Backend is not available for fallback/legacy builder

[jaraco]

Today I tried running build for the first time, but it failed:

lock master $ pip-run build -- -m build
Collecting build
  Using cached build-0.0.4-py2.py3-none-any.whl (8.8 kB)
Collecting pep517
  Using cached pep517-0.9.1-py2.py3-none-any.whl (18 kB)
Collecting toml
  Using cached toml-0.10.1-py2.py3-none-any.whl (19 kB)
Collecting packaging
  Using cached packaging-20.4-py2.py3-none-any.whl (37 kB)
Collecting six
  Using cached six-1.15.0-py2.py3-none-any.whl (10 kB)
Collecting pyparsing>=2.0.2
  Using cached pyparsing-2.4.7-py2.py3-none-any.whl (67 kB)
Installing collected packages: toml, six, pyparsing, pep517, packaging, build
Successfully installed build-0.0.4 packaging-20.4 pep517-0.9.1 pyparsing-2.4.7 six-1.15.0 toml-0.10.1
WARNING: You are using pip version 20.2.3; however, version 20.2.4 is available.
You should consider upgrading via the '/Library/Frameworks/Python.framework/Versions/3.9/bin/python3.9 -m pip install --upgrade pip' command.
ERROR Backend 'setuptools.build_meta:__legacy__' is not available

Probably if build is going to support legacy builds using setuptools, it should also include that dependency.

[FFY00]

It should be injecting that dependency. Can I see your pyproject.toml?

[gaborbernat]

Is this latest released? Have you tried with master?

https://github.com/pypa/build/blob/master/src/build/__init__.py#L151

[FFY00]

It should be working in the latest release.

https://github.com/pypa/build/blob/0.0.4/src/build/__init__.py#L153

I suspect pyproject.toml might have an incomplete build-system table.

[jaraco]

Yes, pip-run uses the same semantics, so grabs the latest from PyPI unless a specific version is specified. You can see in the trace that 0.0.4 was used.

The issue doesn't exist with master.

lock master $ pip-run git+https://github.com/pypa/build -- -m build
Collecting git+https://github.com/pypa/build
  Cloning https://github.com/pypa/build to /private/var/folders/c6/v7hnmq453xb6p2dbz1gqc6rr0000gn/T/pip-req-build-yif51n19
  Installing build dependencies ... done
  Getting requirements to build wheel ... done
    Preparing wheel metadata ... done
Collecting pep517>=0.9
  Using cached pep517-0.9.1-py2.py3-none-any.whl (18 kB)
Collecting toml
  Using cached toml-0.10.1-py2.py3-none-any.whl (19 kB)
Collecting packaging
  Using cached packaging-20.4-py2.py3-none-any.whl (37 kB)
Collecting six
  Using cached six-1.15.0-py2.py3-none-any.whl (10 kB)
Collecting pyparsing>=2.0.2
  Using cached pyparsing-2.4.7-py2.py3-none-any.whl (67 kB)
Building wheels for collected packages: build
  Building wheel for build (PEP 517) ... done
  Created wheel for build: filename=build-0.0.4-py2.py3-none-any.whl size=10425 sha256=fa0b15dd4286c4bb356a9e77cddc47be8927a997876327af2174efeac4f61346
  Stored in directory: /private/var/folders/c6/v7hnmq453xb6p2dbz1gqc6rr0000gn/T/pip-ephem-wheel-cache-i44dz5zr/wheels/57/59/86/6612f27ab3ddb5f55e0e6d6027bfb04eff0c0345dc23f29c68
Successfully built build
Installing collected packages: toml, six, pyparsing, pep517, packaging, build
Successfully installed build-0.0.4 packaging-20.4 pep517-0.9.1 pyparsing-2.4.7 six-1.15.0 toml-0.10.1
WARNING: You are using pip version 20.2.3; however, version 20.2.4 is available.
You should consider upgrading via the '/Library/Frameworks/Python.framework/Versions/3.9/bin/python3.9 -m pip install --upgrade pip' command.
Collecting wheel
  Using cached wheel-0.35.1-py2.py3-none-any.whl (33 kB)
Collecting setuptools>=40.8.0
  Using cached setuptools-50.3.2-py3-none-any.whl (785 kB)
Installing collected packages: wheel, setuptools
Successfully installed setuptools-50.3.2 wheel-0.35.1
WARNING: You are using pip version 20.2.3; however, version 20.2.4 is available.
You should consider upgrading via the '/Library/Frameworks/Python.framework/Versions/3.9/bin/python3.9 -m pip install --upgrade pip' command.
running sdist
running egg_info
writing flufl.lock.egg-info/PKG-INFO
writing dependency_links to flufl.lock.egg-info/dependency_links.txt
writing namespace_packages to flufl.lock.egg-info/namespace_packages.txt
writing requirements to flufl.lock.egg-info/requires.txt
writing top-level names to flufl.lock.egg-info/top_level.txt
reading manifest file 'flufl.lock.egg-info/SOURCES.txt'
reading manifest template 'MANIFEST.in'
package init file 'dist/__init__.py' not found (or not a regular file)
package init file 'flufl/__init__.py' not found (or not a regular file)
package init file 'dist/tmp20on0myv/__init__.py' not found (or not a regular file)
warning: no files found matching '*.po' anywhere in distribution
warning: no files found matching '*.mo' anywhere in distribution
warning: no previously-included files found matching '.gitignore'
no previously-included directories found matching 'build'
no previously-included directories found matching '.tox'
no previously-included directories found matching 'dist'
writing manifest file 'flufl.lock.egg-info/SOURCES.txt'
running check
creating flufl.lock-5.0.3
creating flufl.lock-5.0.3/docs
creating flufl.lock-5.0.3/flufl.lock.egg-info
creating flufl.lock-5.0.3/flufl
creating flufl.lock-5.0.3/flufl/lock
creating flufl.lock-5.0.3/test
copying files to flufl.lock-5.0.3...
copying .readthedocs-req.txt -> flufl.lock-5.0.3
copying LICENSE -> flufl.lock-5.0.3
copying MANIFEST.in -> flufl.lock-5.0.3
copying README.rst -> flufl.lock-5.0.3
copying conftest.py -> flufl.lock-5.0.3
copying setup.cfg -> flufl.lock-5.0.3
copying setup.py -> flufl.lock-5.0.3
copying setup_helpers.py -> flufl.lock-5.0.3
copying tox.ini -> flufl.lock-5.0.3
copying docs/NEWS.rst -> flufl.lock-5.0.3/docs
copying docs/apiref.rst -> flufl.lock-5.0.3/docs
copying docs/index.rst -> flufl.lock-5.0.3/docs
copying docs/theory.rst -> flufl.lock-5.0.3/docs
copying docs/using.rst -> flufl.lock-5.0.3/docs
copying flufl.lock.egg-info/PKG-INFO -> flufl.lock-5.0.3/flufl.lock.egg-info
copying flufl.lock.egg-info/SOURCES.txt -> flufl.lock-5.0.3/flufl.lock.egg-info
copying flufl.lock.egg-info/dependency_links.txt -> flufl.lock-5.0.3/flufl.lock.egg-info
copying flufl.lock.egg-info/namespace_packages.txt -> flufl.lock-5.0.3/flufl.lock.egg-info
copying flufl.lock.egg-info/not-zip-safe -> flufl.lock-5.0.3/flufl.lock.egg-info
copying flufl.lock.egg-info/requires.txt -> flufl.lock-5.0.3/flufl.lock.egg-info
copying flufl.lock.egg-info/top_level.txt -> flufl.lock-5.0.3/flufl.lock.egg-info
copying flufl/lock/__init__.py -> flufl.lock-5.0.3/flufl/lock
copying flufl/lock/_lockfile.py -> flufl.lock-5.0.3/flufl/lock
copying test/test_api.py -> flufl.lock-5.0.3/test
copying test/test_lock.py -> flufl.lock-5.0.3/test
Writing flufl.lock-5.0.3/setup.cfg
Creating tar archive
removing 'flufl.lock-5.0.3' (and everything under it)
running bdist_wheel
running build
running build_py
package init file 'dist/__init__.py' not found (or not a regular file)
package init file 'flufl/__init__.py' not found (or not a regular file)
package init file 'dist/tmph0c5cu48/__init__.py' not found (or not a regular file)
creating build
creating build/lib
creating build/lib/flufl
creating build/lib/flufl/lock
copying flufl/lock/_lockfile.py -> build/lib/flufl/lock
copying flufl/lock/__init__.py -> build/lib/flufl/lock
running egg_info
writing flufl.lock.egg-info/PKG-INFO
writing dependency_links to flufl.lock.egg-info/dependency_links.txt
writing namespace_packages to flufl.lock.egg-info/namespace_packages.txt
writing requirements to flufl.lock.egg-info/requires.txt
writing top-level names to flufl.lock.egg-info/top_level.txt
reading manifest file 'flufl.lock.egg-info/SOURCES.txt'
reading manifest template 'MANIFEST.in'
warning: no files found matching '*.po' anywhere in distribution
warning: no files found matching '*.mo' anywhere in distribution
warning: no previously-included files found matching '.gitignore'
no previously-included directories found matching 'build'
no previously-included directories found matching '.tox'
no previously-included directories found matching 'dist'
writing manifest file 'flufl.lock.egg-info/SOURCES.txt'
installing to build/bdist.macosx-10.9-x86_64/wheel
running install
running install_lib
copying flufl/lock/_lockfile.py -> build/bdist.macosx-10.9-x86_64/wheel/flufl/lock
copying flufl/lock/__init__.py -> build/bdist.macosx-10.9-x86_64/wheel/flufl/lock
running install_egg_info
Copying flufl.lock.egg-info to build/bdist.macosx-10.9-x86_64/wheel/flufl.lock-5.0.3-py3.9.egg-info
Installing build/bdist.macosx-10.9-x86_64/wheel/flufl.lock-5.0.3-py3.9-nspkg.pth
running install_scripts
adding license file "LICENSE" (matched pattern "LICEN[CS]E*")
creating build/bdist.macosx-10.9-x86_64/wheel/flufl.lock-5.0.3.dist-info/WHEEL
creating '/Users/jaraco/code/public/flufl/lock/dist/tmph0c5cu48/flufl.lock-5.0.3-py3-none-any.whl' and adding 'build/bdist.macosx-10.9-x86_64/wheel' to it
adding 'flufl.lock-5.0.3-py3.9-nspkg.pth'
adding 'flufl/lock/__init__.py'
adding 'flufl/lock/_lockfile.py'
adding 'flufl.lock-5.0.3.dist-info/LICENSE'
adding 'flufl.lock-5.0.3.dist-info/METADATA'
adding 'flufl.lock-5.0.3.dist-info/WHEEL'
adding 'flufl.lock-5.0.3.dist-info/namespace_packages.txt'
adding 'flufl.lock-5.0.3.dist-info/top_level.txt'
adding 'flufl.lock-5.0.3.dist-info/RECORD'
removing build/bdist.macosx-10.9-x86_64/wheel

So all that's need to close this issue is to cut a release.

[gaborbernat]

The issue is most likely related to macOS framework python also does not respect env vars properly, we fixed this by moving to venv in #18