pyproject_buildrequires choked on mistune

[Michel Alexandre Salim]

I'm packaging python-mistune as a dependency for hyperkitty (so we can
finally pull off a Mailman3/Hyperkitty migration from the current
RHEL7+custom repo setup - tracked in
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=2030061)

python-mistune review: https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=2031262

One weird thing is, pyproject_buildrequires fails:

```
Executing(%generate_buildrequires): /bin/sh -e /var/tmp/rpm-tmp.KZ4hKk                                
+ umask 022                                                                                            + cd /builddir/build/BUILD                                                                             
+ cd mistune-2.0.0    
+ echo python3-devel                               
+ echo 'python3dist(pip) >= 19'
+ echo 'python3dist(packaging)'  
+ '[' -f pyproject.toml ']'      
+ echo 'python3dist(toml)'                    
+ rm -rfv '*.dist-info/'                                                                               
+ '[' -f /usr/bin/python3 ']'                      
+ RPM_TOXENV=py310                                                                                     
+ HOSTNAME=rpmbuild                                
+ /usr/bin/python3 -s /usr/lib/rpm/redhat/pyproject_buildrequires.py --generate-extras --python3_pkgver
sion 3                                             
Handling setuptools from build-system.requires     
Requirement satisfied: setuptools                                                                      
   (installed: setuptools 58.5.3)                                                                      
Handling wheel from build-system.requires
Requirement not satisfied: wheel                   
Traceback (most recent call last):                                                                     
  File "/usr/lib/rpm/redhat/pyproject_buildrequires.py", line 421, in main                             
    generate_requires(                                                                                 
  File "/usr/lib/rpm/redhat/pyproject_buildrequires.py", line 354, in generate_requires
    backend = get_backend(requirements)                                                                
  File "/usr/lib/rpm/redhat/pyproject_buildrequires.py", line 219, in get_backend
    raise FileNotFoundError('File "setup.py" not found for legacy project.')
FileNotFoundError: File "setup.py" not found for legacy project.   
```

so I had to manually add the BRs in https://salimma.fedorapeople.org/specs/python/python-mistune.spec

the `pyproject.toml` is super simple:
```
$ cat python/mistune-2.0.0/pyproject.toml 
[build-system]
requires = [ "setuptools", "wheel" ]
```

because the project really didn't have any dependency (beyond pytest for
running tests).

Is this a problem with our tooling or with upstream's pyproject.toml?
Happy to follow up with them if they need a more fleshed-out project
definition.

Thanks,

[Miro Hrončok]

On 10. 12. 21 22:30, Michel Alexandre Salim wrote:
> I'm packaging python-mistune as a dependency for hyperkitty (so we can
> finally pull off a Mailman3/Hyperkitty migration from the current
> RHEL7+custom repo setup - tracked in
> https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=2030061)
>
> python-mistune review: https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=2031262
>
> One weird thing is, pyproject_buildrequires fails:
> Executing(%generate_buildrequires): /bin/sh -e /var/tmp/rpm-tmp.KZ4hKk
> + umask 022                                                                                            + cd /builddir/build/BUILD
> + cd mistune-2.0.0
> + echo python3-devel
> + echo 'python3dist(pip) >= 19'
> + echo 'python3dist(packaging)'
> + '[' -f pyproject.toml ']'
> + echo 'python3dist(toml)'
> + rm -rfv '*.dist-info/'
> + '[' -f /usr/bin/python3 ']'
> + RPM_TOXENV=py310
> + HOSTNAME=rpmbuild
> + /usr/bin/python3 -s /usr/lib/rpm/redhat/pyproject_buildrequires.py --generate-extras --python3_pkgver
> sion 3
> Handling setuptools from build-system.requires
> Requirement satisfied: setuptools
>     (installed: setuptools 58.5.3)
> Handling wheel from build-system.requires
> Requirement not satisfied: wheel
> Traceback (most recent call last):
>    File "/usr/lib/rpm/redhat/pyproject_buildrequires.py", line 421, in main
>      generate_requires(
>    File "/usr/lib/rpm/redhat/pyproject_buildrequires.py", line 354, in generate_requires
>      backend = get_backend(requirements)
>    File "/usr/lib/rpm/redhat/pyproject_buildrequires.py", line 219, in get_backend
>      raise FileNotFoundError('File "setup.py" not found for legacy project.')
> FileNotFoundError: File "setup.py" not found for legacy project.
>
> so I had to manually add the BRs in https://salimma.fedorapeople.org/specs/python/python-mistune.spec
>
> the `pyproject.toml` is super simple:
> $ cat python/mistune-2.0.0/pyproject.toml
> [build-system]
> requires = [ "setuptools", "wheel" ]
>
> because the project really didn't have any dependency (beyond pytest for
> running tests).
>
> Is this a problem with our tooling or with upstream's pyproject.toml?

The problem is with upstream's pyproject.toml. They don't specify build backed, 
hence setup.py approach is used as a fallback and setup.py does not exist.

Either they need to to specify build backend to setuptools (preferred) or 
setup.py needs to exist in sdist.

See also 
https://lists.fedoraproject.org/archives/list/[e-mail]...
Search for "%pyproject_buildrequires fallbacks to setuptools only if setup.py 
exists."