[Rust] Release 0.50.0

Added

• CanonicalSchema::union and CanonicalSchema::subtract.
• CanonicalizationError::UnsupportedResult, reported where the canonical form does not support a set operation's result.
• OperandMismatch::DocumentRoots, reported where both operands read # and it names a different document on each side.
• CLI: jsonschema validate -i INSTANCE without a SCHEMA argument validates each instance against the schema named in its own $schema property. #1470

Changed

• CanonicalSchema::is_satisfiable is now CanonicalSchema::satisfiability, answering Yes, No, or Unknown - Yes wherever a value can be exhibited, not only for the forms listing their members.
• CanonicalSchema::covers decides through the difference as well: No where the argument keeps values the receiver rejects, Yes where nothing is left over.
• CanonicalSchema::is_subset_of is now CanonicalSchema::covers, answering Yes, No, or Unknown for whether the receiver admits every value the argument admits.
• CanonicalSchema::negate returns Result rather than Option.
• CanonicalizationError::UnmodeledOperand is now CanonicalizationError::UnsupportedOperand, and means only that an operand is a Raw pass-through.
• A conjunction over a $ref folds through the body it names, so canonicalizing a document and combining its parts with the set operations reach one form; a document holding a reference cycle keeps the form it had.

Fixed

• Combining nodes of two different documents repointing a $ref to # at the combined result instead of the document it was written in, including one named by a definition the result keeps.
• Intersecting a $ref whose target is true or false, which panicked.
• A key constraint left un-narrowed once a run is out of intersections, which panicked on the next read of it.
• CanonicalSchema::covers answering Unknown for a schema against itself, where that schema is a $ref.
• CanonicalSchema::union keeping a $ref beside the schema it names, where the other three operations read through it.
• CanonicalSchema::covers and CanonicalSchema::subtract cancelling two nodes written the same way whose # names a different document.
• Two results accepting the same values comparing unequal over the part of their documents neither reads.
• additionalProperties reaching a key the pattern map matches when a finite key constraint closes the map, which dropped values both operands accept.
• A recursive definition stopping every other pointer in the document from being read through.
• One $defs entry read past a wider schema written out at every use, rather than kept as the pointer it was.
• Set operations rejecting one document canonicalized twice, and a pruned result rejected against the document it came from, where the maps resolve every shared reference the same way.
• Set operations comparing a $ref as a pointer instead of reading through it, so a schema written with a $ref did not cancel against the same schema written out.
• CanonicalSchema::subtract asking for a complement where the difference is one of the operands or empty, declining on schemas it can subtract.
• Set operations keeping $defs entries the result no longer references, which then showed up in the emitted schema.
• CanonicalSchema::union declining over an approximated intersection, where the union itself is exact.
• Resolving a reference against a base URI that carries a fragment, which happens when a Draft 4-7 $id contains one. #1473
• unevaluatedProperties and unevaluatedItems ignoring an $id on a subschema they walk through, so a relative $ref inside it resolved against the enclosing resource.

Performance

• CLI: ~25% less CPU per run from compile-time meta-schema validators.