Add Cantera dependency and pre-install Python venv

Install Cantera and create a Python virtual environment during formula
installation, eliminating the need for mfc to create its own venv on
first run. This enables full functionality immediately after installation.

Changes to formula:
- Add cantera as a runtime dependency
- Move [email protected] from build-only to runtime dependency
- Create Python venv in libexec/venv during installation
- Install MFC Python package and all dependencies into venv
- Update wrapper to activate pre-installed venv
- Link venv into build directory so mfc.sh uses existing environment
- Add venv verification to test block
- Re-enable mfc --help test since venv is ready

Changes to CI:
- Add cantera to dependency installation step
- Verify venv contains cantera and mfc packages

Benefits:
- mfc commands work immediately (no setup on first run)
- All examples including those requiring Cantera work out of the box
- Much faster execution since venv is reused
- No cantera==3.1.0 not found errors

Author: sbryngelson

.github/workflows/homebrew.yml

@@ -35,7 +35,7 @@ jobs:
       - name: Install formula dependencies
         run: |
           echo "Installing MFC dependencies..."
-          brew install cmake gcc [email protected] boost fftw hdf5 open-mpi openblas
+          brew install cmake gcc [email protected] boost cantera fftw hdf5 open-mpi openblas
       
       - name: Validate formula syntax
         run: |
@@ -100,6 +100,11 @@ jobs:
           ls -la $(brew --prefix)/libexec/mfc.sh
           ls -la $(brew --prefix)/share/mfc/examples/
           
+          echo "Checking Python venv..."
+          ls -la $(brew --prefix)/Cellar/mfc/*/libexec/venv/
+          $(brew --prefix)/Cellar/mfc/*/libexec/venv/bin/python --version
+          $(brew --prefix)/Cellar/mfc/*/libexec/venv/bin/pip list | grep -E "(cantera|mfc)"
+          
           echo "Installation verified successfully!"
       
       - name: Uninstall and cleanup

packaging/homebrew/mfc.rb

@@ -12,13 +12,14 @@ class Mfc < Formula
 
   depends_on "cmake" => :build
   depends_on "gcc" => :build
-  depends_on "[email protected]" => :build
 
   depends_on "boost"
+  depends_on "cantera"
   depends_on "fftw"
   depends_on "hdf5"
   depends_on "open-mpi"
   depends_on "openblas"
+  depends_on "[email protected]"
 
   def install
     # MFC uses a Python wrapper script for building
@@ -46,12 +47,24 @@ def install
     # Install examples
     pkgshare.install "examples"
 
+    # Create Python virtual environment with MFC dependencies
+    venv = libexec/"venv"
+    system Formula["[email protected]"].opt_bin/"python3.12", "-m", "venv", venv
+    
+    # Install MFC Python package and dependencies into venv
+    system venv/"bin/pip", "install", "--upgrade", "pip", "setuptools", "wheel"
+    system venv/"bin/pip", "install", "-e", prefix/"toolchain"
+
     # Create a wrapper that sets up a working environment for mfc.sh
-    # The wrapper uses a temporary directory since Cellar is read-only
+    # The wrapper uses a temporary directory since Cellar is read-only and
+    # activates the pre-installed Python virtual environment
     (bin/"mfc").write <<~EOS
       #!/bin/bash
       set -e
 
+      # Activate the pre-installed Python virtual environment
+      source "#{libexec}/venv/bin/activate"
+
       # Create a working directory for MFC in user's cache
       MFC_WORK_DIR="${TMPDIR:-/tmp}/mfc-homebrew-$$"
       mkdir -p "$MFC_WORK_DIR"
@@ -67,6 +80,10 @@ def install
       ln -sf "#{prefix}/toolchain" toolchain
       ln -sf "#{libexec}/mfc.sh" mfc.sh
       ln -sf "#{pkgshare}/examples" examples
+      
+      # Link the venv so mfc.sh doesn't try to create its own
+      mkdir -p build
+      ln -sf "#{libexec}/venv" build/venv
 
       # Set up environment variables
       export MFC_INSTALL_DIR="#{prefix}"
@@ -114,8 +131,16 @@ def caveats
     assert_path_exists prefix/"toolchain"
     assert_path_exists prefix/"toolchain/mfc"
 
+    # Verify Python venv was created with dependencies
+    assert_path_exists libexec/"venv"
+    assert_path_exists libexec/"venv/bin/python"
+    assert_path_exists libexec/"venv/bin/pip"
+
     # Verify examples were installed
     assert_path_exists pkgshare/"examples"
     assert_path_exists pkgshare/"examples/1D_sodshocktube/case.py"
+
+    # Test mfc wrapper functionality with pre-installed venv
+    system bin/"mfc", "--help"
   end
 end