pip version

21.0.1

Python version

3.9

OS

macOS

Additional information

No response

Description

• pip can output "Successfully installed mypackage-1.0" even if it wasn't successfully installed
• pip can leave a .dist-info subdirectory lying around if the installation wasn't successful

Expected behavior

• don't log the message "Successfully installed mypackage-1.2.3" unless the installation was actually successful
• if the installation was not successful, rollback any metadata files/subdirectory which was written

How to Reproduce

Setup:

$ mkdir /tmp/example
$ python3 -m pip install six==1.14 --target=/tmp/example
Collecting six==1.14
  Using cached six-1.14.0-py2.py3-none-any.whl (10 kB)
Installing collected packages: six
Successfully installed six-1.14.0
$ ls /tmp/example
__pycache__          six-1.14.0.dist-info six.py

Reproducer:

$ python3 -m pip install six==1.15 --target=/tmp/example
Collecting six==1.15
  Using cached six-1.15.0-py2.py3-none-any.whl (10 kB)
Installing collected packages: six
Successfully installed six-1.15.0
WARNING: Target directory /tmp/example/__pycache__ already exists. Specify --upgrade to force replacement.
WARNING: Target directory /tmp/example/six.py already exists. Specify --upgrade to force replacement.
$ ls /tmp/example
__pycache__          six-1.14.0.dist-info six-1.15.0.dist-info six.py
$ grep __version__ /tmp/example/six.py
__version__ = "1.14.0"

Output

As you can see, it logged "Successfully installed six-1.15.0" but the code at the target is still the previous version.

Using --upgrade, as the warning message mentioned, does indeed replace files. However, it also leaves files from the old version around too (with six.py there is only one source file, though the old .dist-info subdir also remains). I would normally expect pip to fully remove the previous version before installing new version.

Code of Conduct

• I agree to follow the PSF Code of Conduct