python: Avoid no-build-isolation for 3p deps

Pip installs should not use --no-build-isolation for 3rd party Python
packages that have C/C++ extensions.

Change-Id: Ia9744343ff59ed442617a89c612efafd473b3ac3
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/103100
Commit-Queue: Anthony DiGirolamo <tonymd@google.com>
Reviewed-by: Wyatt Hepler <hepler@google.com>

pw_build/python.gni

@@ -517,10 +517,12 @@ template("pw_python_package") {
  args = [
  "install",
 
- # This speeds up pip installs. At this point in the gn build the
- # virtualenv is already activated so build isolation isn't required.
- # This requires that pip, setuptools, and wheel packages are
- # installed.
+ # This speeds up pip installs. Build isolation isn't required for
+ # in-tree packages unless that package includes C/C++ extension
+ # modules:
+ # https://setuptools.pypa.io/en/latest/userguide/ext_modules.html
+ # For packages witout extensions this option requires that pip,
+ # setuptools, and wheel packages are available.
  "--no-build-isolation",
  ]
 

pw_build/python_venv.gni

@@ -168,7 +168,6 @@ template("pw_python_venv") {
  _skip_installing_external_python_deps = true
  args = [
  "install",
- "--no-build-isolation",
  "wheel",
  ]
  inputs = _constraints
@@ -190,10 +189,11 @@ template("pw_python_venv") {
  module = "pip"
  _pw_internal_run_in_venv = true
  _skip_installing_external_python_deps = true
- args = [
- "install",
- "--no-build-isolation",
- ]
+ args = [ "install" ]
+
+ # Note: --no-build-isolation should be avoided for installing 3rd party
+ # Python packages that use C/C++ extension modules.
+ # https://setuptools.pypa.io/en/latest/userguide/ext_modules.html
  inputs = _constraints + _requirements
 
  # Constraints

pw_env_setup/py/pw_env_setup/virtualenv_setup/install.py

@@ -264,7 +264,10 @@ def pip_install(*args):
  requirements = constraints
 
  if requirements:
- requirement_args = ['--no-build-isolation']
+ requirement_args = []
+ # Note: --no-build-isolation should be avoided for installing 3rd party
+ # Python packages that use C/C++ extension modules.
+ # https://setuptools.pypa.io/en/latest/userguide/ext_modules.html
  requirement_args.extend('--requirement={}'.format(req)
  for req in requirements)
  combined_requirement_args = requirement_args + constraint_args