PureXML/Tests/SchemaReferenceTests.swift

import Testing
@testable import PureXML

/// Every QName a schema names (a `type`/`base`/`itemType`/`memberTypes` type, an
/// element/attribute/group/attributeGroup `ref`, an element `substitutionGroup`)
/// must resolve to a declared component or a built-in. An undeclared reference
/// was previously accepted at compile time and only surfaced (if at all) lazily
/// during instance validation. The check is skipped when the document pulls in
/// external definitions through `import`/`include`/`redefine`, which the default
/// compile does not load.
@Suite("Schema reference resolution")
struct SchemaReferenceTests {
    private func compile(_ body: String) throws {
        _ = try PureXML.Schema.Document("""
        <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
        \(body)
        </xs:schema>
        """)
    }

    private func rejects(_ body: String) -> Bool {
        do { try compile(body)
            return false
        } catch { return true }
    }

    @Test("a reference to a declared component or a built-in resolves")
    func test_resolves() throws {
        try compile(#"<xs:element name="a" type="xs:string"/>"#)
        try compile(#"<xs:simpleType name="t"><xs:restriction base="xs:integer"/></xs:simpleType><xs:element name="a" type="t"/>"#)
        try compile(#"<xs:element name="g" type="xs:string"/><xs:complexType name="c"><xs:sequence><xs:element ref="g"/></xs:sequence></xs:complexType>"#)
    }

    @Test("an undeclared reference is rejected")
    func test_undeclared() {
        #expect(rejects(#"<xs:element name="a" type="DoesNotExist"/>"#))
        #expect(rejects(#"<xs:simpleType name="t"><xs:restriction base="Missing"/></xs:simpleType>"#))
        #expect(rejects(#"<xs:complexType name="c"><xs:sequence><xs:element ref="ghost"/></xs:sequence></xs:complexType>"#))
        #expect(rejects(#"<xs:complexType name="c"><xs:group ref="noGroup"/></xs:complexType>"#))
    }

    @Test("a reference value tolerates surrounding whitespace (whiteSpace collapse)")
    func test_whitespacePadded() throws {
        try compile("<xs:simpleType name=\"t\"><xs:restriction base=\"  xs:string \"/></xs:simpleType>")
    }

    @Test("a ref resolving to the XSD namespace is undeclared")
    func test_refResolvingToXSDNamespaceIsUndeclared() throws {
        // The default xmlns is the XSD namespace, so an unprefixed `ref="root"`
        // resolves to {XSD}root, not {foo}root, and the XSD namespace declares no
        // referenceable user element: undeclared (XSTS xsd013/xsd014).
        let refRoot = """
        <schema xmlns="http://www.w3.org/2001/XMLSchema" xmlns:foo="foo" targetNamespace="foo">
          <element name="root"><complexType><sequence><element ref="root"/></sequence></complexType></element>
        </schema>
        """
        #expect(throws: (any Error).self) { _ = try PureXML.Schema.Document(refRoot) }
        let refUndef = """
        <schema xmlns="http://www.w3.org/2001/XMLSchema" xmlns:foo="foo" targetNamespace="foo">
          <element name="root"><complexType><sequence><element ref="undef"/></sequence></complexType></element>
        </schema>
        """
        #expect(throws: (any Error).self) { _ = try PureXML.Schema.Document(refUndef) }
        // Guard: the same shape with the ref qualified to the target resolves, so the
        // XSD-namespace rule does not reject a correctly-namespaced reference.
        let qualified = """
        <schema xmlns="http://www.w3.org/2001/XMLSchema" xmlns:foo="foo" targetNamespace="foo">
          <element name="root"><complexType><sequence><element ref="foo:root"/></sequence></complexType></element>
        </schema>
        """
        _ = try PureXML.Schema.Document(qualified)
    }

    @Test("references are not checked when an import may supply them")
    func test_importSkipsCheck() throws {
        // A dangling reference into an imported namespace is tolerated: the default
        // compile does not load the import, so the reference cannot be verified.
        try compile(#"""
        <xs:import namespace="urn:other"/>
        <xs:element name="a" type="other:Foo" xmlns:other="urn:other"/>
        """#)
    }

    @Test("references are checked strictly against the targetNamespace")
    func test_referenceNamespaceChecking() throws {
        // Without targetNamespace, unprefixed ref resolves to no namespace and is accepted
        _ = try PureXML.Schema.Document("""
        <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
            <xs:attribute name="number" type="xs:integer"/>
            <xs:element name="elementWithAttr">
                <xs:complexType>
                    <xs:attribute ref="number" use="required"/>
                </xs:complexType>
            </xs:element>
        </xs:schema>
        """)

        // With targetNamespace, unprefixed ref without default namespace resolves to no namespace but declaration is in targetNamespace -> rejected
        #expect(throws: Error.self) {
            _ = try PureXML.Schema.Document("""
            <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="AttrUse/attrDecl" xmlns:tn="AttrUse/attrDecl">
                <xs:attribute name="number" type="xs:integer"/>
                <xs:element name="elementWithAttr">
                    <xs:complexType>
                        <xs:attribute ref="number" use="required"/>
                    </xs:complexType>
                </xs:element>
            </xs:schema>
            """)
        }

        // With targetNamespace, prefix matching targetNamespace is accepted
        _ = try PureXML.Schema.Document("""
        <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="AttrUse/attrDecl" xmlns:tn="AttrUse/attrDecl">
            <xs:attribute name="number" type="xs:integer"/>
            <xs:element name="elementWithAttr">
                <xs:complexType>
                    <xs:attribute ref="tn:number" use="required"/>
                </xs:complexType>
            </xs:element>
        </xs:schema>
        """)

        // With targetNamespace, default namespace matching targetNamespace is accepted
        _ = try PureXML.Schema.Document("""
        <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="AttrUse/attrDecl" xmlns="AttrUse/attrDecl">
            <xs:attribute name="number" type="xs:integer"/>
            <xs:element name="elementWithAttr">
                <xs:complexType>
                    <xs:attribute ref="number" use="required"/>
                </xs:complexType>
            </xs:element>
        </xs:schema>
        """)
    }
}