commit 4725d98a3a53ebf90c45d29245691fa060f9c734
author Reid D McKenzie <me@arrdem.com> Tue Nov 28 11:03:01 2023 -0700
committer GitHub <noreply@github.com> Tue Nov 28 18:03:01 2023 +0000
tree 44e6d11e286da8d43d48905663b293df59aa1388
parent 69abe80724c8ef353fec3d59e578e949dad540a0

feat(pip_repository): Support pip parse cycles (#1166)

This patch reworks the `pip_repository` machinery to allow users to
manually annotate groups of libraries which form packaging cycles in
PyPi and must be simultaneously installed.

The strategy here is to transform any dependencies `A` and `B` which
have dependencies and are mutually dependent

```mermaid
graph LR;
    A-->B;
    A-->D;
    A-->E;
    B-->A;
    B-->F;
    B-->G;
```

into a new "dependency group" `C` which has `A*` and `B*` as
dependencies, defined as `A` and `B` less any direct dependencies which
are members of the group. This is viable _for python_ because Python
files just need to be emplaced into a runfiles directory for the
interpreter. We don't actually have a true hard dependency between the
build definition of `A` requiring the build product `B` be available
which requires that the build product of `A` be available.

```mermaid
graph LR
     C-->A*;
     A*-->D;
     A*-->E;
     C-->B*;
     B*-->F;
     B*-->G;
```
This gets us most of the way there, as a user can now safely write
`requirement("A")` and we can provide them with `C`, which has the
desired effect of pulling in `A`, `B` and their respective transitives.

There is one remaining problem - a user writing `deps =
[requirement("A"), requirement("B")]` will take a double direct
dependency on `C`. So we need to insert a layer of indirection,
generating `C_A` and `C_B` which serve only as unique aliases for `C` so
that we can support the double dependency. Our final dependency graph
then is as follows

```mermaid
graph LR
     C_A-->C;
     C_B-->C;
     C-->A*;
     A*-->D;
     A*-->E;
     C-->B*;
     B*-->F;
     B*-->G;
```

Addresses #1076, #1188

## To do
- [x] Get rebased
- [x] Get re-validated manually
- [x] Buildifier
- [x] Get CI happy
- [x] Update documentation
- [x] Update changelog

---------

Co-authored-by: Ignas Anikevicius <240938+aignas@users.noreply.github.com>