[mshr-h]

Summary

Fixes #15907, #24417

Fresh uv virtual environments do not include pip, causing installation to fail while bootstrapping packaging.

Prefer pip when available; otherwise use uv targeting the running Python environment. Keep the installer choice fixed throughout installation and document uv setup.

Test plan

Verify that source installation completes successfully in all three configurations below. Use a fresh .venv for each case.

1. uv available, pip initially unavailable

uv venv --python 3.12
source .venv/bin/activate
./install_executorch.sh --editable --verbose
python3 -I -c 'from executorch.extension.pybindings import portable_lib; print("Pass")'

2. Both uv and pip available

uv venv --python 3.12
source .venv/bin/activate
uv pip install pip
./install_executorch.sh --editable --verbose
python3 -I -c 'from executorch.extension.pybindings import portable_lib; print("Pass")'

3. pip available, uv unavailable

python3.12 -m venv .venv
source .venv/bin/activate
pip3 install pip
./install_executorch.sh --editable --verbose
python3 -I -c 'from executorch.extension.pybindings import portable_lib; print("Pass")'

Result: All three configurations passed.

cc @nil-is-all

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/24419

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⚠️ 28 Awaiting Approval, 1 Unrelated Failure

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[github-actions]

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[Copilot]

🟡 Changes recommended

Installer selection and caching lack automated test coverage, leaving fallback behavior and sticky installer selection unprotected against regressions.

1 open issue

• Add tests for installer selection and cached installer choice · New

What changed in this PR

This PR enables source installation in fresh uv environments without pip, addressing the installation failures described in #15907 and #24417.

Changes:

• Adds cached installer selection that prefers pip and otherwise uses uv targeting the running Python.
• Routes dependency bootstrapping and package installation through the shared helper.
• Documents uv environment setup.

File	Description
install_utils.py	Adds installer selection and uses it to bootstrap packaging.
install_requirements.py	Uses the shared installer for dependencies and removes a pip-specific option.
install_executorch.py	Uses the shared installer for ExecuTorch installation.
docs/​source/​using-executorch-building-from-source.md	Documents uv setup and installer fallback behavior.

_{Review effort: Balanced}

[Copilot]

🔵 Needs a closer look

Installer selection and caching lack automated regression tests covering pip preference, uv fallback targeting the running interpreter, neither installer being available, and retention of the cached uv choice.

1 open issue

• Add tests for installer selection and cached installer choice

_{Review effort: Balanced}