bind style merge not as expected

[yeli19950109]

Version

2.7.14

Reproduction link

codesandbox.io

Steps to reproduce

click mStyle button twice

What is expected?

show red border-right and blue border-bottom

What is actually happening?

only show red border-right. is not similar as setAttribute but vue3 is similar like setAttribute

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is this a bug?

[edison1105]

@posva
What he means is that the results of the two operations are inconsistent, but works fine in vue-core.
This might be a bug.

[posva]

Right, I misread

[ayush-pandey-9]

can I take this bug and try fixing it?

[ljf1834]

After the border style is set for the element, the browser will automatically format the style when the border-* style is set. The code is optimized for style reuse, resulting in bugs

After adding border-bottom