tree a2bfa9247a230866a489d907b36d41a68c569772
parent 7b222cfdb4e59b9fd2a609e1fbb233e94fdcde7c
author Jon Brandvein <brandjon@google.com> 1573842889 -0500
committer GitHub <noreply@github.com> 1573842889 -0500
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Add pip3_import (#256)

This adds `pip3_import` as a wrapper around `pip_import` that sets `python_interpreter` to `"python3"`. This is important for requesting the Python 3 version of a package on systems where the `"python"` command is Python 2 (which is most of them).

We decline to add an analogous `pip2_import` wrapper at this time, because the command `"python2"` does not exist on all platforms by default (e.g. macOS).

`piptool.py` is updated to prefix the names of the wheel repos (an implementation
detail of rules_python) with the name given to `pip_import`. This is needed to
avoid shadowing wheel repos when the same wheel name is used by separate
`pip_import` invocations -- in particular when the same wheel is used for both
PY2 and PY3. (Thanks to @joshclimacell for pointing this detail out in
his prototype 90a70d5a550a01646966ce61156e6f83f02b4b73.)

Regenerated the .par files and docs.

Also updated the README to better explain the structure of the packaging rules. This includes mentioning `pip3_import`, concerns around versioning / hermeticity, and not depending on the wheel repo names (use `requirement()` instead).