Add --explicit-index flag to uv add command

[Copilot]

When adding a package from a custom index, the index is globally available for all subsequent package resolutions, causing "No solution found" errors or unintended dependency confusion. Users must manually edit pyproject.toml to add explicit = true or use unsafe index strategies.

Changes

CLI: Added --explicit-index flag to uv add that marks indexes as explicit, restricting them to packages that explicitly reference them via tool.uv.sources.

TOML generation: Modified add_index() to write/remove the explicit field based on flag presence, ensuring clean updates when toggling between explicit and non-explicit indexes.

Settings propagation: Threaded explicit_index parameter through AddSettings and command invocation chain.

Usage

# Add package with explicit index
uv add paddlepaddle==3.0.0 --index https://example.org/simple --explicit-index

# Other packages now use default index, not the custom one
uv add matplotlib  # Uses PyPI, not example.org

Generates:

[[tool.uv.index]]
url = "https://example.org/simple"
explicit = true

[tool.uv.sources]
paddlepaddle = { index = "..." }

Fixes astral-sh#16291

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• astral-sh.github.io
  • Triggering command: /home/REDACTED/work/uv/uv/target/debug/uv add --cache-dir /tmp/uv/tests/.tmpIC8fVP/cache iniconfig==2.0.0 --index pytorch=REDACTED --explicit-index (dns block)
  • Triggering command: /home/REDACTED/work/uv/uv/target/debug/uv add --cache-dir /tmp/uv/tests/.tmpTq1kkS/cache jinja2 --index pytorch=REDACTED (dns block)
• pypi-proxy.fly.dev
  • Triggering command: /home/REDACTED/work/uv/uv/target/debug/uv add --cache-dir /tmp/uv/tests/.tmpSjulWT/cache iniconfig==2.0.0 (dns block)
  • Triggering command: /home/REDACTED/work/uv/uv/target/debug/uv add --cache-dir /tmp/uv/tests/.tmpxXvNQQ/cache iniconfig --index ./test-index (dns block)
  • Triggering command: /home/REDACTED/work/uv/uv/target/debug/uv add --cache-dir /tmp/uv/tests/.tmpxhBu6c/cache anyio (dns block)
• test.pypi.org
  • Triggering command: /home/REDACTED/work/uv/uv/target/debug/uv add --cache-dir /tmp/uv/tests/.tmpF3JuIW/cache iniconfig --default-index REDACTED (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

I want you to work on this issue astral-sh#16291 - add the option to pass in a explicit flag when adding a dependency from a specific index

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