I mistakenly sent the following letter to luatex@tug.org yesterday. I hope it won't cause anyone any trouble. Thanks to luigi for pointing out the error.

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Hi all,
I just updated my ConTeXt to

system > ConTeXt ver: 2022.07.06 21:42 LMTX fmt: 2022.7.12 int: english/english

yesterday and got a error message in using tex.linebreak(head) as follow:

luatex warning > linebreak: no [ leftinit | rightinit | leftfill | rigthfill] expected

I can't get any information about them. The head and the list going to tex.linebreak() like:

<node :    nil <=   2371 =>   2873 : par vmodepar>
<node :   2371 <=   2873 =>   2879 : glue indentskip>
<node :   2873 <=   2879 =>   2891 : glyph unset>
<node :   2879 <=   2891 =>   2897 : glue userskip>
...
<node :    636 <=   3077 =>    639 : glyph unset>
<node :   3077 <=    639 =>   3089 : kern userkern>
<node :    639 <=   3089 =>   2334 : glue userskip>
<node :   3089 <=   2334 =>   3095 : rule normal>
<node :   2334 <=   3095 =>   3101 : glue spaceskip>
<node :   3095 <=   3101 =>    642 : glue spaceskip>
<node :   3101 <=    642 =>   3107 : penalty userpenalty>
<node :    642 <=   3107 =>    nil : glue userskip>

My question is:
Which of them is necessary, and
How can I node.new() one and
Where should it go in the list?

Any hint would be appreciated,
Huang Fusyong(黄复雄)