Intersect all ranges in and chains - #50
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Range.allows_any?/2, Version.allows_any?/2 and Union.allows_any?/2 returned true for an empty constraint, so a positive term with an empty constraint related as overlapping instead of disjoint to any assignment. When a dependency's constraint was empty and the depender had another version to backtrack to, unit propagation derived the same term from the no-versions incompatibility forever.
ericmj
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August 26, 2026 21:31
Requirements with more than two and terms, two bounds in the same direction, == inside an and, or two pessimistic ranges either crashed with FunctionClauseError or were rejected, even though Version.parse_requirement/1 accepts them and hexpm allows publishing them. Fold each and group through Constraint.intersect/2 instead of the special-cased to_range/4 clauses. An empty intersection raises UnsatisfiableRequirementError naming the two disjoint parts. Closes #49.
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HexSolver.Requirementonly handled two-termandgroups and special-cased their operator combinations, so requirements thatVersion.parse_requirement/1accepts and hexpm lets through on publish either crashed withFunctionClauseError(>= 1.0.0 and < 2.0.0 and > 1.5.0,>= 1.0.0 and > 1.5.0,== 1.0.0 and >= 1.0.0,~> 1.0 and >= 2.0.0) or were rejected (~> 1.0.0 and ~> 1.0).delex/2now folds everyandgroup throughConstraint.intersect/2, which replaces allto_range/4clauses. Semantics match core: a property checksConstraint.allows?/2againstVersion.match?/2for random one to four term chains over a version grid.An empty intersection raises the new
HexSolver.UnsatisfiableRequirementError, whose message names the two disjoint parts:requirement "~> 1.0 and >= 2.0.0" is unsatisfiable because "~> 1.0" and ">= 2.0.0" are disjoint.parse_constraint/1keeps returning:error.The first commit fixes a separate solver bug found while checking what an empty constraint does downstream. When a dependency's constraint is
%Empty{}(reachable with a published< 0.0.0-0requirement since #44) and the depender has another version to backtrack to,HexSolver.run/4never returned:allows_any?/2returnedtrueagainst an empty constraint, so the no-versions incompatibility related as overlapping and unit propagation derivednot bar emptyindefinitely. TheRange,VersionandUnionclauses now returnfalse.Empty.allows_any?/2is unchanged on purpose: flipping it too makes the dependency incompatibility conflict with itself and the failure message degrades todepends on both "bar empty" and "bar empty".Closes #49.