A new script brp-fix-pyc-reproducibility creates an opt-in way of how to fix
problems with the reproducibility of byte-compiled Python files. The script
uses marshalparser [0] which currently doesn't provide solutions for all issues
but can fix at least problems with reference flags. For more info see
this Bugzilla [1].
If you want to use this new feature, you need to define
`%py_reproducible_pyc_path` to specify a path you want to fix `.pyc`
files in (recursively) and build-require /usr/bin/marshalparser.
if you forget to build-require the parser. The error message is:
```
+ /usr/lib/rpm/redhat/brp-python-bytecompile '' 1 0
Bytecompiling .py files below /builddir/build/BUILDROOT/tldr-0.5-2.fc33.x86_64/usr/lib/python3.9 using /usr/bin/python3.9
+ /usr/lib/rpm/redhat/brp-fix-pyc-reproducibility /builddir/build/BUILDROOT/tldr-0.5-2.fc33.x86_64
ERROR: If %py_reproducible_pyc_path is defined, you have to also BuildRequire: /usr/bin/marshalparser !
error: Bad exit status from /var/tmp/rpm-tmp.UUJr4v (%install)
```
A build fails if the parser is not able to parse any of the `.pyc` files.
And finally, if a build is properly configured it produces fixed `.pyc` files.
Currently, `.pyc` files in the tldr package contain a lot of unused reference flags:
```
$ dnf install -y tldr
$ marshalparser --unused /usr/lib/python3.9/site-packages/__pycache__/tldr.cpython-39.pyc
… long output …
190 - Flag_ref(byte=9610, type='TYPE_SHORT_ASCII_INTERNED', content=b'init', usages=0)
191 - Flag_ref(byte=9633, type='TYPE_SHORT_ASCII_INTERNED', content=b'source', usages=0)
192 - Flag_ref(byte=9651, type='TYPE_SHORT_ASCII_INTERNED', content=b'argv', usages=0)
193 - Flag_ref(byte=9657, type='TYPE_SHORT_ASCII_INTERNED', content=b'print_help', usages=0)
194 - Flag_ref(byte=9669, type='TYPE_SHORT_ASCII_INTERNED', content=b'stderr', usages=0)
195 - Flag_ref(byte=9682, type='TYPE_SHORT_ASCII_INTERNED', content=b'parse_args', usages=0)
196 - Flag_ref(byte=9737, type='TYPE_SHORT_ASCII_INTERNED', content=b'encode', usages=0)
197 - Flag_ref(byte=9782, type='TYPE_SHORT_ASCII_INTERNED', content=b'parser', usages=0)
198 - Flag_ref(byte=9790, type='TYPE_SHORT_ASCII_INTERNED', content=b'options', usages=0)
199 - Flag_ref(byte=9799, type='TYPE_SHORT_ASCII_INTERNED', content=b'rest', usages=0)
200 - Flag_ref(byte=9821, type='TYPE_SHORT_ASCII_INTERNED', content=b'result', usages=0)
202 - Flag_ref(byte=10022, type='TYPE_SHORT_ASCII_INTERNED', content=b'__main__', usages=0)
203 - Flag_ref(byte=10102, type='TYPE_SHORT_ASCII_INTERNED', content=b'argparse', usages=0)
204 - Flag_ref(byte=10433, type='TYPE_SHORT_ASCII_INTERNED', content=b'__name__', usages=0)
205 - Flag_ref(byte=10463, type='TYPE_SHORT_ASCII_INTERNED', content=b'<module>', usages=0)
```
This new feature fixes them:
```
$ marshalparser --unused /usr/lib/python3.9/site-packages/__pycache__/tldr.cpython-39.pyc
<empty output>
```
[0] https://github.com/fedora-python/marshalparser
[1] https://bugzilla.redhat.com/show_bug.cgi?id=1686078
The Python compileall2 module in /usr/lib/rpm/redhat/
can be executed by various different Python interpreters.
We don't want to write several different `*.pyc` files
to this location - in most cases, that's not possible,
but somebody might run this as root.
Resolves: rhbz#1595265
The problem this change is intended to solve is with how `real_libdir`
is calculated. Let's assume we want to recursively byte-compile all
`*.py` files in
`/builddir/build/BUILDROOT/python-scales-1.0.9-250.fc32.x86_64/usr/lib/python3.8`.
Then, `real_libdir` is this path without `$RPM_BUILD_ROOT` with
the filename at the end which displays in the error message like this:
```
Bytecompiling .py files below /builddir/build/BUILDROOT/python-scales-1.0.9-250.fc32.x86_64/usr/lib/python3.8 using /usr/bin/python3.8
*** Error compiling '/builddir/build/BUILDROOT/python-scales-1.0.9-250.fc32.x86_64/usr/lib/python3.8/site-packages/greplin/bar.py'...
File "/usr/lib/python3.8/bar.py", line 1
import sin from math
^
SyntaxError: invalid syntax
```
`/usr/lib/python3.8/bar.py` is obviously wrong.
One of the new features of the `compileall2` module (which will
be available in stdlib in Python 3.9) is that the path byte-compiled to
`*.pyc` files is calculated for each file. This means that by using
`-s` and `-p` we can strip `$RPM_BUILD_ROOT` and prepend `/` for each
file individually which will fix the problem.
```
Bytecompiling .py files below /builddir/build/BUILDROOT/python-scales-1.0.9-250.fc32.x86_64/usr/lib/python3.8 using /usr/bin/python3.8
*** Error compiling '/builddir/build/BUILDROOT/python-scales-1.0.9-250.fc32.x86_64/usr/lib/python3.8/site-packages/greplin/bar.py'...
File "/usr/lib/python3.8/site-packages/greplin/bar.py", line 1
import sin from math
^
SyntaxError: invalid syntax
```
This change has an effect only for Python >= 3.4.
Lumir Balhar
Tomas Orsava
Miro Hrončok