndex(name) < 0) return
+    const plugin = environment.plugins.get(name)
+    if (plugin && plugin.options) plugin.options.test = COMPRESSED_TYPES
+  })
+}
+
 module.exports = environment

package.json

@@ -40,6 +40,7 @@
   },
   "resolutions": {
     "@types/minimatch": "^3.0.5",
+    "baseline-browser-mapping": "^2.11.13",
     "chokidar": "^3.4.0",
     "minimatch": "^3.1.2",
     "rails_admin/@fortawesome/fontawesome-free": "^5.15.0"

yarn.lock

@@ -1845,15 +1845,10 @@ base@^0.11.1:
     mixin-deep "^1.2.0"
     pascalcase "^0.1.1"
 
-baseline-browser-mapping@^2.10.12:
-  version "2.10.13"
-  resolved "https://registry.yarnpkg.com/baseline-browser-mapping/-/baseline-browser-mapping-2.10.13.tgz#5a154cc4589193015a274e3d18319b0d76b9224e"
-  integrity sha512-BL2sTuHOdy0YT1lYieUxTw/QMtPBC3pmlJC6xk8BBYVv6vcw3SGdKemQ+Xsx9ik2F/lYDO9tqsFQH1r9PFuHKw==
-
-baseline-browser-mapping@^2.8.3:
-  version "2.8.9"
-  resolved "https://registry.yarnpkg.com/baseline-browser-mapping/-/baseline-browser-mapping-2.8.9.tgz#fd0b8543c4f172595131e94965335536b3101b75"
-  integrity sha512-hY/u2lxLrbecMEWSB0IpGzGyDyeoMFQhCvZd2jGFSE5I17Fh01sYUBPCJtkWERw7zrac9+cIghxm/ytJa2X8iA==
+baseline-browser-mapping@^2.10.12, baseline-browser-mapping@^2.11.13, baseline-browser-mapping@^2.8.3:
+  version "2.11.13"
+  resolved "https://registry.yarnpkg.com/baseline-browser-mapping/-/baseline-browser-mapping-2.11.13.tgz#660073103c1bee93e54df55f117b7528adf6af19"
+  integrity sha512-k9HNuUVMlqVjQ9UHzfPjIqiDbWw7WqT1AoT7GL8VwvF3r0ZfArtgiSPAlmupyNquNgOJHTuH4CKYf8ttMTWBTQ==
 
 batch@0.6.1:
   version "0.6.1"
@@ -2209,15 +2204,10 @@ caniuse-api@^3.0.0:
     lodash.memoize "^4.1.2"
     lodash.uniq "^4.5.0"
 
-caniuse-lite@^1.0.0, caniuse-lite@^1.0.30000981, caniuse-lite@^1.0.30001109, caniuse-lite@^1.0.30001741:
-  version "1.0.30001745"
-  resolved "https://registry.yarnpkg.com/caniuse-lite/-/caniuse-lite-1.0.30001745.tgz#ab2a36e3b6ed5bfb268adc002c476aab6513f859"
-  integrity sha512-ywt6i8FzvdgrrrGbr1jZVObnVv6adj+0if2/omv9cmR2oiZs30zL4DIyaptKcbOrBdOIc74QTMoJvSE2QHh5UQ==
-
-caniuse-lite@^1.0.30001774, caniuse-lite@^1.0.30001782:
-  version "1.0.30001784"
-  resolved "https://registry.yarnpkg.com/caniuse-lite/-/caniuse-lite-1.0.30001784.tgz#bdf9733a0813ccfb5ab4d02f2127e62ee4c6b718"
-  integrity sha512-WU346nBTklUV9YfUl60fqRbU5ZqyXlqvo1SgigE1OAXK5bFL8LL9q1K7aap3N739l4BvNqnkm3YrGHiY9sfUQw==
+caniuse-lite@^1.0.0, caniuse-lite@^1.0.30000981, caniuse-lite@^1.0.30001109, caniuse-lite@^1.0.30001741, caniuse-lite@^1.0.30001774, caniuse-lite@^1.0.30001782:
+  version "1.0.30001809"
+  resolved "https://registry.yarnpkg.com/caniuse-lite/-/caniuse-lite-1.0.30001809.tgz#e6cf71f14ddfe008f114dd2a846923be3c03a07b"
+  integrity sha512-xxWVywk6a6Arlk+hymeycyn/VgqEfLDxupvhH/xiY5SJ/18kmi9o6MiO320DCUzypORHLtvh0I4i04tUhCNHNQ==
 
 case-sensitive-paths-webpack-plugin@^2.4.0:
   version "2.4.0"