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    Shakacode logoShakaCodeDeveloped by

    Copyright 2020 ShakaCode

    Rails assets and the Extract Text Plugin

    This doc needs updating for the use of Shakapacker or rails/webpacker with React on Rails

    The Webpack file loader copies referenced files to the destination output directory, with an MD5 hash. The other term for this is a "digest".

    By default, the filename of the resulting file is the MD5 hash of the file's contents with the original extension of the required resource.

    The most common use cases for Webpack processed files are images used for backgrounds in CSS and fonts for CSS. However, this applies to any file that might be processed using the Webpack file loader.

    The Problem

    To understand the problem, it helps to read this article: What is fingerprinting and why should I care Basically, when Rails prepares assets for production deployments, it also adds a digest to the file names. E.g., img1.jpg becomes img1-dbu097452jf2v2.jpg.

    When compiling its native css Rails transforms all urls and links to digested versions, i.e. background-image: image-url(img1.jpg) becomes background-image: url(img1-dbu097452jf2v2.jpg). However, this doesn't happen for JS and CSS files compiled by Webpack on the client side, because they don't use image-url and asset-url. Without some fix, these assets would fail to load.

    When Webpack's client JavaScript uses images in render methods, e.g. <img src='...' /> or in css, e.g. background-image: url(...) The code (such as the CSS) generated by the Webpack will have the Webpack digested name (MD5 hash). Since the Webpack generated CSS expects just one level of "digesting", this "double-digesting" from Rails will cause such assets to fail to load.

    If you are interested in learning how to use assets in your React components, read this doc: Webpack, the Asset Pipeline, and Using Assets w/ React

    Note, this solution was removed in v14. If you're interested in this symlink solution, please create a GitHub issue.

    Example from /spec/dummy

    cd spec/dummy RAILS_ENV=production bundle exec rake assets:precompile rails s -e production

    You will see this. This shows how the file names output by Rails. Note the original names after being processed by Webpack are just MD5's.

    I, [2016-07-17T23:46:56.301981 #77382] INFO -- : Writing /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/server-bundle-42935dea382802a27e91b7df444a2813f74b4e6a0fce5606d863aaa10c0623d7.js I, [2016-07-17T23:46:56.305649 #77382] INFO -- : Writing /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/server-bundle-42935dea382802a27e91b7df444a2813f74b4e6a0fce5606d863aaa10c0623d7.js.gz I, [2016-07-17T23:46:56.370390 #77382] INFO -- : Writing /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/application_static-dfa728160c3cdebc633c2f6fb3823411530b307044f4dfe460790eef00b4e421.js I, [2016-07-17T23:46:56.370566 #77382] INFO -- : Writing /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/application_static-dfa728160c3cdebc633c2f6fb3823411530b307044f4dfe460790eef00b4e421.js.gz I, [2016-07-17T23:46:56.372895 #77382] INFO -- : Writing /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/application_static-17ed778d5061d4797556632b7bfbf405e067d9e7f140060a7f56a09788251f16.css I, [2016-07-17T23:46:56.373012 #77382] INFO -- : Writing /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/application_static-17ed778d5061d4797556632b7bfbf405e067d9e7f140060a7f56a09788251f16.css.gz I, [2016-07-17T23:46:56.374531 #77382] INFO -- : Writing /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/2ac2dd94f9b7e54292f6d051f1e4e756-ab14eebb171a9a5c9bfdeb2f88933d2dc4904ea8bb09444984e52b13d230e251.svg I, [2016-07-17T23:46:56.374818 #77382] INFO -- : Writing /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/2ac2dd94f9b7e54292f6d051f1e4e756-ab14eebb171a9a5c9bfdeb2f88933d2dc4904ea8bb09444984e52b13d230e251.svg.gz I, [2016-07-17T23:46:56.392207 #77382] INFO -- : Writing /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/5cf5db49df178f9357603f945752a1ef-033650e1d6193b70d59bb60e773f47b6d9aefdd56abc7ccdba3c7bed4e57ccad.png I, [2016-07-17T23:46:56.393208 #77382] INFO -- : Writing /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/8970f5e1e92aea933b502a2d73976b76-877bde3739dc7080c3fb00ee9012db6f21ed0dbbf11cd596dbb6e1a35bfb71f9.png I, [2016-07-17T23:46:56.395490 #77382] INFO -- : Writing /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/ecb4572a5e478b107dfcb60c16a7eefa-6d1ab3741d5a164dc2aab48bb74429aebe2e2e29606feca581081697624dc18c.ttf I, [2016-07-17T23:46:56.395846 #77382] INFO -- : Writing /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/ecb4572a5e478b107dfcb60c16a7eefa-6d1ab3741d5a164dc2aab48bb74429aebe2e2e29606feca581081697624dc18c.ttf.gz I, [2016-07-17T23:46:56.396979 #77382] INFO -- : Writing /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/fbd0d00cc9b670f05c17893a40da08d0-5731789fd0d7847a582b52b55a83e7a0ad4684acd5a9b487557635a08c112d0e.svg I, [2016-07-17T23:46:56.397669 #77382] INFO -- : Writing /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/fbd0d00cc9b670f05c17893a40da08d0-5731789fd0d7847a582b52b55a83e7a0ad4684acd5a9b487557635a08c112d0e.svg.gz I, [2016-07-17T23:46:56.399261 #77382] INFO -- : Writing /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/fc2dcaaf2057331ff76c5d37e1aa7056-efba50c701b697fc8160603b9e876adcf47511f35af68701db285272c965a45f.svg I, [2016-07-17T23:46:56.399660 #77382] INFO -- : Writing /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/fc2dcaaf2057331ff76c5d37e1aa7056-efba50c701b697fc8160603b9e876adcf47511f35af68701db285272c965a45f.svg.gz React On Rails: Symlinking /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/2ac2dd94f9b7e54292f6d051f1e4e756-ab14eebb171a9a5c9bfdeb2f88933d2dc4904ea8bb09444984e52b13d230e251.svg to /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/2ac2dd94f9b7e54292f6d051f1e4e756.svg React On Rails: Symlinking /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/2ac2dd94f9b7e54292f6d051f1e4e756-ab14eebb171a9a5c9bfdeb2f88933d2dc4904ea8bb09444984e52b13d230e251.svg.gz to /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/2ac2dd94f9b7e54292f6d051f1e4e756.svg.gz React On Rails: Symlinking /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/5cf5db49df178f9357603f945752a1ef-033650e1d6193b70d59bb60e773f47b6d9aefdd56abc7ccdba3c7bed4e57ccad.png to /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/5cf5db49df178f9357603f945752a1ef.png React On Rails: Symlinking /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/8970f5e1e92aea933b502a2d73976b76-877bde3739dc7080c3fb00ee9012db6f21ed0dbbf11cd596dbb6e1a35bfb71f9.png to /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/8970f5e1e92aea933b502a2d73976b76.png React On Rails: Symlinking /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/ecb4572a5e478b107dfcb60c16a7eefa-6d1ab3741d5a164dc2aab48bb74429aebe2e2e29606feca581081697624dc18c.ttf to /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/ecb4572a5e478b107dfcb60c16a7eefa.ttf React On Rails: Symlinking /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/ecb4572a5e478b107dfcb60c16a7eefa-6d1ab3741d5a164dc2aab48bb74429aebe2e2e29606feca581081697624dc18c.ttf.gz to /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/ecb4572a5e478b107dfcb60c16a7eefa.ttf.gz React On Rails: Symlinking /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/fbd0d00cc9b670f05c17893a40da08d0-5731789fd0d7847a582b52b55a83e7a0ad4684acd5a9b487557635a08c112d0e.svg to /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/fbd0d00cc9b670f05c17893a40da08d0.svg React On Rails: Symlinking /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/fbd0d00cc9b670f05c17893a40da08d0-5731789fd0d7847a582b52b55a83e7a0ad4684acd5a9b487557635a08c112d0e.svg.gz to /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/fbd0d00cc9b670f05c17893a40da08d0.svg.gz React On Rails: Symlinking /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/fc2dcaaf2057331ff76c5d37e1aa7056-efba50c701b697fc8160603b9e876adcf47511f35af68701db285272c965a45f.svg to /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/fc2dcaaf2057331ff76c5d37e1aa7056.svg React On Rails: Symlinking /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/fc2dcaaf2057331ff76c5d37e1aa7056-efba50c701b697fc8160603b9e876adcf47511f35af68701db285272c965a45f.svg.gz to /Users/justin/shakacode/react_on_rails/spec/dummy/public/assets/fc2dcaaf2057331ff76c5d37e1aa7056.svg