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Source map reference fails in Edge/IE 11

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
55/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Stale
Tech stack
javascript
Domain
build-system

Research direction

Start with the clean-css plugin path exercised by lessc --source-map --clean-css main.less main.css, then inspect how the CSS output appends the source map comment. Done means the generated main.css places the comment after a newline and Edge requests main.css.map while showing main.less in the Styles panel.

Written by the indexing model from the issue text.

Description

enhancement

Problem

Microsoft Edge doesn't attempt to load the .map file due to the location of the source map comment in the CSS output.

This is somewhat a known phenomenon (with both CSS and JavaScript): https://stackoverflow.com/q/34687049/404623

Reproduce

main.less

html{color:red}
body{color:blue}

index.html

<!DOCTYPE html>
<link rel=stylesheet type=text/css href=main.css>
<p>Hello world</p>

Run lessc with the clean-css plugin:

lessc --source-map --clean-css main.less main.css

Output (main.css)

html{color:red}body{color:#00f}/*# sourceMappingURL=main.css.map */

Upon loading index.html in Microsoft Edge and opening Debugger in the F12 Developer Tools, there is no request made to the server for the map file, and inspect element shows main.css references in the Styles panel instead of main.less

Expected results

Edge should attempt to load the main.css.map file and refer to the code in the main.less file in the Styles panel in the F12 Developer Tools.

Expected output of main.css (note the newline)

html{color:red}body{color:#00f}
/*# sourceMappingURL=main.css.map */

Manually editing the files to add the newline character fixes the problem but defeats the purpose of the build tool.

Dominant language
JavaScript
Stars
193
Forks
41
Avg merge
8h 15m
Merged PRs (30d)
4

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