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incompatibility.rs
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incompatibility.rs
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// SPDX-License-Identifier: MPL-2.0
//! An incompatibility is a set of terms for different packages
//! that should never be satisfied all together.
use std::fmt::{self, Debug, Display};
use std::sync::Arc;
use crate::internal::{Arena, Id, SmallMap};
use crate::{
term, DefaultStringReportFormatter, DependencyProvider, DerivationTree, Derived, External, Map,
Package, ReportFormatter, Set, Term, VersionSet,
};
/// An incompatibility is a set of terms for different packages
/// that should never be satisfied all together.
/// An incompatibility usually originates from a package dependency.
/// For example, if package A at version 1 depends on package B
/// at version 2, you can never have both terms `A = 1`
/// and `not B = 2` satisfied at the same time in a partial solution.
/// This would mean that we found a solution with package A at version 1
/// but not with package B at version 2.
/// Yet A at version 1 depends on B at version 2 so this is not possible.
/// Therefore, the set `{ A = 1, not B = 2 }` is an incompatibility,
/// defined from dependencies of A at version 1.
///
/// Incompatibilities can also be derived from two other incompatibilities
/// during conflict resolution. More about all this in
/// [PubGrub documentation](https://github.com/dart-lang/pub/blob/master/doc/solver.md#incompatibility).
#[derive(Debug, Clone)]
pub(crate) struct Incompatibility<P: Package, VS: VersionSet, M: Eq + Clone + Debug + Display> {
package_terms: SmallMap<P, Term<VS>>,
kind: Kind<P, VS, M>,
}
/// Type alias of unique identifiers for incompatibilities.
pub(crate) type IncompId<P, VS, M> = Id<Incompatibility<P, VS, M>>;
pub(crate) type IncompDpId<DP> = IncompId<
<DP as DependencyProvider>::P,
<DP as DependencyProvider>::VS,
<DP as DependencyProvider>::M,
>;
#[derive(Debug, Clone)]
enum Kind<P: Package, VS: VersionSet, M: Eq + Clone + Debug + Display> {
/// Initial incompatibility aiming at picking the root package for the first decision.
///
/// This incompatibility drives the resolution, it requires that we pick the (virtual) root
/// packages.
NotRoot(P, VS::V),
/// There are no versions in the given range for this package.
///
/// This incompatibility is used when we tried all versions in a range and no version
/// worked, so we have to backtrack
NoVersions(P, VS),
/// Incompatibility coming from the dependencies of a given package.
///
/// If a@1 depends on b>=1,<2, we create an incompatibility with terms `{a 1, b <1,>=2}` with
/// kind `FromDependencyOf(a, 1, b, >=1,<2)`.
///
/// We can merge multiple dependents with the same version. For example, if a@1 depends on b and
/// a@2 depends on b, we can say instead a@1||2 depends on b.
FromDependencyOf(P, VS, P, VS),
/// Derived from two causes. Stores cause ids.
///
/// For example, if a -> b and b -> c, we can derive a -> c.
DerivedFrom(IncompId<P, VS, M>, IncompId<P, VS, M>),
/// The package is unavailable for reasons outside pubgrub.
///
/// Examples:
/// * The version would require building the package, but builds are disabled.
/// * The package is not available in the cache, but internet access has been disabled.
Custom(P, VS, M),
}
/// A Relation describes how a set of terms can be compared to an incompatibility.
/// Typically, the set of terms comes from the partial solution.
#[derive(Eq, PartialEq, Debug)]
pub(crate) enum Relation<P: Package> {
/// We say that a set of terms S satisfies an incompatibility I
/// if S satisfies every term in I.
Satisfied,
/// We say that S contradicts I
/// if S contradicts at least one term in I.
Contradicted(P),
/// If S satisfies all but one of I's terms and is inconclusive for the remaining term,
/// we say S "almost satisfies" I and we call the remaining term the "unsatisfied term".
AlmostSatisfied(P),
/// Otherwise, we say that their relation is inconclusive.
Inconclusive,
}
impl<P: Package, VS: VersionSet, M: Eq + Clone + Debug + Display> Incompatibility<P, VS, M> {
/// Create the initial "not Root" incompatibility.
pub(crate) fn not_root(package: P, version: VS::V) -> Self {
Self {
package_terms: SmallMap::One([(
package.clone(),
Term::Negative(VS::singleton(version.clone())),
)]),
kind: Kind::NotRoot(package, version),
}
}
/// Create an incompatibility to remember that a given set does not contain any version.
pub(crate) fn no_versions(package: P, term: Term<VS>) -> Self {
let set = match &term {
Term::Positive(r) => r.clone(),
Term::Negative(_) => panic!("No version should have a positive term"),
};
Self {
package_terms: SmallMap::One([(package.clone(), term)]),
kind: Kind::NoVersions(package, set),
}
}
/// Create an incompatibility for a reason outside pubgrub.
#[allow(dead_code)] // Used by uv
pub(crate) fn custom_term(package: P, term: Term<VS>, metadata: M) -> Self {
let set = match &term {
Term::Positive(r) => r.clone(),
Term::Negative(_) => panic!("No version should have a positive term"),
};
Self {
package_terms: SmallMap::One([(package.clone(), term)]),
kind: Kind::Custom(package, set, metadata),
}
}
/// Create an incompatibility for a reason outside pubgrub.
pub(crate) fn custom_version(package: P, version: VS::V, metadata: M) -> Self {
let set = VS::singleton(version);
let term = Term::Positive(set.clone());
Self {
package_terms: SmallMap::One([(package.clone(), term)]),
kind: Kind::Custom(package, set, metadata),
}
}
/// Build an incompatibility from a given dependency.
pub(crate) fn from_dependency(package: P, versions: VS, dep: (P, VS)) -> Self {
let (p2, set2) = dep;
Self {
package_terms: if set2 == VS::empty() {
SmallMap::One([(package.clone(), Term::Positive(versions.clone()))])
} else {
SmallMap::Two([
(package.clone(), Term::Positive(versions.clone())),
(p2.clone(), Term::Negative(set2.clone())),
])
},
kind: Kind::FromDependencyOf(package, versions, p2, set2),
}
}
pub(crate) fn as_dependency(&self) -> Option<(&P, &P)> {
match &self.kind {
Kind::FromDependencyOf(p1, _, p2, _) => Some((p1, p2)),
_ => None,
}
}
/// Merge dependant versions with the same dependency.
///
/// When multiple versions of a package depend on the same range of another package,
/// we can merge the two into a single incompatibility.
/// For example, if a@1 depends on b and a@2 depends on b, we can say instead
/// a@1||2 depends on b.
///
/// It is a special case of prior cause computation where the unified package
/// is the common dependant in the two incompatibilities expressing dependencies.
pub(crate) fn merge_dependents(&self, other: &Self) -> Option<Self> {
// It is almost certainly a bug to call this method without checking that self is a dependency
debug_assert!(self.as_dependency().is_some());
// Check that both incompatibilities are of the shape p1 depends on p2,
// with the same p1 and p2.
let self_pkgs = self.as_dependency()?;
if self_pkgs != other.as_dependency()? {
return None;
}
let (p1, p2) = self_pkgs;
let dep_term = self.get(p2);
// The dependency range for p2 must be the same in both case
// to be able to merge multiple p1 ranges.
if dep_term != other.get(p2) {
return None;
}
return Some(Self::from_dependency(
p1.clone(),
self.get(p1)
.unwrap()
.unwrap_positive()
.union(other.get(p1).unwrap().unwrap_positive()), // It is safe to `simplify` here
(
p2.clone(),
dep_term.map_or(VS::empty(), |v| v.unwrap_negative().clone()),
),
));
}
/// Prior cause of two incompatibilities using the rule of resolution.
pub(crate) fn prior_cause(
incompat: Id<Self>,
satisfier_cause: Id<Self>,
package: &P,
incompatibility_store: &Arena<Self>,
) -> Self {
let kind = Kind::DerivedFrom(incompat, satisfier_cause);
// Optimization to avoid cloning and dropping t1
let (t1, mut package_terms) = incompatibility_store[incompat]
.package_terms
.split_one(package)
.unwrap();
let satisfier_cause_terms = &incompatibility_store[satisfier_cause].package_terms;
package_terms.merge(
satisfier_cause_terms.iter().filter(|(p, _)| p != &package),
|t1, t2| Some(t1.intersection(t2)),
);
let term = t1.union(satisfier_cause_terms.get(package).unwrap());
if term != Term::any() {
package_terms.insert(package.clone(), term);
}
Self {
package_terms,
kind,
}
}
/// Check if an incompatibility should mark the end of the algorithm
/// because it satisfies the root package.
pub(crate) fn is_terminal(&self, root_package: &P, root_version: &VS::V) -> bool {
if self.package_terms.len() == 0 {
true
} else if self.package_terms.len() > 1 {
false
} else {
let (package, term) = self.package_terms.iter().next().unwrap();
(package == root_package) && term.contains(root_version)
}
}
/// Get the term related to a given package (if it exists).
pub(crate) fn get(&self, package: &P) -> Option<&Term<VS>> {
self.package_terms.get(package)
}
/// Iterate over packages.
pub(crate) fn iter(&self) -> impl Iterator<Item = (&P, &Term<VS>)> {
self.package_terms.iter()
}
// Reporting ###############################################################
/// Retrieve parent causes if of type DerivedFrom.
pub(crate) fn causes(&self) -> Option<(Id<Self>, Id<Self>)> {
match self.kind {
Kind::DerivedFrom(id1, id2) => Some((id1, id2)),
_ => None,
}
}
/// Build a derivation tree for error reporting.
pub(crate) fn build_derivation_tree(
self_id: Id<Self>,
shared_ids: &Set<Id<Self>>,
store: &Arena<Self>,
precomputed: &Map<Id<Self>, Arc<DerivationTree<P, VS, M>>>,
) -> DerivationTree<P, VS, M> {
match store[self_id].kind.clone() {
Kind::DerivedFrom(id1, id2) => {
let derived = Derived {
terms: store[self_id].package_terms.as_map(),
shared_id: shared_ids.get(&self_id).map(|id| id.into_raw()),
cause1: precomputed
.get(&id1)
.expect("Non-topological calls building tree")
.clone(),
cause2: precomputed
.get(&id2)
.expect("Non-topological calls building tree")
.clone(),
};
DerivationTree::Derived(derived)
}
Kind::NotRoot(package, version) => {
DerivationTree::External(External::NotRoot(package, version))
}
Kind::NoVersions(package, set) => {
DerivationTree::External(External::NoVersions(package.clone(), set.clone()))
}
Kind::FromDependencyOf(package, set, dep_package, dep_set) => {
DerivationTree::External(External::FromDependencyOf(
package.clone(),
set.clone(),
dep_package.clone(),
dep_set.clone(),
))
}
Kind::Custom(package, set, metadata) => DerivationTree::External(External::Custom(
package.clone(),
set.clone(),
metadata.clone(),
)),
}
}
}
impl<'a, P: Package, VS: VersionSet + 'a, M: Eq + Clone + Debug + Display + 'a>
Incompatibility<P, VS, M>
{
/// CF definition of Relation enum.
pub(crate) fn relation(&self, terms: impl Fn(&P) -> Option<&'a Term<VS>>) -> Relation<P> {
let mut relation = Relation::Satisfied;
for (package, incompat_term) in self.package_terms.iter() {
match terms(package).map(|term| incompat_term.relation_with(term)) {
Some(term::Relation::Satisfied) => {}
Some(term::Relation::Contradicted) => {
return Relation::Contradicted(package.clone());
}
None | Some(term::Relation::Inconclusive) => {
// If a package is not present, the intersection is the same as [Term::any].
// According to the rules of satisfactions, the relation would be inconclusive.
// It could also be satisfied if the incompatibility term was also [Term::any],
// but we systematically remove those from incompatibilities
// so we're safe on that front.
if relation == Relation::Satisfied {
relation = Relation::AlmostSatisfied(package.clone());
} else {
return Relation::Inconclusive;
}
}
}
}
relation
}
}
impl<P: Package, VS: VersionSet, M: Eq + Clone + Debug + Display> Display
for Incompatibility<P, VS, M>
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(
f,
"{}",
ReportFormatter::<P, VS, M>::format_terms(
&DefaultStringReportFormatter,
&self.package_terms.as_map()
)
)
}
}
// TESTS #######################################################################
#[cfg(test)]
pub(crate) mod tests {
use proptest::prelude::*;
use super::*;
use crate::term::tests::strategy as term_strat;
use crate::Range;
proptest! {
/// For any three different packages p1, p2 and p3,
/// for any three terms t1, t2 and t3,
/// if we have the two following incompatibilities:
/// { p1: t1, p2: not t2 }
/// { p2: t2, p3: t3 }
/// the rule of resolution says that we can deduce the following incompatibility:
/// { p1: t1, p3: t3 }
#[test]
fn rule_of_resolution(t1 in term_strat(), t2 in term_strat(), t3 in term_strat()) {
let mut store = Arena::new();
let i1 = store.alloc(Incompatibility {
package_terms: SmallMap::Two([("p1", t1.clone()), ("p2", t2.negate())]),
kind: Kind::<_, _, String>::FromDependencyOf("p1", Range::full(), "p2", Range::full())
});
let i2 = store.alloc(Incompatibility {
package_terms: SmallMap::Two([("p2", t2), ("p3", t3.clone())]),
kind: Kind::<_, _, String>::FromDependencyOf("p2", Range::full(), "p3", Range::full())
});
let mut i3 = Map::default();
i3.insert("p1", t1);
i3.insert("p3", t3);
let i_resolution = Incompatibility::prior_cause(i1, i2, &"p2", &store);
assert_eq!(i_resolution.package_terms.as_map(), i3);
}
}
}