8.3.0 introduces dependency loop with importlib_metadata on Python < 3.10 #1131
Description
Hi, thanks for working on and maintaining setuptools-scm.
fc2d841 introduced a dependency on importlib_metadata for Python < 3.10, which causes a dependency loop when building from source, because importlib_metadata depends on setuptools-scm. From what I can tell this is the same loop that was identified as problematic in #722 (2022), and then again in #918 (2023). Maybe there needs to be some stronger mechanism to prevent it in the future?
A simple reproducer (some output omitted to make it more readable):
$ podman run --rm -it python:3.9 bash -c "pip install --no-binary=:all: --no-cache-dir setuptools-scm==8.3.0"
Collecting setuptools-scm==8.3.0
Downloading setuptools_scm-8.3.0.tar.gz (78 kB)
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 78.0/78.0 kB 4.4 MB/s eta 0:00:00
Installing build dependencies ... error
error: subprocess-exited-with-error
× pip subprocess to install build dependencies did not run successfully.
│ exit code: 1
╰─> [99 lines of output]
...
Collecting importlib-metadata>=4.6
Downloading importlib_metadata-8.6.1.tar.gz (55 kB)
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 55.8/55.8 kB 13.0 MB/s eta 0:00:00
Installing build dependencies: started
Installing build dependencies: finished with status 'error'
error: subprocess-exited-with-error
× pip subprocess to install build dependencies did not run successfully.
│ exit code: 2
╰─> [60 lines of output]
Collecting setuptools_scm[toml]>=3.4.1
Downloading setuptools_scm-8.3.0.tar.gz (78 kB)
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 78.0/78.0 kB 2.8 MB/s eta 0:00:00
ERROR: Exception:
Traceback (most recent call last):
...
File "/usr/local/lib/python3.9/site-packages/pip/_internal/operations/build/build_tracker.py", line 92, in add
raise LookupError(message)
LookupError: https://files.pythonhosted.org/packages/ae/c1/0eb89ad8a0aa7033bbd0cc9fb44a0090c20edaba495f291e31be010e6ec1/setuptools_scm-8.3.0.tar.gz (from https://pypi.org/simple/setuptools-scm/) (requires-python:>=3.8) is already being built: setuptools-scm==8.3.0 from https://files.pythonhosted.org/packages/ae/c1/0eb89ad8a0aa7033bbd0cc9fb44a0090c20edaba495f291e31be010e6ec1/setuptools_scm-8.3.0.tar.gz