circular dependency when building LaTeX?

[Thiago Jung Bauermann]

Hello,

[ Please keep me on Cc: since I’m not subscribed to this list. ]

I’m trying to update the TeX Live version in Guix¹ to 2021. I’m running 
into an issue and I’d appreciate if someone could offer some advice.

When trying to build texlive-latex-base, it complains that “! LaTeX 
requires expl3”. I then add texlive-latex-l3kernel as a build dependency, 
but that just makes the Guix build system go crazy because (at least on 
Guix), texlive-latex-l3kernel uses LaTeX to run `source/latex/l3kernel/
l3.ins`.

Is this circular build dependency (LaTeX → l3kernel → LaTeX) real? If not, 
how do I undo this circle?

If it is real, what is the recommended approach to build LaTeX from 
scratch?

I tried using LaTeX from TeX Live 2020 (but running on top of TeX from TeX 
Live 2021 to minimize build steps) to build texlive-latex-l3kernel. It 
appears to work (since the build of texlive-latex-l3kernel completes), but 
during the build of texlive-latex-base I get errors such as:

! Undefined control sequence.
l.2633 \NewDocumentCommand
                           \NewHook             { m }{ \hook_new:n {#1} }

during fmtutil’s remake of latex formats (such as mllatex, lualatex and 
latex).

-- 
Thanks,
Thiago

¹ https://guix.gnu.org/