[web] Do not delete source map from production build

[dgdavid]

Problem

In the context of https://trello.com/c/hInThumV (internal link), we realized that source maps are missing in the production build.

Source map error: Error: request failed with status 404
Resource URL: http://127.0.0.90/cockpit/@localhost/agama/index.js
Source Map URL: index.js.map
Source map error: Error: request failed with status 404
Resource URL: http://127.0.0.90/cockpit/@localhost/agama/index.css
Source Map URL: index.css.map

They would have been useful for debugging the error we were facing. In fact, there is a Webpack recommendation about serving source maps in production too

We encourage you to have source maps enabled in production, as they are useful for debugging as well as running benchmark tests — https://webpack.js.org/guides/production/#source-mapping

The weird thing is that we already had the devtool webpack option set to "source-map", the value recommended for production builds. But, surprisingly, files were not there.

After closely checking the webpack configuration file, the culprit came to scene: the deleteOriginalAssets option of the CompressionWebpackPlugin. It was set as true and it does not honor the pattern given in test option.

Solution

Fortunately, it's something that was fixed long time ago. For us is just about switching from true to "keep-source-map" value.

Tests

Tested manually by checking the dist/ content after running the NODE_ENV=production npm run build command.

Click to show/hide ls -l dist/ output BEFORE the change

Sep 28 17:28 favicon.svg
Sep 28 17:28 fonts
Sep 28 17:28 index.css.gz
Sep 28 17:28 index.html.gz
Sep 28 17:28 index.js.gz
Sep 28 17:28 index.js.LICENSE.txt.gz
Sep 28 17:28 manifest.json
Sep 28 17:28 po.cs.js.gz
Sep 28 17:28 po.ja.js.gz
Sep 28 17:28 po.nl.js.gz
Sep 28 17:28 po.ru.js.gz
Sep 28 17:28 po.sv.js.gz
Sep 28 17:28 po.uk.js.gz

Click to show/hide ls -l dist/ output AFTER the change

Sep 28 17:31 favicon.svg
Sep 28 17:31 fonts
Sep 28 17:31 index.css.gz
Sep 28 17:31 index.css.map
Sep 28 17:31 index.html.gz
Sep 28 17:31 index.js.gz
Sep 28 17:31 index.js.LICENSE.txt.gz
Sep 28 17:31 index.js.map
Sep 28 17:31 manifest.json
Sep 28 17:31 po.cs.js.gz
Sep 28 17:31 po.ja.js.gz
Sep 28 17:31 po.nl.js.gz
Sep 28 17:31 po.ru.js.gz
Sep 28 17:31 po.sv.js.gz
Sep 28 17:31 po.uk.js.gz

[coveralls]

coverage: 74.747%. remained the same when pulling 3264f51 on keep-source-map into f39b3b0 on master.