mirror of https://github.com/astral-sh/uv
f7bed37a4e
When we generate conflict markers for each resolution after the
resolver runs, it turns out that generating them just from exclusion
rules is not sufficient.
For example, if `foo` and `bar` are declared as conflicting extras, then
we end up with the following forks:
A: extra != 'foo'
B: extra != 'bar'
C: extra != 'foo' and extra != 'bar'
Now let's take an example where these forks don't share the same version
for all packages. Consider a case where `idna==3.9` is in forks A and C,
but where `idna==3.10` is in fork B. If we combine the markers in forks
A and C through disjunction, we get the following:
idna==3.9: extra != 'foo' or (extra != 'foo' and extra != 'bar')
idna==3.10: extra != 'bar'
Which simplifies to:
idna==3.9: extra != 'foo'
idna==3.10: extra != 'bar'
But these are clearly not disjoint. Both dependencies could be selected,
for example, when neither `foo` nor `bar` are active. We can remedy this
by keeping around the inclusion rules for each fork:
A: extra != 'foo' and extra == 'bar'
B: extra != 'bar' and extra == 'foo'
C: extra != 'foo' and extra != 'bar'
And so for `idna`, we have:
idna==3.9: (extra != 'foo' and extra == 'bar') or (extra != 'foo' and extra != 'bar')
idna==3.10: extra != 'bar' and extra == 'foo'
Which simplifies to:
idna==3.9: extra != 'foo'
idna==3.10: extra != 'bar' and extra == 'foo'
And these *are* properly disjoint. There is no way for them both to be
active. This also correctly accounts for fork C where neither `foo` nor
`bar` are active, and yet, `idna==3.9` is still enabled but `idna==3.10`
is not. (In the [motivating example], this comes from `baz` being enabled.)
That is, this captures the idea that for `idna==3.10` to be installed,
there must actually be a specific extra that is enabled. That's what
makes it disjoint from `idna==3.9`.
We aren't quite done yet, because this does add *too many* conflict
markers to dependency edges that don't need it. In the next commit,
we'll add in our world knowledge to simplify these conflict markers.
[motivating example]: https://github.com/astral-sh/uv/issues/9289
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