console_scripts are not created or removed on subsequent package installations

Environment

• pip version: 20.2.4
• Python version: 3.7.6
• OS: Solus 4.1 Fortitude

Description

If a user had previously installed a package that had no console_scripts entrypoints, then installs the package again without uninstalling it first, pip will not create (or remove) any console_scripts.

This happens when installing in development mode (-e) or when not in development mode.

Expected behavior

pip checks if console_scripts entrypoints have changed on each install and creates (or removes) console scripts as needed.

How to Reproduce

1. Create a new package without any console_scripts
2. Install the package
3. Add a console_scripts entrypoint
4. Install the package again
5. Observe lack of wrapper script for entrypoint
6. Uninstall the package
7. Install the package
8. Observe presence of wrapper script for entrypoint

$ cd $(mktemp -d)
$ python -m venv .venv
$ source .venv/bin/activate
$ python -m pip install -U pip setuptools wheel
Collecting pip
  Using cached https://files.pythonhosted.org/packages/cb/28/91f26bd088ce8e22169032100d4260614fc3da435025ff389ef1d396a433/pip-20.2.4-py2.py3-none-any.whl
Collecting setuptools
  Using cached https://files.pythonhosted.org/packages/6d/38/c21ef5034684ffc0412deefbb07d66678332290c14bb5269c85145fbd55e/setuptools-50.3.2-py3-none-any.whl
Collecting wheel
  Using cached https://files.pythonhosted.org/packages/a7/00/3df031b3ecd5444d572141321537080b40c1c25e1caa3d86cdd12e5e919c/wheel-0.35.1-py2.py3-none-any.whl
Installing collected packages: pip, setuptools, wheel
  Found existing installation: pip 19.2.3
    Uninstalling pip-19.2.3:
      Successfully uninstalled pip-19.2.3
  Found existing installation: setuptools 41.2.0
    Uninstalling setuptools-41.2.0:
      Successfully uninstalled setuptools-41.2.0
Successfully installed pip-20.2.4 setuptools-50.3.2 wheel-0.35.1
$ mkdir testpkg
$ cat > setup.py <<'EOF'
from setuptools import setup, find_packages

setup(
    name="testpkg",
    version="0.0.1",
    description="My test package",
    long_description="# testpkg\nMy test package",
    long_description_content_type="text/markdown",
    author="test",
    author_email="[e-mail]",
    maintainer="test",
    maintainer_email="[e-mail]",
    url=f"https://git.example.com/test/testpkg/blob/master/README.md",
    license="MIT",
    classifiers=[
        "Development Status :: 3 - Alpha",
        "Intended Audience :: Developers",
        "License :: OSI Approved :: MIT License",
        "Natural Language :: English",
        "Operating System :: OS Independent",
        "Programming Language :: Python :: 3 :: Only",
        "Programming Language :: Python :: 3.7",
        "Programming Language :: Python :: Implementation :: CPython",
    ],
    packages=find_packages(),
)
EOF
$ cat > testpkg/cli.py <<'EOF'
def main():
    print("Hello World")
EOF
$ find $VIRTUAL_ENV -name testpkgcli
$ python -m pip install --use-feature=2020-resolver -e .
Obtaining file:///tmp/tmp.pYPp8bLmjq
Installing collected packages: testpkg
  Running setup.py develop for testpkg
Successfully installed testpkg
$ find $VIRTUAL_ENV -name testpkgcli
$ patch -p1 <<'EOF'
--- ./setup.py    2020-11-07 15:59:04.823235435 -0800
+++ ./setup.py    2020-11-07 15:59:20.927199879 -0800
@@ -23,4 +23,9 @@
         "Programming Language :: Python :: Implementation :: CPython",
     ],
     packages=find_packages(),
+    entry_points={
+        "console_scripts": [
+            "testpkgcli = testpkg.cli:main"
+        ],
+    }
 )
EOF
patching file setup.py
$ python -m pip install --use-feature=2020-resolver -e .
Obtaining file:///tmp/tmp.pYPp8bLmjq
$ find $VIRTUAL_ENV -name testpkgcli                    
$ python -m pip uninstall -y testpkg
Found existing installation: testpkg 0.0.1
Uninstalling testpkg-0.0.1:
  Successfully uninstalled testpkg-0.0.1
$ python -m pip install --use-feature=2020-resolver -e .
Obtaining file:///tmp/tmp.pYPp8bLmjq
Installing collected packages: testpkg
  Running setup.py develop for testpkg
Successfully installed testpkg
$ find $VIRTUAL_ENV -name testpkgcli
/tmp/tmp.pYPp8bLmjq/.venv/bin/testpkgcli

[uranusjr]

Oh BTW I forgot to mention, pip has a shorthand for the uninstall-install combination: pip install --force-reinstall.

[pdxjohnny]

Very true.

So to summarize

• Users should uninstall and then install if they want changes to entry_points (or anything else) to take effect
• Users could run python setup.py egg_info to update the entry_points and console_scripts