Missing support for xsd::import / xsd::include

[elmeunick9]

While trying to validate XSD documents from UBL 2.4:
https://docs.oasis-open.org/ubl/cs01-UBL-2.4/UBL-2.4.html

In particular:
https://docs.oasis-open.org/ubl/cs01-UBL-2.4/xml/UBL-BusinessCard-2.2-Example.xml

Example main.rs:

use std::fs;
use std::path::Path;
use xmloxide::Document;
use xmloxide::catalog::Catalog;
use xmloxide::tree::NodeKind;
use xmloxide::validation::xsd::{parse_xsd, validate_xsd};

fn main() {
    // 1. Setup your paths
    let catalog_path = "xsd/ubl/UBL-2.4-catalog.xml";
    let base_dir = Path::new("xsd/ubl/"); // The root where 'maindoc' and 'common' folders live

    // 2. Load the UBL Catalog
    let catalog_content = fs::read_to_string(catalog_path).expect("Could not find catalog file");
    let catalog = Catalog::parse(&catalog_content).expect("Failed to parse catalog");

    // 3. Parse your BusinessCard XML
    let xml_content = fs::read_to_string("UBL-BusinessCard-2.2-Example.xml").expect("Could not find XML file");
    let doc = Document::parse_str(&xml_content).expect("Failed to parse XML");

    // 4. Correctly extract the root namespace from NodeId
    let root_id = doc.root_element().expect("XML has no root element");
    let root_node = doc.node(root_id);
    
    let target_ns = if let NodeKind::Element { ref namespace, .. } = root_node.kind {
        // namespace is an Option<String> in this struct
        namespace.as_deref().unwrap_or("")
    } else {
        ""
    };

    println!("Looking for XSD for namespace: {}", target_ns);

    // 5. Use the Catalog to find the relative path
    // In UBL 2.4, this usually resolves to "maindoc/UBL-BusinessCard-2.4.xsd"
    let xsd_rel_path = catalog.resolve_system(target_ns)
        .or_else(|| catalog.resolve_uri(target_ns)) // Fallback to URI just in case
        .expect("Namespace not found in catalog as systemId or URI");

    // 6. Join paths and validate
    let full_xsd_path = base_dir.join(xsd_rel_path);
    let xsd_content = fs::read_to_string(full_xsd_path).expect("Resolved XSD file not found");
    
    let schema = parse_xsd(&xsd_content).expect("Failed to parse XSD");
    let result = validate_xsd(&doc, &schema);

    if result.is_valid {
        println!("✅ Validation Successful!");
    } else {
        println!("❌ Validation Failed: {:?}", result.errors);
    }
}

[jonwiggins]

This is now supported in v0.3.2 (just published to crates.io).

What changed

The XSD validator now supports xsd:import and xsd:include via a new SchemaResolver trait and parse_xsd_with_options() function. The existing parse_xsd() function is unchanged for backward compatibility.

Updated example for your UBL use case

use std::fs;
use std::path::Path;
use xmloxide::Document;
use xmloxide::catalog::Catalog;
use xmloxide::tree::NodeKind;
use xmloxide::validation::xsd::{parse_xsd_with_options, validate_xsd, XsdParseOptions};

fn main() {
    let catalog_path = "xsd/ubl/UBL-2.4-catalog.xml";
    let base_dir = Path::new("xsd/ubl/");

    let catalog_content = fs::read_to_string(catalog_path).expect("Could not find catalog file");
    let catalog = Catalog::parse(&catalog_content).expect("Failed to parse catalog");

    let xml_content = fs::read_to_string("UBL-BusinessCard-2.2-Example.xml")
        .expect("Could not find XML file");
    let doc = Document::parse_str(&xml_content).expect("Failed to parse XML");

    let root_id = doc.root_element().expect("XML has no root element");
    let root_node = doc.node(root_id);
    let target_ns = if let NodeKind::Element { ref namespace, .. } = root_node.kind {
        namespace.as_deref().unwrap_or("")
    } else {
        ""
    };

    let xsd_rel_path = catalog.resolve_system(target_ns)
        .or_else(|| catalog.resolve_uri(target_ns))
        .expect("Namespace not found in catalog");

    let full_xsd_path = base_dir.join(&xsd_rel_path);
    let xsd_content = fs::read_to_string(&full_xsd_path).expect("Resolved XSD file not found");

    // NEW: Use a resolver so xsd:import and xsd:include are followed
    let xsd_dir = full_xsd_path.parent().unwrap_or(base_dir);
    let resolver = |location: &str, _base: Option<&str>| -> Option<String> {
        fs::read_to_string(xsd_dir.join(location)).ok()
    };
    let opts = XsdParseOptions {
        resolver: Some(&resolver),
        base_uri: None,
    };

    let schema = parse_xsd_with_options(&xsd_content, &opts).expect("Failed to parse XSD");
    let result = validate_xsd(&doc, &schema);

    if result.is_valid {
        println!("Validation Successful!");
    } else {
        println!("Validation Failed: {:?}", result.errors);
    }
}

The key change is replacing parse_xsd(&xsd_content) with parse_xsd_with_options(&xsd_content, &opts) and providing a resolver closure that reads schema files from disk. The resolver is called whenever the parser encounters <xsd:import schemaLocation="..."/> or <xsd:include schemaLocation="..."/>.

Features:

• xsd:include — merges declarations from schemas in the same namespace (including chameleon includes)
• xsd:import — resolves cross-namespace type references via QName prefix maps
• Cycle detection — circular import/include chains are handled safely
• Backward compatible — parse_xsd() still works for single-file schemas

See the changelog for full details.