venv_upgrade

#!/bin/bash
#
# Did you upgrade your OS and Python with it, or just Python and now your venv doesn't work.
# Piffle, activate your venv and run this script and hope for the best, it will try and fix
# things for you. 
#
# The problems and fixes:
#
# 1. pip no longer works in the venv. The fix: in the active venv run ensurepip to fix it.
# 2. lib is missing: 
#		The lib will be in $VIRTUAL_ENV/lib/pythonM.m/site-packages (M.mm is Major.minor like 3.10)
#		This has the old Python version in it.
#       The fix: pip freeze on the old lib dir, and install all the packages with pip into the new lib dir
# Afterwards dumps a diff for review, and you can just use pip freeze as usual and all should be fine.
# Being Python and pip, there is plenty of scope for htings to go wrong ;-). Tee hee.   

# Detect if a virtual environment is activated
if [ -z "$VIRTUAL_ENV" ]; then
    echo "No virtual environment detected. Please activate a virtual environment first."
    exit 1
fi

# Upgrade pip first
# This will create a new venv lib in the active venv 
echo "Ensuring we have the latest pip ..."
python -m ensurepip --upgrade

# Set paths dynamically based on the active venv
LIB_DIR="$VIRTUAL_ENV/lib"

# Sort the Python directories and take the second-to-last as the old venv and the last as the new venv
PYTHON_DIRS=($(ls -d "$LIB_DIR"/python* | sort -V))
OLD_VENV_LIB="${PYTHON_DIRS[-2]}"
NEW_VENV_LIB="${PYTHON_DIRS[-1]}"

# Check if we have two Python directories to work with
if [ -z "$OLD_VENV_LIB" ] || [ -z "$NEW_VENV_LIB" ]; then
    echo "Error: we need at least two lib dirs. What we found was:"
    ls -l "$LIB_DIR"
    exit 1
else
    echo "Migrating from $(basename $OLD_VENV_LIB) to $(basename $NEW_VENV_LIB)"
fi

# Extract version numbers from the directory names (python3.10, python3.12, etc.)
OLD_VERSION=$(basename "$OLD_VENV_LIB" | sed 's/python//')
NEW_VERSION=$(basename "$NEW_VENV_LIB" | sed 's/python//')

# Check if old venv exists
if [ ! -d "$OLD_VENV_LIB/site-packages" ]; then
    echo "Old venv directory ($OLD_VENV_LIB) not found!"
    exit 1
fi

# List installed packages in the old venv
echo "Extracting package names from old venv ($OLD_VENV_LIB)..."
OLD_REQ="$LIB_DIR/requirements_$OLD_VERSION.txt"
pip freeze --path $OLD_VENV_LIB/site-packages > "$OLD_REQ"

# Check if old requirements are empty
if [ ! -s "$OLD_REQ" ]; then
    echo "No packages found in the old venv's site-packages. Exiting."
    exit 0
fi

echo "Created $OLD_REQ based on old venv's site-packages."

# Install packages in new venv from old venv's extracted packages
echo "Installing packages in new venv..."
while read -r pkg; do
    echo "Installing $pkg..."
    pip install "$pkg" || echo "Failed to install $pkg"
done < "$OLD_REQ"

# Save new installed packages to a file
NEW_REQ="$LIB_DIR/requirements_$NEW_VERSION.txt"
pip freeze > "$NEW_REQ"
echo "Created $NEW_REQ for new venv."

# Compare old packages with the newly installed packages
echo "Comparing old and new installed packages..."
diff -u "$OLD_REQ" "$NEW_REQ"

echo "Migration complete. Review the comparison above."