Read and enforce the XSD 1.0 derivation controls that were previously
ignored:
- abstract elements may not appear in an instance directly, only through
a substitution member; an element of an abstract complex type must
supply an xsi:type naming a concrete derived type.
- block on a type forbids the disallowed xsi:type substitutions; block on
an element drops substitution-group members that derive by a blocked
method.
- final on a type rejects, at compile time, any type that derives from it
by a final method.
- xs:redefine requires the redefined type to derive from itself.
Track each named complex type's base and derivation method as the
backbone these checks walk. Also compose complexContent extension and
restriction content models, which were previously dropped: an extension
now inherits its base's attributes and content (base first, then the
extension, in sequence).
Complex-type restriction is not verified to be a structurally valid
subset of its base (Particle Valid (Restriction)); that limit is
documented at its sites.
Closes#76
Closes#75, on the validation framework. XSD instance-level features:
- nillable elements: an xsi:nil="true" element is accepted (its content model is
not checked) only when the element is declared nillable and carries no content;
xsi:nil on a non-nillable element, or a nilled element with content, is a
located error.
- fixed value constraints: a present fixed attribute must equal its fixed value,
and a fixed element's text must match.
- default/fixed are parsed onto AttributeUse (per use) and collected per element
name (nillable set + value constraints), threaded through XSDContext to the
ComplexValidator.
All findings are located ValidationErrors. Collection and helper methods move to
same-file extensions to stay within type-body limits.
Slice 4 of #92. The XSD complex-type and identity-constraint validators move
onto the validation framework, producing located results.
- ComplexValidator threads a coding path through its (inherently recursive)
descent, so every content-model, attribute, and simple-type violation is now
a ValidationError located by path ("... at path: order/qty"). Child steps
carry a sibling index only when a name repeats.
- IdentityValidator returns ValidationError instead of Issue.
- A new XSD rules enum wraps both as Validation<Node, XSDContext> values gated to
the document root, combined by Validator<XSDContext>. XSDContext carries the
type table, the identity constraints, and the root declaration.
- Schema.Document.validate builds the context and runs the validator, returning
[ValidationError].
XSD content-model validation is recursive by nature (a child's type depends on
its position), so the rules delegate to the recursion while contributing to one
error collection. Schematron is the last validator on Issue and migrates next.
