CSS minifier warning on "star property hack"

[silverwind]

While minifying a dependency, I came around this warning:

warnings when minifying css:
 > <stdin>:191:30201: warning: Expected identifier but found "*"
    191 │ ...fter{clear:both}.swagger-ui .cf{*zoom:1}.swagger-ui .cl{clear:le...

Strictly speaking, a * in a CSS property name is invalid, but I wonder whether an exception should be made in esbuild to not warn on it because it has active usage in some legacy code.

Refs:

• https://stackoverflow.com/a/1690683/808699
• Remove IE7 CSS hack swagger-api/swagger-ui#7526

[evanw]

I think I'd like to keep this warning. IE aside, this is invalid CSS and is a syntax error. And since esbuild esbuild emits this as a warning, it also doesn't prevent you from using esbuild on this code. You can always use --log-level=error if you don't want to see warnings. There are likely many syntax errors that IE allows so it seems strange to special-case this one. An alternative could be to turn off all esbuild warnings about CSS syntax errors, but I don't think that makes sense since IE 7 is ancient and unsupported and irrelevant. I think the correct fix in this case is to remove the invalid CSS, which is what was done in this case. Closing.