Simplified formatting for deppy.NotSatisfiable error

[m1kola]

Today deppy.NotSatisfiable is being formated in a not very human friendly way: it is challenging to understand what exactly went wrong from the error message.

We need to explore error formatting options which:

• Describes in natural language what went wrong
• Does not include the description of the whole problem. Deppy (gini) already produces a minimised list of assumptions which together caused unsat - we need to keep this property.

This probably should be plugable.

[m1kola]

I really like how pip does it. Few examples I found on the internet (probably from different pip versions):

pandas-profiling 3.6.1 requires numpy<1.24,>=1.16.0, but you have numpy 1.24.1 which is incompatible.
numba 0.54.1 requires numpy<1.21,>=1.17, but you have numpy 1.24.1 which is incompatible.

Or more complex one:

The conflict is caused by:
    The user requested six==1.10.0
    bcrypt 3.2.0 depends on six>=1.4.1
    cvxpy 1.0.25 depends on six
    django-anymail 0.5 depends on six
    django-compat 1.0.15 depends on six>=1.10.0
    django-extensions 2.2.1 depends on six>=1.2
    drf-yasg 1.16.1 depends on six>=1.10.0
    fake-factory 0.6.0 depends on six
    google-api-core 1.26.0 depends on six>=1.13.0

[m1kola]

This repo with examples on how to format errors might be useful: https://github.com/perdasilva/deconflictor.

[m1kola]

I updated the description of the issue beucase it was initially not factually true: I origianlly said that deppy.NotSatisfiable contains description of the whole problem. It is not true: Deppy (thanks to Gini) only produces a minimised list of assumptions which together caused unsat.

I think readability of deppy.NotSatisfiable will be greatly influenced by the approach taken to building the constraints on the users side (e.g. IDs used, and how dependencies structured).

[joelanford]

IDs used

I think we have overlooked this particular aspect as well. We should define a standard for how to structure IDs and perhaps add a package (not sure where) to help users build IDs that will be easier to reason about.

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