The uri-template format regex listed ' in its excluded character set, so
"a'b" was reported invalid. An apostrophe in a literal is valid; remove it
from the exclusion set.

* Reject empty labels in idn-hostname format

RFC5892.isValid skipped empty labels with continue, so a leading or interior
empty label -- ".example" or "a..b" -- validated as a valid idn-hostname.
String.split already drops trailing empty labels, so the skip only ever hit
leading/interior empties, which are invalid. Reject them.

* Reject a hostname made up only of label separators

String.split returns an empty array for a value that is all separators
("..." or "。。"), so the loop was skipped and it validated as true. Reject
when there are no labels; this also subsumes the single-separator case.

* Fix comment wording to reference label separators generically, not just '.'

* Fix nullable check for allOf + $ref compositions

A property declared nullable: true and composed via allOf containing
only a $ref (e.g. OpenAPI 3.0 style composition) incorrectly rejected
null values. The schema owning the failing type keyword is resolved
through $ref and is a cached object whose lexical parent reflects
where it is declared in the document, not where it was referenced
from, so the existing one-hop parent/grandparent nullable check never
found the nullable declaration on the referencing schema.

Walk the dynamic evaluation stack instead, following through any
chain of $ref schemas, to find the referencing schema and check it
(and its lexical parent) for nullable: true.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

* Add regression test confirming nullable allOf+$ref fix is dialect-scoped

Confirms, per maintainer feedback on the upstream issue, that the
dynamic evaluation stack walk added for nullable allOf + $ref
compositions has no effect outside dialects that enable the nullable
keyword (currently only OpenAPI 3.0.x) — null is still rejected for
the same schema shape under draft-07.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

* Ignore nullable declared directly beside $ref

Per PR review feedback (#1279), the
dynamic evaluation stack walk added to support nullable allOf + $ref
compositions incorrectly honored nullable: true declared as a direct
sibling of $ref. That's a Reference Object, and the OpenAPI 3.0
specification requires siblings of $ref to be ignored, so it must
never grant nullability on its own.

Track whether the current frame in the walk was reached via $ref and,
if so, skip checking that frame's own nullable — only its lexical
parent (the schema actually composing it, e.g. the allOf owner) is
consulted. The allOf + $ref case that motivated the original fix
still passes.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>

#1281)

#1272 made SchemaException render the schema location with the configured
PathType, through SchemaRegistry.formatSchemaLocation, and applied it to
the two "Schema at ..." throws in that class. DiscriminatorValidator
throws the same message at three sites and still concatenates the raw
SchemaLocation.

With pathType(PathType.JSON_PATH) the message mixes the two notations in
one sentence, because instanceLocation is already a NodePath built from
the configured PathType:

  Schema at #/allOf/1/discriminator is redefining the discriminator
  property that has already been set for at $

Adds the same private helper the registry uses, so the default
JSON_POINTER output is unchanged.

Jackson 3.2 parses YAML .nan/.inf/-.inf as numeric values, and #1241
already handles non-finite numbers during validation. Cover the default
YAML mapper path so these inputs keep producing a type error instead of
a parser exception.

Test contributed by @patpatpat123 in #1228.


Claude-Session: https://claude.ai/code/session_01XJ3SkCprrZVpASPFMADg1h

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

Resolves the OpenAPI nullable keyword by descending the engine's own
evaluation stacks rather than reconstructing provenance from schema
structure. The previous walk climbed lexical parents and sniffed for
$ref members, which misattributed nullable across reference sites,
was sensitive to schema-node identity, and missed $dynamicRef and
$recursiveRef entirely.

The walk pairs evaluationSchema with evaluationSchemaPath to recover
the keyword each schema was entered by, propagating nullable through
allOf/oneOf/anyOf, if/then/else and the three referencing keywords,
and stopping at any keyword that moves to a different value. As a
result nullable no longer leaks into a container's properties, items
or additionalProperties children, and no longer reaches inside not.

Applies the same walk to enum, which previously decided at
construction time whether null was accepted, and relaxes only the
oneOf cardinality check for a nullable null, leaving branch errors
reported when nothing matches.

Ported from #1280. Two adaptations
were needed for this branch rather than a straight copy:

  - isNodeNullable now calls asBoolean(false). Jackson 3 throws on a
    node it cannot coerce where Jackson 2 returns false, and the walk
    reads nullable on every composing ancestor, so a malformed member
    anywhere in the chain would abort the validation.

  - The typeLoose enum change concerns the empty string here, not the
    string "null". NullNode.asString() is "" in Jackson 3, so that is
    the value the accepted set silently permitted.

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>