Let the latexmkrc PythonTeX cus_dep use the configured interpreter

[dbosk]

Problem

latexmkrc's PythonTeX custom dependency hardcoded its own invocation, so a project that points PythonTeX at a different interpreter was silently ignored whenever latexmk drove the build — latexmk reaches PythonTeX through the cus_dep, not through tex.mk's rule.

This bites exactly the projects that need PythonTeX most: those whose document executes the package it documents, and so must run under a virtualenv interpreter that can import it. Setting

PYTHONTEXFLAGS= --interpreter "python:poetry run python3"

in the project's makefile had no effect on the latexmk path.

53e54b0 had already aligned the cus_dep with tex.mk's default invocation, which fixed portability. But copying a default is not the same as sharing a configuration point — the two paths still diverge the moment anyone overrides it.

The failure is silent and remote from its cause: LaTeX succeeds, latexmk reports the cus_dep as run, and the only symptom is a Python traceback about a missing module several build stages later.

Change

Made in tex.mk.nw; tex.mk and latexmkrc are regenerated.

• tex.mk now exports PYTHONTEX and PYTHONTEXFLAGS. A latexmkrc is Perl read by a separate process, so it cannot see make's variables — the environment is the one channel that crosses that boundary.
• The cus_dep reads both back from %ENV, keeping the literal defaults as Perl fallbacks so a hand-run latexmk (no make, empty environment) behaves exactly as before. // rather than || for the flags, so a project can deliberately pass no flags without silently getting the defaults back.

The sub pythontex body moved into its own <<run PythonTeX with the configured interpreter>> chunk, with prose explaining the departure from the CTAN original.

Verification

Against dbosk/ladok3, whose doc build sets PYTHONTEXFLAGS= --interpreter "python:poetry run python3":

	before	after
ModuleNotFoundError: No module named 'ladok3'	2	0
PythonTeX	never ran	0 error(s), 0 warning(s), 58 outputs
make -C doc all	Error 12	exit 0
pages	169 (stub)	1438

perl -c latexmkrc passes, and both tangled outputs were diffed against fresh notangle runs.

Note

make latexmkrc in this repo does not tangle — the included tex.mk's latexmkrc: symlink target overrides the Makefile tangle rule, which is #76. I tangled by hand with notangle -R"[[latexmkrc]]" tex.mk.nw | cpif latexmkrc.

🤖 Generated with Claude Code

https://claude.ai/code/session_01QiBv9BVhRKCyYJJNDhiowW