What does the Compatibility mode 'properties.merging' mean?

[XIYU11864]

Acoding to the readme, it 'controls property merging based on understandability', but I don't get it and it is nothing differents between enable and disanle it.

[jakubpawlowicz]

Hey @XIYU11864 - please see https://github.com/clean-css/clean-css/blob/1ab8b7f8f5a4a40b926e740746eb1481621fada0/test/optimizer/level-2/properties/override-properties-test.js#L631 as an example.

There's no difference in your case because all properties you use are equally understandable by browsers.

However if you had "background: #f5f5f5;" followed by "background: linear-gradient(#f5f5f5, #ffffff);" in body styling, then turning off 'properties.merging' would leave both properties in the output file because linear-gradient is not understandable by some browsers so browser that don't understand it would fall back to #f5f5f5.

Hope I made it clear enough.

[XIYU11864]

Hi @jakubpawlowicz
How about turning on 'properties.merging' in your case? I also see both properties in the output file which same as turning off it.

[jakubpawlowicz]

@XIYU11864 can you check what version of clean-css do you use? Or check it here with the latest version of clean-css?

[XIYU11864]

@jakubpawlowicz
5.6.3.
I think the option of 'properties.merging' doesn't work as we wish. It seems like the option is on by default and can not turn off.