Handling Debian Python packages with pdm-backend backend
--------------------------------------------------------

If you are preparing Python packages that use pdm-backend as build
backend as well as its Dynamic Version feature [1] with
`source = "scm"`, the automatic version detection may not work
out-of-box because of the lack of .git directory during packaging.
pdm-backend then takes the version from the environment variable
PDM_BUILD_SCM_VERSION instead.

[1] https://backend.pdm-project.org/metadata/#dynamic-project-version

* * *

1. Automatic handling by dh-python

When the package is built with pybuild and one of the Build-Depends*
fields lists python3-pdm-backend, pybuild sets PDM_BUILD_SCM_VERSION to
the version in debian/changelog with the epoch and the Debian revision
removed and the first "~" replaced by "-". You do not need to do
anything.

Repack suffixes are kept: 1.2.3+dfsg-1 gives the Python version
"1.2.3+dfsg". pybuild does not override a value that is already set.

* * *

2. Setting the version yourself

If the upstream version contains a repack suffix, or the package does
not Build-Depend on python3-pdm-backend directly, set the variable in
debian/rules, for example:

```makefile
include /usr/share/dpkg/pkg-info.mk
export PDM_BUILD_SCM_VERSION = $(DEB_VERSION_UPSTREAM:%+dfsg=%)
```

The variable applies to every pdm-backend build in that environment,
including projects that the test suite builds. If such tests expect a
version read from git, set it for dh_auto_build only, as the
debian/rules of pdm-backend itself does.

The "file" and "call" version sources do not use this variable.

 -- Boyuan Yang <byang@debian.org>  Wed, 07 Oct 2026 13:14:11 -0400