old issue killing most content is back

[jirilebl]

Same as in #890

The file http://www.jirka.org/nlin-sierpinski-mbx.svg
gets totally destroyed by svgo. Disabling the plugin convertPathData it is not as good as in the past, but it doesn't delete content.

Last version where it worked was 3.0.4 and it starting eating the content in 3.0.5 and is broken in all subsequent versions it seems.

Tried with the newest version 4.0.0, same result: mostly empty output file (the actually sierpinski triangle is gone).

[johnkenny54]

A number of plugins have serious problems with accuracy and scalability. In this case the culprits are mergePaths and convertPathData, if you disable those it seems to work.

I eventually gave up on getting these issues addressed in SVGO and forked my own version focused on lossless compression (svgo-ll).

I ran a few tests on this file with svgo-ll and various configurations of SVGO 4.0, here's what I found.

Config	Time (ms)	Compression	Visual Result
svgo-ll 5.6	2039	2583.887 KiB - 85.2% = 381.451 KiB	no difference
SVGO 4.0 without both convertPathData and mergePaths	7552	2583.887 KiB - 7.4% = 2392.973 KiB	no difference
SVGO 4.0	25922	2583.887 KiB - 99.4% = 15.077 KiB	Sierpiński triangle disappears
SVGO 4.0 without convertPathData	40433	2583.887 KiB - 86.2% = 355.787 KiB	Sierpiński triangle appears, but intensity is different
SVGO 4.0 without mergePaths	8449	2583.887 KiB - 20.7% = 2050.008 KiB	Sierpiński triangle disappears

[KTibow]

Isolating minimal repros is always helpful; here I've made one:

<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100">
<path d="M 50 50 h 0" fill="none" stroke="#00f" stroke-linecap="round" stroke-linejoin="round"/>
</svg>

Edit: this was the fault of my z optimization again... SVG optimization is hard man. PR soon.