Module resolver 

Schema resolution for include, import, and redefine directives

This module handles resolving and loading external schema documents referenced by xs:include, xs:import, and xs:redefine directives.

Resolution Process

1. Include - Same target namespace, required schemaLocation

   • Loads the referenced schema
   • Merges components into the same namespace
   • Supports chameleon includes (no targetNamespace)

2. Import - Different namespace, optional schemaLocation

   • Loads schema for the specified namespace
   • Components remain in their declared namespace
   • Without schemaLocation, relies on catalog or pre-loaded schemas

3. Redefine - Same namespace, extends/restricts existing types

   • Deprecated in XSD 1.1 (use override instead)
   • Allows redefining types/groups from included schema

Circular Dependencies

The resolver tracks loaded schema locations to:

• Detect circular includes (allowed, just skip)
• Prevent infinite loops
• Enable caching of resolved schemas

URI Resolution

The resolver supports:

• Absolute file paths
• Relative paths (resolved against base URI)
• HTTP/HTTPS URLs (via async trait)
• Catalog-based resolution

Customizable Loading

The SchemaLoader trait allows custom loading strategies:

• FileSystemLoader - Loads from local file system
• EmbeddedLoader - Loads from embedded static assets
• LoaderChain - Combines multiple loaders with priority

Structs

CatalogEntry

A single catalog entry

EmbeddedLoader

Embedded resource loader for built-in schemas.

FileSystemLoader

File system schema loader (default).

LoaderChain

Composite loader that chains multiple loaders.

ResolutionResult

Result of resolving all directives in a schema

ResolverConfig

Configuration for schema resolution

SchemaCatalog

Catalog for mapping namespaces to schema locations

SchemaResolver

Schema resolver for loading external schema documents.

Enums

LoadOutcome

Result of a single load_schema call, distinguishing three outcomes.

Traits

SchemaLoader

Trait for loading schema content from various sources.

Functions

decode_xml_bytes

Decode raw XML bytes into a UTF-8 String, sniffing common Unicode encodings per XML 1.0 §F.1. See decode_xml_to_utf8_bytes.

decode_xml_to_utf8_bytes

Decode raw XML bytes into UTF-8 bytes, sniffing common Unicode encodings per XML 1.0 §F.1.

fixup_composition_edges

Fixup pass: fill in target_doc on cycle edges whose target has since been loaded. Call after all directive resolution rounds complete.

resolve_all_directives

Resolve all directives in a schema document