Example error: ResolutionImpossible

What if there are user-provided pinned packages?

Where a user wants to install packages (with 1 or more pinned version) with default verbose level

$ pip install peach=1.0 apple=2.0

Due to conflicting dependencies pip cannot install Peach1.0 and Apple2.0:

* Peach 1.0 depends on Banana 3.0
* Apple2.0 depends on Banana2.0

There are a number of possible solutions. You can try:
1. removing package versions from your requirements, and letting pip try to resolve the problem for you
2. Trying  a version of Peach that depends on Banana2.0. Try `pip-search peach —dep banana2.0`
3. replacing Apple or Peach with a different package altogether
4. patching Apple2.0 to use Banana3.0
5. force installing (Be aware!)

For instructions on how to do these steps visit: https://pypa.io/SomeLink
To debug this further you can run `pip-tree` to see all of your dependencies.

with verbose level -vv

If a user ran the same pip command with more verbosity, what would they see?

with verbose level -vvv

If a user ran the same pip command with more verbosity, what would they see?

What if there are no user-provided version restrictions?

NB: We are assuming this resolver behaviour gets implemented, based on GH issues 8249.

with default verbose level

$ pip install apple peach

Due to conflicting dependencies pip cannot install apple or peach. Both depend on banana, but pip can't find a version of either where they depend on the same banana version.

There are a number of possible solutions. You can try:
1. replacing apple or peach with a different package altogether
2. patching apple or peach to use the same version of banana
3. force installing (Be aware!)

To debug this further you can run pip-tree to see all of your dependencies.

with verbose level -vv

If a user ran the same pip command with more verbosity, what would they see?

with verbose level -vvv

If a user ran the same pip command with more verbosity, what would they see?

What should be in the “documentation” page?

  • ways to swap a package for another

  • how to patch a package to support a version (various ways)

Recommendations

  • Write official documentation / guide “How to resolve dependency conflicts” explaining:

    • Why conflicts can exist

    • How you can avoid them (pinning)

    • How you can resolve them

      • Use alternative package

      • Use older version

      • Patch package

  • Introduce new commands to pip, inspired by poetry:

    • Tree: Show full tree of dependencies

    • Show <package> Show details of a package, including it’s dependencies

    • latest - shows latest vs installed versions

    • outdated - shows only outdated versions

  • Expose commands / help link in output??

    • when particular issue happens provide ways to move on (ala pipenv), e.g.

      • run this command to see X

      • is it your internet connection?

      • is it the pypi website?

  • Aspirational commands

    • pip search PackageName —dep PackageNameVersion

      • a command that will search for a version of a package that has a dependency on another packageversion